HomeMy WebLinkAboutOrdinance 26963-06-2024ORDINANCE NO.26963-06-2024
AN ORDINANCE ADOPTING THE 2024 STORMWATER CRITERIA
MANUAL OF THE CITY OF FORT WORTH; PROVIDING THAT THIS
ORDINANCE SHALL BE CUMULATIVE OF ALL PRIOR ORDINANCES
AND REPEAL CONFLICTING ORDINANCES; PROVIDING FOR A
SEVERABILITY CLAUSE; PROVIDING FOR A SAVINGS CLAUSE; AND
PROVIDING AN EFFECTIVE DATE.
WHEREAS, the City Council of the City of Fort Worth seeks to provide in the City to
ensure the health, safety, welfare, and quality of life of the citizens of Fort Worth; and
WHEREAS, Section 212.002 of the Texas Local Government Code provides that after a
public hearing, the governing body of a municipality may adopt rules governing plats and
subdivision of land within the municipality's jurisdiction to promote the health, safety, morals, or
general welfare of the municipality and the safe, orderly, and healthful development of the
municipality; and
WHEREAS, Section 212.0021 of the Texas Local Government Code provides that the
governing body of a municipality, by ordinance and after notice is published in a newspaper of
general circulation in the municipality, may adopt, based on the amount and kind of travel over
each street or road in a subdivision, reasonable specification s related to the construction of each
street or road, and adopt reasonable specifications to provide adequate drainage for each street or
road in a subdivision in accordance with standard engineering practice; and
WHEREAS, the City of Fort Worth Storm Drainage Criteria and Design Manual was
developed in 1967 and over the years was amended and revised with the most recent version being
the 2015 edition of the Stormwater Criteria Manual; and
WHEREAS, the City Council finds it necessary to revise the Stormwater Criteria Manual
to incorporate amendments to the Floodplain Ordinance and the Grading Permit Ordinance, and
to clarify the City's requirements, and revise regulations based on new data and information;
WHEREAS, the City Council finds this Ordinance to be reasonable and necessary;
NOW, THEREFORE, BE IT ORDAINED BY THE CITY COUNCIL OF THE CITY
OF FORT WORTH, TEXAS, THAT:
SECTION 1.
The Stormwater Criteria Manual of the City of Fort Worth, Texas, which is attached hereto
as Exhibit "A" and incorporated herein by reference is adopted in its entirety.
SECTION 2.
Ordinance No. 26963-06-2024
Page 1 of 2
This ordinance shall be cumulative of all provisions of ordinances and of the Code of the
City of Fort Worth, Texas (2015), as amended, except where the provisions of this ordinance are
in direct conflict with the provisions of such ordinances and such Code, in which event conflicting
provisions of such ordinances and such Code are hereby repealed.
SECTION 3.
It is hereby declared to be the intention of the City Council that the phrases, clauses,
sentences, paragraphs and sections of this ordinance are severable, and, if any phrase, clause,
sentence, paragraph or section of this ordinance shall be declared unconstitutional by the valid
judgment or decree of any court of competent jurisdiction, such unconstitutionality shall not affect
any of the remaining phrases, clauses, sentences, paragraphs and sections of this ordinance, since
the same would have been enacted by the City Council without the incorporation in this ordinance
of any such unconstitutional phrase, clause, sentence, paragraph or section.
SECTION 4.
All rights and remedies of the City of Fort Worth, Texas, are expressly saved as to any and
all violations of the provisions of the Code of the City of Fort Worth, or any other ordinances of
the City, that have accrued at the time of the effective date of this ordinance; and, as to such accrued
violations and all pending litigation, both civil and criminal, whether pending in court or not, under
such ordinances, same shall not be affected by this ordinance, but may be prosecuted until final
disposition by the courts.
SECTION 5.
This ordinance shall take effect on July 15, 2024.
APPROVED AS TO FORM AND LEGALITY
-9�
RicharQM1,l,CS.If+{IC@11 (Jun 28
. )0
24 16:17 tnn
Richard A. McCracken
Sr. Assistant City Attorney
ADOPTED: June 11, 2024
EFFECTIVE: July 15, 2024
Ordinance No.26963-06-2024
Page 2 of 2
ATTEST:
Jannette Goodall
City Secretary
City of Fort Worth, Texas
Mayor and Council Communication
DATE: 06/11/24 M&C FILE NUMBER: M&C 24-0484
LOG NAME: 20SW REGULATION UPDATES 2024
SUBJECT
(ALL) Conduct Public Hearing and Adopt Ordinance Amending Chapter 7 "Buildings," Article VIII "Floodplain Provisions" of the City Code to
Establish and Regulate Critical Flood Risk Areas, Adopt Ordinance Amending Chapter 12.5 "Environment Protection and Compliance" of the City
Code to Amend Regulations Governing Grading Permits, and Adopt Ordinance Adopting Revisions to the Stormwater Criteria Manual
(PUBLIC HEARING - a. Report of City Staff: Stephen Nichols; b. Public Comment; c. Council Action: Close Public Hearing and Act on M&C)
RECOMMENDATION:
It is recommended that the City Council:
1. Conduct a public hearing in accordance with Section 212.0021 of the Texas Local Government Code;
2. Adopt the attached ordinance amending Chapter 7 "Buildings," Article Vill "F[oodplain Provisions" of the City Code to establish and regulate
critical flood risk areas;
3. Adopt the attached ordinance amending Chapter 12.5 "Environmental Protection and Compliance" of the City Code to amend regulations
governing grading permits; and
4. Adopt the attached ordinance adopting revisions to the Stormwater Criteria Manual.
DISCUSSION:
The purpose of this Mayor and Council Communication (M&C) is to adopt an ordinance establishing and regulating critical flood risk areas, adopt
an ordinance amending regulations governing grading permits, and adopt an ordinance adopting updates to the Stormwater Criteria Manual.
,Floodplain Provisions Ordinance:
In 2018, the Storrnwater Management Program began an initiative to determine how to communicate non-FEMA flood risk information and how to
regulate small sized developments (under 1 acre) in non-FEMA flood prone areas. The initiative was developed due to increasing instances of
property owners and developers outside of the FEMA floodplain being surprised by flood events impacting their properties and development
plans. The significant, and often undefined risk of flooding outside of FEMA floodplains is a nationwide issue.
Since that time, Stormwater staff have held public and community group meetings to discuss and receive feedback on non-FEMA flood risk
regulations and worked closely with stakeholder groups, including the Real Estate Guidance Group and stakeholder groups associated with the
American Council of Engineering Companies, Floodplain Management Plan, Stormwater Master Plan, and Stormwater Program. The
stakeholders consisted of residents, engineers, lenders, appraisers, title lawyers, insurance agents, surveyors, developers, and builders and
included the Rea[ Estate Council of Greater Fort Worth, the Greater Fort Worth Association of Realtors, the FortWorth Builders Association, the
Development Advisory Committee (DAC), and the Tarrant Appraisal District.
The proposed ordinance will establish non-FEMA City Flood Risk Areas (CFRAs). CFRA regulations would regulate all residential and
commercial development activity less than one (1) acre that is located in a CFRA. The development activity ranges from fences, accessory
structures, room additions, and new construction, up to commercial or mixed -use site development projects on less than one acre. Such
development activity would require:
• Elevation of structures two (2) feet above the 100-year flood elevation, and;
• Submission of a certificate from an engineer to document that the development will not cause increased flood risk to neighboring properties,
The City Flood Risk Area regulations shall take effect on July 15, 2024.
Grading Permit Ordinance:
Coordination and collaboration with development community representatives, started three (3) years ago on the proposed updates to the Grading
Permit Ordinance to make the permitting process more efficient and effective. The most significant improvement is that this update will replace
the Final integrated Storm Water Management (iSWM) Plan requirement with a grading permit, eliminating one step in the development review
process. In addition, the updates will produce the following benefits:
• Clarify submission requirements and apply review requirements uniformly across development projects;
• Better define Early Grading Permits and clarify requirements for Early Grading Permits; and
• Clarify exemptions and simplify review processes for public infrastructure.
The amended Grading Permit Ordinance shall take effect on July 15, 2024.
Stormwater Criteria Manual
In 2019, the Texas State Legislature passed House Bill 3167 which amended Chapter 212 of the Texas Local Government Code. The new law
required, in part, for developer construction plans to be approved by the City Plan Commission, to place a "shot clock" on review and approval
deadlines for developer construction plans, and for any review comments on construction plans to cite to specific laws, regulations, or design
criteria when the construction plans were not approved by the City. During the 88th Texas Legislative Session, the state law was amended to
remove these requirements.
While no longer mandatory, City staff and development representatives have maintained self-imposed review deadlines and clear regulations that
can be cited to during construction plan reviews. To that end, City staff have prepared revisions to the Stormwater Criteria Manual to ensure that
the City's requirements are clear and can be easily cited to in construction plan review comments.
In addition, staff recommends changes to the Stormwater Criteria Manual based on new data and information, lessons learned from how current
regulations are implemented, and to integrate the proposed revisions to the Floodplain Provisions Ordinance and the Grading Permit Ordinance.
The revisions will provide clarity to the development community, and help to ensure development and public infrastructure design contribute to a
safe and sustainable Fort Worth.
Throughout the process, staff engaged with external and internal stakeholders to coordinate and get feedback on document revisions. Draft
documents were coordinated with the DAC for review and comment.
A summary of the updates to the Stormwater Criteria Manual include:
• CFRA guidance and regulations are incorporated;
• Final iSWM Plans are no longer required;
• Drainage studies are better defined and introduced as a separate submittal to replace iSWM plans;
• Use of specific types of polypropylene pipe in lieu of concrete pipe are allowed;
• Stormwater detention facility maintenance requirements are defined;
• Runoff coefficients for more dense residential developments are updated;
• Easement sizing requirements are revised; and
• Administrative procedures for processing applications and conducting pre -submittal meetings are revised.
The revised Stormwater Criteria Manual shall take effect on July 15, 2024.
In accordance with Section 212.0021 of the Texas Local Government Code, notice of the public hearing on the proposed ordinances was
published in the Fort Worth Star -Telegram on May 24, 2024.
A Form 1295 is not required because: This M&C does not request approval of a contract with a business entity.
FISCAL INFORMATION t CERTIFICATION:
The Director of Finance certifies that approval of these recommendations will not have no material effect on City funds.
Submitted for Cijy Manager's Office b1c Jesica McEachern 5804
Originating Business Unit Head:, Lauren Prieur 6035
Additional Information Contact: Monty Hall 8662
Exhibit A CITY OF FORT WORTH
AN iSWM COMMUNITY
STORMWATFR
CRITERIA MANUAL
r � F
i
June, 2024
FORT WORTH '
Stormwater
Table of Contents
Foreword.....................................................................................................................................................................6
Acknowledgements.....................................................................................................................................................8
ErrataSheet
................................................................................................................................................................9
Overview of the NCTCOG iSWM Program..............................................................................................................
10
I Stormwater Goals and Objectives.................................................................................................................... 11
1.1
Introduction....................................................................................................................................
11
1.2
Abbreviations and Definitions........................................................................................................ 12
1.3
Application of Stormwater Criteria................................................................................................. 14
2 Stormwater Development Process................................................................................................................... 16
2.1
Stormwater and Floodplain Submissions......................................................................................
16
2.2
Stormwater Submission Requirements......................................................................................... 17
2.3
Preparation of Stormwater Submittals........................................................................................... 19
2.4
Floodplain Development & Flood Study........................................................................................
29
2.5
Non-FEMA City Flood Risk Area Development Requirements..................................................... 30
3 Stormwater Design Criteria..............................................................................................................................
37
3.1
Design Options..................•............................................................................................. .............. 37
3.2
Design Storms............................................................................................................................... 40
3.3
Design Criteria...............................................................................................................................
40
3.4
Hydrologic Design Criteria............................................................................................................. 42
3.5
Water Quality Protection................................................................................................................ 47
3.6
Streambank Protection..................................................................................................................
52
3.7
Flood Mitigation.............................................................................................................................. 53
3.8
Stormwater Conveyance Systems................................................................................................. 56
3.9
Stormwater Control Selection......................................................................................................
108
3.10
General Design Standards..........................................................................................................
122
3.11
Easements, Plats, and Maintenance Agreements.......................................................................
124
3.12
Plan and Document Preparation Requirements..........................................................................
130
4 Stormwater Construction Criteria...................................................................................................................
134
4.1
Applicability..................................................................................................................................134
4.2
Introduction..................................................................................................................................
134
4.3
Criteria for BMPs during Construction.........................................................................................
135
5 References.....................................................................................................................................................
142
Appendix A —Checklists and Forms......................................................................................................................
143
Appendix B: Stormwater Computer Models..........................................................................................................
168
B.1
Introduction..................................................................................................................................
168
B.2
Types of Models...........................................................................................................................
168
City of Fort Worth Stormwater Criteria Manual 2
B.3 Summary of Acceptable Models..................................................................................................
170
Appendix C — City of Fort Worth Miscellaneous Details and Specifications.........................................................
172
CAStraight Drop Spillways................................................................................................................
172
C.2 Baffled Chutes.............................................................................................................................
174
Appendix D -- Sediment and Erosion Control Guidelines for Small Sites.............................................................
176
Appendix E -- Single Family Residential Lot Drainage..........................................................................................
178
E.1 Lot Drainage Types......................................................................................................................
178
E.2 Block Grading Types....................................................................................................................
179
Appendix F — Stormwater Utility Fee Credit Policy................................................................................................
182
City of Fort Worth Stormwater Criteria Manual 3
List of Tables
Table1.1 One Acre Threshold................................................................................................................................ 14
Table 2.1 Comparison of FEMA SFHA and Non-FEMA CFRA...............................................................................
32
Table 3.1 Zone of Influence and Adequate Outfall Determination..........................................................................
38
Table 3.2 Summary of Options for Design Focus Areas.........................................................................................
39
Table3.3 Storm Events......................................................................................................... ....
40
Table 3.4 City of Fort Worth Constraints on Using Recommended Hydrologic Methods .......................................
42
Table3.5 Runoff Coefficients..................................................................................................................................
44
Table 3.6 Integration of Site Design Practices with Site Development Process .....................................................
48
Table 3.7 Suitability of Stormwater Controls to Meet integrated Focus Areas ........................................................
51
Table 3.9 Velocity in Storm Drains..........................................................................................................................
67
Table 3.10 Minimum Grades for Storm Drains........................................................................................................
67
Table 3.11 Manning's Coefficients for Storm Drain Conduits..................................................................................
68
Table 3.12 Junction or Structure Coefficient of Loss...............................................................................................
72
Table 3.13 Head Loss Coefficients Due To Obstructions.......................................................................................
72
Table 3.14 Head Loss Coefficients Due To Sudden Enlargements and Contractions ...........................................
73
Table 3.15 City of Fort Worth Manning's Roughness Coefficients for Design........................................................
84
Table 3.16 Roughness Coefficients (Manning's n) and Allowable Velocities for Natural Channels .......................
84
Table 3.17 Maximum Velocities for Vegetative Channel Linings............................................................................
85
Table 3.18 Classification of Vegetal Covers as to Degrees of Retardance............................................................
91
Table 3.19 Recommended Loss Coefficients for Bridges....................................................................................... 94
Table 3.20 Rock Riprap Sizing -- Culvert Outfall Protection..................................................................................
100
Table 3.21 Rock Riprap Sizing - Gregory Method................................................................................................
101
Table 3.22 Dry Detention Pond Inspection, Maintenance, & Repair.....................................................................
104
Table 3,23 Underground Detention Inspection, Maintenance, & Repairs.............................................................
107
Table 3.24 Stormwater Treatment Suitability........................................................................................................
111
Table 3.25 Water Quality Performance.................................................................................................................
112
Table 3.26 Site Applicability......................................................................................................... ..
113
Table 3.27 Implementation Considerations..........................................................................................................
114
Table3.28 Physiographic Factors.........................................................................................................................
116
Table3.29 Soils ......................... ...................................:........................................................................................
117
Table 3.30 Special Watershed Considerations.....................................................................................................
118
Table 3.31 Location and Permitting Checklist.......................................................................................................
120
Table 3.32 Closed Conduit Easements.................................................................................................................
125
Table 4.1 Requirements for Materials and Wastes...............................................................................................
140
City of Fort Worth Stormwater Criteria Manual 4
List of Figures
Figure 1 iSWM Program Support Documents and Tools........................................................................................ 10
Figure 2.1 Example of CFRA, PHWA, and SFHA Mapping ............................... ........
31
Figure 2.2 Generalized Stormwater Development Review Process.......................................................................
36
Figure 3.1 Sample Calculation Sheet for Runoff Coefficient "C...............................................................................
45
Figure 3.2 Computation Summary Sheet for Hydrology by Unit Hydrograph Method ............................................
46
Figure 3.3 Grading Requirements Next to Building Foundation..............................................................................
57
Figure3.4 Type CO-S Inlet......................................................................................................................................
61
Figure 3.5 Computation Sheet for Curb Opening and Drop Inlets.........................................................................
62
Figure3.6 Type CO-D Inlet........................................................................................................... ...
64
Figure 3.7 Computation Summary Sheet for On Grade Curb Inlets.......................................................................
65
Figure 3.8 Minor Head Losses at Structures (1 of 2)..............................................................................................
74
Figure 3.9 Minor Head Losses at Structures (2 of 2)..............................................................................................
75
Figure 3.10 Computations Sheet for Storm Drains.................................................................................................
79
Figure 3.11 Plan View - Trapezoidal Concrete Lined Channel...............................................................................
86
Figure 3.12 Section View - Trapezoidal Concrete Lined Channel..........................................................................
87
Figure 3.13 Man View - Trapezoidal Earthen Channel ..................
Figure 3.14 Section View - Trapezoidal Earthen Channel......................................................................................
89
Figure 3.15 Typical Section -- Rural Roadside Ditch...............................................................................................
90
Figure 3.16 Dry Detention Pond Schematic............................................................................................................
97
Figure 3.17 Dry Detention Pond with Pilot Channel Schematic..............................................................................
98
Figure 3.18 Typical Detention Pond Exhibit B — Example.....................................................................................
129
City of Fort Worth Stormwater Criteria Manual 5
Foreword
Adoption of Manual by City of Fort Worth
This Stormwater Criteria Manual ("Manual") is adopted and becomes effective on June 1, 2024. The North Central
Texas Council of Government ("NCTCOG") iSWM Technical Manuals are adopted and incorporated herein by
reference. To the extent a conflict exists between this Manual and the NCTCOG iSWM Technical Manuals, this
Manual shall control.
City staff shall develop and implement administrative processes, procedures and documents in order to administer
and manage the requirements outlined in this Manual.
Relationship to Previous Manuals
The original City of Fort Worth (City) Storm Drainage Criteria and Design Manual was developed in 1967 and
amended in 1975, 1986, and 1994. In 2006, updated design criteria were developed in conjunction with the first
version of the NCTCOG's iSWM ManualT1. In 2012, the manual was revised to incorporate the City's Grading
Permit requirements and revised values for impervious cover in hydrologic calculations. The City criteria presented
in the 2015 manual are generally consistent with those in the 2012 version. The 2015 revision incorporates local
provisions into the document and reflects the development process changes implemented by the City of Fort Worth
in 2013 — 2015.
This 2024 Manual revision is primarily to adjust the stormwater development review process and clarify criteria and
design requirements. This is in response to Texas House Bill 3167 that was passed by the 86th Legislature and
became effective September 1, 2019. As in 2012 and 2015 versions, the over -arching motivation for this Manual
is to provide efficient guidance for effective mitigation of the impacts of new development and construction on the
character of stormwater runoff.
Purpose and Limitations of Manual; Waivers
This Manual provides requirements for the most commonly encountered stormwater or flood control designs in the
City. It shall be used for watershed master plans and for design of remedial measures for existing facilities. This
Manual was developed for users with knowledge and experience in the applications of standard engineering
principles and practices of stormwater design and management. There will be specific situations not completely
addressed or covered by this Manual. Other methods of design or waivers to the criteria shall be requested using
the Stormwater Waiver Request Form CFW-7. Any waivers from the requirements of this Manual must have the
express approval of the Director of the Department of Transportation and Public Works (TPW) or the Director's
designee (Director). For construction plans submitted to the City's Infrastructure Plan Review Center, any waivers
from the requirements of this Manual must have the approval of the Director of the Development Services
Department, or their designee, who will consult with the Director of TPW before making a determination. Close
coordination with the staff of the City is recommended and encouraged during the planning, design and construction
of all stormwater facilities.
The design procedures as presented herein are based on the historical rainfall records of duration, intensity, and
frequency of storms that have occurred in the past in the Fort Worth area. This is the customary and accepted basis
for the design of drainage facilities. There is no assurance, however, that rainfall will not occur in the future that will
temporarily overload the drainage facilities. The degree of protection afforded by the requirements included herein
is considered consistent with good municipal practice in this region. The requirements in this Manual are the
minimum standards for stormwater management in the City of Fort Worth and shall be applied to all studies, plans
and plats. In addition to the City's requirements, all studies, plans, and plats must comply with all applicable state,
federal, and local laws.
Please note that all references to iSWM Technical Manuals refer to the 2014 NCTCOG iSWM Technical Manuals,
such as Planning, Hydrology, Hydraulics, and Site Development Controls.
Goals and Objectives for Stormwater Management
A proper understanding of the City's adopted goals and objectives for stormwater management, as summarized in
Chapter 1 is essential for the proper application of this Manual.
City of Fort Worth Stormwater Criteria Manual 6
Contact Information
Additional information on the City of Fort Worth's Stormwater Management program and policies can be obtained
at www.fortworthtexas.gov/stormwater/ or by contacting the Stormwater Development Services (SDS) Team at
SDS@fortworthtexas.gov. For information on the iSWM regional manual and program, contact the NCTCOG at
817-695-9220 or at the website http:/IiSWM.nctcog.org/.
City of Fort Worth Stormwater Criteria Manual 7
Acknowledgements
The City of Fort Worth acknowledges the extensive efforts of the North Central Council of Governments and their
consultants in the development of the iSWM regional program and manuals. The City also wishes to acknowledge
the significant contribution by consulting engineers, planners, developers, and community leaders in the Fort Worth
area who dedicated many hours of meetings, review of policy and criteria, and development of specific
recommendations that were incorporated in the previous editions and in the 2024 version:
Brian Agbulos
Richard Albin
Jean-Marie Alexander
Don Allen
Darrel Andrews
Shamsul Arefin
Mark Assaad
Travis Attanasio
Greg Baker
Robert Bardo
Craig Barnes
Terry Barr
Joe Barrow
Grady Beachum
George Behmanesh
Curtis Beitel
Jonathan Bengfort
Robert Bergeron
Scott Berman
Paul Berry
Dana Burghdoff
Jeana Booker
Paul Bounds
Mike Brennan
Ray Bromley
Lesley Brooks
Thad Brundrett
Thomas Caffarel
Abe Calderon
Gary Caldwell
Kenny Calhoun
Kervin Campbell
Amy Cannon
Lori Chapin
Richard Contreras
Clair Davis
Ken Davis
Jeff Davis
Tom Dayton
Steve DeFilippo
Mike Dellies
Jim DeOtte
Rich DeOtte
Kelly Dillard
Glen Dixon
Eddie Eckart
Cuneyt Erbatur
Mark Ernst
Steve Eubanks
Tom Galbreath
Brenda Gasperich
Wade Goodman
Matt Goodwin
James Gossie
Allison Gray
Alan Greer
Jill Griffin
Ryan Hague
Walter Hardin
Jim Harris
Michael Hobbs
Katie Hogan
Josh Hollon
David Hosseiny
Steve Howard
Joe Howell
Tom Huffhines
Michael James
Chris Johnson
Dena Johnson
Garrett Johnston
April Karr
Debbie Kearns
Jim Keith
Kiran Konduru
Ann Kovich
Brent Lewis
Lynn Lovell
Thanaa Maksimos
Steve Mason
Joe Masterson
Don McChesney
Richard McCracken
Daniel McCullough
Morgan McDermott
Dan McInnis
David McLendon
Kevin Miller
Janie Morels
Ronald Morrison
Ryan Mortensen
Cindy Mosier
Mike Moya
Vincent Muzidi
Osama Neshed
Stephen Nichols
Erika Nordstrom
Jason Oliver
Brian O'Neill
Justin Oswald
Jerry Parche
Richard Payne
Raul Pena
Angela Pereira
Joshua Pettijohn
Phillip Poole
Benjamin Pylant
Ron Rackley
Ragu Rao
Kelly Rattan
Jeff Rice
Jerry Roberts
Cindy Robinson
David Rubenkoenig
Scott Rutledge
Joe Schneider
Richard Shaheen
Derek Sellers
Bryan Sherrieb
Tony Sholola
Greg Simmons
Steve Slater
David Speicher
Susan Stewart
Erin Storey
Zubin Sukheswalla
Caleb Tandy
Gary Teague
Audra Valamides
Rhonda Visintainer
Mike Wayts
Jason Weaver
Billy Wendland
Julie Westerman
Tim Whitefield
Mathew Williamson
Angela Wright
Linda Young
Halff Associates, Inc. coordinated the development of the 2012 Fort Worth local criteria. Freese and Nichols, Inc.
coordinated the revisions to the 2012 criteria that were incorporated into the 2015 manual. City Staff have prepared
these 2024 revisions to the Manual.
City of Fort Worth Stormwater Criteria Manual 8
Errata Sheet
City of Fort Worth Stormwater Criteria Manual
Overview of the NCTCOG iSWM Program
The iSWM Program for Construction and Development is a cooperative initiative that assists municipalities and
counties to achieve their goals of water quality protection, streambank protection, and flood mitigation, while also
helping communities meet their construction and post -construction obligations under state stormwater permits.
Development and redevelopment by their nature increase the amount of imperviousness in our surrounding
environment. This increased imperviousness translates into loss of natural areas, more sources for pollution in
runoff, and heightened flooding risks. To help mitigate these impacts, more than 60 local governments are
cooperating to proactively create sound stormwater management guidance for the region through the "integrated"
Stormwater Management (iSWM) Program.
The iSWM Program is comprised of four types of documentation and tools as shown in Figure 1. These are used
to complement each other and to support the development process.
Figure 1 iSWM Program Support Documents and Tools
The four parts of iSWM are:
Stormwater Criteria Manual (this Manual) — This Manual provides a description of the development process,
utilizing the design concepts and regional criteria adopted as part of the iSWM focus areas. This Manual
incorporates locally adopted design criteria as required by the City in conjunction with the iSWM criteria.
iSWM Technical Manual — This set of documents provides technical guidance including equations, descriptions of
methods, fact sheets, etc. necessary for design. The iSWM Technical Manual includes categories for Planning,
Water Quality, Hydrology, Hydraulics, Site Development Controls, Construction Controls and Landscape. The
iSWM Technical Manual is referenced in this document.
iSWM Tools — This includes web -served training guides, examples, design tools, etc. that could be useful during
design.
iSWM Program Guidance -- This includes reference documents that guide programmatic planning rather than
technical design.
The iSWM Technical Manual, Tools, and Program Guidance provide references and additional information that
will be helpful in the development of a Drainage Study and Construction Plans which will comply with the City
criteria.
City of Fort Worth Stormwater Criteria Manual 10
I Stormwater Goals and Objectives
1.1 Introduction
The purpose of this Manual is to provide design criteria and a framework for incorporating effective and
environmentally sustainable stormwater management into the site development and construction processes.
The City's primary goal is to manage stormwater so that drainage conditions do not get worse as new areas are
developed —while making improvements in the areas of the City that are already developed.
This goal can be accomplished by:
1. Developing detailed watershed plans that promote orderly growth and result in an integrated system of public
and private stormwater infrastructure.
2. Adopting development policies and standards that prevent flooding, preserve streams and channels, and
minimize water pollution without discouraging either new or infill development.
3. Fully complying with regulatory permit requirements.
4. Operating the stormwater system in a more efficient and effective manner.
5. Informing the public about stormwater issues in the community.
6. Securing funding that is adequate for meeting these needs and is recognized by the public as fair and
equitable.
The City's planning and design objectives described in this manual are to:
1. Regulate the drainage policy and criteria for new development and redevelopment so property development
does not increase flooding problems, cause erosion, or pollute downstream water bodies.
2. Facilitate the development of comprehensive watershed planning that promotes orderly growth and results in
an integrated system of public and private stormwater infrastructure.
3. Minimize flood risks to citizens and properties, and stabilize or decrease streambank and channel erosion on
creeks, channels, and streams.
4. improve stormwater quality in creeks, rivers, and other water bodies, remove pollutants, enhance the
environment and mimic the natural drainage system, to the extent practicable, in conformance with the Texas
Pollutant Discharge Elimination System (TPDES) permit requirements.
5. Support multi -use functions of stormwater facilities for trails, green space, parks, greenways or corridors,
stormwater quality treatment, and other recreational and natural features, provided they are compatible with
the primary functions of the stormwater facility.
6. Encourage a more standardized, integrated land development process.
The criteria provided in this manual will help to meet sustainable development goals and objectives. There are many
ways that sustainable development may be achieved while following these criteria.
Chapter Summary
The Stormwater Criteria Manual consists of five chapters:
Chapter 1 — Stormwater Goals and Objectives
Chapter 2 — Stormwater Development Process
Chapter 3 — Stormwater Design Criteria
Chapter 4 — Stormwater Construction Criteria
Chapter 5 -- References
City of Fort Worth Stormwater Criteria Manual 11
1.2 Abbreviations and Definitions
For convenience, two terms which are used frequently throughout this manual are abbreviated:
City — City of Fort Worth
TPW — Department of Transportation and Public Works
Several stormwater and development terms are used in this manual which have unique or special meanings. They
are defined below:
Adequate Outtall — Outfall that does not create adverse flooding or erosion conditions downstream (No Adverse
Impact) from the development through the downstream end of the zone of Influence. In all cases shall be subject
to the approval of the Director of the Transportation and Public Works Department. Refer to Section 3.1, Table 3.1.
Adverse Impact Assessment —A determination of the downstream and upstream limit of properties that could be
impacted by a development (also see Zone of Influence).
BMP or Best Management Practice — A physical, chemical, structural, or managerial practice or device that
prevents, reduces, or treats the pollution of stormwater, or reduces or treats erosion, or minimizes runoff.
Common Plan of Development (also Common Plan) — Any development or construction activity completed in
stages, separate phases, or in combination with other construction activities on land consisting of 1.0 acres or more
as determined by the City based upon its evaluation of development plans, applications, or activities.
Developer — A person or entity that owns, manages, controls or influences a development or Common Plan of
development. A Developer may manage, control, or influence development owned by multiple persons or entities.
Development — A contiguous tract of land, regardless of whether easements such as right-of-way, public access
easements, drainage easements, or utility easements are located on the land, that is proposed to or has been
improved by making a different use of the land or by making alterations or improvements to the land.
Drainage Study— Studies of a proposed Development and drainage areas, drainage facilities, and flood risk. A
Drainage Study for a Development or Common Plan of Development shall include an Adverse Impact Assessment
throughout the Zone of Influence.
Early Grading Permit A permit issued by the City for a land disturbance that involves only earthwork in
conformance with the Grading Permit Ordinance and this Manual.
Engineer or Engineer of Record — The person authorized to practice engineering in Texas who is responsible for
preparing engineering plans for a Development.
Erosion and Sediment Control (ESC) Plan — A plan and notes indicating the installation and maintenance of
BMPs and application of pollution prevention procedures used to control erosion, sediment, construction materials,
and waste during the construction phase of improvements in conformance with the criteria contained in this Manual.
This plan shall be included within the construction plan set required for Development within the City. The ESC Plan
was previously referred to as an iSWM Construction Plan.
Flood Study— A hydrologic and hydraulic analysis that complies with all local, state, and federal requirements,
guidance, and criteria for FEMA SFHA Flood Study submissions, and complies with all hydrologic and hydraulic
modelling best practices as defined by the relevant FEMA, USACE, FHWA and NCTCOG technical publications,
guidance and manuals.
Floodplain Development Permit — A permit required before any Development activity shall begin within a
floodplain or FEMA designated Special Flood Hazard Area (SFHA). This shall require a separate submittal to the
City Floodplain Administrator.
Fully Developed Conditions — For watershed hydrology, fully developed conditions include all existing developed
areas which shall reflect current land use or current zoning, whichever yields the greatest runoff, and all existing
undeveloped areas which shall reflect anticipated future land use designated by zoning classification, by the City's
Comprehensive Plan, or by an accepted concept plan, or in the ETJ, NCTCOG future land use maps.
Grading Permit — A permit issued by the City for a land disturbance in conformance with the Grading Permit
Ordinance and this Manual.
City of Fort Worth Stormwater Criteria Manual 12
Maintenance Plan or Operations and Maintenance Plan — A plan prepared in accordance with this Manual for
the purpose of describing maintenance and operational requirements of a structural BMP and interchangeably used
with the "City Stormwater Facility Maintenance Plan."
Master Drainage Study —A "Drainage Study" that is submitted in support of a concept plan or other multi -phased
Development. The Master Drainage Study shall establish baseline hydrologic and hydraulic conditions from which
impacts are measured. It shall provide a framework, including hydrologic and hydraulic models, to support future
Development phases.
Natural Creeks --Those drainageways that are generally unimproved, that often exhibit a meandering course, and
which are not proposed to be improved to City standards for earthen channels. Natural creeks are generally not
dredged, mowed or otherwise maintained by the City and shall be contained within floodplain easements rather
than drainage easements.
Offsite Drainage Area — An area which drains to the proposed Development.
Private Water— Runoff water which is generated on private property and flowing within the property or from one
property to another. Drainage easements and drainage facilities which contain only private water shall not be
maintained by the City.
Public Water— The concentration of surface water flowing through or from public land or right-of-way. Public water
must be contained within a dedicated right-of-way, floodplain or drainage easement.
Redevelopment— See Development.
Stormwater Fee Credits —An incentive provided bythe City to encourage the voluntary use of BMPs which improve
stormwater management. See Appendix F.
Stormwater Facility Maintenance Agreement or Maintenance Agreement (SWFMA) — A legal agreement
between the City and a property owner, including HOAs and POAs, for perpetual maintenance of a structural BMP.
Stormwater Management Plan (SWMP) —A stormwater management plan (SWMP) that conforms to the criteria
contained in this Manual (also see Drainage Study). The previous terminology for a SWMP was an integrated
Stormwater Management Plan, or iSWM Plan.
Stormwater Pollution Prevention Plan or SWPPP — The site design, operations, and inspections plan required
by the Environmental Protection Agency (EPA) and the Texas Council on Environmental Quality (TCEQ) for the
control of erosion and sediment during construction.
Stormwater Pre -Construction Check -- A verification that applicable items and permits were completed and
provided before beginning construction, issuing a Grading Permit, or scheduling an 1PRC Pre -Construction meeting.
Zone of Influence — A "Zone of Influence" from a proposed Development extends to a point downstream where
the discharge from a proposed Development no longer has a significant impact, as defined in Chapter 3, upon the
receiving stream or storm drainage system, and downstream properties. The Zone of Influence for any proposed
Development must be defined by the development engineer by a Drainage Study that: (1) determines the extent of
the downstream drainage route subject to impacts from a proposed Development, and (2) delineates what existing
conditions are in place or what proposed mitigation is planned so that "no adverse impacts" from the new
Development will occur.
City of Fort Worth Stormwater Criteria Manual 13
1.3 Application of Stormwater Criteria
1.3.1 Adverse Impact Assessment Threshold
The requirement to submit a downstream assessment and no adverse impact analysis to the City for review applies
under the following conditions for Development and Redevelopment as illustrated below and in Table 1.1. Note
that Developments that fall below this threshold should still follow the downstream assessment and no adverse
criteria; however, that information would not be reviewed by the City.
table 1.1 One Acre Threshold I
Land disturbing activity or platting of 1.0 acre or more
XV
Land disturbing activity or platting of less than 1.0 acre where the
is part of a Common Plan of Development that is 1.0 acre or more.
A Common Plan of Development consists of construction activity that is completed in separate stages, separate
phases, or in combination with other construction activities. To be considered as a Common Plan of Development
for purposes of this policy, a tract must meet one or more of the following characteristics:
• Included in a single concept plan submitted to the City,
• Included in a single preliminary plat submitted to the City,
• Included in a single final plat submitted to the City,
• Is comprised of contiguous land (or land separated only by roadway and/or drainage rights -of -way or
easements) under the same root ownership or control,
• Is encumbered by a single Master Drainage Study, Drainage Study, Flood Study or Plan,
• Is encumbered by a single Developer's Agreement, T1F, 380 Agreement or other public/private
partnership agreement,
• Is overlaid by a common Homeowner's or Property Owner's Association (HOA, POA), or
• is owned or managed by a common Developer.
The City requires a Grading Permit prior to any land disturbance of 1.0 acre or more, and less than 1.0 acre of
disturbance when the construction is a part of a Common Plan. After construction and grading activities are
completed and disturbed areas are stabilized, a Grading Certificate must be provided by the Contractor or Engineer
which affirms that construction has been completed in substantial compliance with plans accepted by the City and
all temporary BMP's have been removed.
This manual does not consider Development and Redevelopment separately; rather criteria are applied based on
land disturbance and platting activities.
If an existing site has been cleared and/or graded within the prior five years of the date of the Developer's initial
application submittal, the Developer may consider the land conditions prior to the clearing and grading to be the
existing site conditions.
New Development or Redevelopment, subject to the applicability requirements shown in Table 1.1, which are
located in critical, sensitive, or potentially flood -prone areas, or as identified through a watershed study or plan, are
subject to additional performance and regulatory criteria. Furthermore, these sites shall utilize certain structural
controls in order to protect a special resource or address certain water quality or drainage problems identified for a
drainage area or watershed.
City of Fort Worth Stormwater Criteria Manual 14
1.3.2 Site Design below One Acre
Although a plat or construction plan application might not meet the land distance or platting thresholds in Table 1.1;
plat and construction plan applications shall require a Drainage Study to determine the size and type of drainage
improvements, easements, and assess and mitigate flood risk. Furthermore, all Developments within the city limits
and ETJ shall comply with the City of Fort Worth Subdivision Ordinance and Development permitting requirements,
including but not limited to building permits, Floodplain Development Permits, SWPPP, Grading Permits, and urban
forestry permits.
If Development or Redevelopment activity that is comprised of pieces less than one acre is later shown to be part
of a Common Plan, then all pieces shall be required to come into compliance with this Manual. For example, a
Common Plan might consist of individual land disturbing activities and plats of less one acre. However, if these
pieces were all owned, managed or controlled by a common Developer then the work shall be considered a
Common Plan.
Refer to Section 2.2.2 for the conditions under which no Drainage Study is needed.
1.3.3 Adoption of Standards
For projects which have an accepted Drainage Study and/or iSWM plan, including phased Developments which
have some existing constructed phases after the adoption of the iSWM criteria in June 2006, findings in accepted
studies will remain valid. The applicability of the current drainage criteria is presented below in the Applicability of
the iSWM Standards Adoption Language.
Concept, Preliminary and Final iSWM Plans, as well as drainage design calculations accepted by the City
of Fort Worth after the adoption of the City's drainage design standards and criteria on June 1, 2006 shall
be considered valid when:
• The proposed project is a phase of a multi -phase Development that has a valid preliminary plat
• The drainage infrastructure of the proposed phase will connect directly to drainage infrastructure
of a phase of the same Development with drainage infrastructure designed and constructed based
on the standards in previous versions of the City's iSWM manual.
All iSWM plans and stormwater design projects submitted after the September 29, 2015 adoption date not
meeting the criteria above shall use the current Stormwater Criteria and iSWM standards and will be valid
for a period of time that is concurrent with the accepted preliminary or final plat for the project.
It a proposed Development maintains or decreases the percent imperviousness onsite, a Drainage Study,
Construction Plans and landscape plans shall be required to provide confirmation of maintained or decreased
percent imperviousness and show no additional impacts.
For Developments for which stormwater criteria is applicable as set forth in Table 1.1, the building permit process
shall require a drainage review of the Grading Permit and Construction Plans to ensure that the site runoff is
consistent with the accepted Drainage Study, existing runoff patterns and stormwater management has been
appropriately addressed.
City of Fort Worth Stormwater Criteria Manual 15
2 Stormwater Development Process
This chapter discusses the submittal process, development paths and subsequent stormwater submissions that are
required for a Development or Redevelopment project.
2.1 Stormwater and Floodplain Submissions
2.1.1 Document Management
Drainage Studies and Flood Studies shall be submitted to the Stormwater Development Services (SIDS) team of
the Development Service Department at the City of Fort Worth. All documents shall be submitted in a digital format.
Documents comprised of text or images should be provided as a portable document format'(.PDF) file. All model
files shall be provided so that they are executable and the model can be recreated. Although revisions might only
require portions of the submission to be updated; a complete submission of project documents shall be provided
with each revision/response submission. For information on the procedure for digital submittals, visit the City's
website or contact the Stormwater Development Services team at SDS@fortworthtexas.gov
2.1.2 Pre -Submittal Meetings
Before submitting a Drainage Study or Flood Study, the applicant shall meet with SIDS and Floodplain Management
staff to gather information, build consensus, and determine the scope of the studies. Contact staff at
SDS@fortworthtexas.gov to schedule a Pre -Submittal meeting. The meeting request form shall be completed and
returned with attachments to SIDS before a meeting can be scheduled.
2.1.3 Application Fee
The City Council has adopted a fee structure for the review of stormwater and floodplain submissions. The City
Council may amend the fee structure in the future. Fees are due at the time of application submission. The
application shall be considered incomplete, and the review shall not proceed, until the fee is paid in full.
2.1.4 Completeness Checks
Upon receiving stormwater or floodplain submissions for review, the submittal package shall initially be reviewed
for completeness.
Incomplete submissions, and incomplete revisions or responses, shall not be accepted for review and the applicant
notified of the deficiencies and incomplete items. Review shall not proceed until a complete application, revision
and response is received.
2.1.5 Checklists
Application checklists shall be furnished by the City and the applicant shall provide the applicable checklist with
each application submission. Checklists shall be provided in a digital format and may be obtained from the City's
website or by contacting the SIDS team at SDS@fortworthtexas.gov
These checklists are intended as a guide, not an exhaustive list, to help the applicant include the most commonly
required items in the submission. The checklists may be refined and updated by City staff. Applicants shall
complete and provide the latest checklist available at the time of submitting an application.
2.1.6 Review and Acceptance
City staff, or a contractor, shall review application submissions for general compliance with this Manual. An
acceptance (or approval) does not relieve the owner, Developer, engineer, or designer from responsibility for
ensuring that the calculations, plans, specifications, construction and record drawings are in compliance with this
Manual and all other applicable local, state and federal requirements, and will accomplish the necessary or desired
drainage, floodplain or stormwater management outcomes.
City of Fort Worth Stormwater Criteria Manual 16
An accepted Drainage Study is one that was submitted, reviewed, revised to correct all deficiencies, and was found
to be in conformance with all applicable design criteria and standards. If errors or omissions are later identified in
the Drainage Study, then they shall be corrected and subsequent Development applications revised to conform to
the corrected study.
Information that is not required to be submitted for review shall not be reviewed by the City. If a Drainage Study for
a Development less than one acre and not part of Common Plan of Development was submitted then it may be
rejected for review; or only the relevant and required parts of the study would receive a review. For example, a
Drainage Study for a 0.6 acre Development would be reviewed for easement and infrastructure requirements, but
not reviewed for adverse impacts resulting from additional impervious cover.
2.2 'Stormwater Submission Requirements
2.2.1 Overview
The requirements of each Stormwater submission is dependent on the Development path underway, as shown in
Figure 2.1 at the end of this chapter. The process diagram provided in Figure 2.1 is for Stormwater Development
reviews only and does not include additional reviews required by other City of Fort Worth Departments. It shall be
the applicant's responsibility to inquire regarding pertinent permitting and review submittals required for their project.
The scope of drainage analysis and review is dependent on the type of Development application and area of land
disturbance. Stormwater reviews including Drainage Studies are required for Grading Permits, Construction Plans,
Concept Plans, and all types of Plats. A Drainage Study Acceptance letter (DSAL.) form shall be provided with the
Development application to confirm that a Drainage Study was submitted, reviewed and accepted as meeting City
criteria for the specific type of Development application.
Drainage studies shall be submitted in support of concept plans, preliminary plats, public infrastructure plans, final
plats, and Grading Permit applications. The necessary hydrologic and hydraulic analyses to clearly demonstrate
that the limits of the Zone of Influence have been identified shall be included. Drainage studies shall include all
required models, exhibits, analysis and supporting analysis and information. Refer to the relevant chapters of this
Manual for more details.
A Drainage Study shall include an analysis of existing, proposed, and fully developed watershed conditions for each
design storm. The Drainage Study is necessary to determine infrastructure and easement needs, and perform an
Adverse impact Assessment to determine the zone of Influence and required mitigation. The Drainage Study shall
provide an analysis to determine onsite controls and to establish adequate downstream capacity throughout the
Zone of Influence to support future development of the project. A Drainage Study shall contain volume and location
information when detention is to be utilized. Detailed design calculations for detention requirements shall be
required for submission of public infrastructure construction documents, Grading Permits, preliminary plats and final
plats. The Drainage Study must include the necessary hydrologic and hydraulic analysis to clearly demonstrate that
the limits of the Zone of Influence have been identified, and that along the drainage route to that location, the
parameters listed in Table 3.1 and Section 3.7.3 of this Manual are met. Furthermore, drainage studies shall
demonstrate that proposed public infrastructure conforms to the relevant design criteria in Section 3.8. Drainage
studies shall be signed and sealed bythe engineer, including the initial submission. All Drainage Study submissions,
including revisions, shall be submitted as a combined report document.
2.2.2 Concept Plan
A concept plan is intended for multi -phase Developments and is required by the City Subdivision Ordinance when:
Preliminary plats are proposed to be presented in phases; or
Total land area of contiguous parcels under the same ownership and control is greater than one square
mile (640 acres),
An acceptable Drainage Study is required before submitting a Concept Plan application. The limit of the Zone of
Influence shall be based on the concept plan area. All subsequent Development applications and studies within
the bounds of the concept plan shall conform to ensure that the Development of the concept plan as a whole does
not cause an adverse impact. Additional information regarding the required Drainage Study in support of a concept
plan is provided below and in Section 2.3, Step 2.
City of Fort Worth Stormwater Criteria Manual 17
2.2.3 Platting
An accepted Drainage Study is required before applying for a preliminary plat. Drainage Studies are also required
before making application for a final plat, minor plat, short form final plat, re -plat or any other type of plat.
A Drainage Study is not required when all of the following conditions are met:
1. The plat area and anticipated total onsite and offsite land disturbance are both less than 1 acre (a land
disturbance plan or site plan shall be required to verify land disturbance area);
2. The Development is not a part of a Common Plan of Development;
3. There are no offsite drainage areas, or existing or proposed public or private drainage facilities, that drain to
or through the project limits; and
4. There is no known, adjacent, suspected or regulated flood risks that potentially impact the project.
Note that a Drainage Study, Flood Study, Floodplain Development Permit, or other City requirements shall apply at
later stages in the Development process as applicable.
2.2.4 Grading Permit Application
After acceptance of a Drainage Study, if a proposed Development of 1.0 acre or more, or a Common Plan of
Development requires earthwork only, an Early Grading Permit application may be submitted. A Grading Permit
shall be required for any other construction activities and shall be applied for by making a second Grading Permit
application. During the Grading Permit application, staff will perform a detailed review of the construction plans for
compliance with the Drainage Study, City standards and criteria. Additional information regarding the application
for a Grading Permit is provided in Section 2.3, Step 4. Grading Permit applicants shall refer to the City of Fort
Worth website for more information and detailed application and review checklists.. All items on the documents
and checklists published on the City's website shall be required before a Grading Permit can be issued. These
checklists may be updated by City staff in order to improve guidance for the applicant. The applicant shall use the
latest checklist available at the time of application submission.
2.2.5 Stormwater Pre -Construction Check
Before issuance of a Grading Permit, scheduling an IPRC Pre -Construction Meeting, or otherwise proceeding to
construction, other stormwater and Floodplain approvals related to and applicable to the work shall be in place.
These include:
• Accepted Drainage Study and Flood Study that meets all City criteria
• Issued Floodplain Development Permit, Grading Permit, Parkway Permit
• Submitted SWFMA
• Executed or recorded encroachment agreements, future improvement agreements, and easements
• Other Agency approvals, such as:
o State permits from TxDOT and TCEQ
o FEMA approved CLOMR,
o Clean Water Act related permits and approvals (e.g. 404 (individual & NWP), 408, etc.)
o Park conversion, and TRWD permits
2.2.6 Additional Development Information
Proposed Developments may require an urban forestry permit, SWPPP, and Water department review. Questions
regarding external requirements shall be directed to the responsible City department.
Prior to a Certificate of Occupancy being issued, a Final Grading Certificate prepared by a licensed Professional
Engineer or the contractor shall be submitted. The Final Grading Certificate shall state that the site grading and
drainage improvements are constructed in substantial compliance with the accepted plans. If the improvements
were not constructed in substantial compliance with the plans, appropriate documentation shall be provided to
substantiate changes and compliance with Stormwater criteria and other applicable City requirements. If changes
were made to public facilities, the City shall require an engineer to document field changes by submitting: certified
City of Fort Worth Stormwater Criteria Manual 18
as -built plans and documenting changed calculations and proposed corrective actions. The final grading certificate,
building permit, and certificate of occupancy are administered by the Development Services Department.
2.2.7 Construction Plans
Construction of public infrastructure shall require submittal of construction plans for review through the Infrastructure
Plan Review Center (IPRC). These plans will be reviewed for conformance with the City stormwater criteria and
consistency with the accepted Drainage Study.
2.3 Preparation of Stormwater Submittals
This Section describes the required contents and general procedure for preparing a Drainage Study, final
construction plans, an Erosion and Sediment Control (ESC) Plan. The level of detail involved in each submittal will
depend on the project size and the individual site and development characteristics. Detailed criteria for the
calculations required in the Drainage Study and construction plans are covered in Chapter 3 of this Manual.
Stormwater master plans are an important tool used to assess and prioritize both existing and potential future
stormwater problems and to consider alternative stormwater management solutions. The City may have individual
watershed plans, or several Developers may choose to work cooperatively to develop a unified approach to
watershed planning, development controls, permit compliance, multi -objective use of floodplain and other areas,
and property protection. The City Stormwater staff shall be consulted on any regional approaches considered.
There are five steps defined in the preparation of Stormwater Development review submittals. In general, each of
the following steps builds on the previous step to result in the Drainage Study, Construction Plans and ESC Plan.
Step 1 — Baseline Data Collection and Analysis
Step 2 —Conceptual Stormwater Design and Planning
Step 3 — Prepare Drainage Study
Step 4 -- Prepare Drainage Study Updates, Construction Drawings, and Stormwater Facilities Maintenance
Agreement (SWFMA)
Step 5 -- Prepare Grading Permit Application
2.3.1 Preparation Overview
Step 1 —Baseline Data Collection and Analysis
The site Developer shall become familiar with the City stormwater management, Development requirements and
design criteria that apply to the site. These requirements include:
City of Fort Worth Stormwater Criteria Manual 19
• Stormwater Criteria Manual (this
manual)
• Available online iSWM Program
documents, which include:
• iSWM Technical Manual
• iSWM Tools
• iSWM Program Guidance
• State and Federal Regulatory
Requirements
• Other City Ordinances and Criteria (Not
regulated by the Stormwater Division)
n Platting Procedures
o Zoning Requirements
o Development Codes and Procedures
o Tree and Landscape Requirements
o Special Use Permits
o Drainage Master Plans and Watershed
Plans
o Erosion Control Plans
o `Floodplain Development Ordinance
o Grading Plan Ordinance
o Construction/Building Permit
Notifications and Requirements
o Urban Forestry Requirements
Information regarding the above items can be obtained from this Manual, at a pre- Development conference with
the City, or from the relevant state and federal agencies.
A critical part of any project involves the proposed Developer working closely with various departments within the
City. Integrating the stormwater management practices with other regulatory requirements will promote a
sustainable -Development.
Opportunities for special types of Development (e.g., clustering) orspecial land use opportunities (e.g., conservation
easements or tax incentives) should be investigated. In addition, there may be an ability to partner with the local
community for the development of greenways or other riparian corridor or open space developments.
All applicable state and federal regulatory requirements must also be met.
In addition to understanding all applicable regulations and ordinances, it is also necessary to collect and review
information on the existing site conditions and map the following site features:
• Topography
• Drainage patterns and basins'
• Intermittent and perennial streams on -
site and off -site waters that will receive
discharges from the proposed
Development
• Soil types and their susceptibility to
erosion
• Ground cover and vegetation,
particularly unique or sensitive
vegetation areas to be protected during
Development.
• Existing Development
• Existing Stormwater facilities on -site and
off -site facilities that will be receive
discharges from the proposed
Development Property lines, adjacent
areas and easements
• Wetlands and critical habitat areas
• Boundaries of wooded areas and tree
clusters
• Floodplain boundaries
• Steep slopes
• Required buffers and setbacks along
water bodies
• Proposed stream crossing locations
• Other required protection areas
Upon completion of the baseline data collection and analysis, it is recommended and encouraged to schedule a
Stormwater Pre -Development Conference with the Stormwater Development Services staff. This meeting will allow
a dialogue to begin between the Developer and the City regarding the site conditions and potential areas of concern
prior to work being done for the Development. To schedule a pre- Development conference with the Stormwater
staff, please send an email to sds@fortworthtexas.gov.
City of Fort Worth Stormwater Criteria Manual 20
The site analysis shall be summarized in the relevant Stormwater review submission along with any other supporting
documents. The data collected and analyzed during this step of the Development process shall be used as the
starting point for preparing the Drainage Study, Construction Plans and the ESC Plan.
Step 2 —Conceptual Stormwater Design and Planning
If a concept plan is not required or submitted, proceed to Step 3.
For larger master plan Developments with multiple phases of Development, a concept plan may be required. The
concept plan allows the design engineer to propose a potential site layout and gives the Developer and City a "first
look" at the stormwater management system for the proposed Development. Specific requirements for the concept
plan shall be obtained through the City Development Services Department. If a concept plan is required, an
accepted Drainage Study will be required before filing an application.
The following conceptual stormwater design and planning practices shall be followed in analyzing the drainage
conditions, especially for concept plans:
1. Use integrated Site Design Practices. Note: integrated Site Design Practices are encouraged but not required
within the City. Examples include:
• Preserving the natural feature conservation areas defined in the site analysis
• Fitting the Development to the terrain and minimizing land disturbance
• Reducing impervious surface area through various techniques
• Preserving and utilizing the natural drainage system wherever possible
2. Determine the credits for integrated Site Design (Appendix F) and water quality volume reduction (Appendix
F) as applicable, to be accounted for in the design of structural and non-structural stormwater controls on the
site.
3. Calculate conceptual estimates of the design requirements for streambank protection and flood mitigation
based on the conceptual plan site layout.
4. Perform screening and conceptual selection of appropriate temporary and permanent structural stormwater
controls and identification of potential site locations.
The stormwater planning and design concepts in this step become the foundation for developing the Drainage
Study.
Step 3 — Prepare Drainage Study
The Drainage Study ensures that requirements and criteria are complied with and opportunities are taken to
minimize adverse impacts from the Development. An accepted Drainage Study is a prerequisite of all preliminary
plat, construction plan and final plat applications. This step builds on the data compiled in Step 1 by developing the
existing and proposed runoff calculations and identifying proposed stormwater controls as well as the Zone of
Influence associated with the Development. The Drainage Study Checklist outlines the data that shall be included
in the Drainage Study.
At a minimum the information listed in this Manual and the Drainage Study Checklist shall be required. The study
shall include an Adverse Impact Assessment of properties that could be impacted by the Development. These
studies shall include the hydrologic analysis to determine the existing, proposed, and fully -developed runoff for the
watershed and drainage areas that is affected by the proposed Development. Existing and proposed hydrologic
conditions shall assume existing land use for offsite conditions. The study shall include a hydraulic analysis that
defines the Adequate Outfall as defined in Table 3.1. It shall include a capacity analysis of all existing constraint
points such as pipes, culverts/bridges, or channels from the point of stormwater discharge from the Development
(edge condition) downstream through the Zone of Influence.
For Development projects involving properties 100 acres or less, the Adverse Impact Assessment may be limited
to the Zone of Influence as determined by either the Drainage Study (analysis extends further downstream than
10% rule) or established as the point where the property being developed comprises less than 10% of the total
drainage area (see the iSWM Hydrology Technical Manual, Section 2.4). Consideration of critical infrastructure and
logical analysis end points (i.e. bridges, road crossings, and creek or river confluences) shall be required when
City of Fort Worth Stormwater Criteria Manual 21
using the 10% rule. The Adverse Impact Assessment shall extend beyond the 10% point and include critical
downstream infrastructure. Also see Section 3.7 for more information.
For Development projects involving properties more than 100 acres in size, the limit of the Zone of Influence shall
be defined by the hydrologic and hydraulic analyses. The limit of the Zone of Influence shall not be less than what
would have been required by the 10% rule. If a Development proposes to detain to pre -developed flows at the
Development property boundary, then hydrologic and hydraulic analysis shall extend downstream to a logical
stopping point, typically the next major tributary confluence beyond the point defined by the 10% rule. If a project
does not detain to pre -developed flows, then hydrologic and hydraulic analysis shall extend downstream, beyond
the next tributary confluence after the 10% point, and extend to where the hydrologic analysis shows pre -
Development and post- Development flows are the same.
It shall be noted that acceptance of the Drainage Study does not imply acceptance of any subsequent
Development or stormwater applications. Those submissions will be required and reviewed as
Development proceeds.
Step 4 — Prepare Drainage Study Updates, Construction Drawings, and Stormwater
Facilities Maintenance Agreement
An updated Drainage Study (if applicable) and Construction Plans shall be prepared and submitted to the City for
review and approval priorto final plat application or any construction activities on the Development site. An updated
Drainage Study shall be required before Construction Plan or Grading Permit application to reflect changes that
occurred as the detailed drainage and grading design progressed. When public infrastructure will be constructed,
submittals also must conform to the Infrastructure Plan Review Center (IPRC) requirements. Changes identified
during IPRC or Grading Permit Plan Review which result in changes to the Drainage Study shall require a
resubmittal of the Drainage Study for review. The constructions plan submitted to IPRC or with a Grading Permit
shall include an ESC Plan.
If applicable, then a stormwater facility maintenance agreement (SWFMA) shall be required to be submitted or
recorded. Refer to Section 2.2.5 and Section 3.11.3.2 for specific process details of when a SWFMA must only be
submitted or must be recorded.
Step 5 — Prepare Grading Permit Application
If required by the Grading Permit Ordinance, then a Grading Permit must be obtained for grading a Development,
of 1.0 acre or more, or for a Common Plan of Development. Early Grading Permits are available for only earthwork
such as clearing, grubbing, and grading, with no construction allowed. A Grading Permit is required even if an Early
Grading Permit is obtained. An approved Grading Permit is required prior to infrastructure and building construction.
The Grading Permit application is provided on the City's website. All single-family residential grading plans must
conform to Section 3.8.2 (Subdivision Drainage Site Grading) and Appendix E (Single Family Residential Lot
Drainage Types). Proposed lot grading that does not comply shall submit an individual lot grading plan sheet for
each lot that does not comply.
Changes in existing drainage divides shall be identified and data shall be required to document that capacity is
available in the existing system to carry the additional flow to the system.
Grading permit applications shall be submitted through the City Permit Center or via the online Accela Citizen
Access portal. A completed Grading Permit application form, administrative fee, signed/sealed plan sheet(s) and
a digital copy of the executed SWPPP is required to be submitted with the application for a Grading Permit.
The Early Grading Permit is for earthwork only and will be at the risk of the owner/ Developer. A Drainage Study
accepted by the City will be required for the issuance of an Early Grading Permit or a Grading Permit. An approved
Floodplain Development Permit (FDP) is required before any Grading Permits will be issued for work within 50 feet
of a SFHA (floodplain). For projects with stormwater detention facilities (or other facilities requiring a maintenance
agreement), a SWFMA shall be required to be submitted before issuance of a Grading Permit. All applicable local,
state, and federal permits shall be obtained before beginning site construction activity.
Please note:
City of Fort Worth Stormwater Criteria Manual 22
1. Drainage calculations presented on the construction plans must conform to calculations and analysis
submitted in the Drainage Study. Where City approval of construction plans is not required, the above
information required for the Drainage Study and permit approval, as well as construction plans for any
drainage improvements shall be submitted.
2. If a stormwater facility is provided which qualifies for a Stormwater Utility Fee Credit, the engineer must submit
an application to the City along with supporting documentation which shows compliance with the Stormwater
Utility Fee Credit Policy and iSWM standards for water quality treatment. Refer to Appendix F — Stormwater
Utility Fee Credit Policy.
3. A Grading Permit and accepted Drainage Study will be required prior to the issuance of a commercial building
permit associated with a project causing 1.0 acre or more land disturbance, or smaller sites that are part of a
Common Plan of Development. See the Grading Permit Application Form for submittal information. A Grading
Permit will be required, even if an Early Grading Permit was obtained at an earlier stage.
4. Construction phase requirements shall comply with IPRC requirements.
A Stormwater Facility Maintenance Agreement (SWFMA) is required for each stormwater control that will not be
wholly maintained by the City. This agreement must outline both preventive maintenance tasks as well as major
repairs, identify the schedule for each task, assign clear roles to effected parties, and provide a maintenance
checklist to guide future owners including an annual self -inspection to be provided to the City. Please refer to the
Stormwater Facility Maintenance Agreement Checklist.
A customized facility specific Operations and Maintenance Plan shall be developed in accordance with City
Stormwater Criteria Manual and NCTCOG iSWM Technical Manuals, and shall be included with the SWFMA. It
shall clearly state which entity has responsibility for operation and maintenance of temporary and permanent
stormwater controls and drainage facilities to ensure they function properly from the time they are first installed.
The Operations and Maintenance Plan shall include:
• Responsible party for all tasks in the plan
• Inspection and maintenance requirements
• Maintenance of permanent stormwater controls and drainage facilities during construction
• Cleaning and repair of permanent stormwater controls and drainage facilities before transfer of
ownership
• Frequency of inspections for the life of the permanent structures
• Description of maintenance tasks and frequency of maintenance
• Access and safety issues
• Maintenance easements
• Reviewed and accepted maintenance agreements
Guidance for development of Operation and Maintenance Plans has been provided with each temporary and
permanent Best Management Practice (BMP) included in the iSWM Technical Manual.
2.3.2 Drainage Study
The Drainage Study shall demonstrate that the overall Development plan (e.g. concept plan) does not cause an
adverse impact. Subsequent drainage studies shall demonstrate how the new phase (e.g. preliminary plat) ensures
that the overall Development plan does not cause adverse impacts. Impacts shall be measured from the baseline
pre- Development conditions at time of the original Drainage Study submitted in support of the overall Development
plan (e.g. concept plan).
All maps and exhibits provided with the Drainage Study shall include, at a minimum, all of the features noted below.
Features shall be delineated, labeled and described on the exhibit or map.
A Drainage Study submission shall include, but not be limited to, the following:
1. A completed copy of the latest Drainage Study checklist furnished by the City.
2. Project summary information (Name, location, description, land use, sitelplat area, disturbance area, etc.)
3. Contact information for the owner and engineer:
City of Fort Worth Stormwater Criteria Manual 23
a. Owners name, company name, phone number, email, and address.
b. Engineers name, firm name, phone number, email, and address.
4. The purpose of the Drainage Study, and specifically which type of Development application the study would
support. Note that a Drainage Study that was reviewed and accepted for a concept plan or preliminary plat
only, would not support an application for a final plat, Grading Permit or infrastructure (IPRC) application.
5. A report or technical memo that is signed and sealed by a professional engineer licensed in the State of
Texas, that includes:
a. Description of the design methods, key assumptions and unusual conditions or site constraints
b. Description and results of the Adverse Impact Assessment and Zone of Influence
c. Response to specific questions or issued raised during the pre -submittal meeting
d. Summary of results and comparison of pre- Development and post- Development condition.
e. Results based confirmation that Development impacts do not meet or exceed the no adverse
impact thresholds.
f. Description and summary results for the impact mitigation plan and provision of an Adequate
Outfall. Note this would include detention pond sizing and proposed storm drain extensions.
g. Response to review comments, clearly describing how the comments were addressed and what
changes were made to plans and models.
h. Detailed description and explanation of all model input parameter changes.
6. Document, include and describe specific planning concerns and data sources. These items include but are
not limited to:
a. List and reference previous drainage studies, iSWM Plans or watershed plans that considered the
project area.
b. Note the source and date of contour or topography information. Note that LiDAR contours are
freely available from the City G!S website.
c. Known or suspected flooding or erosion downstream of the project.
d. Known or suspected downstream constrictions, such as undersized culverts or storm drains.
e. FEMA floodplains that require a Flood Study, CLOMR, LOMR, etc. If yes, list and reference any
existing studies.
f. Known or suspected wetland areas, mitigation areas, waters of the US, or other natural habitat
features that may require consideration, 404 permit, nationwide permit, or state or federal permit.
g. Existing impoundments or dams that could be, or become, subject to TCEQ permitting.
h. Environmental concerns that would require special treatment or design consideration (e.g. fuel
station, vehicle maintenance, auto recycling, illegal dump sites, industrial facilities, etc.).
7. Description of how Low impact design (LID) principles were applied to the project, such as the following:
a. Preserved floodplains, streams, drainage patterns, natural storage, or steep slopes?
b. Preserved trees, natural vegetation, wetlands, or other natural features?
c. Drained runoff to pervious or vegetated areas?
d. Utilized natural drainage systems (without erosion) instead of storm drain systems.
e. Reduced pavement, minimize impervious cover or use alternative materials such as porous
pavement
8. Pre -Development conditions map to document baseline pre -Development conditions, including.
a. Project boundaries
b. Aerial photo representing pre -Development conditions (imagery captured within 5 years of
submission and before land disturbance started)
c. Label and identify perennial and intermittent streams
d. Delineate effective FEMA floodplains and label with zone, panel number, and effective date
e. Delineate and label wetlands and natural habitat areas
f. Label, delineate and identify location of dams and impoundments
g. Label and identify existing roads, buildings and other impervious features
City of Fort Worth Stormwater Criteria Manual 24
h. Label and identify existing major utilities, pipelines and easements
i. Label, delineate and identify existing stormwater conveyance systems, including: overland flow,
storm drains, inlets, catch basins, channels, swales, culverts, and bridges. Include plan number
reference and facility size.
9. Post -Development map and site plan, including:
a. Limits of clearing and grading
b. Proposed street and lot layout
c. Site plan elements (buildings, facilities, parking lot, etc.)
d. Construction phasing plan
e. Location and size of proposed storm drains and other stormwater controls (e.g. ponds)
f. Location and size of existing storm drains, including plan reference number.
g. Proposed dams or ponds subject to TCEQ requirements
h. Proposed FEMA floodplain limits
10. Pre -Development Drainage Area Map
a. Project boundaries
b. Existing topography (1 or 2 foot contour interval, 5 or 10 foot for areas more than one square mile)
c. USDA hydrologic soil types (or separate soils maps)
d. Perennial or intermittent stream centerlines
e. Delineate FEMA floodplains, studied floodplains, floodplain easements and open channels
f. Location of wetlands, dams and impoundments
g. Existing roads, buildings and other impervious areas
h. Locations and size major utility lines and easements
i. Location, size, and City File Number for existing stormwater conveyance systems such as storm
drains, inlets, catch basins, channels, swales, and areas of overland flow
j. Locations and dimensions of channels, bridges, or culvert crossings
k. Delineation of watershed or drainage area boundaries, with correctly orientated flow arrows
I. Delineate offsite drainage areas (1 or 2 foot contour interval, 5 or 10 foot for areas more than one
square mile)
m. Contours extend beyond project limits and offsite drainage areas to ensure the entire watershed
has been delineated
n. Delineate longest flow path each drainage area
o. Provide time of concentration calculations for each area and lag time calculations for hydrograph
methods.
p. Computation table showing drainage areas, runoff coefficients or curve numbers, time of
concentration or lag times, rainfall intensities and peak discharges for the 1, 5, and 100 year storms.
Include a column to identify the collection point for each drainage area.
q. Location of all site outfalls or where runoff leaves the site
r. Delineate entire Zone of Influence and identify analysis points.
s. Existing zoning and land use
t. Composite calculations for runoff coefficients or curve numbers
u. Drainage area and analysis point labels consistent with hydrologic and hydraulic calculations tables
11. Post -development Drainage Area Map
a. Project boundaries
b. Existing and proposed topography (1 or 2 foot contour interval, 5 or 10 foot for areas more than
one square mile)
c. USDA hydrologic soil types (or separate soils maps)
d. Perennial or intermittent stream centerlines
e. Delineate FEMA floodplains, studied floodplains, floodplain easements and open channels
City of Fort Worth Stormwater Criteria Manual 25
f. Location of wetlands, dams and impoundments
g. Roads, buildings and other impervious areas
h. Locations and sizes of major utility lines and easements
i. Location, size, and City File Number for existing stormwater conveyance systems such as storm
drains, inlets, catch basins, channels, swales, and areas of overland flow
j. Locations and dimensions of channels, bridges, or culvert crossings
k. Delineation of watershed or drainage area boundaries, with flow arrows
1. Delineate offsite drainage areas (1 or 2 foot contour interval, 5 or 10 foot for areas more than one
square mile)
m. Contours extend beyond project limits and offsite drainage areas to ensure the entire watershed
has been delineated
n. Delineate longest flow path for each drainage area
o. Provide time of concentration calculations for each area and lag time calculations for hydrograph
methods.
p. Computation table showing drainage areas, runoff coefficients or curve numbers, time of
concentration or lag times, rainfall intensities and peak discharges for the 1, 5, and 100 year storms,
for existing, proposed and ultimate conditions. Include a column to identify the collection point for
each drainage area.
q. Location of all site outfalfs or where runoff leaves the site, including labels with pre/postlultimate
discharges.
r. Proposed and ultimate zoning and land use
s. Identify changes to watershed boundaries
t. Composite calculations for runoff coefficients or curve numbers
u. Delineate entire Zone of Influence and identify analysis points.
v. Show downstream constrictions with runoff controls
w. When the Development is a multi -phase project provide an overall drainage area map with all
phases labeled.
x. Proposed stormwater facilities with private maintenance (includes private storm drains, if detention
is proposed, provide volume required)
y. Drainage area and analysis point labels consistent- with hydrologic and hydraulic calculations
tables.
12. Ultimate Development Drainage Area Map shall illustrate the full guild out and final condition of the overall
Development that future phase shall adhere too. The map shall include all of the features noted above for
a post Development drainage area map.
13. Hydrologic analysis and models shall adhere to all of the criteria listed throughout this Manual, as well as
the following:
a. Analysis methodology and inputs conform to Section 3.4 and relevant sections of the NCTCOG
iSWM Technical Manuals.
b. Selected hydrologic methods per Table 3.4
c. Runoff coefficient and curve numbers per Table 3.5
d. On site existing conditions per actual land use, not zoning
e. Offsite conditions modelled as existing land use for comparison of pre- and post -development
conditions
f. Entire watershed (onsite and offsite areas) modelled per zoning or land use, which ever yields the
highest peak discharge, for ultimate conditions hydrology.
g. Ultimate conditions hydrology used for easement and stormwater facility sizing
h. Unit hydrograph analysis performed using acceptable software package and model files provided.
i. Modified Rational Method, if selected, was calculated using the equations described in the
NCTCOG Hydrology Technical Manual, and not using a software package.
j. The hydrologic analysis and Adverse Impact Assessment is carried to, or beyond, the zone of
City of Fort Worth Stormwater Criteria Manual 26
Influence based on the 10% rule of thumb. This is required even when detention is provided (except
for the specific small site waiver).
k. Hydrologic work map was provided and shows model basins and routing
1. Junctions or calculation nodes provided at critical analysis points (e.g. at outfalls, culvert crossings,
ponds, etc.)
m. Reach modelling approaches applied per this Manual and standard modelling conventions
n. Pre- and post -development modelling include onsite storage (e.g. upstream of a road culvert) and
floodplain storage to determine impacts of any watershed storage loss that result from the
Development
o. Where a project discharges to more than one outfall, provide a corresponding analysis and Adverse
Impact Assessment for each outfall
p. Include mitigation design and analysis.
q. Provide all applicable hydrologic condition analyses, including but not limited to: existing, proposed,
proposed with mitigation if applicable, and ultimate. A multi -phased Development would include
an additional condition for each phase.
r. Rainfall depths per NCTCOG iSWM Hydrology Technical Manual.
s. A summary results and comparison table was provided, and includes all junctions and design
storms.
t. Analysis for a zone A floodplain includes all applicable design storms and complies with FEMA
guidelines.
u. Land use maps for existing pre -development condition, proposed condition and ultimate (greater
intensity of zoning and comprehensive plan)
v. Soils maps provided
w. Adverse Impact Assessment —see Chapter 3
14. Hydraulic analysis and models
a. Analysis methodology and inputs conform to Section 3.8 and other relevant sections of the
Stormwater Criteria Manual, the NCTCOG iSWM Technical Manuals, and applicable references
(e.g. HEC-RAS manual).
b. Standard modelling conventions are adhered to (e.g. ineffective flow areas at culverts, cross -
sections perpendicular to flow, bank stations contained well inside the floodplain, etc.)
c. For 1 D analysis, Manning's n per Table 3.15, Table 3.16 and other relevant technical references.
d. Proposed multi -barrel culverts designed with one of the barrel flow lines at the stream centerline,
and other barrels set higher to establish a single low flow drainage path
e. Provide a hydraulic work map including, but not limited to: aerial imagery, cross sections, inundation
limits, stream centerline, structures, flow change locations, labels, proposed easement limits, etc.
f. Provide a summary table that correlates cross -sections to hydrologic nodes or add hydrologic
nodes to RAS workmap
g. Analysis considers appropriate tail water and effect of coincidental peaks
h. Analysis sizes all driveway culverts and demonstrates that roadside ditch design meets design
.standards.
i. Mixed flow regime analysis is included if Froude number(§) is 0.9 or above (supercritical flow
check).
j. Analysis shows compliance with all applicable design criteria in Section 3.8.
k. Analysis shows compliance with all No Adverse Impact criteria throughout the entire Zone of
Influence
I. Results summaries for all design storms and watershed conditions are tabulated.
m. Summary tables include a comparison of pre- and post -development conditions at all cross sections
and critical locations.
n. Culvert and bridge hydraulics checklists are completed and attached for all proposed hydraulic
structures.
o. Where a project discharges to more than one outfall, provide a corresponding analysis for each
City of Fort Worth Stormwater Criteria Manual 27
outfall.
p. A dam breach analysis was performed and the results, dam maintenance plan and EAP are
attached
q. Drainage structure sizes and easement delineations (ultimate conditions 100-year flow)
r. Flood elevations and corresponding minimum finished floor elevations for all potentially affect and
proposed lots (ultimate conditions 100-year flow) are shown.
s. Any other information pertinent to the preparation and review of project documents, including plat
and construction plans are provided.
15. Detention pond checklist — attach a completed checklist for each stormwater detention facility
16. Culvert hydraulics checklist — attach a completed checklist (or equivalent) for each roadway culvert
17. Bridge hydraulics checklist -- attach a completed checklist (or equivalent) for each bridge crossing
18. Dam Maintenance and Emergency Action Plan — attach a completed checklist and plan for each facility
subject to the requirement
19. Record Drawings — List the referenced record drawings and provide a copy of all record drawings used in
the design; include only the relevant sheets necessary to document compliance with past drainage design,
capacity and existing drainage facilities. Highlight pertinent information on the sheets provided.
20. Previous Stormwater Management Plans — list the referenced plans and describe how the content was
used. If a model was used then note the source of the model in the report I memo discussion. If the plans
or models were prepared by another engineer but for the basis of your design then affirm that you have
reviewed and agreed with the findings. Include relevant plan sheets to illustrate how the past studies
support your project.
21. Identifies future permitting, regulatory and documentation needs:
a. Maintenance
b. Easements
c. Grading Permit
d. FDP, CDC, CLOMR and LOMR
e. Public infrastructure and CFA
f. Park Conversion
g. USACE permits (nationwide, 404, etc.)
h. TCEQ Water Rights
i. TxDOT permit — required when project outfali includes connection to a TxDOT storm drain, inlet,
open channel, ditch or other TxDOT drainage infrastructure
j. Future improvements agreement
k. TRWD Permit — required when connecting to a TRWD facility
1. Adjacent property letters
m. Encroachment Agreement
n. Parkway Permit
2.3.3 Construction Plans
Construction plans shall incorporate and utilize the latest standard details that are promulgated by the City. Plans
shall adhere to all requirements listed in this Manual and other criteria documents or ordinances.
Grading Permit Plans shall provide all items listed on the Grading Permit checklist furnished by the City.
Driveway Culvert plans shall adhere to all requirements of this Manual for constructions plans. Plan and profile
sheets, stationing, and survey shall extend to the nearest upstream and downstream culvert. Minimum roadside
ditch slopes shall be maintained between all driveway culverts and other drainage structures. if there are no nearby
driveway culverts or drainage structures then the plan, profile and survey shall extend a minimum of 500 feet
upstream and 500 feet downstream of the proposed driveway culvert.
Connection to the back of inlet of a private storm drain shall require review and acceptance of engineering plans
that meet the requirements for constructions plans.
City of Fort Worth Stormwater Criteria Manual 28
Sidewalk flumes shall meet the design described in this Manual and standards for construction plans.
2.4 Floodplain Development & Flood Study
2.4.1 Introduction
As an active participant in the National Flood Insurance Program (NF1P), the City maintains and enforces a
floodplain management program consistent with Federal requirements (Title 44, Code of Federal Regulations)
through implementation of standards outlined in Chapter 7, Article Vlll of the Fort Worth City Code. Under these
regulations, the City is responsible for the review and approval of all proposed floodplain Development projects and
ensuring that permits required by Federal, State, and Local laws have been received. Approval of the Floodplain
Development Permit is contingent upon approval of the Floodplain Development Study. The City is also responsible
for submitting all revised flood hazard information and data to FEMA in order to update affected Flood Insurance
Rate Map (FIRM) panels to reflect the present condition of flood risk in all FEMA basins within City limits.
The City has adopted some standards that are higher that the requirements in the NF1P. The City's specific higher
standards include the following:
A regulatory design storm defined as the 1.0% annual chance event occurring on ultimate development
land use conditions within drainage basins shall be used.
Finish floor elevations shall be 2.0 feet above the water surface resulting from the regulatory design
storm. Critical facilities as defined by the floodplain ordinance shall have a minimum finished floor
above the 0.2% annual chance event.
Proposed Developments shall not increase flood elevations during the regulatory design storm unless
contained within a dedicated floodplain easement, and all other applicable criteria are met.
The City also participates in the regional Corridor Development Certificate (CDC) program managed by the North
Central Texas Council of Governments (NCTCOG), and reviewed by the U.S. Army Corps of Engineers (USACE).
Projects located in or affecting the floodplains of the West Fork Trinity River and Clear Fork Trinity River are within
the Trinity River Regulatory Zone and must meet CDC criteria in addition to City & FEMA floodplain development
criteria.
2.4.2 Flood Study
The Flood Study is a key component to the City's review and approval process for any proposed Development
project in a FEMA floodplain. This study allows the applicant to clearly document that all proposed floodplain
Development activities comply with local, state, and federal (FEMA) floodplain regulations. The Flood Study is a
stand-alone document that is different from the Drainage Study report for a proposed project or activity. More
specifically, the Flood Study demonstrates compliance with federal requirements, not just municipal requirements.
All Flood Study reports must be submitted for review through the SDS electronic submittal process.
• Due to the complexity and frequently -changing nature of regulatory models available across the
City, a pre -submittal meeting is required prior to submitting a floodplain study for review.
• The City reserves the right to reject any submittals delivered without a pre -submittal meeting.
Based on the varying complexity of floodplain Development projects submitted annually, the
City reserves the right to request additional information and/or technical analyses beyond that
which is outlined in this Manual at any time during the review if determined necessary.
A CLOMR, LOMR, or Flood Study shall be required by the City for any of the following activities within an effective
FEMA- or other City -regulated floodplain:
• Proposed Development within a designated floodway;
• Proposed Development resulting in any change to the floodplain and/or floodway boundaries or base
flood elevation;
Proposed activities that alter a natural floodplain, stream channel, or natural protective barriers (e.g.
riparian zones) or result in a waterway alteration or change of watercourse location;
FEMA Conditional Letter of Map Revision (CLOMR) and Letter of Map Revision (LOMR) submittals for
areas previously studied under detailed and approximate methods, or;
City of Fort Worth Stormwater Criteria Manual 29
Other unique special hazard projects.
2.4.3 Floodplain Development Permits
A Floodplain Development Permit is required before performing any construction activity, or causing physical
alterations to property, within the FEMA SFHA (Floodplain). Refer to the City's Floodplain Ordinance for more
information. Floodplain Development Permit (FDP) application fees were categorized into three tiers and
differentiated by the scope of work to be performed in the FEMA Floodplain.
1. Basic. Limited to: storm drain outfall(s), underground utility crossings, at grade improvements that have
no effect on floodplain hydraulic conditions and do not require a Flood Study, single family improvements
that do not require an Elevation Certificate (EC) and do not require a Substantial Damage / Substantial
Improvement (SD/SI) evaluation.
2. Fill. Includes: cut or fill in the FEMA floodplain, or any activity within the CDC area. Work that would
typically cause a physical change to floodplain delineation or inundation limits.
3. Single Family Lot. Includes one (1) single family lot that requires a pre -construction or post construction
EC, or SD/SI evaluation. For example: pre-LOMR new construction or significant work performed on
existing or damaged houses.
Note that FDP application fees are separate and in addition to Flood Study, CLOMR, and LOMR application fees.
2.5 Non-FEMA City Flood Risk Area Development Requirements
2.5.1 Introduction
Where it rains, it can flood. Between 2014 and 2018, more than 40 percent of flood
insurance claims in the U.S. came from outside the FEMA floodplains.
The Floodplain Provisions Ordinance has proven to be very successful in reducing flood damages in or near the
FEMA/City regulatory floodplains, but it does not address flood risks in areas outside of the FEMA regulatory
floodplains. The City Flood Risk Area Policy has been created to build upon the successes of the Floodplain
Provisions Ordinance to reduce the flood risk in areas outside the FEMA/City regulatory floodplains by establishing
consistent Development guidelines managed with local resources. The three key components to reducing flood
damages in City Flood Risk Areas (CFRA) are mapping the risk areas, communicating the risk to end users, and
regulating how Development occurs in risk -prone areas.
This section explains the difference between the different flood risk areas within the city and outlines the
requirements for developing within a designated CFRA. The City Floodplain Provisions Ordinance and the
Stormwater Criteria Manual specify the requirements and prohibitions that apply to a particular property. The City
ordinances can be found at https://www.amlegal.com/codes/client/fort-worth tx/. Specific questions or comments
about these CFRA Development requirements can be directed to Stormwater Development Services
(SDSCa�fortworthtexas.gov).
2.5.2 Flood Risk Area Definitions
The City utilizes three different flood risk areas to determine the level of flood risk for properties. It is important to
note that these flood risk areas do not overlap. See Figure 1 for examples.
FEMA Special Flood Hazard Area (SFHA)/City Regulatory Floodplain — Typically areas of riverine flooding that
are flooded by a storm that has a 1% chance of equaling or exceeding that intensity in any given year. The FEMA
floodplain is mapped using existing land use conditions, while the City has implemented higher standards and
requires that fully -developed basin conditions be considered. Development in the basin is assumed to be the
maximum allowable under the adopted zoning for the land. These floodplains are adopted and enforced in order to
participate in the National Flood Insurance Program (NFIP). All Development within this area requires a Floodplain
Development Permit (FDP).
City of Fort Worth Stormwater Criteria Manual 30
City Flood Risk Area (CFRA) — Areas located generally upstream of the FEMAICity regulatory floodplains, where
detailed engineering studies prepared for specific basins indicate where stormwater runoff accumulates. The CFRA
is regulated by the City, but not FEMA.
Potential High Water Area (PHWA) — Areas located generally upstream of the FEMAICity regulatory floodplains
and created for advisory purposes and planning efforts, which indicates that stormwater runoff accumulates to a
depth of six (6) inches or greater due to concentration of flow and obstructions based on topography. The PHWA
is also used to aid in the review of Drainage Studies submitted to Stormwater Development Services (SDS) for
projects not in CFRA that will disturb greater than 1 acre of land as well as to inform Developers of projects under
1 acre of the flood risks.
Figure 2.1 Example of CFRA, PHWA, and SFHA Mapping
City of Fort Worth Stormwater Criteria Manual 31
2.5.3 Where to Find the Flood Risk Information
The City's Flood Risk Viewer website located at Flood Risk Viewer (fortworth texas. gov) provides the location and
extents of SFHAs, CFRAs and PHWAs. This information is also made available to residents, Developers, and
engineers using the zoning map tool found on the Zoning Website located at
https://www.fortworthtexas.gov/departments/development-services/zoning. Additionally, the One Address tool
located at https://oneaddress.fortworthtexas.gov, includes basic information for both CFRAs and PHWAs along with
to the FEMA flood risk areas. Property owners or Developers should use this information as a starting point to
determine actual flood risks at a specific location. Future evaluations prepared for Stormwater Management
Program planning purposes or in support of individual Development projects will be used to update the City Flood
Risk Area and Potential High Water Area extents.
2.5.4 Comparison of NFIP and CFRA
Since CFRAs are regulated by the City and not by FEMA, the City with Stakeholder assistance created provisions
to minimize public and private losses due to flood conditions within the identified CFRA that were not addressed by
the NFIP regulations. The following table provides a comparison of notable differences between the two.
Table 2.1 Comparison of FEMA SFHA and Non-FEMA CFRA
SFHAs CFRAs
3
Critical Facilities- Federally -funded facilities must be Critical Facilities- If outside the FEMA 500-year
located outside the 500-year floodplain. (Hospitals, floodplain, could be located in CFRAs if adequately
nursing homes, childcare facilities, emergency protected from flooding. (1)(3)
responder, etc.) State licensing requires location
outside 100-year floodplain.
Renovations / Remodels- "Substantial Damage or
Improvements" regulations require that the entire
structure be brought into compliance with current codes
if repairing damage or constructing improvements that
cumulatively equal or exceed 50% of the existing
structure's value.
Basements- New construction of residential
basements not allowed in FEMA floodplains unless
properly elevated above the flood elevation.
Commercial basements must be properly floodproofed.
Waivers & Appeals- The waiver and appeals process
for FEMA floodplain permitting may require action by
the construction & fire prevention board of appeals and
the City Plan Commission.
Flood Insurance- Flood insurance is required by
Federal regulations for any Federally -backed loan or
mortgage. Some Federal grant funds also require the
purchase of flood insurance. Cash transactions do not
require flood insurance, and the flood insurance
requirement expires upon the full payment of a
Federally -backed loan.
Flood Protection- Lowest floor elevations for
residential projects in FEMA floodplains must be
elevated 2.0 feet above the 100-year fully developed
flood elevation.
Commercial projects may provide wet or dry
floodproofing certification to the same elevation. (2)
Renovations / Remodels- "Substantial Damage or
Improvements" regulations are not required outside
the FEMA 100-year floodplain, so cumulative
improvements would not need to be tracked.
Basements- New construction of residential or
commercial basements allowed in CFRAs if properly
floodproofed. (2)
Waivers and Appeals- The waiver and appeals
process for CFRAs may be handled administratively
by Stormwater Development Services and Floodplain
Management staff.
Flood Insurance- Since all CFRAs are located
outside the FEMA floodplains, flood insurance is not a
mandatory part of any loan or grant. However, flood
insurance is available to anyone in the City, and any
lender could require flood insurance as a condition of
their loan.
Flood Protection- Because CFRAs are managed by
the City, elevation is not mandatory for residential
projects in CFRAs. A variety of flood protection options
could be considered as long as the necessary flood
protection is provided. Commercial projects may use
wet or dry floodproofing techniques to achieve the
necessary flood protection. (2)
City of Fort Worth Stormwater Criteria Manual 32
Flood Map Revisions Due to Projects- Map changes
Flood Map Revisions Due to Projects- City -
are submitted to FEMA after project construction
managed floodplain maps can be quickly and easily
through the letter Of Map Revision (LOMR) process.
updated using digital files prepared for the project plat
Approval time is typically 9-18 months depending on
and plans. A compliance certificate can also be
the project.
provided as needed to ensure finance needs are met
on schedule.
FEMA Map Corrections Due to Inaccuracies- FEMA
CFRA Map Corrections Due to Inaccuracies- CFRA
floodplain maps are corrected through the official
maps are easier to correct more quickly because the
LOMRILOMA process. Certified existing conditions are
maps are maintained locally. Evidence of correct
submitted to FEMA for approval. This process
elevations (4) can be provided at any time to show
averages 3-9 months and may take longer for
accurate CFRA limits.
significant errors.
0) Texas Health & Human Services Commission
(2) F000dproofing and Flood Protection — FEMA flood damage reduction and floodproofing guidelines
(3) Adequate Flood Protection — Lowest floor elevation or floodproofing to an elevation of at least 2.0 feet above the 100-
year ultimate development flood elevation.
(4) Elevation Certificate or survey
2.5.5 CFRA Development Requirements
For the purposes of CFRA regulation, Development activities include but are not limited to the construction or
alteration of buildings or other structures (i.e. residential structures, non-residential structures, fences, sheds,
garages, and retaining walls), filling, grading, paving, excavation, drilling operations or storage of equipment or
materials.
A CFRA Certificate of Compliance is required for proposed projects with less than one acre of disturbance to
ensure compliance with the provisions of the Floodplain Provisions in Chapter 7 Article 8 Division 7 of the City Code,
For Development activities with areas of disturbance one acre or more, the CFRA Certificate of Compliance will not
be required but submission and approval Stormwater Drainage Study will be required. If the proposed Development
is considered to be part of a Common Plan of Development then the criteria for sites with area of disturbance of
one acre or more will apply.
For all structures mitigated via elevation, a post -construction elevation certificate must be submitted to the city
within 60 days of completion of construction. The certificate must be completed by a registered public land surveyor
or licensed professional engineer and include the elevation in relation to mean sea level of the lowest floor including
basement, finished garage and lowest elevation of machinery or equipment servicing the building.
For all structures mitigated via floodproofing, the floodproofing method must be shown on the construction plans.
The structure and attendant utility and sanitary facilities must be floodproofed to or above the DFE. All wet or dry
floodproofing shall be completed in accordance to FEMA floodproofing guidance.
The City will not approve any Development activity in the CFRA until either the CFRA Certificate of Compliance or
the Stormwater Drainage Study have been reviewed and approved by the City. This means no building permits or
other permits will be issued for a property within the CFRA until either the CFRA Certificate of Compliance or
Stormwater Drainage Study is approved. The only exceptions to this will be in the cases of either a minor project
or waiver both of which require prior approval from the Floodplain Administrator or designee.
2.5.6 CFRA Development Procedures
1. Is the Proposed Development Located in a CFRA?
First, the owner or representative of any proposed public or private Development located in the vicinity of a CFRA
shall determine if the proposed work is located within the CFRA using the City's websites before submitting a
building permit. Continue to the next step only if the proposed Development is located within the CFRA.
2. How large is the Proposed Development?
Proposed Developments inside a CFRA with a land disturbance of one acre or greater will need to adhere to the
established SDS Drainage Study submittal and review process and will not follow the steps for a CFRA Certificate
City of Fort Worth Stormwater Criteria Manual 33
of Compliance. Models used to produce the CFRA can be utilized by Developers/engineers in the drainage studies
for projects greater than one acre.
Proposed Development inside a CFRA with a land disturbance of less than one acre will require a CFRA Certificate
of Compliance to ensure compliance with the City of Fort Worth Floodplain Provisions Ordinance. This certificate
must be stamped by a licensed professional engineer registered with the State of Texas who certifies that the
proposed structure is safe from flood risk and that the proposed project will not cause any adverse impacts to flood
risk on adjacent properties. A Flood Study and/or Drainage Study will not be required to be submitted to the City
for review. Continue to next step.
3. Complete CFRA Certificate of Compliance
For proposed Development requiring submittal of a CFRA Certificate of Compliance, the form may be requested
from the Stormwater Development Services group at sdsCc-)fortworthtexas.gov or downloaded from the city website.
This certificate must be completed, signed and sealed by a licensed professional engineer registered with the State
of Texas.
All sections of the Project Information section must be filled out except for the surveyor information if no surveyor
was required. The Property Owner Name should not be the same as the Engineer unless said Engineer owns the
property.
The DFE for the property and how it was determined must be included within the CFRA Information section on the
certificate. The DFE can be a single elevation or a range of elevations for those areas with steeper inclines. This
information can be determined from either a City provided engineering study (available on request) or an
independent engineering evaluation performed following guidance from the Stormwater Criteria Manual. In those
instances where an independent engineering study is used, additional information may be requested by the City in
support of the review.
It must be noted on the certificate if the proposed structure is to be mitigated against flood risk by either elevating
to DFE, floodproofing (wet or dry), or some other means.
While an engineering study is not required to be submitted for City review for projects disturbing less than one acre,
the engineer of record shall describe on the certificate how potential adverse impacts were considered. See Texas
Water Code, Chapter 11, Subchapter B for more information on the State law prohibiting Development on a
property from creating adverse drainage impacts on others. The following are considerations when addressing
potential impacts:
• Estimated flood depth or velocity
• Potential change or block of existing drainage patterns
• Potential to increase flooding on, or otherwise adversely impact, adjacent properties
• Potential to adversely impact public Right of Way (ROW) or facilities
All submittals must also include a Project Boundary Map which shows the proposed Development activities in
relation to the CFRA.
If the property owner feels a waiver from the CFRA Certificate of Compliance is justified or that the proposed work
meets the definition of a minor project, then contact the SIDS team for discussion and review. Waiver requests will
be submitted on the Stormwater Waiver Form and reviewed following the Stormwater Waiver process.
4. Pre -Submittal Meeting (Optional for CFRA)
Before submitting a CFRA Certificate of Compliance, the property owner or engineer can request a meeting with
SIDS and Floodplain Management staff to discuss the proposed project and Development requirements. Contact
staff at sds _ fortworthtexas.gov to schedule the pre -submittal meeting. The meeting request form shall be
completed and returned with attachments to SIDS before a meeting can be scheduled.
5. Submittal of CFRA Certificate of Compliance
The completed and sealed CFRA Certificate of Compliance along with any supporting documentation must be
submitted with the associated building permit application for review. For information on the procedure for digital
submittals, visit the City's website or contact the Stormwater Development Services team at
sds@fortworthtexas.gov.
6. Review and Acceptance
City of Fort Worth Stormwater Criteria Manual 34
Upon receiving a CFRA Certificate of Compliance, the submittal will be initially reviewed for completeness. If found
to be incomplete then the submission will be rejected for review and the applicant notified of deficiencies. Review
will not proceed until a complete submittal is received.
City staff, or a contractor, will review the CFRA Certificate of Compliance submissions for general compliance with
the Stormwater Criteria Manual and the Floodplain Provisions ordinance. Acceptance of the certificate does not
relieve the property owner or engineer from responsibility ensuring the proposed project is in compliance with the
Stormwater Criteria Manual and all other applicable local, state and federal requirements, and will accomplish the
goal of CFRA management.
7. Post Construction Requirements
For all structures mitigated via elevation, a post -construction elevation certificate must be submitted to the city within
60 days of completion of construction. The certificate must be completed by a registered public land surveyor or
licensed professional engineer and submitted to sds(ZDfortworthtexas.gov.
2.5.7 Guidance for CFRA Models
For those projects located within the CFRA with a land disturbance of one acre or more, the CFRA models can be
provided for use in the SIDS Drainage Study submittal. These models are two-dimensional (2D) and as such require
advanced software, an understanding of 2D modeling principles and model parameters, and experience and
expertise in advanced hydrologic and hydraulic modeling. The following best practice guidelines are provided for
Developers/engineers choosing to develop a model or use one of the City's CFRA models:
• Schedule a Stormwater PDC to discuss and fully document the proposed modeling approach
• For modifying the CFRA model:
o Compare pre- and post -development conditions to current CFRA models
o Limit model modifications (such as model parameters, re -meshing, roughness polygon n-values,
etc.) to those relevant to the proposed site changes
o Use the Fact Sheets made available with specific guidance (such as standard assumptions,
boundary conditions, hydrology methods, meshing, limitations, etc.)
• Model Alternatives:
Depending on specific site location and conditions, alternative software models may be allowed,
based on City staff concurrence
o Drainage Study submittal must document alternate model approach circumstances and
comparisons to the current CFRA model
• Tolerances and 2D unconfined flow models:
a Due to software methodologies and technology, some variations or tolerances can be considered
when comparing model results
o A comparison of model output for pre- and post -project conditions should document any changes
that result from software version or model assumptions.
o Spatially varied impacts may be tolerated in circumstances that do not adversely impact (i.e.
increase depth or velocity)
Drainage study submittal:
o Document in the technical memo what software was used, all model changes and include tables
comparing existing and proposed conditions model results.
o Include an exhibit showing the model structure link -node diagram for existing and proposed
condition models comparison.
a Include an exhibit correlating model link -node elements to site layout and design plans for existing
and proposed conditions.
NOTE: This package is intended to be an informational guide to the CFRA Development review process. There
may be additional information and documentation required based on individual circumstances.
HAVE QUESTIONS? To address questions concerning your project contact the Stormwater Development Services
Team at sd�fortworthtexas.aov or call 817-392-1234,
City of Fort Worth Stormwater Criteria Manual 35
SDS Pre -
submittal
Meeting
Drainage No
Pub.
Study & Infra. LFi-,
*Flood 7
Study
Yes
Yes
(final short
plat)
r
concept
P
F Flood Study &
Platting Drainage
Plan &
I Drainage I
Study
Preliminary
I Study I
Yes
plat
I Updates I
(concept plan
or
— ^ —' —,
preliminary
plat)
No
(grading
permit) Fy.
Drainage Pub.
Study & Infra.
'Flood 7
------------------
=Grading
;
Stormwater Building
Pre -Con Permit
' Check
*FDP ! I SWFMA I
'--------- ----
IPRC
Construction
Drawings
r---------------
Grading
radin
Permit
No Stormwater Building
—Pre-Can Check Permit
"FDP IE SWFMA 1 ;
Figure 2.2 Generalized Stormwater Development Review Process
City of Fort Worth Stormwater Criteria Manual 36
IPRC and CFA
documents
----------------' Final Plat
Grading I
' I Permit 1
Stormwater IPRC
M Pre Can Pre -Can
Check Meeting
i r--jr— —1,
I *FDP II SWFMA 1
I IE I�
----------------'
* FEMA floodplain compliance
(as applicable)
- ; If applicable
3 Stormwater Design Criteria
This chapter presents an integrated approach for meeting stormwater runoff quality and quantity management goals
by addressing the key adverse impacts of Development on stormwater runoff. Its framework consists of three focus
areas, each with options in terms of how the focus area is applied.
Design Focus Areas
The stormwater management focus areas and goals are:
• Water Quality Protection: Remove pollutants in stormwater runoff to protect water quality. Note: Water
quality protection is encouraged and incentivized, but not a mandatory requirement in the City.
• Streambank Protection: Regulate discharge from the site to minimize downstream bank and channel
erosion.
Flood Mitigation and Conveyance: Control runoff within and from the site to minimize flood risk to
people and properties for the conveyance storm as well as the flood mitigation storm.
Water quality design criteria are voluntary in City of Fort Worth. The controls may be used, however, to obtain
Stormwater Fee Credits, in which case iSWM standards are applicable. Information on Stormwater Utility Fee
Credits is contained in Appendix F of this manual.
While water quality protection is encouraged but not required in the City, steps for water quality protection are
beneficial to sustainable Development and are recommended in the Development process.
Each of the Design Focus Areas shall be used in conjunction with the others to.address the overall stormwater
impacts from a Development site. When used as a set, the Design Focus Areas are intended to control the entire
range of hydrologic events, from the smallest runoff -producing rainfalls up to the 100- year, 24-hour storm.
3.1 Design Options
There are multiple options provided to meet the criteria for water quality protection, streambank protection,
conveyance, and flood mitigation. These design options are summarized in Table 3.2 and described in additional
detail in Section 3.7.2.
Design criteria for streambank protection and flood mitigation are primarily based on an Adverse Impact
Assessment. The purpose of the downstream assessment Adverse Impact Assessment is to protect downstream
properties and channels from increased flooding and erosion potential due to upstream Development. An Adverse
Impact Assessment is required to determine the zone of Influence and the extent of improvements necessary for
streambank protection and flood mitigation. An Adverse Impact Assessment shall be performed for streambank
protection, conveyance, and flood mitigation storm events as described in Table 3.1, Table 3.3 and Section 3.7.3.
Note that Developments that demonstrate no increase in impervious cover and sites proposing detention storage,
with a total land disturbance of less than 5 acres and a contributing drainage area of less than 25 acres at outfall
will not require a Adverse Impact Assessment. In cases where detention is proposed to waive Adverse Impact
Assessment, detention volume must adequately address the increase in discharge due to the proposed
Development.
If calculations indicate that a Development causes no adverse impacts to existing conditions, then it is possible that
mitigation would not be required.
City of Fort Worth Stormwater Criteria Manual 37
able 3.1 Zone of Influence and Adequate Outfall Determination
Item
Parameter
Requirements
• No new or increased flooding (0.00 feet) of existing insurable (FEMA) structures
Habitable
1
Structures
(habitable buildings).
• No increase greater than 0.1 feet in 1-, 5-, and 100-year flood elevations over
Flood
existing roadways. No increase greater than 0.1 feet and 100-year flood
2
Elevations
elevations, unless contained in existing public channel, roadway, drainage
easement and/or R.O.W.
` Where provisions of the City's floodplain ordinance may be more restrictive, the
3
F000dplain
floodplain ordinance shall have authority over the above provisions.
Ordinance
• ;proposed channel velocities for 1-, 5-, and 100-year storms cannot exceed the
applicable maximum permissible velocity shown in Table 3.16 and Table 3.17 of
this manual. Exceptions to these criteria will require certified geotechnical
Channel
/geomorphologic studies that provide documentation that the higher velocities will
4
Velocities
not create additional erosion.
If existing channel velocities exceed maximum permissible velocities shown in
Table 3.16 and Table 3.17, no more than a 5% increase in velocities will be
allowed.
No increase in downstream discharges caused by the proposed Development
5
Downstream
that, in combination with existing discharges, exceeds the existing capacity of the
Discharges
downstream storm drainage system or existing right -of- way.
• A Development of 5 acres or less, with proposed detention and draining a
watershed less than or equal to 25 acres, a Adverse Impact Assessment is not
required. The detention volume must adequately address the increase in
discharge due to the proposed Development.
• For watersheds of one hundred (100 ac) acres or less at any proposed outfall, the
Adverse Impact Assessment may use the 10% rule of thumb when detention is
Adverse
proposed (as delineated in Section 2A of the Hydrology Technical Manual) or a
6
Impact
detailed study (no detention) in order to determine the Zone of Influence (where
Assessment
pre -development and post -development flows are the same).
• For all other watersheds, the Zone of Influence will be defined by a detailed
hydrologic and hydraulic analysis (see Section 3.7 for more details).
• In all cases, Adverse Impact Assessment shall always extend to or beyond the
10% point.
• A Adverse Impact Assessment exemption may be acquired for small infill
Developments which meet the specific criteria outlined in Section 3.7.2.
`Section 2.0 of the Hydrology Technical Manual provides additional information on calculating discharges and velocities, as
welf as determining the downstream extent of the assessment.
City of Fort Worth Stormwater Criteria Manual 38
Table 3.2 Summary of Options for Design Focus Areas
D&sighF6difs.-Area'',AdVbtse,
mpact
Assessmehl' -
:bbsiqn, Options
Water Quality
Protection
Option 1: Use integrated Site Design Practices for conserving natural
features, reducing impervious cover, and using the natural drainage
systems
Option 2: Treat the Water Quality- Protection Volume (WQV) by reducing
total suspended solids from the Development site for runoff resulting from
rainfalls of up to 1.5 inches (85th percentile storm)
(Not currently
required by the City)
Please note, water
quality protection
No
may be required by
TRWD or other
Option 3: Assist in implementing off -site community stormwater pollution
agencies,
prevention programsiactivities as designated in an accepted stormwatet
master plan or TPDES Stormwater permit
Option 1: Reinforcelstabilize downstream conditions
Option 2: Install stormwater controls to maintain or improve existing
downstream conditions
Streambank
Protection
Yes
Option 3: Provide on -site controlled release of the 1- year, 24-,hour storm
event over a period of 24 hours (Streambank Protection Volume, SPV)
Flood Mitigation (3.7)
Option 1: Provide adequate downstream conveyance systems
(Requires a Adverse Impact Assessment or application of the Simplified
Finding of No Significant Impact as presented in Section 3.7.2)
Option 2: Install stormwater controls on -site to maintain or improve
existirig downstream conditions. A Adverse Impact Assessment is no
required for on -site controls in the form of detention when proposed site
has less than 5 acres of land disturbance and is draining less than 25
acres at the outlet of the basin. Detention must completely mitigate the
Flood Mitigation and
increase in peak discharge due to proposed Development.
Conveyance
Yes/No
-
Option 3: In lieu of a Adverse Impact Assessment, mimic existing on -site
runoff conditions (Does not require a Adverse Impact Assessment)
Option 4: If downstream impacts are limited to a single adjacent property
,notarized
and involve only private runoff, then the Developer may obtain
letter of permission from the affected property ownei
acknowledging the impacts from the subjected property in lieu ol
mitigation. The letter is not an option when public runoff is involved.
Conveyance (3.8)
Minimize localized site flooding of streets, sidewalks, and properties by a
combination of on -site stormwater controls and conveyance systems
City of Fort Worth Stormwater Criteria Manual 39
3.2 Design Storms
The City requires the following storm events to be used in the integrated stormwater design. Throughout the manual
the storms will be primarily referred to by their storm event names.
Table 3.3 Storm Events
Storm Event Name
Storm Event Descri tioh
'_.' Desi n,Standard 2
"Water Quality"
Criteria based on a volume of
1.5 inches of rainfall, not a
storm frequency
Streambank Protection"
1-year return period
• Low flow channels and velocity check
"Conveyance"
5-year return period
. Secondary check for street inundation
and open travel lanes
"Flood Mitigation"
100-year return period
. Open channels
• Primary standard for street and storm
drain in conjunction
9 Currently encouraged and incentivized but not required in the City
2 See Section 3.8 for specific design criteria
3.3 Design Criteria
The Design requirements for the City are:
1. All Development within the City Limits or its Extra -territorial Jurisdiction (ETJ) shall include planning, design,
and construction of storm drainage systems in accordance with this Stormwater Criteria Manual, the
Subdivision Ordinance, City's design manuals, and the CFA Ordinance_ Please see definition of Development
and project size limitations for specific design requirements under "Abbreviations and Definitions" in Section
1.2.
2. All drainage related plans and studies shall be prepared and sealed by a Licensed Professional Engineer with
a valid license and a valid registered Firm number from the State of Texas. The engineer shall attest that the
design was conducted in accordance with this Manual.
3. For currently developed areas within the City with planned Redevelopment, stormwater discharges and
velocities from the project shall not exceed discharges and velocities from the existing developed conditions.
Alternatively, a notarized letter of permission may be obtained from the affected property owner,
acknowledging the proposed impact, as shown in Table 3.2, Option 4 under Flood Mitigation. The letter option
is only available for private runoff, this option is not available when public runoff is involved. For public runoff,
easements shall be obtained by the Developer.
4. All drainage analyses and design plans shall be formulated and based upon fully developed watershed or
drainage area runoff conditions from the upstream area. Where detention is in place with a valid SWFMA or
a master plan has been adopted, a Development may plan to receive less than fully developed flow from
upstream. The rainfall frequency criteria for stormwater facilities, as enumerated within this Criteria Manual,
shall be utilized for all drainage studies and design plans.
5. Stormwater must be carried to an "adequate or acceptable outfall". An Adequate Outfall is one that does not
create or increase flooding or erosion conditions downstream and is in all cases subject to the approval of the
TPW. See additional clarification in Table 3.1 and Section 3.7.3. An Adequate Outfall typically consists of a
public storm drain, inlet, channel, culvert, creek or other public drainage facility that can be analyzed to
determine adequate capacity or no adverse impact.
City of Fort Worth Stormwater Criteria Manual 40
6. Proposed stormwater discharge rates and velocities from a Development shall not exceed the rates and
velocities from existing conditions, unless a detailed study is prepared that demonstrates that no adverse
impacts will be created, as defined in Table 3.1 and Section 3.7.3.
7. If a proposed Development drains into an improved channel or stormwater drainage system designed under
a previous City drainage policy (Prior to 2006), then the hydraulic capacities of downstream facilities must be
checked to verify that increased flows, caused by the new Development, will not exceed the capacity of the
existing system or cause increased downstream structure flooding. If there is not sufficient capacity to prevent
exceedance of existing rights of way or increased downstream flooding, then detention or other acceptable
measures must be adopted to accommodate the increase in runoff due to the proposed Development. For
projects which have an accepted Drainage Study and/or iSWM plan, including phased Developments which
have some existing constructed phases after the adoption of the iSWM criteria in June 2006, findings in
accepted studies will remain valid.
8. Stormwater runoff may be stored in detention and retention basins to mitigate potential downstream impacts
caused by a proposed Development. Proposed detention or retention basins shall be analyzed both
individually and as a part of the watershed system, to assure compatibility with one another and with the City's
overall Stormwater Management Master Plan for that watershed (if available). Storage of stormwater runoff,
near to the points of rainfall occurrence, such as the use of parking lots, ball fields, property line swales, parks,
road embankments, borrow pits and on -site ponds is desirable and encouraged.
9. When detention is used to attenuate peak discharge from a proposed Development, runoff must be controlled
for the applicable storms listed in Table 3.3 so that detained proposed peak discharges do not adversely
impact downstream flooding and stream bank conditions, as described in Design Guidelines 5 and 6, above.
Where detention is used to completely offset the impact of the Development, the proposed site is 5.0 acres
or less and the contributing basin has a drainage area less than 25 acres at outlet, a Adverse Impact
Assessment is not required.
10. Alternatives to detention or retention, for mitigation of potential downstream impacts caused by proposed
Development, include: acquisition of expanded drainage easements, ROW, or letter of consent; downstream
channel and/or roadway drainage system improvements or stream bank erosion protection. These
alternatives will be considered, as presented by the Developer, by the Director of the Development Services
Department, on a case -by -case basis.
11. Stream bank stabilization and protection features to reduce or prevent erosion and sedimentation for creeks,
streams, and channels shall be required, as specified in this Manual, and to ensure the intent of Design
Guidelines 5 and 6, above.
12. All proposed Developments within the City Limits or Extra -territorial Jurisdiction (ETJ) shall comply with all
local, county, state and federal regulations; whichever is more stringent. All required permits or approvals
shall be obtained by the Developer from the governing jurisdiction.
13. The policy of the City is to avoid substantial or significant transfer of stormwater drainage runoff from one
basin to another and to maintain historical drainage paths whenever possible. However, the transfer of
stormwater drainage from basin to basin may be necessary in certain instances and will be reviewed and a
waiver shall be requested using the Stormwater Waiver Request Form CFW-7.
14. All studies, design, construction plans, analysis, hydrology, hydraulics, exhibits and documents that are
submitted to the City for review shall comply with this Manual.
City of Fort Worth Stormwater Criteria Manual 41
3.4 Hydrologic Design Criteria
3.4. 1 Types of Hydrologic Methods
There are a number of empirical hydrologic methods available to estimate runoff characteristics for a site or drainage
sub basin. However, the following methods are authorized by the City to be used to support hydrologic site analysis
for the design methods and procedures included in this manual subject to the limitations on their use included in
this Manual:
• Rational and Modified Rational Method
• SCS Unit Hydrograph Method
• Snyder's Unit Hydrograph Method
• USGS & TXDOT Regression Equations
• iSWM Water Quality Protection Volume Calculation
• Water Balance Calculations
Table 3.4 provides the City limitations on the use of several accepted hydrologic methods
Table 3.4 City of Fort Worth Constraints on Using Recommended Hydrologic Methods
'Method
Ske,Liibitations'
Comments
Rational'
0 — 200 acres
Method authorized for estimating peak flows and the design of small
site or subdivision storm sewers stems.
Method can be used for final design in single basins up to 25 acres.
Modified Rational',2.3
0 — 25 acres
However, modified rational method is not allowed for basins in series
or when drainage area is diverted from pre -development outfalls.
Unit Hydrograph (SCS)
Any Size
Method can be used for estimating peak flows and hydrographs for all
design applications.
Unit Hydrograph
100 acres and
Method can be used for estimating peak flows and hydrographs for all
(Snyder's)
larger
design applications.
TXDOT Regression
10 to 100 mi2
Method can be used for estimating peak flows for rural design
Equations
applications.
USGS Regression
Equations
3 — 40 mi2
Method can be used for comparison with other methods
I Note: Calculations previously accepted by the City using "C" coefficients from the 2006 manual shall be acceptable.
2 MRM Methodology shall be as defined in Section 1.5.2 of the iSWM Hydrology Technical Manual.
3 A City provided Modified Rational Method too[ is available and its use is encouraged. Please contact SIDS staff at
SDS@fortworthtexas.gov.
• The City requires that the "C" coefficients presented in Table 3.5 be used in all Rational and modified
Rational Method computations. Calculations previously accepted by the City using "C" coefficients from
the June 2006 Manual shall be acceptable, as described in Section 1.3. Where existing land use does
not correspond to Table 3.5, a composite "C" value may be calculated using 0.9 for impervious areas
and 0.3 for pervious areas.
• For existing Development site conditions, a composite calculation shall be provided, and used as the
baseline for comparing impacts.
City of Fort Worth Stormwater Criteria Manual 42
• Rainfall distribution for the SCS Unit Hydrograph shall be based on the Frequency Rainfall Data
provided in Section 5 0 of the Hydrology Technical Manual centered at the midpoint of the rainstorm
(12th hour of a 24-hour storm).
• The percent impervious values presented in Table 3.5 shall be used in the SCS Unit Hydrograph
calculations.
• The "Frequency Factors" referenced in Section 1.2.3 of the Hydrology Technical Manual are not
required by the City.
• Figure 3.1 presents a sample computation summary sheet for the presentation of unit hydrograph
method results. This form shall be completed even if the computations are performed on an acceptable
computer program such as HEC-1 or HEC-HMS. Refer to Appendix B for acceptable modeling
programs.
• An alternative method to determine Snyder's Lag is to determine the time of concentration (travel time)
by the methodology described in Section 1.3.6 of the Hydrology Technical Manual and multiply this
time of concentration by O.B.
• The TxDOT and USGS Regression methods shall only be used for comparison of the reasonableness
of other accepted determinations, not for final results or design iSWM Water Quality Protection Volume
(WQv) calculation method is not required by the City.
• Fully Developed Conditions — For watershed hydrology, fully developed conditions include:
o All existing developed areas shall reflect current land use, current zoning, or future land use per
City's Comprehensive Plan, whichever yields the greatest runoff.
o All existing undeveloped areas shall reflect anticipated future land use designated by zoning
classification, by the City's Comprehensive Plan, or by an approved concept plan; whichever yields
the greatest runoff.
• If the anticipated offsite future Development is unknown (not zoned or included in a comprehensive
plan or other land plan), a minimum weighted runoff coefficient of 0.75 or equivalent SCS Curve Number
with 75% impervious cover shall be used.
• The 100 year inundation limits in a detention pond shall be considered to be impervious cover (C=0.9,
CN=98).
• Reach routing methods: lag routing is acceptable for pipes only, modified puls routing shall be used
when a HEC-RAS model is available.
• Proposed rural residential subdivisions comprised of lots sizes 2 acres (net) or greater shall be
considered to have no less than 20% impervious cover for proposed conditions (C=0.42).
Table 3.5 presents the Rational Method Runoff "C" Coefficients for the City. The basis of these coefficients
is the standard zoning classification used by the City ("A-5, "A-21", etc.) An example of the determination
of these coefficients is presented in Figure 3.2.
3.4.2 Rainfall Estimation
Rainfall intensities are provided in Section 5.0 of the Hydrology Technical Manual for the sixteen (16) counties
within the North Central Texas Council of Governments. The intensities are based on a combination of data from
Hydra-35 and USGS. These intensities, or those sourced from Atlas 14, shall be used for all hydrologic analysis
within the applicable county.
City of Fort Worth Stormwater Criteria Manual 43
Table 3.5 Runoff Coefficients
�Runoff'Cdefficient
Desdfiption oftand Use % Impervious ..C„
Single Family
Residential "A-43" one -acre lots (1) (2)
35
0.51
Residential "A-21" half -acre lots
37
0.52
Residential "A-10" 10,000 SF lots
49
0.59
Residential "A-7.5"
55
0.63
Residential "A-5"
61
0.67
Residential "MI -I", "A-R", "B",
65
0.69
Multi Family
"CR"
65
0.69
I.C.
79
0.77
"D"
93
0.86
Commercial, Industrial, House of Worship, School,
Planned Development, Urban Residential (3)
4% Open Space (Default if no site plan)
96
0.88
10% Open Space (Site plan required)
90
0.84
20% Open Space (Site plan required)
80
0.78
Parks, Cemeteries
7
0.34
Railroad Yard Areas
29
0.47
Streets & ROW: Asphalt, Concrete, or Brick
100
0.90
Drives, Walks, Roofs, Detention Ponds (4)
100
0.90
Gravel Areas
43
0.56
unim roves Areas U U.Ju
Assumptions:
(1) For Residential Calculations:
- Current City Development standards for minimum lot size and maximum lot coverage (structure) for each classification
- Assumed 10.5' Parkway and 18' driveway
- Assumed 29' B-B street dimension
- Calculated by applying 90% runoff from impervious areas and 30% runoff from pervious areas
(2) Calculated from designated set -backs
(3) Includes R-1, R-2, UR and similarly intensive uses
4 100 year inundation limits
City of Fort Worth Stormwater Criteria Manual 44
m
---_—__m F-_-_-._..------ rL RESIDENTIAL STREET -----
a1
N
0.5
so, uiu+r. I
20, MIN. i 3 I
FRONT =
YARD c
ExIlTO' L1iN.
MAX FLOOR AREA■
2.500 S.F.
ra% LOT -9M WIL LOT AREAo
SAW S.F.
R.O.W.
REAR YARD
APPROX. USE OF LOT
AREA= 5,000 S.F. + R.O.W. (2S'xS0')
Q 6,260 S.F. MAX.
C
USE
A
MAX. CA
0.9
STREET(14.5x150)
725
652.6
0.9
DRIVEWAYAIID SIDEWALK
677
609.3
0.9
ROOF
21500
2,250.0
0.3
LAUDSCAPE AREA
2.348
704.4
TO TAL CA
4,216.2
CALC. -MA
0.67
PROMMATIOII OF RUII OFF COEFFICIEIIT
r0.67
Figure 3.1 Sample Calculation Sheet for Runoff Coefficient "C"
City of Fort Worth Stormwater Criteria Manual 45
D
DATE
°ICDt
DATE:
LOSS RATE METHOD
COMPUTATION SUMMARY -SHEET
SHEET 1 °�
SUBWA"fI=RSHED
WATERSHED
MAJOR JDBlFILE LEN°.:
N
STREAM ROUTING
HYDROLOGY BY UNIT,HYDROGRAPH METHOD
ANALYSIS
POINT
SUBWATERSHED
AREA -(AC)
WATERSHED
AREA (AC)
UNITAYDROGRAPH COEFFICIENTS
PEAK DISCHARGES (GFSJ
COMMENTS
SCS METHOD,
SNYDER'S METHOD
CN
Lag
HR
C P
Ty
HR
Q,
as
Imo
1
2
3
4
5
8
7
8
9
11
12
REMARKS, SKETCHES AND COMPUTATIONS
Figure 3.2 Computation Summary Sheet for Hydrology by Unit Hydrograph Method
City of Fort Worth Stormwater Criteria Manual 46
3.5 Water Quality Protection
3.5. 1 Introduction
iSWM requires the use of integrated Site Design Practices as the primary means to protect the water quality of our
streams, lakes, and rivers from the negative impacts of stormwater runoff from Development. The integrated Site
Design Practices shall be designed as part of the Drainage Studies and Construction Plans. In addition to the
integrated Site Design Practices, required water quality protection can be achieved by two additional options: (1)
by treating the water quality protection volume and (2) assisting with off -site pollution prevention activities. These
three approaches are described below.
The City has currently opted to implement the streambank protection and flood mitigation and conveyance
goals, but not the water quality protection component The City does not require water quality protection
for Development but strongly encourages this to be done. The City provides a stormwater fee credit
(reduction) as an incentive for voluntary compliance with this component of stormwater management See
Appendix F for more information regarding fee credits.
3.5.2 Option 1: integrated Site Design Practices and Credits
The integrated Site Design Practices are methods of Development that reduce the "environmental footprint" of a
site. They feature conservation of natural features, reduced imperviousness, and the use of the natural drainage
system. In this option, points are awarded for the use of different Site Design Practices. A minimum number of
points are needed to meet the iSWM requirements for Water Quality. Additional points can be gained to qualify for
Development incentives. See Appendix F for additional details.
3.5.2.1 List of integrated Site Design Practices and Techniques
Twenty integrated Site Design Practices are grouped into four categories listed below. Not all practices are
applicable to every site.
• Conservation of Natural Features and Resources
1. Preserve.Undisturbed Natural Areas
2. Preserve Riparian Buffers
3. Avoid Floodplains
4. Avoid Steep Slopes
5. Minimize Siting on Porous or Erodible Soils
• Lower Impact Site Design Techniques
1. Fit Design to the Terrain
2. Locate Development in Less Sensitive Areas
3. Reduce Limits of Clearing and Grading
4. Utilize Open Space Development
5. Consider Creative Designs
• Reduction of Impervious Cover
1. Reduce Roadway Lengths and Widths
2. Reduce Building Footprints
3. Reduce the Parking Footprint
4. Reduce Setbacks and Frontages
5. Use Fewer or Alternative Cul-de-Sacs
City of Fort Worth Stormwater Criteria Manual 47
6. Create Parking Lot Stormwater "Islands"
• Utilization of Natural Features for Stormwater Management
1. Use Buffers and Undisturbed Areas
2. Use Natural Drainageways Instead of Storm Sewers
3. Use Vegetated Swale Instead of Curb and Gutter
4. Drain Rooftop Runoff to Pervious Areas
More detail on each site design practice is provided in the integrated Site Design Practice Summary Sheets in
Section 2.2 of the Planning Technical Manual.
3.5.2.2 Integration of Site Design Practices into Site Development Process
During the site planning process described in Section 2.3, Step 1, there are several steps involved in site layout
and design, each more clearly defining the location and function of the various components of the stormwater
management system. To be more effective and easier to incorporate, integrated Site Design Practices shall be part
of this overall Development process as outlined in Table 3.6.
Table 3.6 Integration of Site Design Practices with Site Development Process
Site Development Phase
Site Design Practice Activity
•
Identify and delineate natural feature conservation areas
(natural areas and stream buffers)
Site Analysis
•
Perform site reconnaissance to identify potential areas for
and types of credits
•
Determine stormwater management requirements
•
Preserve natural areas and stream buffers during site layout
•
Reduce impervious surface area through various techniques
Conceptual Plan
Identify locations for use of vegetated channels and
groundwater recharge
•
Look for areas to disconnect impervious surfaces
•
Document the use of site design practices
•
Perform layout and design of credit areas — integrating them
into treatment trains
Preliminary and Final Plan
Ensure integrated Focus Areas are satisfied
•
Ensure appropriate documentation of site design credits
according to local requirements
City of Fort Worth Stormwater Criteria Manual 48
Table 3.6 Integration of Site Design Practices with Site Development Process
Site Development Phase
Site Design Practice Activity
• Ensure protection of key areas
Ensure correct final construction of areas needed for credits
Construction
Inspect and maintain implementation of BMPs during
construction
• Develop maintenance requirements and documents
Final Inspection
• Ensure long term protection and maintenance
• Ensure credit areas are identified on final plan and plat if
applicable
3.5.3 Option 2: Treat the Water Quality Protection Volume
Treat the Water Quality Protection Volume by reducing total suspended solids from the Development site for runoff
resulting from rainfall of 1.5 inches (85th percentile storm). Stormwater runoff equal to the Water Quality Protection
Volume generated from sites may be treated using a variety of on -site structural and nonstructural techniques with
the goal of removing a target percentage of the average annual total suspended solids
A system has been developed by which the Water Quality Protection Volume can be reduced, thus requiring less
structural control. This is accomplished through the use of certain reduction methods, where affected areas are
deducted from the site area, thereby reducing the amount of runoff to be treated. For more information on the Water
Quality Volume Reduction Methods see Section 1.3 of the Water Quality Technical Manual.
3.5.3.1 Water Quality Protection Volume
The Water Quality Protection Volume (WQv) is the runoff from the first 1.5 inches of rainfall. Thus, a stormwater
management system designed for the WQv will treat the runoff from all storm events of 1.5 inches or less, as well
as a portion of the runoff for all larger storm events. For methods to determine the WQv, see Section 1.3 of the
Water Quality Technical Manual.
Water Quality requirements are encouraged but not required by the City. Information is included for reference if the
Developer chooses to pursue such alternatives.
3.5.3.2 Recommended Stormwater Control Practices
Below is a list of recommended structural stormwater control practices. While these stormwater control practices
are not mandatory in the City, they are highly recommended for sustainable Development. This information is
provided for reference if the Developer chooses to pursue such an option. These structural controls are
recommended for use in a wide variety of applications and have differing abilities to remove various kinds of
pollutants. It may take more than one control to achieve a certain pollution reduction level. A detailed discussion of
each of the controls, as well as design criteria and procedures, can be found in the Site Development Controls
Technical Manual. Refer to Table 3.7 for details regarding primary and secondary controls.
• Bioretention
• Enhanced swales (dry, wet, wetland)
• Alum treatment
• Detention
• Filter strips
• Sand filters, filter boxes, etc.
• Infiltration wells and trenches
• Ponds
• Porous surfaces
• Proprietary systems
• Green roofs
• Rainwater harvesting
• Wetlands
• Submerged gravel
City of Fort Worth Stormwater Criteria Manual 49
3.5.3.3 Using Other or New Structural Stormwater Controls
Innovative technologies are encouraged and will be reviewed for applicability. Any such system will be required to
provide sufficient documentation as to its effectiveness and reliability. Third party proof of performance,
maintenance, application requirements, and limitations will be required prior to approval of innovative new
technology.
More specifically, new structural stormwater control designs will not be accepted until independent performance
data shows that the structural control conforms to local and/or state criteria for treatment, conveyance, maintenance,
and environmental impact.
3.5.3.4 Suitability of Stormwater Controls to Meet Stormwater Management Goals
The stormwater control practices recommended in this manual vary in their applicability and ability to meet
stormwater management goals:
Primary Controls
Primary structural stormwater controls have the ability to fully address ore or more of the steps in the integrated
focus areas if designed appropriately. Structural controls are recommended for use with a wide variety of land uses
and Development types. These structural controls have a demonstrated ability to effectively treat the Water Quality
Volume (WQv) and have been shown to be able to remove 70% to 80% of the annual average total suspended
solids (TSS) load in typical proposed urban runoff when designed, constructed, and maintained in accordance with
recommended specifications. Several of these structural controls can also be designed to provide primary control
for downstream streambank protection (SPv) and flood mitigation. These structural controls are recommended
stormwater management facilities for a site wherever feasible and practical.
Secondary Controls
A number of structural controls are recommended only for limited use or for special site or design conditions.
Generally, these practices either: (1) do not have the ability on their own to fully address one or more of the Steps
in the integrated Focus Areas, (2) are intended to address hotspot or specific land use constraints or conditions,
and/or (3) may have high or special maintenance requirements that may preclude their use. These types of
structural controls are typically used for water quality treatment only. Some of these controls can be used as
pretreatment measures or in series with other structural controls to meet pollutant removal goals. Such structural
controls are not recommended for residential Developments.
Table 3.7 summarizes the stormwater management suitability of the various stormwater controls in addressing the
integrated Focus Areas. The Site Development Controls Technical Manual provides guidance on the use of
stormwater controls as well as how to calculate the pollutant removal efficiency for stormwater controls in series.
The Site Development Controls Technical Manual also provides guidance for choosing the appropriate
stormwater control(s) for a site as well as the basic considerations and limitations on the use of a particular
stormwater control.
City of Fort Worth Stormwater Criteria Manual 50
Table 3.7 Suitability of Stormwater Controls to Meet integrated Focus Areas
Category
integrated Stormwater
Controls
TSSI
Sediment
Removal`
Rate
Water
Quality
-Protection
Streambank
' 'Protection
On -Site Flood
-Cohtrol
Downstream .
Flood Control,
Bioretention
Areas
Bioretention Areas
80%
P
S
S
-
Channels
Enhanced Swales
80%
P
S
S
S
Channels, Grass
50%
S
S
P
S
Channels, Open
-
-
-
P
S
Chemical
Treatment
Alum Treatment System
90%
P
-
-
-
Culverts
-
-
-
P
P
Conveyance
System
Components
Energy Dissipation
-
-
P
S
S
Inlets/Street Gutters
-
-
-
P
-
Pipe Systems
-
-
P
P
P
Detention, Dry
65%
S
P
P
P
Detention, Extended Dry
65%
S
P
P
P
Detention
Detention, Multi -purpose
Areas
-
_
P
P
P
Detention, Underground
-
-
P
P
P
Filter Strips
50%
S
-
-
-
Organic Filters
80%
P
-
-
-
Filtration
Planter Boxes
80%
P
-
-
-
Sand Filters,
Surface/Perimeter
80%
P
S
-
-
Sand Filters, Underground
80%
P
-
-
-
Hydrodynamic
Devices
Gravity (Oil -Grit) Separator
40%
S
-
-
-
Infiltration
Downspout Drywell
80%
P
-
-
-
Infiltration Trenches
80%
P
S
-
-
Soakage Trenches
80%
P
S
Wet Pond
80%
P
P
P
P
Ponds
Wet ED Pond
80%
P
P
P
P
Micropool ED Pond
80%
P
P
P
P
Multiple Ponds
80%
P
P
P
P
Porous
Surfaces
Green Roof
85%
P
S
-
-
Modular Porous Paver
Systems
z
S
S
-
-
Porous Concrete
2
S
S
-
-
Proprietary
Systems
Proprietary Systems'
I
SIP
S
S
S
Re -Use
Rain Barrels
-
P
-
-
-
Wetlands, Stormwater
80%
P
P
P
P
Wetlands
Wetlands, Submerged
Grave!
80%
P
P
S
-
City of Fort Worth Stormwater Criteria Manual 51
P = Primary Control: Able to meet design criterion if properly designed, constructed and maintained.
S = Secondary Control: May partially meet design criteria. Designated as a Secondary control due to considerations such
as maintenance concerns. For Water Quality Protection, recommended for limited use in accepted community -designated
areas.
= Not typically used or able to meet design criterion.
= The application and performance of proprietary commercial devices and systems must be provided by the manufacturer
and should be verified by independent third -party sources and data, if used as a primary control. Third -party sources could
include Technology Acceptance Reciprocity Partnership, Technology Assessment Protocol — Ecology, or others.
2 = Porous surfaces provide water quality benefits by reducing the effective impervious area.
3.5.4 Option 3: Assist with Off -Site Pollution Prevention Programs and
Activities
The City does not currently require off -site pollution prevention activities; however, some communities have
implemented pollution prevention programs/activities in certain areas to remove pollutants from the runoff after it
has been discharged from the site. This may be especially true in intensely urbanized areas facing site
Redevelopment where many of the BMP criteria would be difficult to apply.
3.6 Streambank Protection
The second focus area is in Streambank protection. There are three options by which a Developer can provide
adequate streambank protection downstream of a proposed Development. The first step is to perform the required
downstream assessment as described in Table 3.1, Table 3.2 and Section 3.7.3. If it is determined that the proposed
project does not exceed acceptable downstream velocities or the downstream conditions are improved to
adequately handle the increased velocity through the limits of the Zone of Influence, then no additional streambank
protection is required. If on -site or downstream improvements are required for streambank protection, easements
will need to be obtained in accordance with Section 3.11. If the downstream assessment shows that the velocities
are within acceptable limits, then no streambank protection is required. Acceptable limits for velocity control are
contained in Table 3.16 and Table 3.17,
3.6.1.1 Option 1: Reinforce/Stabilize Downstream Conditions
If the increased velocities are greater than the allowable velocity of the downstream receiving system, then the
Developer must reinforce/stabilize the downstream conveyance system. The proposed modifications must be
designed so that the downstream system is protected from the proposed velocities. The Developer must provide
supporting calculations and/or documentation that the downstream velocities do not exceed the allowable range
once the downstream modifications are installed.
Allowable bank protection methods include stone riprap and bio-engineered methods. Section 3.8.4 of this manual
and Sections 3.2 and 4.0 of the Hydraulics Technical Manual provide design requirements g for open channels,
culvert outfall protection, riprap aprons for erosion protection at outfalls, and riprap basins for energy dissipation.
3.6.1.2 Option 2: Install Stormwater Controls to Maintain Existing Downstream
Conditions
The Developer may use on -site controls to keep downstream proposed discharges at or below allowable velocity
limits. The Developer must provide supporting calculations and/or documentation that the on -site controls will be
designed such that downstream velocities for the three storm events (Streambank Protection, Conveyance, and
Flood Mitigation) are within an allowable range once the controls are installed.
3.6.1.3 Option 3: Control the Release of the 1-yr, 24-hour Storm Event
Twenty-four hours of extended detention may be provided for on -site, post -developed runoff generated by the 1-
year, 24-hour rainfall event to protect downstream channels. The required volume for extended detention is referred
City of Fort Worth Stormwater Criteria Manual 52
to as the Streambank Protection Volume (denoted SPv). The reduction in the frequency and duration of bankfull
flows through the controlled release provided by extended detention of the SPv will reduce the bank scour rate and
severity.
To determine the SPv refer to Section 3.0 of the Hydrology Technical Manual,
A 10% stormwater fee credit is available as an incentive for using this option. See Appendix F for more information.
3.7 Flood Mitigation
3.7.1 Introduction
Flood analysis is based on the design storm events as defined in Section 3.2, Table 3.3 for the conveyance storm
and the flood mitigation storm.
The intent of the flood mitigation criteria is to provide for public safety; to minimize on -site and downstream flood
impacts from the three storm events; to maintain the boundaries of the mapped 100-year floodplain; and to protect
the physical integrity of the on -site stormwater controls and the downstream stormwater and flood mitigation
facilities.
Flood mitigation must be provided for on -site conveyance systems, as well as downstream outfalls as described in
the following sections.
3.7.2 Flood Mitigation Design Options
There are four options by which a Developer may address downstream flood mitigation. These options closely
follow the four options for Streambank Protection. When on -site or downstream modifications are required for
downstream flood mitigation, easements will need to be obtained in accordance with Section 3.11.
The Developer will provide all supporting calculations and/or documentation to show that the existing downstream
conveyance system has capacity (Qf) to safely pass the fully developed flood mitigation storm discharge, including
any increase due to the proposed Development, or demonstrate no adverse impact.
Flood mitigation criteria are intended to protect public safety by ensuring minimal upstream, on -site and downstream
flood impacts. Table 3.2 of this Criteria Manual provides four options for Flood Mitigation in the City. -
Option 1 — Confirm Adequate Downstream Conveyance Systems (Adverse Impact Assessment)
Option 2 — Provide On -Site Stormwater Controls (Detention)
Option 3 — Mimic Existing On -Site Runoff Conditions (Low Impact Design)
Option 4 — Obtain letter from impacted downstream property owner (limited to impacts of private runoff on one
single adjacent property).
3.7.2.1 Option 1 - Provide Adequate Downstream Conveyance Systems
Provide calculations for analysis of the downstream conveyance system to confirm adequate capacity is available
to convey the increased runoff, due to Development, within a drainage structure, easement, or right-of-way. This
Adverse Impact Assessment can include any available existing conveyances systems (existing drainage pipes,
channels, natural creeks and streams, easements or right-of-ways specified for drainage use). If the existing
drainage systems do not have capacity to convey the increased runoff from the Development, additional stormwater
controls will be necessary to safely discharge runoff without:
1. Causing new or increased flooding upstream of the Development
2. Causing new or increased flooding on the Development site
3. Causing new or increased flooding downstream of the Development
The Developer may provide additional conveyance by providing and/or modifying the off -site, downstream
conveyance system through construction of additional drainage capacity or acquisition of drainage easements to
contain impacts. The design and analysis of such systems will be required to show that the proposed systems safely
City of Fort Worth Stormwater Criteria Manual 53
convey the required design storm events. Systems are required to be analyzed to an Adequate Outfall, (i.e. a
Adverse Impact Assessment is required) as defined in Table 3.1 and Section 3.7.3.
If the Adverse Impact Assessment shows that all above runoff conditions have been met as defined in Table 3.1
and Section 3.7.3 of this manual, no on -site drainage controls are required to mitigate for increased runoff from the
site due to the proposed Development.
Simplified Finding of No Significant Impact
For small infill Developments that meet specific criteria below, the Adverse Impact Assessment shall not be
required.
Requirements:
1. The proposed Development is less than 5 acres of disturbed land;
2. The site developed drains directly to an existing public roadway, not an alley, and does not redirect drainage
area from one street or watershed to another;
3. The receiving roadway has a longitudinal slope of at least 1%;
4. The site area is less than 10% of the existing offsite area drainage to the same receiving roadway;
5. The existing offsite area (excluding the site to be developed) has a rational C value of at least 0.6;
6. The ROW drainage capacity is not already exceeded in the flood mitigation storm event; and
7. The Development is not subject to existing flooding conditions, or overland flow generated from a 100-yr
storm, and would not result in diversion or impoundment of existing offsite runoff.
Submittal of calculations to confirm these conditions will be required with the Drainage Study submission. Once
reviewed and accepted by the City SIDS, the site Development can be considered as having no significant impact
and no mitigation is required.
3.7.2.2 Option 2 - Provide On -Site Stormwater Controls (Detention)
In the event that downstream conveyance systems, including receiving streams, do not have sufficient capacity,
on -site stormwater controls may be proposed to mitigate the impact of increased discharges from the site to a level
that meets the requirements of Table 3.1 and Section 3.7.3.
An Adverse Impact Assessment is not required for Developments that meet all three of the following conditions:
1. Sites proposing detention when the total site disturbance is less than 5.0 acres.
2. Detention facilities are designed to detain to pre -development peak discharge.
3. Proposing a stormwater detention facility with a contributing drainage area of less than 25 acres at detention
outfall;
In cases where detention is proposed which will not require a Adverse Impact Assessment, detention volume must
completely mitigate the increase in discharge due to the proposed Development.
In all other cases, Adverse Impact Assessment shall conform to this Manual and the iSWM Hydrology Technical
Manual. Note that pre -development conditions onsite and offsite shall be the existing watershed condition, not fully
developed conditions.
3.7.2.3 Option 3 -- Mimic Existing On -Site Runoff Conditions
A Adverse Impact Assessment is not required. This option only requires that on -site improvements are provided to
maintain/mimic existing runoff conditions. This option requires reduced percent imperviousness using integrated
Site Design practices to mimic the existing runoff conditions (discharge, velocity, and concentration). No Adverse
Impact Assessment is required in this option, however, a Adverse Impact Assessment may reduce the amount of
on -site detention required. Calculations shall be submitted to substantiate the proposed discharges.
Stormwater controls for this option include the various types of structural and non-structural controls as described
in this manual (Chapter 3) and listed below.
City of Fort Worth Stormwater Criteria Manual 54
1. Stormwater Facilities
2. Integrated Site Design Practices
3. Regional Approaches
4. Erosion Control BMPs
3.7.2.4 Option 4 — Obtain Letter From Impacted Downstream Property Owner
When downstream impacts are limited to a single adjacent property and consist of only private Stormwater
contributions, the Developer may obtain a notarized letter of permission from the affected property owner
acknowledging the specific and quantified impacts in lieu of mitigation. This option is not available for situations
where public runoff or public infrastructure is or would be involved. For situations involving public runoff or future
public runoff, easements would need to be acquired by the Developer. Easements would need to be sized per this
Manual.
3.7.3 Acceptable Downstream Conditions
As part of the Drainage Study, the downstream impacts of Development must be carefully evaluated for the two
focus areas of Streambank Protection and Flood Mitigation. The purpose of the Adverse Impact Assessment is to
protect downstream (and upstream) properties from increased flooding and downstream channels from increased
erosion potential due to upstream Development. The importance of the Adverse Impact Assessment is particularly
evident for larger sites or Developments that have the potential to dramatically impact downstream areas. The
cumulative effect of smaller sites, however, can be just as dramatic and, as such, following the integrated Focus
Areas is just as important for the smaller sites as it is for the larger sites.
The assessment, defined by the Development engineer, shall extend from the outfall of a proposed Development
to a point downstream where the discharge from a proposed Development no longer has a significant impact, as
defined in Table 3.1, on the receiving stream or storm drainage system. The City shall be consulted to obtain
studies, records and maps related to the National Flood Insurance Program and the availability of Flood Insurance
Studies and Flood Insurance Rate Maps (FIRMs) which may be helpful in this assessment. The assessment of
upstream and downstream impacts shall be a part of the Drainage Study for all Development that are platting one
acre or cause one (1) acre or more land disturbance. Items to be included in the Drainage Study can be found in
the Drainage Study Checklist.
• Detailed Drainage Study and calculations for existing, proposed, and fully developed conditions
(include digital submittal of hydrologic and hydraulic models, if utilized)
• Pre- and post -project conditions drainage area maps. Drainage area maps shall be of same scale and
limits for both pre- and post -project conditions. Drainage area maps must clearly delineate all
contributing areas draining to or through the entire site. Drainage area maps shall have topographic
contour intervals no greater than two (2) feet, and show flow paths for each area.
• Discharges at critical downstream design points, including structures, ROW, inlets, storm drains,
culverts, swales, channels, creeks, floodplains, and at locations where the conveyance cross section
or slope change.
• Separate analysis for each outfall from the proposed Development
Delineation of the Zone of Influence and determination of Adequate Outfall s.
• Final hydrology and hydraulics with all calculations and models, required mitigation and final stormwater
controls identified with sizes with the structural details and specifications.
• Written narrative supporting methodology and conclusions of analysis. Include a description of how
the items discussed in the Pre -Submittal meeting were addressed.
• Analysis must confirm that conditions regarding an acceptable outfall, as defined in Table 3.1, are met
at each outfall location.
• Adequate Outfali shall be a public drainage system, or a creek (flow line) draining more than ten times
the Development area.
City of Fort Worth Stormwater Criteria Manual 55
• Discharging runoff from Development to residential properties downstream of the development is not
allowed. Downstream public drainage facilities shall be designed and constructed to provide an
Adequate Outfall if none exist.
• Provide a summary of results confirming compliance. Include Land Use maps and Soil Type maps (unit
hydrograph method). Section 2.0 of the Hydrology Technical Manual provides additional information
on calculating the discharges and velocities, as well as determining the extent of the Adverse Impact
Assessment.
Provide applicable and relevant record drawings to support analysis assumptions.
• Adverse Impact Assessment shall extend to the limit of the Zone of Influence.
• Provide hydrologic and hydraulic work maps to document and illustrate the analysis and relevant
information. This shall include model cross sections with stationing that match the HEC-RAS model,
pre/post outfall and junction flows, stations, inundation limits for existing, proposed and ultimate
conditions, a legend, a scale, and 1 ft contours.
• If modelling includes reservoirs or stormwater detention facilities, then stage -storage discharge tables
and assumed outlet control structure dimensions must be included.
3.8 Stormwater Conveyance Systems
3.8.1 Introduction
Stormwater system design is an integral component of both site and overall stormwater management design. Good
drainage design must strive to maintain compatibility and minimize interference with existing drainage patterns;
control flooding of property, structures, and roadways for design flood events; and minimize potential environmental
impacts on stormwater runoff.
Stormwater collection systems must be designed to provide adequate surface drainage while at the same time
meeting other stormwater management goals such as water quality, streambank protection, habitat protection, and
flood mitigation.
3.8.1.1 Design
Unless regional detention is in place with a recorded SWFMA, or a master plan has been completed which indicates
a plan for reduced discharges which shall be constructed within 12 months of the Development beginning
construction; fully developed watershed conditions shall be used for determining runoff for the conveyance storm
and the flood mitigation storm.
Only those drainage facilities with criteria described by this manual, and its reference manuals, are allowed.
3.8.2 Subdivision Drainage Site Grading
An engineered overall site grading plan shall be submitted with the subdivision's paving and drainage plans. The
plan shall be consistent with the drainage area map included in the Drainage Study and Construction Plans. The
plan shall include flow arrows and Type A, 8, or C drainage for each lot within the subdivision as described in
Federal Housing Administration (FHA) Land Planning Bulletin No. 3, as amended (see Appendix E). Type 1 or 2
block grading as shown in the FHA information is preferred. Type 1 or Type 2 is required for lots proposing a rear
lot wall adjacent to a right of way or HOA draining to a right of way. Type 3 and block 4 grading is allowed only if:
a swale, flume or channel is constructed at the rear of the lot to intercept runoff; and
runoff from 3 or more lots is collected and conveyed within an underground drainage system, swale,
flume or channel contained within a dedicated easement.
The engineer may utilize berms and swales to redirect flows. Grass swales shall have a minimum slope of 2%
except where contained within a drainage easement, in which case a 1 % minimum slope is allowed. The engineer
shall provide more detailed information in addition to the lot grading type (A, B, or C) by indicating spot elevations
City of Fort Worth Stormwater Criteria Manual 56
on each lot. For Type B lots, side -yard swales shall extend from 5 ft (minimum) behind the rear building line to the
street, in order to collect runoff from the roof. Roof drains, if used along the rear building line of these lots, shall
use splash blocks to direct the runoff into the side swales.
The finished floor elevation and surrounding grading must conform to current building codes adopted by the City
and provide a minimum height of the finished floor of twelve (12) inches above the surrounding ground. Areas within
10' of the foundation shall be sloped to drain away from the foundation. Minimum slopes of 2% for structural
improvements and 5% for non-structural elements, respectively, must be maintained away from the footing. See
Figure 3.3.
If the site is complex and an overall site grading plan cannot be developed in accordance with the HUD standards,
an individual grading plan for each lot shall be submitted by an engineer prior to issuing the Building Permit. The
individual grading plans shall be coordinated with surrounding lots. For these complex plans, an "as -built" letter
shall be submitted prior to final inspection.
Subdivision phasing, design and construction shall be executed in such a way that downstream existing or occupied
SFR lots (e.g. Type A) do not receive runoff from upstream lots under construction (e.g. Type C). Where subdivision
boundaries or phase boundaries bisect a block, only block grading Type 1 and 2 shall be used.
The requirement to provide rear lot drainage facility for block grading type 3 is not required when all of the following
conditions are adhered to:
1. The swale shall be continuous and upstream side yard swales shall align (offset shall not exceed 1 foot) with
downstream side yard swales (this requires alignment of lot lines);
2. The swale extending between rear building lines does not exceed 5% slope and retaining walls are not
proposed;
3. The swale cross section shall minimize erosion potential;
4. The design shall include safeguards that ensure runoff is not lost to neighboring side lots and runoff is directed
to the rear swale as intended. For example more pronounced high points (6 inches minimum);
5. The swale through the backyard shall not be less than 3 inches in depth;
6. The vertical distance between the side yard swale flowline and finished floor elevation shall be no less than 9
inches at the upstream end of the swale on the upstream (type C) lot. Everywhere else, including on the
downstream lot (type A), the finished floor elevation shall have a minimum freeboard above the swale flow
line of 12 inches; and
7. The design engineer shall provide standard swale details for each subdivision at a cross section that
represents a worst case scenario for flow depth.
Four (4) inches of topsoil shall be provided for all disturbed areas not protected by impervious cover, in order to
sustain vegetation after construction has been completed.
s' I: al KiG�,T
Cr PLCOR APO
ADJAC NT G:70
r L004
ELEVATION
,.T,$.
Figure 3.3 Grading Requirements Next to Building Foundation
City of For: Worth Stormwater Criteria Manual 57
3.8.3 Hydraulic Design Criteria for Streets and Closed Conduits
3.8.3.1 Introduction
This section is intended to provide criteria and guidance for the design of on -site flood mitigation system
components including:
• Street and roadway gutters
• Stormwater inlets
• Parking lot sheet flow
• Storm drain pipe systems
3.8.3.2 Streets and Stormwater Inlets
Design Frequency
• Streets and roadway gutters: conveyance storm event • Low points: flood mitigation storm event
• Inlets on -grade: conveyance storm event • Combined Street ROW and storm drain
• Parking lots: conveyance storm event pipe systems: flood mitigation storm
event
• Storm drain pipe systems: conveyance storm event • Drainage and floodplain easements:
and flood mitigation storm event. flood mitigation storm event
Design Criteria
The iSWM Inlet Design Methodology (iSWM Hydraulics Technical Manual) is adopted as part of this Manual and
incorporated herein by reference. Under the City classification system, inlets have been classified into two major
groups namely; Inlets in Sumps and Inlets on Grade with Gutter Depression. The only curb inlets that are allowed
by the City are those in sumps and depressed inlets on grade. Grate inlets and combination inlets are not allowed.
Figures presented in the following sections shall be used to document all closed conduit calculations even if
calculations are performed on an acceptable computer program u.
A "rooftop" section shall be used for concrete streets and a parabolic section for asphalt streets. Note that the
nomograph in Figure 1.2 of the iSWM Hydraulics Technical Manual does not completely address cases where
the crown elevation is lower than the top of curb elevation. For those cases a combination of Figure 1.2 and 1.3 in
the iSWM Hydraulics Technical Manual can be used or a standard hydraulics program such as HEC-RAS or
FlowMaster can be applied.
The design storms required by the City are as follows:
Storm Sewer System
The design storm is the fully developed land use conditions for the flood mitigation storm for the combination of the
closed conduit and surface drainage system, to the limits of ROW.
Runoff from the fully developed conveyance storm must be contained within the permissible spread of water in the
gutter. The flood mitigation storm flow must be contained within the ROW. Adequate inlet capacity shall be provided
to intercept surface flows before the ROW capacity is exceeded. Note: the capacity of the underground system may
be required to exceed the conveyance storm in order to satisfy the flood mitigation storm criteria.
The 5-year closed conduit Hydraulic Grade Line (HGL) must be equal to or below the gutter line for pipe systems
and one (1) foot or more below the curb line at inlets. For sump conditions without an existing structural overflow,
the 100-year HGL must be one (1) foot below the curb at the inlet. For situations where no ROW exists, the 100-
year HGL must be below finished ground. The 100-year HGL will be tracked carefully throughout the system and
described in the hydraulic calculations tables provided herein and on the construction drawings.
City of Fort Worth Stormwater Criteria Manual 58
Inlets in Sumps
Curb opening inlets in sumps (Type CO-S) are addressed in Section 1.2.7 of the Hydraulics Technical Manual.
Drop inlets in sumps (Y Inlet) are addressed in Section 1.2.9 of the Hydraulics Technical Manual.
In sag or sump conditions, the storm drain and sump inlets shall be sized to intercept and convey a minimum of the
25-year storm and a positive structural overflow is required to provide for the remainder of the flood mitigation storm.
The positive overflow structure must be concrete or other acceptable non -earthen structure with a minimum bottom
width of four (4) feet extending from the sump inlet to the storm sewer outfall. It must be designed to pass at least
20 cfs with one (1) foot of freeboard from the top of curb to the adjacent finish floor elevations (minimum finish floor
elevations for all lots adjacent to said overflows must be shown on the plat).
All flumes that pass through sidewalks shall have a bolted -down, rust -proof, 3/8-inch (min.) steel plate with a
pedestrian -rated walking surface. The plate shall be recessed into the concrete sidewalk from face of curb to the
property line. The plate must be secured to the concrete with bolts and flush with the top of sidewalk. A center
support shall be added if the width of the flume exceeds two (2) feet. For wider flumes, additional supports shall be
added so that no span exceeds two (2) feet.
Structural overflow for inlets in sumps, shall be a concrete flume. Fences must be kept behind the curb line of the
flume and the flume placed in a drainage easement on a HOA lot. Where a structural overflow is not feasible, a
waiver must be requested. If no structural overflow is constructed, the sump inlets must be designed with a 50%
clogging factor (assume 50% of inlet opening is clogged). In a cul-de-sac where no structural overflow is feasible,
additional on -grade inlet capacity may be provided upstream of the sump in lieu of additional sump inlets.
An explanation of the Inlets in Sumps Calculation Sheet is included in is included in the following sections. The
calculations shall be included in construction plans and be consistent with Figure 3.5.
Inlets on Grade with Gutter Depression (Type CO-D, Figure 3.6)
The hydraulic efficiency of storm -water inlets varies with gutter flow, street grade, street crown, and with the
geometry of the inlet depression. The design flow into any inlet can be greatly increased if a small amount (5% to
10%) of gutter flow is allowed to flow past the inlet. When designing inlets, prevention of clogging or from
interference with traffic often takes precedence over hydraulic considerations. The computation sheet for Type CO-
D Inlet in Table 3.7 shall be used for calculations and included in the construction plans.
The depression of the gutter at a curb opening inlet (See Figure 3.6) below the normal level of the gutter increases
the cross -flow towards the opening, thereby increasing the inlet capacity. Also, the downstream transition out of the
depression causes backwater which further increases the amount of water captured. Depressed inlets shall be used
on all public streets and alleys. Recessed depressed inlets shall be used on all arterials.
The capacity of a depressed curb inlet on grade will be based on the methodology presented in Section 1.2.7 of
the iSWM Hydraulics Technical Manual.
Drop Inlets (Area Drains)
1. Drop inlets serving a drainage area of 10 to 25 acres will be designed with a 50% clogging factor.
2. Grading plans to direct flow into drop inlets will be included in the construction plans. Where earthen swales
or other means of collecting and directing runoff into drop inlets are needed, they shall be contained in
appropriately sized drainage easements.
3. Consideration shall be given to a structural overflow in the same manner as described for sump inlets.
4. Drop inlets shall be contained and centered in a 20 ft x 20 ft easement and located where they can be easily
accessed for inspection and maintenance by the City.
Headwalls
1, A headwall will be used to collect a drainage area of twenty-five (25 ac) acres or more flowing to one spot.
2. Areas that have been channelized or discharged from a storm drain system will use a headwall to reintroduce
the flow to a new storm drain system. These provisions do not apply to special multi -stage outlet structures
draining detention facilities.
City of Fort Worth Stormwater Criteria Manual 59
3.8.3.3 Stormwater Inlets Computation Sheets
Explanation of the Inlets in Sumps Computation Sheet (Type CO-S), Figure 3.4
In order to facilitate the computations required in determining the various hydraulic properties for curb opening inlets
and Y Inlets (drop inlets) in sumps, the Computation Sheet for Curb Opening and Drop Inlets shown in Figure 3.5
See Figure 3.4 for an illustration of a curb opening inlet.
Table Column Description:
Column 1 Inlet number and designation. Column 2 Slope of gutter in ft. per ft.
Column 3 Crown slope of pavement in ft. per ft. For parabolic crowns enter type of street section.
Column 4 Total gutter flow in cfs. For inlets other than the first inlet in a system, gutter flow is the sum of runoff
from contributing area plus carry-over flow from inlet or inlets upstream.
Column 5 Depth of gutter flow in feet from the spread of water calculations in Figure 1.2 (iSWM Hydraulics
Technical Manual), Section 1.2.4 orfrom direct solution of Manning's equation for triangular gutters.
Column 6 Depth of gutter depression in ft. (0.33 ft for a standard recessed curb inlet) Column 7 Depth
of water at inlet opening in ft. Column 5 plus Column 6.
Column 8 Capacity of curb opening inlet or drop inlet in cfs per ft. of length of opening or perimeter around
inlet from Figures 1.10, 1.12 or 1.14 in the iSWM Hydraulics Technical Manual or by direct solution.
Column 9 Assumed length of inlet opening or perimeter in feet. Column 10 Capacity of inlet in cfs. Column 8
times Column 9.
Column 11 Carry -Over flow passing inlet (into overflow swale) in cfs. Column 4 minus Column 10.
Column 12 Percent of flow captured by inlet. Column 10 divided by Column 4 times 100.
City of Fort Worth Stormwater Criteria Manual 60
wi
OF CURS
GUTTER LINE
- - - - - e- - - - - - - - =1=
. 4. -- a - ----
SECTION C-C 3'-0
CURB OPENING INLET IN SUMP (TYPE CO-S)
Figure 3.4 Type CO-S Inlet
9--0.416 t'. .
STD,
SECTION A -A
_ G6
- Ya
SECTION B-B
City of Fort Worth Stormwater Criteria Manual 61
SUMMARY SHEET
COMPUTATION
CAPACTIY OF
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FOR DETERMINING
DROP INLETS IN S�J/M
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[t) lh cakulailon9 i! carrya+of into oyertlox.
t2) include 25year flux and dep
City a For, Worth Storrnwater Criteria Manual
or
Figure 3.5 Computation Sheet for Curb Opening and prop Inlets
62
Explanation of the Inlets On Grade with Gutter Depression (Type CO-D, Figure 3.6) Computation
Sheet
In order to facilitate the computations required in determining the various hydraulic properties for Curb Opening
Inlets Type CO-D on grade (depressed), Figure 3.7, the Computation Sheet for On Grade Curb Inlets has been
prepared.
Table Column Description:
Column 1 Design Point for Inlet Column 2 Inlet number(s)
Column 3 Location of inlet by storm drain station number Column 4 Drainage area designation for
incremental area
Column 5 Drainage area size (acres)
Column 6 Runoff coefficient "C" provided in Table 3.5 located in Section 3.4.1 under "Types of Hydrologic
Methods"
Column 7 Time of concentration (minutes) Column 8 Longitudinal slope (ft/ft)
Column 9 Cross slope of the pavement (ft/ft)
Column 10 Cross slope of the gutter measured from the cross slope of the pavements. The cross slope is
equal to the gutter depression (in) divided by the width of the depressed gutter (in)
Column 11 Depth of gutter flow "yo" in approach gutter from spread of water determinations in the iSWM
Hydraulics Technical Manual, Figure 1.3, or from direct solution of Manning's equation for
triangular gutters: yo = 1.245 Qo3/8 (n3/8/So3/16) (1/z)3/8. When the crown is overtopped, a
composite analysis will be required.
Column 12 Spread of flow is calculated using Figure 1.2 in the iSWM Hydraulics Technical Manual or from
direct solution of Manning's Equation
Column 13 Equivalent cross slope is computed by using Figure 1.3 and 1.4 in the iSWM Hydraulics Technical
Manual to determine the ratio of flow in the depressed gutter section to the total flow
Column 14 Street crown section type (straight crown ["rooftop"] or parabolic)
Column 15 Manning's roughness coefficient (n) for pavement values located in Section 1.2.4 of the iSWM
Hydrologic Technical Manual Table 1.2
Column 16 5-year rainfall intensity (in/hr), From Section 5.0 in the iSWM Hydrology Technical Manual
Tarrant County Rainfall Table
Column 17 5-year runoff, Q=CAi (cfs)
Column 18 5-year carryover flow from upstream inlet (cfs)
Column 19 5-year total gutter flow (Column 17 + Column 18) (cfs)
Column 20 100-year rainfall intensity (in/hr), from Section 5.0 in the iSWM Hydrology Technical Manual
Tarrant County Rainfall Table
Column 21 100-year runoff, Q =CAi (cfs)
Column 22 100-year carryover flow from upstream inlet (cfs)
Column 23 100-year total gutter flow (Column 20 + Column 21) (cfs)
Column 24 Total right-of-way capacity (normally 2.5" over top of curb) (cfs)
Column 25 This indicates the controlling storm for inlet spacing, depending on which criteria (5-year in street
or 100-year in ROW) may be exceeded. This indicates whether the inlet is sized for the 5-year or
100-year flows
City of Fort Worth Stormwater Criteria Manual 63
Column 26 Length required for total interception of the design storm determination in Figure 1.8 of the iSWM
Hydraulics Technical Manual or by direct solution of Manning's Equation. Please note that the
example in Figure 1.8 does not consider inlet depression (slope).
Column 27 Actual length (L) in feet of the inlet which is to be provided (10', 15', or 20')
Column 28 Ratio of the length of inlet provided (L) to the length of the inlet required for 100% interception (LT).
Column 26 divided by Column 29
Column 29 The efficiency of the provided inlet determined by Figure 1.9 in the iSWM Hydraulics Technical
Manual.
Column 30 Discharge (Qi) in cubic feet per second in which the inlet in question actually intercepts in the design
storm. Column 19 or23 multiplied by Column 27
Column 31 Carry-over flow (q) is the amount of water which passes the inlet in a conveyance storm. A
substantial portion of the 5-year flow shall be picked up by the inlet. The carry-over flow shall be
accounted for in further downstream inlets.
Column 32 Carry-over flow (q) is the amount of water which passes the inlet in a flood mitigation storm. The
carry-over flow shall be accounted for in further downstream inlets and shall be reflected in the inlet
bypass flow (Column 17) in the Storm Drain Hydraulics Table, Figure 3.10 (minor variances may
occur due to travel time routing in the Hydraulics Table).
Column 33 Label of the upstream inlet from where the bypass flow originated.
Column 34 Include notes.
PLAN
a PROJECTED
GUTTER LINE M! kE�l.
r.
UPSTREAM SECTION B-B DOWIIlS1REAM
SECTION A -A
Y•
SEc,,, ON C-C
INLETS ON GRADE WITH GUTTER DEPRESSION (TYPE CO-D)
Figure 3.6 Type CO-D Inlet
City of Fort Worth Stormwater Criteria Manual 64
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59
3.8.3.4 Streets and ROW
Depth in the street shall not exceed top of curb or exceed maximum spread of water limits for the fully developed
conveyance storm. Limiting the spread of water allows one or more lanes to remain dry during the conveyance
storm and helps prevent hydroplaning of vehicles. The fully developed flood mitigation storm shall be contained
within the right-of-ways or easements.
Parking Lots
Parking lots shall be designed for the conveyance storm not to exceed top of curb, with maximum ponding at low
points of one (1) foot. The flood mitigation storm shall be contained on -site or within dedicated easements.
Spread of Water Limits
Inlets shall be placed at intersections, low points of grade (sag), and spaced so that the spread of water in the street
for the conveyance storm shall not exceed the guidelines provided below.
For all applications, the engineer/ Developer must use roadway sections as approved by the City. Road pavement
sections shall not be altered, super elevated or warped at intersections to avoid a sag condition. Sag conditions at
intersections (including minor/residential streets) shall be drained using an inlet.
If a roadway or thoroughfare is identified on a Master Thoroughfare Plan (MTP) then the following thoroughfare
spread width criteria shall apply.
The following spread of water values shall be used for the various types of streets.
Thoroughfare (Divided)
1. Permissible Spread of Water -The permissible spread of water in gutters of major divided thoroughfares shall
be limited so that one traffic lane on each side remains clear during the conveyance storm. Gutter flow shall
be based on maximum storm duration of 15 minutes. The flood mitigation storm shall be contained within the
ROW.
2. Conditions - Inlets shall be located at street intersections, at low points of grade, and where the gutter flow
exceeds the permissible spread of water criteria. Inlets shall be located, when possible, on side streets when
grades permit. In no cases shall the gutter depression at inlets exceed the standard. In super -elevated
sections, inlets placed against the center medians shall have no gutter depression. Inlets shall be placed to
intercept flow before it can cross the street.
Thoroughfares (Not Divided)
1. Permissible Spread of Water - The permissible spread of water in gutters of major undivided thoroughfares
shall be limited so that one traffic lane in each direction will remain clear during the conveyance storm.
2. Conditions - Inlets shall be located at street intersections, low points of grades, and where the gutter flow
exceeds the permissible spread of water criteria. Inlets shall be located on the side streets. In no case shall
the gutter depression at inlets exceed the standard.
3. Super -elevated Sections - Intercept gutter flow at the point of zero crossfall to prevent flow from crossing the
thoroughfare. Stormwater will not be allowed to cross major thoroughfares on the surface in valley gutters or
otherwise.
Collector Streets
1. Permissible Spread of Water - The permissible spread of water in gutters of collector streets shall be limited
so that one standard lane of traffic will remain clear during the conveyance storm.
1. Conditions - Inlets shall preferably be located at street intersections, low points of grade, and where the gutter
flow exceeds the permissible spread of water criteria. Inlets shall be located, when at all possible, on the side
streets when grade permits. In no case shall the gutter depression at inlets exceed the standard
Minor Streets (Residential)
City of Fort Worth Stormwater Criteria Manual 66
1. Permissible Spread of Water -The permissible spread of water in gutters for minor streets shall be limited by
the height of the curb for the conveyance storm. The flood mitigation storm shall be contained within the
R.O.W.
2. Conditions - Inlets shall be located at street intersections, low points of grade, and where the gutter flow
exceeds the permissible spread of water criteria, In no case shall the gutter depression at inlets exceed the
standard. Superelevation is not permitted on minor residential streets.
3.8.3.5 Storm Drain Pipe Design
This Section replaces the Closed Conduit System sections 1.2.9, most of 1.2.10, and 1.2.11 of the iSWM Hydraulics
Technical Manual. Storm Drain Outfalls located within section 1.2.10 (page HA-49) of the iSWM Hydraulics
Technical Manual are adopted and incorporated by reference into this Manual. Although, use of Table 1.10 may be
substituted by a detailed hydrologic and hydraulic study, it is the purpose of this Section of the manual to consider
the significance of the hydraulic elements of storm drains and their appurtenances to the storm drainage system.
This Section is generally excerpted from the 1967 City Design Criteria Manual.
Design Criteria
Design Frequency
Flood Mitigation storm, less any gutter, roadway, ROW, and flume flows.
Velocities and Grades
All storm drains shall be free draining and have a positive slope. Adverse slopes are not allowed.
Velocities in sewers are important because of the possibilities of excessive erosion on the storm drain inverts. Table
3.9 shows the maximum velocities for most storm drainage design. Supercritical flow in main lines shall not be
allowed for the conveyance and flood mitigation design storms. Storm drains in partial flow shall provide partial
flow depth and velocity calculations.
The maximum hydraulic gradient shall not produce a velocity that exceeds 20 feet per second (fps). Table 3.9 shows
the maximum velocities for most storm drainage design. Storm drains shall be designed to have a minimum mean
velocity flowing full at 2.5 fps. A main is defined as any pipe connected to two or more inlets.
Table 3.9 Velocity in Storm Drains
i]escripton - °
?Maximum Allowable Velocity
Culverts (All types)
15 fps
Storm Drains (Inlet laterals)
25 fps
Storm Drains (Mains)
20 fps
Storm drains shall operate with velocities of flow sufficient to prevent excessive deposits of solid materials,
otherwise objectionable clogging may result. The controlling velocity is near the bottom of the conduit and
considerably less than the mean velocity of the sewer. Storm drains shall be designed to have a minimum velocity
of 2.5 fps. Table 3.10, Minimum Grades for Storm Drains, indicates the minimum grades for concrete pipe (n =
0.013), flowing at 2.5 fps. The maximum slope for a lateral shall be 30%.
Table 3.10 Minimum Grades for Storm Drains
!Pipe Size,(Inches)
Coricrete'Pipe:(Slope•.ftlft):`%
21
0.0015
24
0.0013
City of Fort Worth Stormwater Criteria Manual 67
27 0.0011
30-96 0.0010
Materials
Reinforced concrete pipe (RCP): Only RCP is allowed under pavement for public storm drains in the City. For
pipe materials, other than RCP, only products on the Stormwater Approved Products List shall be used.
Polypropylene (PP) pipe products on the Stormwater Approved Products List may be used (up to a diameter of 60
inches) are allowed under pavement for public storm drains.
Profile -wall thermoplastic pipe (corrugated exterior with smooth interior), including High- Density Polyethylene
(HDPE) pipe and Corrugated PVC (CPVC), may be used in the following specific situations:
• Profile -wall thermoplastic pipe is permitted for use in driveway culverts (i.e. across roadside ditches).
Minimum allowable size shall be fifteen (15) inch internal diameter. Driveway permits will be required
from the TPW Street Management office.
• Profile -wall thermoplastic pipe may be allowed for certain off -pavement applications (using Request for
Waiver Form CFW-7).
• A request for waiver (Form CFW-7) shall be required for profile wall HDPE pipe up to thirty-six (36) inch
in diameter under publicly maintained concrete pavement in residential streets. No exceptions to this
rule will be considered for installation of HDPEICPVC pipe under other publicly maintained street
sections.
• Profile -wall thermoplastic pipe used as storm drain shall be installed in accordance with the appropriate
City Standard Detail, and with all manufacturer's specifications, and shall meet or exceed ASTM D-
2321, Standard Practice for Underground Installation of Thermoplastic Pipe for Sewers and Other
Gravity -Flow Applications. Note that Class I aggregate (City Standard Construction Specification
Documents -- Section 330510 (Old TPW Item 402.2) or NCTCOG Aggregate Grade 4) shall be required
for pipe embedment.
All contractors shall be trained and certified by the manufacturer prior to installing PPIHDPEICPVC pipe. A copy of
the training certification and proof of insurance shall be provided to the City before any work shall commence.
Roughness Coefficients
In selecting roughness coefficients for concrete pipe, consideration will be given to the average conditions at the
site during the useful life of the structure. Then' value of 0.015 for concrete pipe shall be used primarily in analyzing
existing sewers where alignment is poor and joints have become rough. For example, concrete pipe is being
designed at a location where it is considered suitable and there is reason to believe that the roughness would
increase through erosion or corrosion of the interior surface, slight displacement of joints or entrance of foreign
materials. A roughness coefficient will be selected which in the judgment of the designer, will represent the average
condition.
For the design of new public storm drain and culvert infrastructure, the "design n" value noted in Table 3.11 shall
be applied. Calculations for new public concrete or polypropylene pipe shall use a Manning's n of 0.013 and new
public concrete boxes shall use a Manning's n of 0.015.
Table 3.11 Manning's Coefficients for Storm Drain Conduits
type'ofStorm Drain s '
Manning's n
Concrete and Polypropylene Pipe (Design n = 0.013)
0.012 — 0.015
Concrete Boxes (Design n = 0.015)
0.012 — 0.015
City of Fort Worth Stormwater Criteria Manual 68
Corrugated Metal Pipe (CMP),
Pipe -Arch and Box
(Annular or Helical Corrugations - see Table 1.8 in iSWM Hydraulics Technical Manual.
0.022-0.037"
NOTE: CITY OF FORT WORTH DOES NOT ALLOW CMP FOR NEW CONSTRUCTION
Profile Wall Thermoplastic High Density Polyethylene (HDPE) or Polyvinyl Chloride (PVC).
(Design n = 0.013)
0.010-0.013
NOTE: Actual field values for conduits may vary depending on the effect of abrasion, corrosion, deflection, and joint
Ic onditions.
"Note: analysis of existing conditions may require a different value than the stated design coefficients.
Manholes
Manholes shall be located at intervals not to exceed 550 feet on mains and laterals. Manholes must be installed at
the upstream end of a storm drain main line, and where a storm drain leaves the pavement, unless the outfall is
within fifty (50) feet of the roadway and directly accessible via an obstacle free path and slopes less than 6%.
Manholes shall be located at street intersections, sewer junctions, changes of grade and changes of alignment.
When the storm drain is a concrete box instead of an RCP, four (4) foot diameter manhole risers may be installed
instead of vaults to provide access. In all cases, steps or ranges shall be installed from the ground surface to the
flowline of the pipe. Manholes shall not exceed 20 feet from rim elevation to flow line.
Full or Part Full Flow in Storm Drains
All storm drains shall be designed by the application of the Continuity Equation and Manning's Equation either
through the appropriate charts or nomographs or by direct solutions of the equations as follows:
Q = AV, and
1.486
z 1
Q = n A r3 $f, where
A = Cross -sectional area of pipe or channel.
V = Velocity of flow.
n = Coefficient of roughness of pipe or channel.
r = Hydraulic radius = AiP
Sf = friction slope in feet per foot in pipe or channel.
P = Wetted perimeter.
The size of pipe required to transport a known -quantity of storm runoff is obtained by substituting known values in
the formula. In practice, the formula is best utilized in the preparation of a pipe flow chart which interrelates values
of runoff, velocity, slope, and pipe geometry. With two of these variables known or assumed, the other two are
quickly obtained from the chart. A pipe flow nomograph for circular conduits flowing full graph is shown in iSWM
Hydraulics Technical Manual Figure 1.17. Equations for flow in conduits with other cross -sections are available in
the TxDOT Hydraulic Design Manual, dated October 2011, Chapter 6, and Section 2. For circular conduits flowing
partially full, graphs are presented in iSWM Hydraulics Technical Manual Figure 1.19a.
City of Fort Worth Stormwater Criteria Manual 69
Hydraulic Gradient and Profile of Storm Drain
In storm drain systems flowing full (or partially full as discussed above), all losses of energy through resistance with
flow in pipes, by changes of momentum, or by interference with flow patterns at junctions, must be accounted for
by accumulative head losses along the system from its initial upstream inlet to its outlet. The purpose of accurate
determinations of head losses at junctions is to include these values in a progressive calculation of the hydraulic
gradient along the storm drain system. In this way, it is possible to determine the water surface elevation which will
exist at each structure. The rate of loss of energy through the storm drain system shall be represented by the
hydraulic grade line, which measures the pressure head available at any given point within the system.
The HGL shall be established for all storm drainage design in which the system operates under a head. The HGL
is often controlled by the conditions of the sewer outfall; therefore, the elevation of the tailwater must be known.
The hydraulic gradient is calculated upstream from the downstream end, taking into account all of the head losses
that may occur along the line. The iSWM Hydraulics Technical Manual Table
1.10 provides a table of coincident design frequencies to assist with tailwater determination. The hydraulic
gradient shall begin at the higher of the tailwater or depth of flow in the pipe at the downstream end. An alternative
to the use of Table 1.10 is the performance of a detailed hydrologic and hydraulic study to determine coincident
tailwater.
All head losses shall be calculated if the storm drain system is in a subcritical flow regime whether the system is
flowing partially full or surcharged. Hydraulic calculations shall reflect partially full pipe where flow conditions would
not surcharge the pipe. Supercritical flow is not allowed in main lines for design flow rate. If the. system is in
supercritical regime the section shall be marked "SUPERCRITICAL FLOW." The presence of supercritical regime
shall be confirmed by analyzing from downstream as well as upstream.
The friction head loss shall be determined by direct application of Manning's Equation or by appropriate nomographs
or charts as discussed in the first paragraph of this Section. Minor losses due to turbulence at structures shall be
determined by the procedure of last section of this chapter ("Minor Head Losses at Structures) or in the iSWM
Hydraulics Technical Manual. All HGL calculations will be carried upstream to the inlet.
The HGL shall in no case be above the surface of the ground or street gutter for the conveyance storm. Allowance
of head must also be provided for future extensions of the storm drainage system. In all cases the maximum HGL
must be twelve (12) inches below top of curb at any inlet for the conveyance storm.
Minor Head Losses at Structures
Detailed information on the calculation of minor head losses at structures is provided in the proceeding section.
Figure 3.8 and Figure 3.9 provide details of minor losses for manholes, wye branches, and bends in the design of
closed conduits. Minimum head loss used at any structure shall be 0.10 foot.
Hydrologic Methodology with MWH 1nf6W6rks/SWMM Programs
InfoWorks SD by MWH Soft and the Stormwater Management Model (SWMM) family of programs have been
applied to several complex storm sewer systems in the City. These programs include several hydrologic subarea
runoff procedures. In addition to the hydrologic methods described in Section 3.4.1, the City accepts the following
procedures when applying these programs:
• With case -by -case approval by TPW, the SWMM Method in which the flow is routed using a single linear
reservoir, whose routing coefficient depends on surface roughness (Manning's n), surface area, ground slope and
catchment width.
• A version of the Unit Hydrograph Method in which a triangular unit hydrograph is developed using the time
to peak (time of concentration times 0.6), total runoff time (time to peak times 2.67) and the peak of the unit
hydrograph (2 divided by total runoff time). Refer to Appendix B, Stormwater computer models for more information.
Minor Head Losses at Structures Calculations
The following head losses at structures shall be determined for manholes, wye branches or bends in the design of
closed conduits. See Figure 3.8 and Figure 3.9 for details of each case. Minimum head loss used at any structure
shall be one -tenth (0.10) foot.
City of Fort Worth Stormwater Criteria Manual 70
Except as otherwise provided herein, the basic equation that shall be used, where there are both upstream and
downstream velocity, is set forth below with the various conditions of the coefficient "Kj" shown in Table 3.12.
Vi R29-)
hj = r29! K1 Where:
hj = Junction or structure head loss in feet.
Vi = Velocity in upstream pipe in fps.
Vz = Velocity in downstream pipe in fps.
Kj = Junction or structure coefficient of loss.
In the case where the manhole is at the very beginning of a line or the line is laid with bends or on a curve, the
equation used shall be the following without any velocity of approach.
VZ
h1 = Kj Zg
60' Bend - 85%; 45' Bend - 70%; 22-112° Bend - 40%
The values of the coefficient "Kj" for determining the loss of head due to obstructions in pipes are shown in Table
3.13 and the coefficients are used in the following equation to calculate the head loss at the obstruction:
v2
H1 = K, 22
City of Fort Worth Stormwater Criteria Manual 71
Table 3.12 Junction or Structure Coefficient of Loss
Case No.
Reference
Description of Condition'
Coefficient Kj
Figdre
1
3.8
Inlet on Main Line
0.50
II
3.8
Inlet on Main Line with Branch Lateral
0.25
III
3.8
Manhole on Main Line with 451 Branch lateral
0.50
IV
3.8
Manhole on Main Line with 901 Branch Lateral
0.25
V
3.8
Manhole on Main Line with no Branch
1.0
VI
3.9
451 Wye Connection or cut -in
0.75
VII
3.9
Inlet or Manhole at Beginning of Line
1.25
Conduit on Curves for 901
Vlll
3.9
Curve radius = diameter
0.50
Curve radius = 2 to 8 diam.
0.25
Curve radius = 8 to 20 diam.
0.10
Bends where radius is equal to diameter:
0.50
901 Bend
0.43
600 Bend 450 Bend
0.35
IX
3.9
22-112' Bend
0.20
Manhole on line with 600 Lateral
0.35
Manhole on line with 22111211 Lateral
0.75
• Where bends other than 90° are used, the 90* bend coefficient can be used with the following percentage factor applied:
60°- 85%, 45° -- 70%, 22.5° - 40%
Table 3.13 Head Loss Coefficients Due to Obstructions
A/Ao*
Kj
AIAo*
Kj
1.05
0.10
3.0
15.0
1.1
0.21
4.0
27.3
1.2
0.50
5.0
42.0
1.4
1.16
6.0
57.0
1.6
2.40
7.0
72.5
1.8
4.00
8.0
88.0
2.0
5.55
9.0
104.0
2.2
7.05
10.0
121.0
2.5
9.70
A/Ao = Ratio of area of pipe to area of opening at obstruction.
City of Fort Worth Stormwater Criteria Manual 72
The values of the coefficient "K�" for determining the loss of head due to sudden enlargements and sudden
contractions in pipes are shown in Table 3.14, and the coefficients shall be used with the following equation to
calculate the head loss at the change in section:
Hj = Kj zy , where,
V = Velocity in smaller pipe
Table 3.14 Head Loss Coefficients Due to Sudden Enlargements and Contractions
D-
i.
Sudden Enlargements K,
'
',� °;S.Oden Contractions K,
1.2
0.10
0.08
1.4
0.23
0.18
1.6
0.35
0.25
1.8
0.44
0.33
2.0
0.52
0.36
2.5
0.65
0.40
3.0
0.72
0.42
4.0
0.80
0.44
5.0
0.84
0.45
10.0
0.89
0.46
0.91
0.47
D21D9 = Ratio of larger to smaller diameter
City of Fort Worth 5tormwater Criteria Manual 73
NOTE: For Any Type of Inlet
p (STREET)
•
CURB
PLAN V�2 v;
e
CURB J 2 q r 2 A CUR8
GUTTER 43 CURB
BUTTER
gv�
SECTION
CASE
INLET ON MAIN LINE
L
PLAN — 2 a25 Vi
2
ea•T.wrd h�� 2� --
p p
22ire iftrw hJ' s2 -a25Y1
o a
SECTION
CASE III
MANHOLE ON MAINLINE
WITH 450 BRANCH LATERAL
— 03 V1
29 V
�9
�
a
(STREE) CURB
PLAN v 2 am v2
hT 3 — �
9 2g
Q4 RB �CpEmfia
C
SECTION
CASE 11
INLET ON MAIN LINE
WITH BRANCH LATERAL
PLAN
SECTION
CASE IV
MANHOLE ON MAINLINE
WITH OW BRANCH LATERAL
MINOR HEAD LOSSES DUE TO TURBULENCE AT STRUCTURES
Figure 3.8 Minor Head Losses at Structures (1 of 2)
`2--
02' %.
City of Fort Worth Stormwater Criteria Manual 74
�J (STREET) CURB
Q2' V2 �O --------0 N --- I a2-Dw
-s !
PLAN
v2 a2sv
----�hr«��20 s g
Q I
3
SECTION
CASE V
450 WYE CONNECTION
OR CUT IN
CASE VII
CONDUIT ON 90° CURVES
NOTE:
Head loss Bpplled at P.C. for "TV ofeurve.
V`1
Radius=Dia.of Pipe hd=a5029 Z
Radius = (2-8) DIa of Pipe h�- 025 2g
2
Radius - (8-20) Dta. of Pips hd- 0.10
IL
29
Radius = Greabr than 20 Di& of PiPa h a 0
' When curves otherthan 80° are used,
apply the fc llaw q factors to 90' curves.
80' curve 85%
45' curve7O%
02.V2
---s
2 PLAN
CURB Q CURB
GUTTER OPENING
1.25 V,2
Q
_2' V2
g�
SECTION
CASE VI
INLET OR MANHOLE AT
BEGINNING OF LINE
or
/ �GN
�ry s
CASE VIII
BENDS WHERE RADIUS IS
EQUAL TO DIAMETER OF PIPE
NOTE:
Head lass applied at � ginmg of bend
ST Bend bj-0.5�0 29
V 2
W Bend )=DA3
2
45• Bend hf 0.35 2Q
V 2
22 IV Bend h j�.20 V2
MINOR HEAD LOSSES DUE TO
TURBULENCE AT STRUCTURES
Figure 3.9 Minor Head Losses at Structures (2 of 2)
City of Fart Worth Stormwater Criteria Manual 75
Storm Drain Design Examples
All storm drains shall be designed by the application of the Manning Equation either directly or through appropriate
charts or nomographs. In the preparation of hydraulic designs, a thorough investigation shall be made of all existing
structures and their performance on the waterway in question.
An example of using the method used in the manual for the design of a storm drainage system is outlined below
and shown on Figure 3.10, Computations Sheet for Storm Drains. The design theory has been presented in the
preceding chapters with their corresponding tables and graphs of information.
Preliminary Design Considerations
• Prepare a drainage map of the entire area to be drained by proposed improvements. The scale of the
map shall not be less than 1 inch = 200 feet for project area although smaller scale maps for large
offsite drainage areas may be used. A maximum contour interval of 2 feet shall be provided.
• Prepare a layout of the proposed storm drainage system, locating all inlets, manholes, mains, laterals,
ditches, culverts, etc.
• Outline the drainage area for each inlet in accordance with present and future street Development.
• Indicate on each drainage area the code identification number and the direction of surface runoff by
small arrows. Provide a runoff table showing area, "C factor for each portion and composite "e", Tc, 15,
Q5, 1100 and Q100. Provide zoning classifications or land use data.
• Show all existing underground utilities.
• Establish design rainfall frequency.
• Establish minimum inlet time of concentration.
• Establish the typical cross section of each street.
• Establish permissible spread of water on all streets within the drainage area.
Plot profile of existing natural ground along the center line of the proposed storm drain.
• Extend downstream plan and profile beyond the end of the pipe to a point of acceptable outfall. The
flowline or invert of proposed outlet shall be equal to or slightly higher (<1 foot) than receiving stream.
Runoff Computations
Storm drain hydraulics are shown on the computation sheet provided on Figure 3.10. The first 18 columns of the
computation sheet cover the tabulation for runoff calculations:
Table Column Description
Column 1 Enter the downstream storm drain station number.
Column 2 Enter the upstream storm drain station number. This is the design point. Design shall start at the
farthest upstream point.
Column 3 Enter the distance (in feet) between the storm drain stations.
Column 4 Enter the designation of the drainage area(s) at the design point in Column 2 corresponding to the
designations shown on the drainage area map.
Column 5 Enter the area in acres for the drainage area identified in Column 4.
Column 6 Enter the total drainage area in acres within the system corresponding to storm drain station shown
in Column 2.
Column 7 Enter the runoff coefficient "C for the drainage area shown in Column 5.
Column 8 Multiply Column 5 by Column 7 for each area.
Column 9 Determine the total "CA" for the drainage system corresponding to the inlet or manhole shown in
Column 2.
Column 10 Determine inlet time of concentration (See Section 1.2.4 iSWM Hydrology Technical Manual).
Column 11 Determine flow time in the storm drain in minutes. The flow time is equal to the distance in Column
3 divided by 60 times the velocity of flow through the storm drain in ftlsec.
City of Fort Worth Stormwater Criteria Manual 76
Column 12 Total time of concentration in minutes. Column 10 plus Column 11. Note that time of concentration
only changes at a downstream junction with another drainage area(s), It remains the same from an
inlet or junction to the next inlet or junction picking up additional drainage areas. The junction of
two paired inlets with each other is not a downstream junction.
Column 13 The intensity of rainfall in inches per hour for the conveyance storm frequency from the appropriate
county rainfall table in the iSWM Hydrology Technical Manual.
Column 14 The intensity of rainfall in inches per hour for the flood mitigation storm frequency from the
appropriate county rainfall table in the iSWM Hydrology Technical Manual.
Column 15 The conveyance storm runoff in cfs. Column 9 times Column 13.
Column 16 The flood mitigation storm runoff in cfs. Column 9 times Column 14.
Column 17 The proposed inlet bypass during a flood mitigation storm. This shall correspond to the carry-over
flow "q" in Column 31 of the On -Grade Inlet Capacity Calculations Table (minor variances may
occur due to travel time routing in the Hydraulics Table).
Column 18 Design Discharge for the storm drain system ("Qpipe") in cfs. This shall be the greater of a
substantial portion of Q5 (Column 15) or Q100-Qbypass (Column 16 minus Column 17).
Hydraulic Design
After the computation of the quantity of storm runoff entering each inlet, the size and gradient of pipe required to
carry the design storm are determined. Any number of computer programs are available to provide design
assistance for pipe sizing to the engineer. However, storm drain hydraulics must be converted and reported in
Figure 3.10, Computation Sheet for Storm Drains. The hydraulic grade line (HGL) must be calculated for all storm
drain mains and laterals using appropriate head loss equations. In all cases, the storm drain HGL must remain
below grade and must be at least one (1) foot below top of curb at any inlet for the conveyance storm.
In partial flow conditions, the HGL represents the actual water surface within the pipe. Note that for partial flow
conditions, the velocity of the flow shall be calculated based on actual area of flow, not the full flow area of the pipe
or box.
Although the table is presented from upstream to downstream, the calculations are normally performed from the
outfall upstream to each inlet. Unless partial flow conditions exist, the beginning hydraulic gradient (Column 22 of
the last downstream section) must begin at either the top of pipe or at the hydraulic gradient of the receiving stream
at the coincident frequency provided in Table 1.10 of the Hydraulic Technical Manual, whichever is higher. It is
also acceptable to perform a detailed hydrologic and hydraulic study of the watershed of the receiving stream to
determine the connected outfall hydraulic gradient.
Table Column Description
Column 19 Enter the selected pipe size.
Column 20 Enter the appropriate Manning's roughness coefficient "n" from Table 3.18
Column 21 Enter the required slope of the frictional gradient (hydraulic gradient) determined by Manning's
equation. The pipe shall be designed on a grade such that the inside crown of the pipe coincides
or is below the HGL when flowing full. In a partial flow condition, the friction slope is the slope of
the water surface and shall follow the slope of the pipe.
Column 22 This is the beginning hydraulic gradient of the line. It is equal to the Design HGL (Column 31) for
the next downstream segment, or the beginning HGL of the system as described above.
Column 23 This is the upstream HGL before the structure and is calculated as Column 22 plus the friction loss
(Column 3 times Column 21).
Column 24 Velocity of flow in incoming pipe (main line) at the junction, inlet or manhole at the design point
identified in Column 2.
Column 25 Velocity of flow in outgoing pipe (i.e. the pipe segment being analyzed) at junction, inlet or manhole
at design point identified in Column 2.
Column 26 Velocity head of the velocity in Column 24.
City of Fort Worth Stormwater Criteria Manual 77
Column 27 Velocity head of the velocity in Column 25.
Column 28 Head loss coefficient "Kj", at junction, inlet or manhole at design point from Table 3.12, Table 3.13,
or Table 3.14, or from Figure 3.8 and Figure 3.9.
Column 29 Multiply Column 26 by Column 28.
Column 30 Head Loss at Structure. At a junction or change in pipe size, this is Column 27 minus Column 29.
At a bend or inlet, this is Column 27 times Column 28. In all cases this is 0.10' minimum.
EXCEPTION. In a supercritical flow regime with partial flow conditions, head losses are not
generated at upstream junctions. These may be designated as "SUPERCRITICAL PARTIAL
FLOW" in the head loss calculations, but must be supported by Froude Number in the comments
column. Any other proposed deviations from standard head loss calculations due to other unusual
flow regimes must be accepted by TPW on a case -by- case basis.
Column 31 Design HGL at the design point identified in Column 2. Column 23 plus Column 30. This is the
beginning HGL (Column 22) for any upstream pipe discharging into that junction.
Column 32 Invert elevation for the pipe being analyzed at the downstream storm drain station in Column 1.
Column 33 Invert elevation for the pipe being analyzed at the design point (upstream storm drain station) in
Column 2.
Column 34 Top of curb elevation at the design point in Column 2.
The above procedure is followed for each section of the storm drain. At the outfall, the hydraulic gradient of the line
must be at the same elevation or above the gradient of the conduit or channel receiving the storm runoff discharge.
See Sections 1.2.10 iSWM Hydraulics Technical Manual for guidance on outfall hydraulic gradients. In lieu of the
guidance in the Sections 1.2.10 iSWM Hydraulics Technical Manual it is acceptable to perform a detailed hydrologic
and hydraulic study of the watershed of the receiving stream to determine the connected outfall hydraulic gradient.
With the hydraulic gradient established for a particular line, considerable latitude is available for the physical
placement of the pipe flow line elevations. The inside top of the pipe must be on or below the hydraulic gradient,
thus allowing the pipe to be lowered where necessary to maintain proper cover and to minimize grade conflicts with
existing utilities.
City of Fort Worth Stormwater Criteria Manual 78
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3.8.4 Hydraulic Design Criteria for Channels, Culverts, Bridges and
Detention Structures
3.8.4.1 Introduction
This Section is intended to provide design criteria and guidance on several on -site flood mitigation system
components, including,culverts, bridges, vegetated and lined open channels, storage design, outlet structures, and
energy dissipation devices for outlet protection.
3.8.4.2 Open Channels
Design Frequency
The City requires that open channels are designed for the flood mitigation storm for fully developed watershed
conditions. Channels may be designed with multiple stages (e.g., a "low -flow" or "pilot" channel section for common
recurring flows, and a high flow section that contains the design discharge). The "low- flow" or "pilot" channel shall
convey 2% of the design flood mitigation storm discharge.
General Criteria
• If relocation of a stream channel is unavoidable, the cross -sectional shape, meander, pattern,
roughness, sediment transport, and slope shall conform to the existing conditions. Energy dissipation
will be necessary when existing conditions cannot be duplicated.
• Streambank stabilization shall be provided, as a result of any stream disturbance such as
encroachment and shall include both upstream and downstream banks as well as the local site.
• HEC-RAS or a hydraulic software program listed in Appendix B, Table B.1, Stormwater Modeling
Programs and Design Tools shall be used to confirm the water surface profiles in open channels.
• The final design of artificial open channels shall be consistent with the velocity limitations for the
selected channel lining. Maximum velocity values for selected lining categories are presented in Table
3.16 and Table 3. 17.
• Seeding and mulch shall only be used when the design value does not exceed the allowable value for
bare soil. Velocity limitations for vegetative linings are reported in Table 3.17. Vegetative lining
calculations and stone riprap procedures are presented in this Chapter and in Section 3.2 of the
Hydraulics Technical Manual.
• The design of stable rock riprap lining depends on the intersection of the velocity (local boundary shear)
and the size and gradation of the riprap material. More information on calculating acceptable riprap
velocity limits is available in Section 3.2.7 of the Hydraulics Technical Manual. The Gregory Method
shall be used for riprap design in the City.
Normal Depth (Uniform Flow)
For uniform flow calculations, the theoretical channel dimensions, computed by the slope -area methods outlined in
this manual, are to be used only for an initial dimension in the design of an improved channel. Exceptions will be
for small outfall channels when the following conditions are true:
• Completely contained on the private Development site for on -site drainage
• Where no off -site drainage easement is required (i.e. not crossing or adjacent to another property that
could be flooded if design storm occurs);
No nearby downstream restrictions that would produce a backwater affect at the design location; and
Where peak discharge is 10 cfs or less.
City of Fort Worth Stormwater Criteria Manual 80
Backwater Profile (Gradually Varied Flow)
The City requires a hand computed or HEC-RAS backwater/frontwater analysis on any proposed open channel to
determine the actual tailwater elevations, channel capacity and freeboard, and impacts on adjacent floodplains. If
a stream or creek has an effective FEMA model, the engineer will be required to use a computer program for the
analysis. If the current effective FEMA model for the stream is a HEC-2 model, the engineer has the option to either
use that model, or convert to HEC-RAS for analysis of proposed conditions.
Supercritical Flow Regime
Supercritical flow will not be allowed. However, for lined channels, the hand computed frontwater or HEC-RAS
analysis shall include a mixed -flow regime analysis, to confirm no supercritical flow occurs. The City requires that
the computed flow depths in designed channels be outside of the range of instability, i.e. depth of flow shall be at
least 1.1 times critical depth.
Channel Transitions or Energy Dissipation Structures or Small Dams
A HEC-RAS model or complete hand computed backwater analysis is a standard requirement for design of channel
transitions (upstream and downstream), energy dissipation structures, and small dams. A backwater analysis will
be required by the City, either hand computed or HEC-RAS, to determine accurate tailwater elevation, head losses,
headwater elevations and floodplains affected by the proposed transition into and out of an improved channel, any
on -stream energy dissipating structures, and small dams (less than six (6) feet). If the current effective FEMA model
for the stream is a HEC-2 model, the engineer has the option to either use that model, or convert to HEC-RAS for
analysis of proposed conditions. For larger dams, a hydrologic routing will be required, as well as hydraulic analysis,
to determine impacts of the proposed structure on existing floodplains and adjacent properties.
Lined Channels
1. Channels shall be trapezoidal in shape and lined with reinforced concrete in accordance with City Standards
and Specifications with side slopes not steeper than two (2) feet horizontal to one (1) foot vertical. The lining
shall extend to and include the water surface elevation of the 100-year design storm plus one (1) foot of
freeboard for the fully developed flood mitigation storm.
2. The channel bottom must be a minimum of eight (8) feet in width. (Overflow structures for storm sewer system
sumps may have a minimum bottom width of six (6) feet.)
3. The maximum water flow velocity in a lined channel shall be fifteen (15) feet per second except that the water
flow shall not be supercritical in an area from 100 feet upstream of a bridge to twenty-five (25) feet downstream
of a bridge. Hydraulic jumps shall not be allowed from the face of a culvert to fifty (50) feet upstream from that
culvert. In general, channels having supercritical flow conditions are discouraged.
4. Whenever flow changes from supercritical to subcritical, channel protection shall be provided to protect from
the hydraulic jump that is anticipated (see comment in Item 3, above).
5. The design of the channel lining shall take into account the super elevation of the water surface around curves
and other changes in direction.
6. A chain link fence six (6) feet in height shall be constructed on each side of the concrete or gabion channel
lining.
7. TPW may require a geotechnical study and/or an underground drainage system design for concrete lined
channels.
8. See City Standard Details for concrete lined channel section.
Earthen Channels
1. An earthen channel shall have a trapezoidal shape with side slopes not steeper than a 4:1 (horizontal and
vertical) ratio and a channel bottom at least twelve (12) feet in width.
2. One (1) foot of freeboard above the flood mitigation frequency fully developed water surface elevation must
be provided within all designed channels at all locations along the channel.
City of Fort Worth Stormwater Criteria Manual 81
3. The side slopes and bottom of an earthen channel shall be smooth, free of rocks, and contain a minimum of
six (6) inches of topsoil. The side slopes and channel bottom shall be re -vegetated with grass. No channel
shall be accepted for maintenance by the City until a uniform (e.g., evenly distributed, without large bare
areas) vegetative cover with a density of 70% has been established.
4. Each reach of a channel must have a ramp for maintenance access. Ramps shall be at least ten (10) feet
wide and have 15% maximum grade. Twelve (12) feet width is required if the ramp is bounded by vertical
walls.
5. Minimum channel slope is 0.0020 ft/ft (0.20%).
6. Erosion protection shall be provided at outfall to the receiving stream. The outfall of the earthen channel shall
meet the flowline of the receiving stream or a drop structure shall be provided.
7. Channel shall be designed for subcritical flow regime; supercritical flow must be contained in flow transition
armored channel sections
Roadside Ditches (Figure 3.15)
1. A roadside ditch ('rural") street section is not permissible, except when the City Plan Commission approves a
waiver to the Master Thoroughfare Plan standard street sections No median ditches are allowed.
2. The design storm for roadside ditches shall be the fully developed conditions for the flood mitigation storm.
The flood mitigation storm shall not exceed the right-of-way capacity defined as the natural ground at the right-
of-way line or top of roadside ditch, unless contained within a designated drainage easement.
Design Considerations
1. For grass lined sections, the maximum design velocity shall be as defined in Table 3.17 for the flood mitigation
design storm (Higher velocities are allowed if justified by a sealed geotechnical study).
2. A grass lined or unimproved roadside ditch shall have minimum two (2) feet bottom width and side slopes no
steeper than four horizontal to one vertical (4:1). There shall be a four (4) foot strip at maximum 2% cross
slope between the edge of pavement and the beginning of the ditch.
3. Minimum grades for roadside ditches shall be 0.0040 ft/ft (0.40%).
4. Manning's roughness coefficient for analysis and design of roadside ditches are presented in Table 3.15,
Table 3.16, and Table 3.17 and in Section 3.2.3 in the iSWM Hydraulics Technical Manual.
5. Maximum depth will not exceed four (4) feet from center -line of pavement (highest elevation in pavement
section).
6. If the ditch extends beyond the right-of-way line, ' an additional drainage easement shall be dedicated
extending at least two (2) feet beyond the top of bank. Utility easements must be separate and beyond any
drainage easements.
7. Hydraulic analysis of roadside ditches will require a HEC-RAS analysis for discharges greater than 10 cfs or
where conditions other than normal depth are anticipated.
Culverts in Roadside Ditches
1. Culverts will be placed at all driveway, roadway crossings, and pedestrian crossings.
2. Erosion protection will be provided at the upstream and downstream ends of all culverts.
3. The size of culvert used shall not create a head loss of more than two -tenths (0.20) foot greater than the
normal water surface profile without the culvert unless one (1) foot of freeboard within the roadside ditch is
provided.
4. Roadside ditch culverts will be no smaller than twenty-four (24) inches inside diameter or equivalent for
roadway crossings and fifteen (16) inches for driveway culverts.
5. A driveway culvert schedule shall be included on the face of the plat. It shall include, for each lot, culvert
flowline depth below top of pavement, number and size of pipe required, and horizontal distance from edge
of pavement to center of culvert (based on horizontal control requirements above).
City of Fort Worth Stormwater Criteria Manual 82
Transitions between urban and rural street drainage
1. Runoff from a curb and gutter street shall be collected in an inlet and discharged to downstream channel or
ditches via a storm drain pipe and headwall.
2. Runoff from a roadside ditch shall be collected using a headwall or Y-inlet, and connected into the urban storm
drain system.
Channel Velocity Limitations
Maximum allowable:
Lined Channels — Maximum velocities equal to fifteen (15 fps) feet per second.
Grass Lined Channels — Maximum velocities refer to Table 3.17. Higher values are allowed if they are
justified by a sealed geotechnical studylanalysis of soil type and conditions.
Critical Flow Calculations
Section 3.2.5 Critical Flow Calculations of the iSWM Hydraulics Technical Manual is for reference only.
Vegetative Design
Section 3.2.6 Vegetative Design of the iSWM Hydraulics Technical Manual is for reference only.
Stone Riprap Design
Riprap design is to be by Method #2 (Gregory Method) described in Section 3.2.7 of the iSWM Hydraulics
Technical Manual. A properly designed geotextile material is required under the granular bedding. The City
standard specifications identify the type of geotextile to be used. Regardless of computed thickness, the minimum
allowable riprap thickness is twelve (12) inches.
Section 3.2.7 of the iSWM Hydraulics Technical Manual, Stone Riprap Design Method #1: Maynard and Reese
is for reference only.
Grouted Riprap
The City will allow grouted stone riprap as an erosion control feature. However, the design thickness of the stone
lining will not be reduced by the use of grout. See the U.S. Army Corps of Engineers' design manual ETL 1110-2-
334 on design and construction of grouted riprap. The Gregory Method shall be utilized. Table 3.20 shall be used
to report results of the rip rap design utilizing the Gregory method.
Uniform Flow — Example Problems
Section 3.2.9 Uniform Flow — Example Problems in the iSWM Hydraulics Technical Manual is for reference
only.
Rectangular, Triangular, and Trapezoidal Open Channel Design
Section 3.2.11 Rectangular, Triangular, and Trapezoidal Open Channel Design — Example Problems in the
iSWM Hydraulics Technical Manual are for reference only.
City of Fort Worth Stormwater Criteria Manual 83
Table 3.15 City of Fort Worth Manning's Roughness Coefficients for Design
Lining Type -
-Manning's n*
Comments
Grass Lined
0.035
0.050
Use for velocity check
Use for channel capacity check (freeboard check)
Concrete Lined
0.015
Rock Riprap
0.040
n = 0.0395d501/6 where d50 is the stone size of which 50% of the
ample is smaller
Grouted Riprap
0.028
FHWA (Federal Highway Administration)
Note: For analysis, Manning's coefficients in chart above shall be used.
Table 3.16 Roughness Coefficients (Manning's n) and Allowable Velocities for Natural Channels
Max. Permissible
Channel Description " .e
:Maiining's n
Channel, Velocity,
MINOR NATURAL STREAMS
Fairly regular section:
1. Some grass and weeds, little or no brush
0.030
3.0 to 6.0
2. Dense growth of weeds, depth of flow materially greater than weed
0.035
3.0 to 6.0
height
3. Some weeds, light brush on banks
0.035
3.0 to 6.0
4. Some weeds, heavy brush on banks
0.050
3.0 to 6.0
5. Some weeds, dense willows on banks
0.060
3.0 to 6.0
For trees within channels with branches submerged at high stage,
0.010
increase above values by
Irregular section with pools, slight channel meander, increase above
0.010
values by
Floodplain -- Pasture
1. Short grass
0.030
3.0 to 6.0
2. Tall grass
0.035
3.0 to 6.0
Floodplain - Cultivated Areas
1. No crop
0.030
3.0 to 6.0
2. Mature row crops
0.035
3.0 to 6.0
3. Mature field crops
0.040
3.0 to 6.0
Floodplain -- Uncleared
1. Heavy weeds scattered brush
0.050
3.0 to 6.0
2. Wooded
0.120
3.0 to 6.0
MAJOR NATURAL STREAMS
Roughness coefficient is usually less than for minor streams of similar
Range from
description on account of less effective resistance offered by irregular
0.028 to 0.060
3.0 to 6.0
banks or vegetation on banks. Values of "n" for larger streams of
mostly regular sections, with no boulders or brush
UNLINED VEGETATED CHANNELS
Clays (Bermuda Grass)
0.035
5.0 to 6.0
Sandy and Silty Soils (Bermuda Grass)
0.035
3.0 to 5.0
City of Fort Worth Stormwater Criteria Manual 84
Table 3.16 Roughness Coefficients (Manning's n) and Allowable Velocities for Natural Channels
Max. Permissible
Channel Description
Manning's n
Channel Velocity
(ftls)
UNLINED NON -VEGETATED CHANNELS
Sandy Soils
0.030
1.5 to 2.5
Silts
0.030
0.7 to 1.5
Sandy Silts
0.030
2.5 to 3.0
Clays
0.030
3.0 to 5.0
Coarse Gravels
0.030
5.0 to 6.0
Shale
0.030
6.0 to 10.0
Rock
0.025
15.0
For natural channels with specific vegetation type, refer to Table 3.17 for more detailed velocity control.
Table 3.17 Maximum Velocities for Vegetative Channel Linings
Vegetation Type
Slope Rarige.(% )1
Maximum Velocity2 (ftls)
Bermuda grass
0-5
6.0
Bahia
4.0
Tall fescue grass mixtures3
0-10
4.0
Kentucky bluegrass
0-5
6.0
Buffalo grass
5-10
5.0
>10
4.0
Grass mixture
0-5'
4.0
5-10
3.0
Sericea lespedeza, Weeping
0-5 4
lovegrass, Alfalfa
3.0
nnuals5
0-5
3.0
Sod
4.0
Lapped sod
5.0
Do not use on slopes steeper than 10% except for side -slope in combination channel.
Use velocities exceeding 5 ft/s only where good stands can be maintained.
Mixtures of Tall Fescue, Bahia, and/or Bermuda
Do not use on slopes steeper than 5% except for side -slope in combination channel.
Annuals - used on mild slopes or as temporary protection until permanent covers are established.
Source: Manual for Erosion and Sediment Control in Georgia, 1996.
City of Fort Worth Stormwater Criteria Manual 85
Drainage Easement
Channel Width
See Fig. 3.12 > See Fig. 3.12
for Section i for Section
I
x' a I ate
Z . Z x
o o
m 0 N m
LL u, LL u_
CL o i o 0
X 10'-00 8'-0.
,(Min.) (Min.) Varies
- i
X 2.0% 2 V 1 2H:1 V X
w (Max.) (Max.) (Max) v
W �1!
LL
Z ] Z
Z Z
U U
0
1
1
Z0,,
x � x
Jr� 1
� x
"12'-09 (Min.) ramp width is required if hound by vertical wails.
Figure 3.11 Plan View - Trapezoidal Concrete Lined Channel
City of Fort Worth Stormwater Criteria Manual 86
6..CvwRLINK,
FENGE.Cirf P•)-
n.-minacle Easevyrt�
. 7ra ezoidal Concrete tined Cannel
Figure 3.12 $ection
View P
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FortWarih Starmwater Criteria Mane'!
87
Drainage
}�
1
See Fig. 3.14 I
lEasement
Channel IMdth
See Fig. 3.14
for Section i
I for Section
m a
m O
i
a ;Y
0 Im
I co
0 0
co
0 10
I
. w
I o a
I
W
o 10
i
I
12'-0°
(Min.)
i
-Varies
„
2 0% 4H:1V
I
12H:1V 112H:1V
4H:1V I
(Max.) (Max.)
(Mir:.) i (Min.)
(Max:)
u�tl
i
1u�3
[
1
,
I
.
1
1
oz 1
I
I
I
I
i
I
�
`12'-W (Min.) ramp width is required
if bound by vertical'walls.
Figure 3.13 Plan View -Trapezoidal Earthen Channel
City of Fort Worth 5tormwater Criteria Manual 88
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.2
Vegetative Design
A two-part procedure is required for final design of temporary and vegetative channel linings.
o Part 1: the design stability component, involves determining channel dimensions for low vegetative
retardance conditions, using Class D as defined in Table 3.18,
o Part 2: the design capacity component, involves determining the depth increase necessary to
maintain capacity for higher vegetative retardance conditions, using Class C as defined in Table
3.18.
If temporary lining is to be used during construction, vegetative retardance Class E shall be used for
the design stability calculations.
If the channel slope exceeds 10%, or a combination of channel linings will be used, additional
procedures not presented below are required. References include HEC-15 (USDOT, FHWA, 1986) and
HEC-14 (USDOT, FHWA, 1983).
Table 3.18 Classification of Vegetal Covers as to Degrees of Retardance
Retardance
Cover
f Condition
AWeeping
Lovegrass
Excellent stand, tall (average 30")
Yellow Bluestem Ischaemum
Excellent stand, tall (average 36")
Kudzu
Very dense growth, uncut
Bermuda grass
Good stand, tall (average 12")
Native grass mixture
Little bluestem, bluestem, blue gamma other
short and long stem Midwest grasses
Good stand, unmowed
B
Weeping lovegrass
Good stand, tall (average 24")
Laspedeza sericea
Good stand, not woody, tall (average 19")
Alfalfa
Good stand, uncut (average 11 ")
Weeping lovegrass
Good stand, unmowed (average 13")
Kudzu
Dense growth, uncut
Blue gamma
Good stand, uncut (average 13")
Crabgrass
Fair stand, uncut (10 — 48")
Bermuda grass
Good stand, mowed (average 6")
Common lespedeza
Good stand, uncut (average 11")
C
Grass -legume mixture:
summer (orchard grass redtop, Italian ryegrass,
and common lespedeza)
Good stand, uncut (6 — 8")
Centipede grass
Very dense cover (average 6")
Kentucky bluegrass
Good stand, headed (6 —12")
Bermuda grass
Good stand, cut to 2.5"
D
Common lespedeza
Excellent stand, uncut (average 4.5")
Buffalo grass
Good stand, uncut (3 — 6")
D
Grass -legume mixture:
all, spring (orchard grass, redtop, Italian
ryegrass, and common lespedeza)
Good stand, uncut (4 — 5")
Lespedeza sericea
After cutting to 2" (very good before cutting)
E
Bermuda grass
Good stand, cut to 1.5"
Bermuda grass
Burned stubble
Note: Covers classified have been tested in experimental channels. Covers were green and generally uniform.
Source: HEC-15, 1988,
City of Fort Worth Stormwater Criteria Manual 91
3.8.4.3 Culverts
Design Frequency
Culverts are cross drainage facilities that transport runoff under roadways or other improved areas.
Culverts shall be designed for the fully developed conditions flood mitigation storm or in accordance
with TxDOT requirements, if in the TXDOT right of way. Consideration when designing culverts
includes: roadway height, tailwater or depth of flow, structures and property subject to flooding,
emergency access, and road replacement costs.
The flood mitigation storm shall be routed through all culverts to confirm building structures (e.g.,
houses, commercial buildings) are not flooded or increased damage does not occur to the roadway or
adjacent property for this design event.
For multiple barrel culverts the City requires the placement of one of the barrels at the flowline of the
stream with the other barrels at a higher elevation to create a single flow path for lower flow and reduce
sediment and debris accumulation. The low -flow portion of the low barrel(s) shall convey at least 2% of
the design 1 DO -year discharge.
Velocity Limitations
The maximum velocity shall be consistent with channel stability requirements at the culvert outlet.
Refer to Table 3.9 for maximum allowable velocities for reinforced concrete pipe. Outlet protection shall
be provided where discharge velocities will cause erosive conditions.
To ensure self-cleaning during partial depth flow, a minimum velocity of two and a half (2.5 fps) feet per
second is required for the streambank protection storm when the culvert is flowing partially full.
Length and Slope
The maximum slope using concrete pipe is 10% before pipe -restraining methods must be taken.
Maximum vertical distance from throat of intake to flowline in a drainage structure is ten (10) feet.
Drops greater than four (4) feet will require additional structural design.
Headwater Limitations
The allowable headwater is the depth of water that can be ponded at the upstream end of the culvert
during the design flood, which will be limited by one or more of the following constraints or conditions:
o Headwater will be non -damaging to upstream property.
o Culvert headwater plus twelve (12) inches of freeboard shall not exceed top of curb or pavement
for low point of road over culvert, whichever is lower.
o Ponding depth will be no greater than the elevation where flow diverts around the culvert.
o Elevations will be established to delineate floodplain zoning.
Either the headwater shall be set to produce acceptable velocities or stabilization/energy dissipation
shall be provided where these velocities are exceeded.
The constraint that gives the lowest allowable headwater elevation establishes the criteria for the
hydraulic calculations.
Tailwater Considerations
If the culvert outlet is operating with a free outfall, the critical depth and equivalent hydraulic grade line
shall be determined.
For culverts that discharge to an open channel, the stage -discharge curve for the channel must be
determined. See Section 2. 1.4 of the Hydraulics Technical Manual on methods to determine a stage -
discharge curve.
If an upstream culvert outlet is located near a downstream culvert inlet, the headwater elevation of the
downstream culvert will establish the design tailwater depth for the upstream culvert.
City of Fort Worth Stormwater Criteria Manual 92
If the culvert discharges to a lake, pond, or other major water body, the expected high water elevation
of the particular water body will establish the culvert tailwater.
Other Criteria
• In designing debris control structures, the Hydraulic Engineering Circular No. 9 entitled Debris Control
Structures is adopted and shall be used.
• If storage is being assumed or will occur upstream of the culvert, refer to Section 2.0 of the Hydraulics
Technical Manual regarding storage routing as part of the culvert design.
• Culvert skews shall not exceed 45 degrees as measured from a line perpendicular to the roadway
centerline without approval.
• The minimum allowable pipe diameter for a roadway culvert shall be twenty-four (24) inches. A
minimum diameter of fifteen (15) inches may be used for driveway culverts.
Erosion, sediment control, and velocity dissipation shall be designed in accordance with Section 4.0
of the Hydraulics Technical Manual.
The City requires a backwater analysis using HEC-RAS to evaluate the proposed structure for final
design.
Corrugated Metal Pipe Culvert
Corrugated Metal Pipe (CMP) is not allowed in the City and shall not be used for any public storm drain or culvert.
Nomographs
Nomographs are not allowed by City for final sizing of culverts. The reference for nomographs is FHWA HDS-5. A
backwater analysis using HEC-RAS is required.
Culvert Design Example
Section 3.3.5 Culvert Design Example of the iSWM Hydraulics Technical Manual is adopted by reference with
the following modification: the nomograph procedure is acceptable for preliminary sizing only.
Design Procedures for Beveled -Edged Inlets
Section 3.3.6 Design Procedures for Beveled -Edged Inlets of the iSWM Hydraulics Technical Manual is
adopted by reference with the following modification: the nomograph procedure is acceptable for preliminary sizing
only.
Flood Routing and Culvert Design
Refer to Section 3.3.7 Flood Routing and Culvert Design of the iSWM Hydraulics Technical Manual.
Erosion, Sediment Control, Velocity Dissipation
Section 3.2.7 iSWM Hydraulics Technical Manual Gregory Method is adopted by reference for culvert outfall
protection for riprap sizing, gradation, and bedding. Use Section 4.0 of that manual for spatial dimensions of riprap
and other energy dissipation design.
City of Fort Worth Stormwater Criteria Manual 93
3.8.4.4 Bridges
Design Frequency
Bridges are cross drainage facilities with a span of twenty (20) feet or larger. Bridges shall be designed for the
flood mitigation storm for fully developed watershed conditions.
Design Criteria
A backwater analysis using HEC-RAS is used for final design of the proposed structure. For bridges up
to 100 feet long, measured from abutment to abutment, two (2) feet of freeboard is required from design
water surface elevation to low chord. For a bridge greater than one hundred (>100) feet long, one (1)
foot of freeboard is required. The Bridge Hydraulics Documentation Checklist must be completed and
submitted to the City with the Drainage Study and construction plans. Backwater analysis will be
required using HEC-RAS, for any proposed bridge, to determine accurate tailwater elevations,
velocities, head losses, headwater elevations, profiles and floodplains affected by the proposed
structure. If the current effective FEMA model is a HEC-2 model, the engineer has the option to either
use that model, or convert to HEC-RAS for analysis of proposed conditions.
The contraction and expansion of water through the bridge opening creates hydraulic losses. These
losses are accounted for through the use of loss coefficients. Table 3.19 gives required values for the
Contraction (Kc) and Expansion (Ke) Coefficients for the most commonly encountered design
situations.
Additional design information is located in Section 3.4 of the Hydraulics Technical Manual.
Table 3.19 Recommended Loss Coefficients for Bridges
Transition Type
Contraction (Kc)
Expansion (Ke)
No losses computed
0.0
0.0
Gradual transition
0.1
0.3
Typical bridge
0.3
0.6
Severe transition
0.6
0.8
3.8.4.5 Detention Structures
Design Frequency
The streambank protection, conveyance, and flood mitigation storms for the 24-hour storm duration shall be used
for design of detention structures. Analysis shall consider both the existing watershed plus developed site conditions
and fully developed watershed conditions.
Design Criteria
Stormwater detention shall be provided to mitigate increased peak flows in the City waterways in specific
circumstances as defined below. The purpose of the mitigation is to mitigate downstream flooding impacts from
upstream Development. In some instances, detention may be shown to exacerbate potential flooding conditions
downstream. Therefore, the Zone of Influence criteria shall be applied in addition to these criteria. Design data for
dams will be submitted to the City on Form CFW-5, Preliminary and Final Dam Maintenance Emergency Action
Plan,
1. Detention Basins shall be required when downstream facilities within the Zone of Influence are not adequately
sized to convey a design storm based on current City criteria for hydraulic capacity.
2. Proposed stormwater discharge from a site shall not exceed the calculated discharges from existing
conditions, unless sufficient downstream capacity above existing discharge conditions is available.
City of Fort Worth Stormwater Criteria Manual 94
3. The Modified Rational Method (see Section 1.5.2 in the iSWM Hydrology Technical Manual) is allowed for
planning and conceptual design for watersheds of 200 acres and less. For final design purposes the Modified
Rational Method is allowed only for watersheds of 25 acres and less. Modified Rational Method is not
acceptable for basins in series. Note that the only Modified Rational Method allowed is defined in Section 1.5
in the iSWM Hydrology Technical Manual. The purpose of the preliminary plat is to denote future
improvements that shall be required. Sizing is not exact and may result in undersized detention/retention pond
requirements.
4. Detention Basins draining watersheds over 25 acres shall be designed using a detailed unit hydrograph
method acceptable to the City of Fort Worth. The acceptable methods are Snyder's Unit Hydrograph (greater
than one hundred (>100) acres) and SCS Dimensionless Unit Hydrograph (any size). The SCS method is
also allowed for basins with watersheds less than 25 acres (see Table 1.2 in the iSWM Hydrologic Technical
Manual).
5. Detention Basins shall be designed for the Stream bank Protection, Conveyance, and Flood Mitigation storms
for the 24-hour storm duration.
6. Detention basin embankments shall have a ten (10) foot crown width. A minimum 10' easement shall be
provided from the outside top of bank. For access to the pond bottom, provide a maintenance ramp of at least
ten (10) feet wide with a maximum slope of 15%. Twelve (12) feet width is required next to vertical walls.
Trees shall not be planted on the crown.
7. Detention Basins shall be designed with at least one ten (10) foot wide maintenance access location, with a
15% maximum grade. Trees shall not be planted with the 10' access.
8. A freeboard of one (1) foot is required for all detention ponds.
9. Grassed side slopes shall be 4:1 or flatter and less than twenty (20) feet in height. Slopes protected with
concrete riprap shall be no steeper than 2:1. A detailed geotechnical investigation and slope stability analysis
is required for grass and concrete slope pavement slopes greater than twelve (12) feet in height. See final
stabilization requirements in Section 4.3.1. Trees shall not be planted on pond side slopes.
10. A calculation summary shall be provided on construction plans. For detailed calculations of unit hydrograph
studies, a separate report shall be provided to the City for review and referenced with date, engineer and title
on the construction plans. Stage -storage -discharge values shall be tabulated and flow calculations for
discharge structures shall be shown on the construction plans.
11. An emergency spillway shall be provided at the 100-year maximum storage elevation with sufficient capacity
to convey the fully urbanized flood mitigation storm assuming blockage of the closed conduit portion outlet
works with six (6) inches of freeboard. Spillway requirements must also meet all appropriate state and federal
criteria. Design calculations will be added for all spillways.
12. All detention basins shall be stabilized against significant erosion and shall include a maintenance plan.
13. A landscape plan shall be provided for all detention ponds.
14. Stormwater Facility Maintenance Agreement (SWFMA) is required for all detention and retention facilities.
15. Detention basin outlet structures shall be designed to minimize the likeliness of clogging and shall include
features to prevent activation of the emergency spillway if such activation would create an uncontrolled
discharge. The use of orifice plates or non-standard structures is not allowed.
16. Dry detention basins are sized to temporarily store the volume of runoff required to provide flood protection
up to the flood mitigation storm. Dry detention basin design shall consider multiple uses such as recreation.
Pilot channels shall follow the edges of the basin to the extent practical. The bottom of the basin shall have a
minimum grade of 1% per Figure 3.17, although swales may have minimum grades of 0.5%. Concrete flumes
shall be provided for slopes less than 0.5% and may have slopes as shallow as 0.2%. They shall be at least
six (6) feet wide. Trees shall not be planted along swales or pilot channels. A minimum of 10' distance
between the swale/channel flow line to trees is required.
17. Extended detention dry basins are sized to provide extended detention of the streambank protection volume
over 24 hours and can also provide additional storage volume for normal detention (peak flow reduction) of
the flood mitigation storm event.
City of Fort Worth Stormwater Criteria Manual 95
18. Routing calculations must be used to demonstrate that the storage volume and outlet structure configuration
are adequate. See Section 2.0 of the Hydraulics Technical Manual for requirements on the design of detention
storage.
19. Stormwater lift stations are not allowed.
20. Underground detention ponds are not allowed for public runoff.
21. State TCEQ rules and regulations regarding impoundments shall be followed. According to current (2009)
guidelines, dams fall under the jurisdiction of the TCEQ Dam Safety Program if they meet one or more of the
following criteria (See NCTCOG iSWM Program Guidance -- Dam Safety and Water Rights):
• they have a height greater than or equal to 25-feet and a maximum storage capacity greater than or
equal to fifteen (15) acre-feet;
• they have a height greater than six (6) feet and a maximum storage capacity greater than or equal to
fifty (50) acre-feet;
• they are a high or significant hazard dam as defined in the regulations (relating to Hazard Classification
Criteria), regardless of height or maximum storage capacity; or
• they are used as a pumped storage or terminal storage facility.
22. In accordance with Texas Water Code §11.142, all permanent surface impoundments not used solely for
domestic or livestock purposes must obtain a water rights permit from the TCEQ. A completed permit for the
proposed use, or written documentation stating that a permit is not required, must be obtained.
23. Underground stormwater detention facilities shall:
Not be allowed for conveyance of public runoff;
• Comply with guidance in the NCTCOG iSWM Technical Manuals;
• Provide adequate access to allow for required cleaning, maintenance and inspection; and
• Be constructed of RCP, PP, CMP, or HDPE and allow for cleaning by a jetter hose.
Items 7, 10, 12, 13, 24 and 25 also apply to amenity ponds.
City of Fort Worth Stormwater Criteria Manual 96
(Min.) I I B
1!2
A
4H:1V V
4 iH V
_
--Now (Mqx.) 2V
.(Mq.)
(Min.) SttrructN-_ IN
EmerOency--
Spii _ , Y
4H:1V
(Max.)
! � Outfai[
! l Strudure
Erosion Protection
(Min.) ramp width B as Necessary
is required rf bound p VfEW
by-vertical walls:
N.T.S.
•101-0" 10'-0"
(Min.) (Min.) 100 Yr. WSEL (Min.)
4H:1 V
(Max)
1.4'l0 {Min.) 4H:1V ,
(Max.)
SECTION A A
K.T.S.
1' of Freeboard (Min.) 100 Yr. WSiFL
4 naL AAir►.�
knnax.)
SECTION B-B
N.T.S:
Figure 3.16 Dry Detention Pond Schematic
(15.00W Max.)
City of Fort Worth Stormwater Criteria Manual 97
Min(Min. ° B
(.)
{rQi
Er
A
o
A
�L
Concrete
Pi[ot Channel
m
4H:1V
61-00
(0.20% Min.)
o c Z
(Max)
(Min.)
.. m
�
G
11
Retaining Wail (Variance Required)
Emergancy
I i
10'-0° Crown
Spillway
Width'(Min.)
i
}�
S ctulne
Erosion Protection
'1Z4" (Mln.) ramp width B *—j as Neoessary
Is required If bound PLAN VIEW
by vertical wails.
N.T.S.
w 1 "
(Min) Foln.) ef 100 Yr. WSEL (Mi-0)
1.0% (Min.)_ 411:1V
(Malt.) (Max.)
SECTION A A RetainingWall
N.T.S. (Variance Rquired)
10'-0"
(Min.) 1' of FneeboOd (Min.) 100 Yr. WSEL
Emergency
'SpUFway = 1.0% (Min.)
�4H:1V 4H:1V
(Max.) (Max.)
Retain[ngg Wall SECTION B-B
(Variance Required) N.T.S. (15.04o Max.)
City of Fort Worth Stormwater Criteria Manual 98
Outlet Structures
Extended detention (ED) orifice sizing is required in design applications that provide extended detention for
downstream streambank protection or the ED portion of the water quality protection volume. The release rate for
both the WQv and SPv shall discharge the ED volume in a period of 24 hours or longer. In both cases an extended
detention orifice or reverse slope pipe must be used for the outlet. For a structural control facility providing both
WQv extended detention and SPv control (wet ED pond, micropool ED pond, and shallow ED wetland), there will
be a need to design two outlet orifices — one for the water quality control outlet and one for the streambank protection
drawdown.
Design Frequency
• Water quality storm
• Streambank protection storm
• Conveyance storm
• Flood mitigation storm
Design Criteria
• Estimate the required storage volumes for streambank protection, conveyance storm, and flood
mitigation.
• Design extended detention outlets for each storm event.
• Outlet velocities shall be within the maximum allowable range based on channel material as shown in
Table 3.16 and Table 3.17.
Design necessary outlet protection and energy dissipation facilities to avoid erosion downstream from
outlet devices and emergency spillway(s).
• Perform buoyancy calculations for the outlet structure and footing. Flotation will occur when the weight
of the structure is less than or equal to the buoyant force exerted by the water.
Additional design requirements are located in Section 2.2 of the Hydraulics Technical Manual.
Energy Dissipation
Design Frequency
All drainage system outlets, whether for closed conduits, culverts, bridges, open channels, or storage facilities, shall
provide energy dissipation to protect the receiving drainage element from erosion,
• Conveyance storm
• Flood mitigation storm (100-year)
• Assume fully developed watershed conditions
Design Criteria
• Energy dissipaters are engineered devices such as rip -rap aprons or concrete baffles placed at the
outlet of stormwater conveyance systems for the purpose of reducing the velocity, energy and
turbulence of the discharged flow.
• Erosion at culvert, pipe and engineered channel outlets are common. Determination of the flow
conditions, scour potential, and channel erosion resistance shall be standard procedure for all designs.
All culvert and pipe outfalls, and channel transitions shall be provided with energy dissipation and
erosion control.
• Energy dissipaters shall be employed at all concentrated outfalls no matter the velocity.
• Energy dissipation devices or controls shall also be employed in downstream channels whenever the
velocity of flows leaving a stormwater management facility exceeds the erosion velocity of the
downstream area channel system.
• Energy dissipater designs will vary based on discharge specifics and tailwater conditions.
• Outlet structures shall provide uniform redistribution or spreading of the flow without excessive
separation and turbulence.
• Energy dissipaters are a required component of the iSWM Construction Plan.
City of Fort Worth Stormwater Criteria Manual 99
Recommended Energy Dissipaters for outlet protection include the following:
• Riprap apron
Riprap outlet basins
• Baffled outlets
• Grade Control Structures
Refer to Section 4.0 of the Hydraulics Technical Manual and the Federal Highway Administration Hydraulic
Engineering Circular No. 14 entitled. Hydraulic Design of Energy Dissipaters for Culverts and Channels, for
the design procedures of other energy dissipaters.
Channel Transitions, Energy Dissipation Structures, or Small Dams
A backwater analysis is required by the City, using HEC-RAS or the computer programs listed in Appendix B. The
backwater analysis shall determine accurate tailwater elevation and velocities, head losses, headwater elevations,
velocities and floodplains affected by the proposed transition into and out of: 1) an improved channel; 2) any on -
stream energy dissipating structures; and 3) small dams (less than six (6) feet). If the current effective FEMA model
for the stream is a HEC-2 model, the engineer has the option to either use that model, or convert to HEC-RAS for
analysis of proposed conditions. For larger dams, a hydrologic routing will be required, as well as hydraulic analysis,
to determine impacts of the proposed structure on existing floodplains and adjacent properties.
Examples of Open Channel Transition Structures
Examples of open channel transition structures are included in the drawings in Appendix C — City of Fort Worth
Miscellaneous Details and Specifications Straight Drop Structure, Bureau of Reclamation Baffled Chute (Basin IX).
The computer program associated with FHWA Hydraulic Engineering Circular No. 14 (HEC-14) is "HY8" dated
March 2012. This program provides the engineer a tool to aid in the design, selection, and sizing of a broad range
of energy dissipaters including some of those listed in Section 4.0 of the iSWM Hydraulics Technical Manual.
Channel transition structures and "drop" structures shall be designed in accordance with the iSWM Hydraulics
Technical Manual and HEC-14.
Stone Rip Rap Design — Gregory Method Results Table
Table 3.21 Rock Rip Rap Sizing — Gregory Method shall be used to report results of the Gregory channel riprap
design method. Table 3.20 shall be used to report the results of the Gregory Culvert Outfall Protection Method. A
properly designed bedding layer is required under the granular bedding.
Table 3.20 Rock Riprap Sizing — Culvert Outfall Protection
From Section 3.2.7 iSWM Hydraulics Technical Manual Se tember 2014
Determine DSO size of riprap stone (size at which 50% of the gradation is
Units
Size by Frequency
Select Lar est)
finer weight):
100- ear
5-year
1- ear
= outfall velocity
ftlsec
y5 = saturated surface dry (SSD) specific weight of stone (150-175 Iblft')
Iblft'
V
SO = YW 11/2
1.8[2y(YsYW )]
Where: yW = 62.4 Ib/ft', and g = 32.2 fls2
feet
If ys is 160 Ib/ft3 or greater, then the equation may reduce to: DSO =
�Tvl
Maximum d50 (controlling size)
inches
City of Fort Worth Stormwater Criteria Manual 100
Table 3.21 Rock Riprap Sizing — Gregory Method
From Section 3.2.7 iSWM Hydraulics Technical Manual. September 2014
Step 1: Calculate Boundary Shear:
Units
Size bv
re uenc(Select
100-year
5-year
1-year
Q = peak discharge
cfs
b = bottom width of channel
feet
= depth of peak flow
feet
S = specific weight of stone (150-175 Ib/ft')
Ib/ft3
= cross -sectional area of flow
ft2
P = wetted perimeter
feet
R = hydraulic radius of channel = AIWP
feet
S = slope of energy gradient
ft
o = average tractive stress on channel bottom
= yw*R`S (yw = 62.4 Iblft3)
lblftz
(P = Angle of side slope (140 for 4:1 slopes)
degrees
O = Angle of repose of rock, usually 40')
degrees
o' = average tractive stress on channel side slopes
= To[1-(Sin20/Sin2O)]1/2
lblft'
Step 2; Determine the tractive stress in a bend in the channel:
= the greater of To or To' from above
Ib/ftz
r = centerline radius of bend (10000' if straight)
feet
= water surface width at upstream end of bend
feet
b = local tractive stress in bend = 3.15T(r/w)-112
Ibift2
Step 3: Determine D50 size of riprap stone (size at which 50% of the gradation
is finer weight):
= Design shear stress (greatest of To, To' or Tb)
Iblft2
D50 = required average stone size = T10.04F]s-Fw)
feet
Maximum d50 (controlling size)
inches
Step 4: Select minimum riprap thickness from grain size curves (Fig. 3.12 to 3.17 iSWM Hydraulic
Technical Manua!).
D50 (max)= (Select from smaller side of band at 50% fine
gradation)
Ib/ft2
Riprap Size = (min thickness is 12") inches
Step 5: Select riprap gradations table (Fig. 3.18 to 3.19 iSWM Hydraulics Technical Manual
Riprap Gradation Figure based on riprap thickness in Step 4
Figure
Step 6: Select bedding thickness from grain size curves (Fig. 3.12 to 3.17 iSWM Hydraulics Technica
Bedding Gradation Figure
Figure
Note: See steps 7-10 in the Section 3.2.7 for iSWM Hydraulics Technical Manual additional guidance.
City of Fort Worth Stormwater Criteria Manual 101
3.8.5 Stormwater Detention Facility Maintenance
3.8.5.1 Dry Detention Ponds
Note: Modifications affecting the storage capacity and/or outlet structure of a detention facility will require a SWFMA
amendment. An O & M manual revision may be required. Revised configuration and calculations must be approved
by Stormwater Development Services.
The following shall be included in a checklist and on the plans:
• Pond Bottom Elevation:
• Depth of pond (ft):
• Pond side slopes (lV:?H):
• Length and width of pond at top bank
• Length and width of pond at pond bottom
• Width (ft) and slope of maintenance access road/pad:
• Fully developed ultimate 100-year WSEL in pond:
• Pond volume at ultimate 100-year WSEL (ft3):
• Depth of sediment requiring removal (10% of pond volume elevation):
• Pond orifice diameter and orifice flowline:
• (if there are multiple orifices/weirs, write the parameters of all)
• Pre-developed/existing 100 Year condition (cfs) generated by site:
• Pond release rate (cfs) at fully developed Ultimate 100 yr WSEL:
• Pond Freeboard Elevation:
• Bottom Width of Emergency Spillway:
• Pond emergency spillway bottom elevation:
• Emergency spillway 100 yr flow elevation:
• Freeboard elevation of Emergency Spillway
• (6" above spillway 100 yr elevation):
Capacity of emergency Spillway (cfs):
• Pond inlet pipe diameter(s), if any:
• Pond outlet pipe diameter(s) and slope:
• Inlet flowline of Pond Outlet Pipe:
Bottom width (min 6') and slope of pilot channel:
Dry Detention Facility
A dry detention pond/basin is a storage basin designed to provide water quantity control through detention of
Stormwater runoff. The purpose of detention is to allow some of the water to exfiltrate into the ground and the
remainder of the water to release slowly over a period of time to reduce downstream water quantity impacts. Dry
detention basins are designed to completely drain following a storm event and are normally dry between rain events.
They provide limited pollutant removal benefits and are not intended for water quality treatment alone.
Scope and Responsibilities
All Stormwater Facilities that serve a land Development shall be privately constructed and owned, and maintenance
shall be the responsibility of the Owner, except as specifically approved in writing by the Director of Transportation
and Public Works. The "Landowner" or "Association" listed on the Stormwater Facility Maintenance Agreement is
responsible for facility operation and maintenance.
The facility operation requires funding for future monitoring and maintenance costs so the facility functions as
designed though the life of the facility. The total annual cost for facility maintenance is estimated to be about 2%
City of Fort Worth Stormwater Criteria Manual 102
to 5% of the construction cost of the facility, associated structures, and landscape. The "Landowner" or
"Association" are solely responsible for funding all monitoring and maintenance costs.
The City will inspect facilities to enforce compliance with the Stormwater Facility Maintenance Agreement, but the
City will not be responsible for operation and maintenance of the Facility.
Reporting and Record Retention
A written report shall be kept of maintenance actions and inspections. At a minimum the report shall document the
condition of the entire Stormwater Facility, its berms, outlet structure, pond areas, access roads, and ancillary
components. Components of the Stormwater Facility which need maintenance or replacement to perform their
design function shall be noted in the inspection report along with the corrective actions taken.
The written reports shall be maintained by the "Landowner" or "Association" and submitted yearly to the City. Annual
reports shall be submitted to:
City of Fort Worth Stormwater Management
200 Texas Street
Fort Worth, TX 76102
Written records regarding the facility operation and maintenance shall be maintained in proper order and available
for the City review at any time.
Upon or prior to the transfer of the ownership of a Stormwater Facility by any method other than heirship, Owner
shall transfer a copy of monthly logs to new Owner.
Facility Construction, Maintenance, and Inspection
When City staff finds deficiency in the operation and maintenance of the facility, the city, its authorized agents and
employees, may, with written mailed or hand delivered notice to the Owner, enter the property on which the
Stormwater Facility is located to inspect the Stormwater Facility. The City shall provide the Owner with a copy of
the inspection findings and a directive to commence with any repairs, if necessary. Noted deficiencies that are not
corrected within the times specified in the City directive will result in fines.
In the event the owner fails to commence with repairs or provide adequate maintenance of the Stormwater Facility
the city, its authorized agents and employees, may, but has no obligation to, enter upon the Stormwater Facility
and (i) take whatever steps necessary to correct deficiencies identified in the inspection report and (ii) make
necessary repairs or perform necessary maintenance. The city shall charge the costs of such repairs to the owner.
In the event that the owner fails to pay the city the amount demanded by the city, the city shall impress a lien for
the costs of such work upon the property owned by Owner.
General Maintenance Procedures
The structural and functional integrity of the Facility shall be maintained at all times by removing and preventing
drainage interference, obstructions, blockages, or other adverse effects into, through, or out of the system.
Routine maintenance should be performed on dry detention basins to ensure that the facility is properly functioning.
In the event of snow, check to make sure that the materials used to de-ice the surrounding areas stay out of the
practice to avoid clogging and further pollution. Note that it might take longer for the water to infiltrate into the
ground during the winter months and early spring. If the dry detention basin is not draining properly, check for
clogging of the outflow/outlet structures.
Typical inspection activities and repair/removal schedule are list below. The items listed below may require more
frequent inspection and maintenance during the first year of facility service. A maintenance checklist is included in
Exhibit D.
City of Fort Worth Stormwater Criteria Manual 103
Table 3.22 dry Detention Pond Inspection, Maintenance, & Repair
Activity
Inspection Schedule
Removal/Repair Schedule
Remove litter, debris, and
Inspect facility for nuisance items
Remove nuisance items promptly either
unwanted vegetation from facility
weekly and after storm events
during inspection or before next rainfall
equal to or greater than 0.5".
event.
Monitor standing water and
Inspect facility for standing water
Determine and address cause of
mosquito activity
weekly and after storm events
standing water. Remove standing water
equal to or greater than 0.5".
promptly either during inspection or
within 24-48 hours of inspection.
Mow side slopes to limit unwanted
Mow monthly between April to
Remove clippings immediately after
vegetation -- REMOVE
October or when vegetation
mowing.
CLIPPINGS FROM FACILITY
exceeds 12" in height.
Monitor and remove sediment
Monitor sediment monthly and
Sediment depth should be noted on
buildup
after storm events equal to or
monthly inspection checklist. When
greater than 0.5". Remove
removal depth is reached, remove
sediment at depth specified by
buildup promptly, prior to next inspection
Engineer in Exhibit B
cycle or before next rainfall event,
whichever will come first.
Remove litter, debris, and
Inspect contributing basin for
Remove nuisance items promptly either
unwanted vegetation from
nuisance items weekly and after
during inspection or before next rainfall
contributing basin to minimize
storm events producing 0.5" or
event.
outlet clogging and improve
greater.
aesthetics
Repair and revegetate undercut
Inspect for undercut/eroded areas
Repair promptly, prior to next inspection
and/or eroded areas.
monthly and after storm events
cycle or before next rainfall event,
equal to or greater than 0.5".
whichever will come first.
Seed or sod to restore dead or
Inspect for dead/damaged ground
Repair promptly, prior to next inspection
damaged ground cover
cover monthly and after storm
cycle 'or before next rainfall event,
events equal to or greater than
whichever will come first.
Inspect for damage to the
Inspect monthly and after storm
Repair promptly, prior to next inspection
embankments, berm, access
event equal to or greaterthan 0.5".
cycle or before next rainfall event,
ramp, outlet control
whichever will come first.
Perform structural repairs to inlets
Inspect inlets and outlets for
Repair promptly, prior to next inspection
and outlets
structural defects monthly and
cycle or before next rainfall event,
after storm events equal to or
whichever will come first.
reater than 0.5".
Ensure that inlet and outlet
Inspect weekly and after storm
Repair promptly, prior to next inspection
devices are free of debris and
events equal to or greater than
cycle or before next rainfall event.
o erational.
0.511.
Storm drain inspection
Yearly visual inspection at joints,
Repair storm drain when sink holes form,
CCTV every 15 years to confirm
when sagging, cracks, leaks, corrosion,
system integrity
or blocksa impact storm drain function
City of Fort Worth Stormwater Criteria Manual 104
3.8.5.2 Underground Stormwater Detention Facilities:
Mote: Modifications affecting the storage capacity and/or outlet structure of a detention facility will require a SWFMA
amendment. An O & M manual revision may be required. Revised configuration and calculations must be approved
by Stormwater Development Services.
The following items shall be on the checklist and construction plans:
• Facility Bottom Elevation:
Depth of facility (ft)
• Depth of base stone (ft)
• Depth of top stone (ft)
• Length and width of facility
• Fully developed ultimate 100-year WSEL in pond:
• Pond volume at ultimate 100-year WSEL (ft3):
• Depth of sediment requiring removal
Facility orifice diameter and orifice flowline:
• (if there are multiple orifices/weirs, write the parameters of all)
Facility outlet pipe diameter(s) and slope:
• Pre-developedlexisting 100 Year condition (cfs) generated by site:
• Facility release rate (cfs) at fully developed Ultimate 100 yr WSEL:
• Facility Freeboard Elevation:
Overflow/Emergency Outlet elevation:
• Capacity of emergency Overflow/Emergency outlet (cfs):
• Facility inlet pipe diameter(s)
Underground Facility
Underground detention is detention storage located in underground tanks or vaults designed to provide water
quantity control through temporary storage of stormwater runoff. In addition they can improve water quality by
removing heavy amounts of sediment.
Scope and Responsibilities
All Stormwater Facilities that serve a land Development shall be privately constructed and owned, and maintenance
shall be the responsibility of the Owner, except as specifically approved in writing by the Director of Transportation
and Public Works. The "Landowner" or "Association" listed on the Stormwater Facility Maintenance Agreement is
responsible for facility operation and maintenance.
The facility operation requires funding for future monitoring and maintenance costs so the facility functions as
designed though the life of the facility. The total annual cost for facility maintenance is estimated to be between
$1,000 and $1,500 depending on the size of the facility. The "Landowner" or "Association" are solely responsible
for funding.
The City will inspect facilities to enforce compliance with the Stormwater Facility Maintenance Agreement, but the
City will not be responsible for operation and maintenance of the Facility.
Reporting and Record Retention
A written monthly report shall be kept of maintenance actions and inspections. At a minimum the report shall
document the condition of the entire Stormwater Facility, its berms, outlet structure, pond areas, access roads, and
ancillary components. Components of the Stormwater Facility which need maintenance or replacement to perform
their design function shall be noted in the inspection report along with the corrective actions taken.
City of Fort Worth Stormwater Criteria Manual 105
The written monthly reports shall be maintained by the "Landowner" or "Association" and submitted yearly to the
City. Annual reports shall be submitted to:
City of Fort Worth Stormwater Management
200 Texas Street
Fort Worth, TX 76102
Written records regarding the facility operation and maintenance shall be maintained in proper order and available
for the City review at any time.
Upon or prior to the transfer of the ownership of a Stormwater Facility by any method other than heirship, Owner
shall transfer a copy of monthly logs to new Owner.
Facility Construction, Maintenance, and Inspection
When City staff finds deficiency in the operation and maintenance of the facility, the city, its authorized agents and
employees, may, with written mailed or hand delivered notice to the Owner, enter the property on which the
Stormwater Facility is located to inspect the Stormwater Facility. The City shall provide the Owner with a copy of
the inspection findings and a directive to commence with any repairs, if necessary. Noted deficiencies that are not
corrected within the times specified in the City directive will result in fines.
In the event the owner fails to commence with repairs or provide adequate maintenance of the Stormwater Facility
the city, its authorized agents and employees, may, but has no obligation to, enter upon the Stormwater Facility
and (i) take whatever steps necessary to correct deficiencies identified in the inspection report and (ii) make
necessary repairs or perform necessary maintenance. The city shall charge the costs of such repairs to the owner.
In the event that the owner fails to pay the city the amount demanded by the city, the city shall impress a lien for
the costs of such work upon the property owned by Owner.
General Maintenance Procedures
The structural and functional integrity of the Facility shall be maintained at all times by removing and preventing
drainage interference, obstructions, blockages, or other adverse effects into, through, or out of the system.
Routine maintenance should be performed on the underground detention facilities to ensure that the facility is
properly functioning. Routine maintenance includes the removal of debris from inlet and outlet structures and
cleaning sediment built up inside the structure. Inspection and maintenance may be difficult for an underground
system, but generally these underground systems can be inspected by looking in an access opening. Sometimes
maintenance requires an individual who is certified in OSHA confined space entry. In a situation where safety
concerns arises, the inspection should stop and the safety concern addressed. Once the concern is addressed, the
inspection can continue. Once site construction is complete the underground facility must be thoroughly cleaned
and inspected prior to service.
Facility inspection and maintenance should follow manufacturers guidelines and develop/adjust a site specific O&M
plan for the underground detention once in normal service. Typical inspection activities and repair/removal schedule
are list below. The items listed below may require more frequent inspection and maintenance during the first year
of facility service. A maintenance checklist is included in Exhibit D.
City of Fort Worth Stormwater Criteria Manual 106
Table 3.23 Underground Detention Inspection, Maintenance, & Repairs
Activity
Inspection Schedule
Removal/Repair Schedule
Remove litter, debris, and
Inspect contributing basin for
Remove nuisance items promptly
unwanted vegetation from
nuisance items weekly and after
either during inspection or before
contributing basin to minimize
storm events producing 0.5" or
next rainfall event.
outlet clogging and improve
greater.
aesthetics
Remove any trash/debris in the
Inspect semi-annually for
Remove nuisance items in the
underground trash racks, vaults or
trash/debris in the facility (min 2x
facility promptly either during
tanks.
per year)
inspection or before next rainfall
event.
Clean underground detention if
Treat hazardous or foreign
hazardous or foreign substances
substances spills per OSHA
are spilled in the contributing
guidelines. Clean facility per
drainage area
Manufacturer guidelines.
Contaminated material must be
disposed of per OSHA guidelines
and shall not be discharged into
the receiving system
Perform structural repairs to inlet
Inspect inlets and outlets for
Repair promptly, prior to next
and outlets.
structural defects monthly and
inspection cycle or before next
after storm events equal to or
rainfall event, whichever will come
reater than 0.5".
first.
Monitor sediment buildup
Monitor sediment monthly and
Sediment depth should be noted
after storm events equal to or
on monthly inspection checklist.
greater than 0.5". Remove
When removal depth is reached,
sediment when depth of sediment
remove buildup promptly, prior to
measures 3"
next inspection cycle or before
next rainfall event, whichever will
come first.
Clean out underground detentions
Monitor sediment monthly and
Vacuum maintenance is
with vacuum or boom trucks.
after storm events equal to or
recommended if sediment has
greater than 0.5". Remove
been collected to an average
sediment when depth of sediment
depth of 3"
measures 3"
Ensure that inlet and outlet
Inspect weekly and after storm
Repair promptly, prior to next
devices are free of debris and
events equal to or greater than
inspection cycle or before next
operational.
0.5".
rainfall event.
Storm drain inspection
Yearly visual inspection at joints,
Repair storm drain when sink
CCTV every 15 years to confirm
holes form, when sagging, cracks,
system integrity
leaks, corrosion, or blockage
impact storm drain function
City of Fort Worth Stormwater Criteria Manual 107
3.9 Stormwater Control Selection
3.9.1 Control Screening Process
Outlined below is a screening process for structural stormwater controls that can effectively treat the water quality
volume, as well as provide water quantity control. This process is intended to assist the site designer and design
engineer in the selection of the most appropriate structural controls for a Development site and to provide guidance
on factors to consider in their location. This information is also contained in the iSWM Technical Manual — Site
Development Controls section.
The following four criteria shall be evaluated in order to select the appropriate structural control(s) or group of
controls for a Development:
• Stormwater treatment suitability
• Water quality performance
• Site applicability
• Implementation considerations
In addition, the following factors shall be considered for a given site and any specific design criteria or restrictions
need to be evaluated:
Physiographic factors
Soils
Special watershed or stream considerations
Finally, environmental regulations shall be considered as they may influence the location of a structural control on
site or may require a permit.
The following steps provide a selection process for comparing and evaluating various structural stormwater controls
using a screening matrix and a list of location and permitting factors. These tools are provided to assist the design
engineer in selecting the subset of structural controls that will meet the stormwater management and design
objectives for a Development site or project.
Step 1 Overall Applicability
The following are the details of the various screening categories and individual characteristics used to evaluate the
structural controls.
Table 3.24 - Stormwater Management Suitability
The first category in the matrix examines the capability of each structural control option to provide water quality
treatment, downstream streambank protection, and flood control. A blank entry means that the structural control
cannot or is not typically used to meet an integrated Focus Area. This does not necessarily mean that it should be
eliminated from consideration, but rather it is a reminder that more than one structural control may be needed at a
site (e.g., a bioretention area used in conjunction with dry detention storage).
Ability to treat the Water Quality Volume (WQv): This indicates whether a structural control provides
treatment of the water quality volume (WQv). The presence of "P" or "S" indicates whether the control
is a Primary or Secondary control, respectively, for meeting the TSS reduction goal.
Ability to provide Streambank Protection (SPv): This indicates whether the structural control can be
used to provide the extended detention of the streambank protection volume (SPv). The presence of a
"P" indicates that the structural control can be used to meet SPv requirements. An "S indicates that
the structural control may be sized to provide streambank protection in certain situations, for instance
on small sites.
Ability to provide Flood Control (00) This indicates whether a structural control can be used to meet
the flood control criteria. The presence of a "P" indicates that the structural control can be used to
provide peak reduction of the flood mitigation storm event.
City of Fort Worth Stormwater Criteria Manual 108
Table 3.25 - Relative Water Quality Performance
The second category of the matrix provides an overview of the pollutant removal performance for each structural
control option when designed, constructed, and maintained according to the criteria and specifications in this
manual.
• Ability to provide TSS and Sediment Removal: This column indicates the capability of a structural
control to remove sediment in runoff. All of the Primary structural controls are presumed to remove 70%
to 80% of the average annual TSS load in typical urban proposed runoff (and a proportional removal of
other pollutants).
• Ability to provide Nutrient Treatment This column indicates the capability of a structural control to
remove the nutrients nitrogen and phosphorus in runoff, which may be of particular concern with certain
downstream receiving waters.
• Ability to provide Bacteria Removal: This column indicates the capability of a structural control to
remove bacteria in runoff. This capability may be of particular concern when meeting regulatory water
quality criteria under the Total Maximum Daily Load (TMDL) program.
• Ability to accept Hotspot Runoff: This last column indicates the capability of a structural control to
treat runoff from designated hotspots. Hotspots are land uses or activities that produce higher
concentrations of trace metals, hydrocarbons, or other priority pollutants. Examples of hotspots might
include: gas stations, convenience stores, marinas, public works storage areas, garbage transfer
facilities, material storage sites, vehicle service and maintenance areas, commercial nurseries, vehicle
washing/steam cleaning, landfills, construction sites, industrial sites, industrial rooftops, and auto
salvage or recycling facilities. A check mark indicates that the structural control may be used on hotspot
site. However, it may have specific design restrictions. Please see the specific design criteria of the
structural control for more details in the Site Development Controls Technical Manual. Local
jurisdictions may have other site uses that they designate as hotspots. Therefore, their criteria shall be
checked by the design engineer as well.
Table 3.26 - Site Applicability
The third category of the matrix provides an overview of the specific site conditions or criteria that must be met for
a particular structural control to be suitable. In some cases, these values are recommended values or limits and
can be exceeded or reduced with proper design or depending on specific circumstances. Please see the specific
criteria section of the structural control for more details.
• Drainage Area: This column indicates the approximate minimum or maximum drainage area
considered suitable for the structural control practice. If the drainage area present at a site is slightly
greater than the maximum allowable drainage area for a practice, some leeway can be permitted if
more than one practice can be installed. The minimum drainage areas indicated for ponds and wetlands
shall not be considered inflexible limits and may be increased or decreased depending on water
availability (baseflow or groundwater), the mechanisms employed to prevent outlet clogging, or design
variations used to maintain a permanent pool (e.g., liners).
• Space Required (Space Consumed): This comparative index expresses how much space a structural
control typically consumes at a site in terms of the approximate area required as a percentage of the
impervious area draining to the control.
• Slope: This column evaluates the effect of slope on the structural control practice. Specifically, the
slope restrictions refer to how fiat the area where the facility is installed must be and/or how steep the
contributing drainage area or flow length can be.
• Minimum Head: This column provides an estimate of the minimum elevation difference needed at a
site (from the inflow to the outflow) to allow for gravity operation within the structural control.
• Water Table: This column indicates the minimum depth to the seasonally high water table from the
bottom or floor of a structural control.
Table 3.27 - Implementation Considerations
The fourth category in the matrix provides additional considerations for the applicability of each structural control
option.
Residential Subdivision Use: This column identifies whether or not a structural control is suitable for
single family residential subdivision development (not including high -density or ultra -urban areas).
City of Fort Worth Stormwater Criteria Manual 109
Ultra -Urban: This column identifies those structural controls appropriate for use in very high -density
(ultra -urban) areas, or areas where space is a premium.
Construction Cost. The structural controls are ranked according to their relative construction cost per
impervious acre treated, as determined from cost surveys.
Maintenance: This column assesses the relative maintenance effort needed for a structural stormwater
control, in terms of three criteria: frequency of scheduled maintenance, chronic maintenance problems
(such as clogging), and reported failure rates. All structural controls require routine inspection and
maintenance by the property owner.
The Site Development Controls iSWM Technical Manual contains an exhaustive discussion and detailed
examples of stormwater controls that can be implemented in land Development to meet the goals of protecting
water quality, minimizing streambank erosion, and reducing flood volumes. It is an excellent planning and design
resource document and has valuable design examples that the City encourages local Developers to consider in
their site planning. Although it is primarily oriented toward water quality issues, these stormwater controls bring
additional and valuable benefits for flood control and streambank protection. Many of the listed stormwater control
features and techniques enhance the aesthetics and value of land Developments, as well as providing a drainage
function.
The City of Fort Worth is currently requiring streambank protection, conveyance and flood control components of
the integrated stormwater management approach. However, the Stormwater Control Selection (Section 3.9) of
applicable features may be applied in local Developments and Redevelopments. The City does not mandate the
use of any of these stormwater controls, but recognizes the inherent values of their application in overall stormwater
management.
Therefore, the City adopts for design guidance and technical reference sections of the iSWM Technical Manual.
There are, however, no City requirements for achieving Stormwater Quality (WQv) or Channel Protection (SPv)
volumes. Stormwater utility fee credits may be available for design practices meeting these standards. See
Appendix F for detailed information.
City of Fort Worth Stormwater Criteria Manual 110
Table 3.24 Stormwater Treatment Suitability
Category
integrated Stormwater°Controls
"
'Stormwater Treatment
Suitabili
Water
Quality, .,
Protection ,
Streambank
•protection
On -Site
Flvod
Control
Downstream
FIood
Control'
Bioretention Areas
Bioretention Areas
P
S
S
-
Channels
Enhanced Swales
P
S
S
S
Channels, Grass
S
S
P
S
Channels, Open
-
-
P
S
Chemical Treatment
Alum Treatment System
P
-
-
-
Conveyance System
Components
Culverts
-
-
P
P
Energy Dissipation
-
P
S
S
Inlets/Street Gutters
-
-
P
-
Pipe Systems
-
P
P
P
Detention
Detention, Dry
S
P
P
P
Detention, Extended Dry
S
P
P
P
Detention, Multi -purpose Areas
-
P
P
P
Detention, Underground
-
P
P
P
Filtration
Filter Strips
S
-
-
-
Organic Filters
P
-
-
-
Planter Boxes
P
-
-
-
Sand Filters, SurfacelPerimeter
P
S
-
-
Sand Filters, Underground
P
-
-
-
Hydrodynamic Devices
Gravity (Oil -Grit) Separator
S
-
-
-
infiltration
Downspout Drywell
P
-
-
-
Infiltration Trenches
P
S
-
-
Soakage Trenches
P
S
-
-
Ponds
Wet Pond
P
P
P
P
Wet ED Pond
P
P
P
P
Micropool ED Pond
P
P
P
P
Multiple Ponds
P
P
P
P
Porous Surfaces
Green Roof
P
S
-
-
Modular Porous Paver Systems
S
S
-
-
Porous Concrete
S
S
-
-
Proprietary Systems
Proprietary Systems'
SIP
S
S
S
Re -Use
Rain Barrels
P
-
-
-
Wetlands
Wetlands, Stormwater
P
P
P
P
Wetlands, Submerged Gravel
P
P
S
-
P = Primary Control: Able to meet design criterion if properly designed, constructed and maintained.
S = Secondary Control: May partially meet design criteria. May be a Primary Control but designated as a Secondary due to other
considerations. For Water Quality Protection, recommended for limited use in accepted community -designated areas.
= Not typically used or able to meet design criterion,
1 = The application and performance of propriety commercial devices and systems must be provided by the manufacturer and
shall be verified by independent third -party sources and data if used as a primary control.
City of Fort Worth Stormwater Criteria Manual ill
Table 3.26 Water Quality Performance
Category
integrated Stormwater Controls
Water Quality -Performance` `
TSSI
Sediment
Removal -Rate
Nutrient
Removal
Rate (TPITN)
Bacteria
Removal
Rate
Hotspot
Application
Bioretention Areas
Bioretention Areas
80%
60%/50%
-
❑
Enhanced Swales
80%
25%140%
-
❑
Channels
Channels, Grass
50%
25%/20%
-
Channels, Open
-
-
-
Chemical Treatment
Alum Treatment System
90%
80%160%
90%
❑
Culverts
-
-
-
Conveyance System
Components
Energy Dissipation
-
-
-
Inlets/Street Gutters
-
-
-
Pipe Systems
-
-
-
Detention, Dry
66%
50%130%
70%
❑
Detention, Extended Dry
65%
50%/30%
70%
❑
Detention
Detention, Mu[ti-purpose Areas
-
-
-
Detention, Underground
-
-
-
Filter Strips
50%
20%120%
-
Filtration
Organic Filters
80%
60%140%
50%
❑
Planter Boxes
80%
60%/40%
-
Sand Filters, Surface/Perimeter
80%
50%/25%
40%
❑
Sand Filters, Underground
80%
50%/25%
40%
❑
Hydrodynamic
Devices
Gravity (Oil -Grit) Separator
40%
5%15%
-
Infiltration
Downspout Drywell
80%
60%160%
90%
Infiltration Trenches
80%
60%/60%
90%
Soakage Trenches
80%
60%/60%
90%
Ponds
Wet Pond
80%
50%130%
70%
❑
Wet ED Pond
80%
50%130%
70%
❑
Micropool ED Pond
80%
50%/30%
70%
❑
Multiple Ponds
80%
50%130%
70%
❑
Green Roof
85%
95%/16%
-
❑
Porous Surfaces
Modular Porous Paver Systems
2
80%180%
-
Porous Concrete
2
50%/650o
-
Proprietary Systems
Proprietary Systems 1
1
1
1
Re -Use
Rain Barrels
-
-
-
Wetlands, Stormwater
80%
40%130%
70%
❑
Wetlands
Wetlands, Submerged Gravel
80%
40%/30%
70%
❑
❑ = Meets suitability criteria.
- = Not typically used or able to meet design criterion.
i = The application and performance of proprietary commercial devices and systems must be provided by the manufacturer and
shall be verified by independent third -party sources and data if used as a primary control.
2 = Porous surfaces provide water quality benefits by reducing the effective impervious area.
City of Fort Worth Stormwater Criteria Manual 112
Table 3.26 Site Applicability
Site
Applicability
Drainage
Space ReWd,'
o
{ /o of
;Minimum
Head`
Depth to '
Cate o
integrated 'Stormwater,
9 ry
Controls
Area (acres)
tributary imp.
Site Slope
Required
Water Table
Bioretention
Areas
Bioretention Areas
5 max3
5-7%
6% max
5 ft
2 ft
Enhanced Swales
1 ft
Below WT
Channels
Channels, Grass
5 max
10-20%
4% max
Channels Open
Chemical
Alum Treatment System
25 min
None
Culverts
Conveyance
Energy Dissipation
System
Components
Inlets/Street Gutters
Pipe Systems
Detention, Dry
2-3%
15%pond across
6 to 8 ft
2 ft
Detention, Extended Dry
2-3%
15% across
pon1%
6 to 8 ft
2 ft
Detention
for Parking
Detention, Multi -purpose
Lot;
Areas
200 max
0.25 in/ft for
Roofto
Detention, Underground
200 max
Filter Strips
2 max3
20-25%
2-6%
Organic Filters
10 max3
2-3%
5 to 8 ft
Planter Boxes
6%
Filtration
Sand Filters,
10 max3 1
2-3%
6% max
5 ft per 2-3 ft
2 ft
Surface/Perimeter
2 max3
Sand Filters,
5 max
None
Hydrodynamic
Gravity (Oil -Grit)
1 max3
None
Devices
Separator
Downspout Drywell
Infiltration Trenches
5 max
2-3%
6% max
1 ft
O ft
Infiltration
Soakage Trenches
5 max
27 ft per 1000
6% max
1 ft
4 ft
ft2 imp. area
Wet Pond
2 ft, if
Wet ED Pond
25 min3
2-3%
15% max
6 t 8 ft
hotspot or
Ponds
Micropool ED Pond
10 min3
aquifer
Multiple Ponds
25 min3
Green Roof
Porous
Modular Porous Paver
5 max
Varies
Surfaces
Systems
Porous Concrete
5 max
Varies
Proprietary
Systems
Proprietary Systems 1
1
1
Re -Use I
Rain Barrels
City of Fort Worth Stormwater Criteria Manual 113
3to5ft
2ft,if
Wetlands, Stormwater
25 min
(shallow) 6hotspot
or
Wetlands
3-5%
8% max
to g ft (pond)
aquifer
Wetlands, Submerged
5 min
2 to 3 ft
Below WT
Gravel
- = Not typically used or able to meet design criterion.
1 = The application and performance of proprietary commercial devices and systems must be provided by the
manufacturer and shall be verified by independent third -party sources and data if used as a primary control.
2 = Porous surfaces provide water quality benefits by reducing the effective impervious area.
3 = Drainage area can be larger in some instances.
Table 3.27 Implementation Considerations
Category
integrated Stormwater
Controls
Implemertation Considerations
Residential
Subdivision
High
Density/Ultra
Capital Cost
Maintenance
Burden
Bioretention
Bioretention Areas
❑
❑
Moderate
Low
Enhanced Swales
❑
High
Low
Channels
Channels, Grass
❑
Low
Moderate
Channels, Open
❑
Low
Low
Chemical
Alum Treatment System
❑
❑
High
High
Conveyance
System
Culverts
❑
❑
Low
Low
Energy Dissipation
❑
❑
Low
Low
Components
Inlets/Street Gutters
❑
❑
Low
Low
Pipe Systems
❑
❑
Low
Low
Detention
Detention, Dry
❑
Low
Moderate to High
Detention, Extended Dry
❑
Low
Moderate to High
Detention, Multi-purpos
Areas
❑
❑
Low
Low
Detention Underground
❑
Moderate
Filter Strips
❑
—High
Low
Moderate
Organic Filters
❑
High
High
Filtration
Planter Boxes
❑
Low
Moderate
Sand Filters,
❑
High
High
Sand Filters, Underground
❑
High
High
Hydrodynamic
Devices
Gravity (Oil -Grit)
Separator
❑
High
High
Downspout Drywell
❑
❑
Low
Moderate
Infiltration
Infiltration Trenches
❑
❑
High
High
Soakage Trenches
❑
❑
High
High
Ponds
Wet Pond
❑
Low
Low
Wet ED Pond
❑
Low
Low
Micropool ED Pond
❑
Low
Moderate
Multiple Ponds
❑
Low
Low
Green Roof
❑
High
High
lsystprns
Modular Porous Paver
❑
Moderate
High
City of Fort Worth Stormwater Criteria Manual 114
Porous
Porous Concrete
❑
High
Proprietary
Proprietary Systems 1
1
-High
❑
High
High
Re -Use
Rain Barrels
❑
❑
Low
High
etlands
Wetlands, Stormwater
❑
Moderate
Moderate
etlands, Submerged❑
Gravel
❑
Moderate
High
I
❑ = Meets suitability criteria
= Not typically used or able to meet design criterion.
1 = The application and performance of proprietary commercial devices and systems must be provided by the
manufacturer and shall be verified by independent third -party sources and data if used as a primary control.
Step 2 Specific Criteria
The last three categories in the Structural Control Screening matrix provide an overview of various specific design
criteria and specifications, or exclusions for a structural control that may be present due to a site's general
physiographic character, soils, or location in a watershed with special water resources considerations.
Table 3.28 - Physiographic Factors
Three key factors to consider are low -relief, high -relief, and karst terrain. In North Central Texas, low relief (very
flat) areas are primarily located east of the Dallas metropolitan area. High relief (steep and hilly) areas are primarily
located west of the Fort Worth metropolitan area. Karst and major carbonaceous rock areas are limited to portions
of Palo Pinto, Erath, Hood, Johnson, and Somervell counties. Special geotechnical testing requirements may be
needed in karst areas. The local reviewing authority shall be consulted to determine if a project is subject to terrain
constraints.
Low relief areas need special consideration because many structural controls require a hydraulic head
to move stormwater runoff through the facility.
High relief may limit the use of some structural controls that need flat or gently sloping areas to settle
out sediment or to reduce velocities. In other cases, high relief may impact dam heights to the point
that a structural control becomes infeasible.
Karst terrain can limit the use of some structural controls as the infiltration of polluted waters directly
into underground streams found in karst areas may be prohibited. In addition, ponding areas may not
reliably hold water in karst areas.
Table 3.29 - Soils
The key evaluation factors are based on an initial investigation of the NRCS hydrologic soils groups at the site. Note
that more detailed geotechnical tests are usually required for infiltration feasibility and during design to confirm
permeability and other factors.
The design of structural stormwater controls is fundamentally influenced by the nature of the downstream water
body that will be receiving the stormwater discharge. In addition, the designer shall consult with the appropriate
review authority to determine if their Development project is subject to additional structural control criteria as a result
of an adopted local watershed plan or special provision.
In some cases, higher pollutant removal or environmental performance is needed to fully protect aquatic resources
and/or human health and safety within a particular watershed or receiving water. Therefore, special design criteria
for a particular structural control or the exclusion of one or more controls may need to be considered within these
watersheds or areas. Examples of important watershed factors to consider include:
Table 3.30 - Special Watershed or Stream Considerations
Nigh Quality Streams (Streams with a watershed impervious cover less than approximately 15%).
These streams may also possess high quality cool water or warm water aquatic resources or
endangered species. The design objectives are to maintain habitat quality through the same techniques
used for cold -water streams, with the exception that stream warming is not as severe of a design
constraint. These streams may also be specially designated by local authorities.
City of Fort Worth Stormwater Criteria Manual 115
Wellhead Protection: Areas that recharge existing public water supply wells present a unique
management challenge. The key design constraint is to prevent possible groundwater contamination
by preventing infiltration of hotspot runoff. At the same time, recharge of unpolluted stormwater is
encouraged to maintain flow in streams and wells during dry weather.
Reservoir or Drinking Water Protection: Watersheds that deliver surface runoff to a public water
supply reservoir or impoundment are a special concern. Depending on the available treatment, a
greater level of pollutant removal may be necessary for the pollutants of concern, such as bacteria
pathogens, nutrients, sediment, or metals. One particular management concern for reservoirs is
ensuring stormwater hotspots are adequately treated so they do not contaminate drinking water.
3.9.1.1 Step 3 Location and Permitting Considerations
In the last step, a site designer assesses the physical and environmental features atthe site to determine the optimal
location for the selected structural control or group of controls. Table 3.29 provides a condensed summary of current
restrictions as they relate to common site features that may be regulated under local, state, or federal law. These
restrictions fail into one of three general categories:
Locating a structural control within an area when expressly prohibited by law
Locating a structural control within an area that is strongly discouraged, and is only allowed on a case
by case basis. Local, state, and/or federal permits shall be obtained, and the applicant will need to
supply additional documentation to justify locating the stormwater control within the regulated area.
Structural stormwater controls must be setback a fixed distance from a site feature.
This checklist is only intended as a general guide to location and permitting requirements as they relate to siting of
stormwater structural controls. Consultation with the appropriate regulatory agency is the best strategy.
Table 3.28 Physiographic Factors
Category
integrated Stormwate
controls
Physiographic Factors
Low Relief High Relief Karst
Bioretention
Areas
Bioretention Areas
Several design
ariations will likely
be limited by low
Use poly -linear o
impermeable
membrane to sea
Channels
Enhanced Swales
Generally feasible.
However, slope
<1% may lead t
standing water in drygreater
Often infeasible i
slopes are 4% o
Channels, Grass
Channels, Open
Chemical
atmpnt
Alum Treatment System
Culverts
Conveyance
System
Energy Dissipation
Components
Inlets/Street Gutters
Pipe Systems
Detention
Detention, Dry
Embankment
heights restricted
Require poly or clay
liner, Max ponding
depth, Geotechnica
Detention, Extended Dry
Detention, Multi -purpose
Arpas
Detention, Underground
NOT ALLOWED
Filter Strips
Organic Filters
City of Fort Worth Stormwater Criteria Manual 116
Planter Boxes
Several design
Use poly -linear o
Filtration
Sand Filters,
variations will likely
impermeable
Surface/Perimeter
be limited by low
membrane to seal
Sand Filters,
Underaround
Table 3.26 Physiographic Factors
Category.
integrated Stormwater
COnftls
Physiographic Factors`
L.ow-Relief i High7Relief Karst
Hydrodynamic
Devices
Gravity (Oil -Grit)
Separator
Infiltration
Downspout Drywell
Minimum distance to
water table of 4 ft
NOT ALLOWED
Infiltration Trenches
Minimum distance t
water table of 2 ft
Maximum slope of
%; trenches must
NOT ALLOWED
Soakage Trenches
Minimum distance to
water table of 4 ft
Maximum slope o
%; trenches must
NOT ALLOWED
Ponds
Wet Pond
Limit maximum
normal pool depth to
about 4 ft (dugout)
Providing pond drainheights
can be problematic
Embankment
restricted
Require poly or clay line
Max ponding depth
Geotechnical tests
Net ED Pond
Micropool ED Pond
Multiple Ponds
Porous
Surfaces
Green Roof
Modular Porous Pave
svqtpmq
Porous Concrete
Proprietary
Proprietary Systems 1
Re -Else
Rain Barrels
Wetlands
Wetlands, Stormwater
Embankment
heights restricted
Require poly -line
Geotechnical tests
Wetlands, Submerged
Gravel
1 = The application and performance of proprietary commercial devices and systems must be provided by the
manufacturer and shall be verified by independent third -party sources and data if used as a primary control.
Table 3.29 Soils
Category,
integrated Stormwater.Controls
Soils
Bioretention Areas
Bioretention Areas
Clay or silty soils may require pretreatment
Enhanced Swales
Channels
Channels, Grass
Channels, Open
Chemical
Trentmpnt
Alum Treatment System
Culverts
Energy Dissipation
City of Fort Worth Stormwater Criteria Manual 117
Conveyance
Inlets/Street Gutters
System
Pipe Systems
Detention
Detention, Dry
Underlying soils of hydrologic group "C" or "D" shall b
adequate to maintain a permanent pool. Most group "A
soils and some group "B" soils will require a pond liner.
Detention, Extended Dry
Table 3.29 Soils
Category
integrated Stormwater Controls
Soils
Detention, Multi -purpose Areas
Detention, Underground
Filter Strips
Organic Filters
Filtration
Planter Boxes
Type A or B
Sand Filters, Surface/Perimeter
Clay or silty soils may require pretreatment
Sand Filters, Underground
Hydrodynamic
Devices
Gravity (Oil -Grit) Separator
Downspout Drywell
Infiltration rate > 0.5 inchlhr
Infiltration
Infiltration Trenches
Infiltration rate > 0.5 inchlhr
Soakage Trenches
Infiltration rate > 0.5 inchlhr
Ponds
Wet Pond
`A" soils may require pond liner "B" soils may require
infiltration testing
Wet ED Pond
Micropool ED Pond
Multiple Ponds
Porous Surfaces
Green Roof
Modular Porous Paver Systems
Infiltration rate > 0.5 inchlhr
Porous Concrete
Proprietary
Proprietary Systems 1
Re -Use
Rain Barrels
Wetlands
Wetlands, Stormwater
A" soils may require pond liner
Wetlands, Submerged Gravel
1 = The application and performance of proprietary commercial devices and systems must be provided by the
manufacturer and shall be verified by independent third -party sources and data if used as a primary control.
Table 3.30 Special Watershed Considerations
Category
=-
integrated Stormwate
Controls
pecia[`Watershed Considerations
High Qualify
Stream
quiferProtection
Reservoir Protection
Bioretention
Areas
Bioretention Areas
Evaluate fo
stream warming
Needs to be designed
with no exfiltration (le.
Enhanced Swales
Hotspot runoff must b
Hotspot runoff mus
City of Fort Worth Stormwater Criteria Manual 118
Channels
Channels, Grass
Channels, Open
Chemical
Treatment
lum Treatment System
Conveyance
Culverts
System
Components
Energy Dissipation
Inlets/Street Gutters
Table 3.30 Special Watershed Considerations
Category
integrated Stormwater
Contio[s
SpecialaWatershed Considerations
High Qual.1tyAquifer
Stream
Protection
Reservoir,Protection
Pipe Systems
Detention
Detention, Dry
Detention, Extended Dry
Detention, Multi -purpose
Arpns
Detention, Underground
Filter Strips
Organic Filters
Filtration
Planter Boxes
Sand Filters,
Surface/Perimeter
Evaluate fo
stream warming
Needs to be designed
with no exfiltration (ie.
Sand Filters, Underground
Hydrodynamic
Devices
Gravity (Oil -Grit)
Separator
Downspout Drywell
Infiltration
Infiltration Trenches
Maintain safe distance
from wells and waterfrorn
able. No hotspot runoff
Maintain safe distant
bedrock and
water table. Pretreat
Soakage Trenches
Ponds
Wet Pond
Evaluate forsoils
stream warming
May require liner if "A"
are present
Pretreat hotspots
to 4 ft separation
distance from water
Wet ED Pond
Micropool ED Pond
Multiple Ponds
Porous
Surfaces
Green Roof
Modular Porous Pave
Porous Concrete
Proprietary
Proprietary Systems 1
Re -Use
Rain Barrels
Wetlands
Wetlands, Stormwater
Evaluate folsoils
stream warming
May require liner if "A"
are present
Pretreat hotspots
2 to 4 ft separation
istance from water
Wetlands, Submerged
Gravel
City of Fort Worth Stormwater Criteria Manual 119
able 3.31 Location and Permitting Checklist
Site Feature 'Location
and Permitting Guidance, '
•
Jurisdictional wetlands must be delineated prior to siting structural
control.
•
Use of natural wetlands for stormwater quality treatment is contrary to
the goals of the Clean Water Act and shall not be allowed.
•
Stormwater shall be treated prior to discharge into a natural wetland.
urisdictional Wetland
•
Structural controls may also be restricted in local buffer zones. Buffer
(Waters of the U.S)
zones may be utilized as a non-structural filter strip (i.e., accept sheet
U.S. Army
flow).
Corps of Engineers Regulatory
•
Shall justify that no practical upland treatment alternatives exist.
Permit
.
Where practical, excess Stormwater flows shall be conveyed away from
jurisdictional wetlands.
•
All Waters of the U.S. (streams, ponds, lakes, etc.) shall be delineated
prior to design.
•
Use of any Waters of the U.S. for stormwater quality treatment is
contrary to the goals of the Clean Water Act and shall be avoided.
•
Stormwater shall be treated prior to discharge into Waters of the U.S.
Stream Channel
•
In -stream ponds for stormwater quality treatment are high)
(Waters of the U.S)
discouraged.
U.S. Army
0
Must justify that no practical upland treatment alternatives exist.
Corps of Engineers Section 404
.
Temporary runoff storage preferred over permanent pools.
Permit
•
Implement measures that reduce downstream warming.
Conserve, preserve, protect, recharge, and prevent waste o
Texas Commission on
groundwater resources through Groundwater Conservation Districts
Environmental Quality
•
Groundwater Conservation District pending for Middle Trinity.
Groundwater Management
.
Detailed mapping available from Texas Alliance of Groundwater
Areas
Districts.
•
Specific stream and reservoir buffer requirements.
•
May be imperviousness limitations
Texas Commission on
•
May be specific structural control requirements.
Environmental Quality
•
TCEQ provides water quality certification — in conjunction with 40
Surface Water Quality
permit
Standards
•
Mitigation will be required for imparts to existing aquatic and terrestrial
habitat.
Table 3.31 Location and Permitting Checklist
Site Feature
Location and, Permittin ,Guidance
City of Fort Worth Stormwater Criteria Manual 120
• Grading and fill for structural control construction is general)
discouraged within the 100-year floodplain, as delineated by FEM
flood insurance rate maps, FEMA flood boundary and floodway maps,
100-year Floodplain
or more stringent local floodplain maps.
Local Stormwater review
• Floodplain fill cannot raise the floodplain water surface elevation b
Authority
more than limits set by the appropriate jurisdiction.
Stream Buffer
• Consult local authority for stormwater policy.
Check with appropriate review
• Structural controls are discouraged in the streamside zone (within 25
authority whether stream
feet or more of streambank, depending on the specific regulations).
Call appropriate agency to locate existing utilities prior to design.
Utilities
. Note the location of proposed utilities to serve Development.
Local Review Authority
• Structural controls are discouraged within utility easements or rights o
way for public or private utilities.
Consult TxDOT for any setback requirement from local roads.
Roads
Consult DOT for setbacks from State maintained roads.
xDOT or DPW
Approval must also be obtained for any stormwater discharges to a local
or state-owned conveyance channel.
• Consult local review authority for structural control setbacks from
Structures
structures.
Local Review Authority
Recommended setbacks for each structural control group are provided
in the performance criteria in this manual.
Consult local health authority.
Septic Drain fields
Recommended setback is a minimum of 50 feet from drain field edge
or spray area.
ater Wells
'I00-foot setback for stormwater infiltration.
Local Health Authority
50-foot setback for all other structural controls.
City of Fort Worth Stormwater Criteria Manual 121
3.10 General Design Standards
3.10.1 Utilities
General — In the design of a storm drainage system, the engineer is frequently confronted with the problem of
crossings between the proposed storm drain and existing or proposed utilities such as water, gas and sanitary
sewer lines.
A minimum of two (2) feet of vertical clearance, and five (5) feet horizontal clearance, shall be provided between
storm drain pipes and other public and private utilities. Clearance shall be measured outside of pipe to outside of
pipe or conduit. If the utility separation required by another utility policy is greater, then the larger separation is
required.
Water Lines —AII existing water lines in the immediate vicinity of the proposed storm drains shall be clearly indicated
on both the plan and profile sheets. When design indicates that an intersection of the storm drain line and the water
main exists and the proposed storm drain cannot be economically relocated, then the existing water line shall be
adjusted per Water Department specifications. A minimum of 2 feet vertical clearance shall be maintained,
measured outside of pipe to outside of pipe.
Sanitary Sewers —All existing or proposed sanitary sewers in the immediate vicinity of the proposed storm drains
shall be clearly indicated on both plan and profile sheets. When design indicates an intersection of the storm drain
line and the sanitary sewer, then either line shall be adjusted by relocation. If neither line can be economically
relocated, then an alternative design may be considered, provided it is supported by hydraulic calculations and
accepted by DSD and the Water Department. The alternative design may include a box section in the storm drain
to go over or under the sanitary sewer, or a sanitary sewer crossing through the storm drain. If the latter is chosen,
the crossing must be installed in a manhole or vault to provide both access and additional capacity. In either
alternative, the sanitary sewer must be ductile iron pipe or other material accepted by the Water Department.
All Other Utilities —All other utilities in the immediate vicinity of the proposed storm drain shall be clearly indicated
on both the plan and profile sheets. Gas lines and other utilities not controlled by elevation shall be adjusted when
the design indicates that an intersection of the storm drain line and the utility exists and the proposed storm drain
cannot be economically relocated.
3.10.2 Headwalls, Culverts, and Other Structures
For headwalls, culverts and other structures, standard details adopted by the Texas Department of Transportation
(TxDOT) shall be used. The appropriate detail sheets shall be included in any construction plans. Existing City
standard headwalls may be used, provided that all slopes are modified to 4:1 or flatter. All headwalls and culverts
shall be extended to or beyond the street right-of-way. TxDOT-accepted pedestrian rail shall be used for any
headwall within ten (10) feet of a sidewalk or other normal pedestrian area.
3.10.3 Minimum Pipe Sizes
Minimum pipe sizes are twenty-four (24) inch diameter for mains and twenty-one (21) inch diameter for inlet leads
(laterals). Minimum sizes of conduits of other shapes shall have equivalent cross -sectional areas. Any storm drain
line with two or more inlets shall be considered a main line. Reinforced concrete box (RCB) sections shall have a
height to width ratio no greater than 1:1.5 for RCB that are 4 feet or less in height. For RCB with a height of 5 feet
or greater, any industry standard RCB size height to width ratio is acceptable. For roadway cross drainage
structures (culverts) that are less than 200 feet in length, RCB that is 4 feet high or greater does not have a height
to width ratio requirement.
3.10.4 Pipe Size Changes
Pipe collars or pre -fabricated transition sections shall be provided for all concrete pipe size changes. For
polypropylene pipe, prefabricated transition sections or manholes shall be provided at pipe size changes.
Pipe invert elevations shall be maintained at pipe size change locations. Manholes shall be provided at pipe size
changes when invert elevation is not maintained.
City of Fort Worth Stormwater Criteria Manual 122
3.10.5 Pipe Connections and Curved Alignment
Prefabricated wye and tee connections and other unusual configurations can usually be fabricated by the pipe
manufacturer. Radial pipe can also be fabricated by the pipe manufacturer and shall be used through all curved
alignments. When field connections or field radii must be used, all joints and gaps must be fully grouted to prevent
voids and cave-ins caused by material washout into the storm drain. The City requires the installation of junction
boxes at locations where new storm drain pipes are proposed to connect directly to existing storm drain pipes
between existing access points, or at angles of greater than 600.
3.10.6 Inlets
Inlets shall be used to drainage all curb and gutter streets (flumes are not allowed). All new curb inlets shall be ten
(10), fifteen (15) or twenty (20) feet in length and shall have depressed openings. Recessed inlets shall be provided
on roadways and thoroughfares that are identified on a MTP, and other four lane (two each direction) divided or
undivided roadways. Locate inlets to avoid conflicts between the inlet and driveway by providing minimum of one
(1) foot between the driveway return and inlet gutter transition. Standard inlet depth is 4.5 feet at the lateral line and
4.0 feet at the opposite end, with the bottom sloped to drain to the lateral line. Manhole steps shall be installed for
any inlet over five (5) feet deep. Lateral lines shall be plumbed into the inlet at a manhole opening to expedite
mechanical cleaning and inspection. Standard, or standard recessed inlets, are required. Type 2 inlets (box under
pavement), or type 2 recessed inlets, shall only be used when there are existing utilities that cannot be relocated
and conflict with the necessary location of a standard inlet.
Drop inlets shall be minimum four (4) foot square and shall have manhole access and steps. Due to excessive
clogging, grate inlets are not allowed on any public storm drain.
Inlets shall be constructed per the standard details.
3.10.7 Streets
To minimize standing water, the minimum street grade shall be 0.50%. Along a curve, this grade shall be measured
along the outer gutter line. The minimum grade along a cul-de-sac or elbow gutter centerline shall be 0.70%. Elbows
may be designed with a valley gutter along the normal outer gutter line, with 2% cross slope from curb to the valley
gutter. The minimum grade for any valley gutter shall be 0.50%. Where a crest or sag on a residential street, a PVI
shall be used instead of a vertical curve where the total gradient change is no more than 1.5% (A 5 1.5%) for a
residential or collector street and no more than 1 % for an arterial street.
3.10.8 Flow in Driveways and Intersections
At any intersection, only one street shall be crossed with surface drainage and this street shall be the lower classified
street. Where an alley or street intersects a street, inlets shall be placed in the intersecting alley or street whenever
the combination of flow down the alley or intersecting street would cause the capacity of the downstream street to
be exceeded. Inlets shall be placed upstream from an intersection whenever possible. Surface drainage from a 5-
year flood may not cross any street classified as a thoroughfare or collector. Not more than three (3.0 cfs) cubic
feet per second in a conveyance storm may be discharged per driveway at a business, commercial, industrial,
manufacturing, or school site. Where flume/curb cuts are used to meet the driveway discharge criteria, they shall
not discharge more than 0.5 cfs per linear foot of flume width. Flumes shall not exceed 4 feet in width and be
spaced no closer than the allowable driveway separation for the given street/roadway classification. In all cases,
the downstream storm drainage system shall be adequate to collect and convey the flow, and inlets provide as
required. The cumulative flows from existing driveways shall be considered and inlets provided as necessary where
the flow exceeds the specified design capacity of the street.
City of Fort Worth Stormwater Criteria Manual 123
3.11 Easements, Plats, and Maintenance Agreements
3. 1 1. 1 Easements
Easements are required for all drainage systems that convey stormwater runoff across a Development and must
include sufficient area for operation and maintenance of the drainage system. Types of easements to be used
include:
• Drainage easements shall be required for both on -site and off -site public stormwater drainage
improvements, including standard engineered channels, storm drain systems, detention and retention
facilities and other stormwater controls (Public Water). The Developer shall obtain downstream
drainage easements until Adequate Outfall is determined. Drainage easements shall include a five (5)
foot margin on both sides beyond actual top of bank for improved earthen channels. Retaining walls
are not permitted within or adjacent to a drainage or floodplain easement in a residential area in order
to reduce the easement width. Retaining walls adjacent to the channel are allowed in non-residential
areas only if the property owner provides an agreement for private maintenance.
• Easement encroachments that may interfere with maintenance or operation of a facility are not allowed.
Structures are not allowed to encroach in an easement or the air space above. An executed
encroachment agreement is required for any private improvements that encroach on a drainage
easement, such as trees, fences, and private utility crossings and connections.
• Retaining walls are not permitted to cross a drainage easement. If a drainage easement is bounded
longitudinally by a retaining wall then a minimum five (5) additional feet of easement width shall be
provided. Retaining walls shall be designed to allow for excavation and replacement of the storm drain
facility without causing structural instability of the wall; documentation sealed by a structural engineer
shall be provided.
• Floodplain easements shall be provided on sites along natural or improved drainageways (other than
standard engineered channels to be maintained by the City) to encompass the fully developed 100-
year floodplain plus a ten (10) foot buffer on both sides. The buffer shall be part of the floodplain
easement itself and not a separate easement. Floodplain easements are not routinely maintained by
the City. Retaining walls are not permitted within or adjacent to a floodplain easement in order to reduce
the easement width.
• Natural creeks shall have a dedicated floodplain easement containing the inundation area of a 100-
year frequency storm based on fully developed conditions, plus a ten (10) foot buffer horizontally
adjacent to the inundation area (both sides of creek). The minimum finished floor elevation for lots
impacted by natural creeks shall be a minimum of two (2) feet above the 100-year fully developed water
surface elevation. In addition, a riparian area along the creek may be placed in a drainage easement
for perpetual, limited maintenance by the City, subject to the approval of the City and an agreement to
preserve natural conditions and habitat within the riparian area.
• Concrete -Lined Channels and Gabion-Lined Channels shall have drainage easements dedicated to
meet the requirements of the width of the channel, the one (1) foot freeboard, access easement and
the fence.
• Temporary drainage easements are not accepted in the City.
• Private drainage easements, not dedicated to the City, are required for private stormwater drainage
improvements (no public runoff), including private detention ponds and storm drains that drain runoff
from more than one lot or for stormwater controls on a property. No Development shall prevent another
from draining to an outfall, or storm drain system, that was intended to serve upstream Development.
Private storm drain facilities, including private drainage easements, shall be extended to ensure that all
existing and planned areas may drain to the intended outfall (defined by design plans or drains studies).
Private drainage easements shall be sized using the same criteria as public drainage easements.
• Access easements small be provided for access to public stormwater drainage improvements where
necessary for maintenance.
• Dam easements shall be provided to encompass any proposed dams (including any dams already
existing) and spillway structures. The 100-year water surface of any impounded lake shall be covered
by a floodplain easement as described above. Dams and spillways shall comply with applicable City
policy and state regulations.
City of Fort Worth Stormwater Criteria Manual 124
• No construction shall be allowed within a floodplain easement without the written approval (floodplain
permit) of the City of Fort Worth flood plain administrator or designee, and then only after detailed
engineering plans and studies,show that no increased flooding will result, and that no obstruction to the
natural flow of water will result.
• In certain circumstances where detention is in place or a master drainage plan has been adopted, a
Development may plan to receive less than fully developed flow conditions from upstream with the
approval of the DSD.
• Any parallel utility easements must be separate and outside of drainage easements for channels,
detention ponds and roadside ditches.
• Easements for stormwater controls, including detention basins, sediment traps and retention ponds,
shall 'be negotiated between the City and the Property Owner, but will normally include essential access
to all embankment areas and inlet and outlet controls. Essential access is defined as access in at least
one location.
• The entire reach or each section of any drainage facility must be readily accessible to maintenance
equipment. Additional easement(s) shall be required at the access point(s) and the access points shall
be appropriately designed to restrict access by the public (including motorcycles).
• Drainage easements for structural overflows, swales, or berms shall be of sufficient width to encompass
the structure or graded area and shall not be less than 15 feet in width.
• Easement Encroachments from structures shall be limited to: awnings and similar overhang
architectural features that can be quickly and easily removed and elevated at 22 feet above the ground.
Minimum easement width requirements for storm drain pipe are shown in Table 3.30 and shall be as follows:
Drainages easements shall be centered on storm drain pipe. The outside face of the proposed storm
drain line shall be placed a minimum of five (5) feet off either edge of the storm drain easement. The
proposed centerline of overflow swales should coincide with the centerline of the easement.
• A minimum of five (5) additional feet shall be dedicated when shared with other City owned utilities.
Utility easements for franchise utilities shall be separate and outside of drainage easements.
• Box culvert minimum easement width shall be determined using Table 3.30 based on an equivalent
box culvert width to pipe diameter.
• For parallel storm drain systems with a combined width greater than eight (8) feet the minimum
easement shall be equal to the width of the parallel storm drain system plus twenty (20) additional feet.
• Drainage easements shall extend at least twenty-five (25) feet past an outfall headwall to provide an
area for maintenance operations. Drainage easements along a required outfall channel or ditch shall
be provided until the flowline reaches an Adequate Outfall. Storm drain centerline shall not be on
property line, and shall be aligned so that the easement is not divided by a property line.
Table 3.32 Closed Conduit Easements
'Pipe Size
Minimum Easement Width Required
39" and under
15 Feet
42" through 54"
20 Feet
60" through 66"
25 Feet
72" through 102"
30 Feet
Box culverts and arch pipes shall have an easement width equal to the width of the box or arch plus
twenty (20) additional feet. The edge of the box shall be located five (5) feet from either edge of the
easement.
City of Fort Worth Stormwater Criteria Manual 125
Drainage easements shall encompass .the entire width of an overflow flume plus five (5) feet on each
side. For an easement containing both a concrete flume and a storm drain, the wider of the two
easement criteria shall control.
• Alternatively, a drainage right -of way or HOA lot (not part of any adjacent lot) may be dedicated for the
width of the flume provided that an additional easement is dedicated for any storm drain pipe to meet
the total width requirements specified above.
• Drainage easements in a Single -Family Residential subdivision shall be located within an HOA open
space lot.
• Additional easement width shall be provided when the top of the pipe is more than 5 feet below the
existing or proposed top of ground (whichever is higher). The easement shall be a minimum 2 feet
wider for each additional foot of depth beyond 5 feet.
3.11.2 Plats
All platting shall follow established Development standards for the City. Plats shall include information such as
drainage easement width and location and minimum finish floor elevations that will be filed with the plat. A final plat
shall include, but not be limited to, the following items:
1. All existing and proposed public and private drainage easements, including those recorded by separate
instrument
2. Easements to be recorded by separate instrument shall be documented on the plat, labelled, and include a
recorded document number.
3. Minimum finished floor elevations shall be 2' above the 100 yearfully developed condition and shall be shown
on plat.
4. Labelled with the100 year fully developed inundation limits referencing the accepted study.
5. All floodplain easements
6. City Flood Risk Areas (CFRA) shall be delineated on plats. An easement would not be required for mapped
and adopted CFRA.
7. FEMA SFHA delineation effective at the time of plat submission to the City
8. Legal disclosure for drainage provisions upon sale or transfer of property
9. Documentation of maintenance responsibilities and agreements including transfer of responsibility upon sale
of the property
10. Floodplain easements and drainage easements that contain an open channel shall be platted as either parks
or HOA open space lots to assure long term maintenance.
11. Drainage easements shall be platted within an open space lot, designated as a X lot, and maintained by a
home owners association or property owners association.
12. Preliminary and final plats shall incorporate adjacent floodplain, open channel, drainage easement, creeks,
or natural flow paths. These features shall not be "out platted". The plat area shall extend to at least the
centerline of the flow path, and may extend beyond to incorporate the entire feature or planned open space
lot.
13. Standard notes and reference to accepted Drainage Study and Flood Study.
14. Driveway culvert table (if the subdivision has a rural street section), see driveway culvert criteria for more
details.
Where plat notes reference a requirement to provide a Preliminary SWMP and Final SWMP, then the project shall
require an accepted Drainage Study and issued Grading Permit before issuance of a building permit.
City of Fort Worth Stormwater Criteria Manual 126
3.11.3 Maintenance Agreements
All drainage improvements constructed within a Development and any existing or natural drainage systems to
remain in use shall require a maintenance agreement that identifies responsible parties for maintenance. Both
private and public maintenance responsibility shall be defined and documented in the agreement. The maintenance
agreement shall be written such that it remains in force upon sale or transfer of the property.
A Stormwater Facility Maintenance Agreement (SWFMA) must be prepared by the engineer for each stormwater
control that will not be wholly maintained by the City, as part of the Operations and Maintenance Plan submittal.
This agreement must outline both preventive maintenance tasks as well as major repairs, identify the schedule for
each task, assign clear roles to affected parties, and provide a maintenance checklist to guide future owners,
including an annual self -inspection to be provided to the City. Multiple stormwater controls may be contained within
a single Stormwater Facility Maintenance Agreement. When areas are identified for detention also serve the
Development as a parking lot, truck court or loading dock then the requirement for a SWFMA may be waived.
Redevelopment of such a design shall provide equivalent detention and detain back to an undeveloped peak
discharge.
3.11.3.1 City Maintenance
The City will provide for perpetual maintenance, in accordance with adopted city maintenance standards, of all
public drainage facilities located within dedicated easements, and designed and constructed to the City standards.
In addition, limited perpetual maintenance may be provided by the City for riparian areas placed in a drainage or
other types of easement preserved in their natural state, subject to the approval of the City. Access shall be provided
and dedicated by the Developer to all public stormwater facilities in Developments for maintenance and inspection
by the City. All facilities shall be provided with access that meets the needs of the equipment used to perform
maintenance activities.
3.11.3.2 Private Maintenance (SWFMA Required)
• Private drainage facilities include those drainage improvements which are located on private property
and which handle only private water.
• Private drainage facilities may also include detention or retention ponds, dams, retaining walls adjacent
to channels in nonresidential areas, and other stormwater controls which collect public water, as well
as drainageways not constructed to City standards but which convey public water. Such facilities must
be designed in accordance with sound engineering practices and reviewed and inspected by the City.
• An agreement for perpetual maintenance of private drainage facilities serving public or private water
shall be executed with the City and recorded with the County. This agreement shall run with the land
and can be tied to commercial or non single family residential property, or to an owner's association,
but not to individual single family residential lots.
• Access shall be provided by the Developer /owner to all private drainage facilities.
• A SWFMA shall be required for all mitigation and water quality devices; including those water quality
devices and facilities required as a condition of Tarrant Regional Water District (TRWD) approval.
• A SWFMA shall be recorded before approval of a final plat for single family residential developments.
A SWFMA shall be recorded before issuance of a building permit (all development types).
3.11.3.3 Maintenance Agreement Requirements
Details of the agreement must be set forth in a series of exhibits:
1. Exhibit Legal Description -This includes the Metes and Bounds, a Surveyor's Drawing of the area occupied
by the facility, and a copy of the preliminary or final plat containing the facility.
2. Exhibit B Design Plan and Specifications -these are summary documents intended for the use of future
owners in conducting routine maintenance, inspections and repairs.
a. Design Data and Calculations -This can be in the form of a letter or statement from the engineer
which summarizes critical design calculations related to the functionality of the facility such as
storage volume or TSS removal, and attest to the facility conforming to applicable City Stormwater
Criteria or iSWM standards.
City of Fort Worth Stormwater Criteria Manual 127
b. Schematic Plan -This shall be prepared by the engineer from construction drawings to show the
general layout of the facility. Major features requiring regular or special maintenance shall be shown
and labeled in general terms understandable to a layman. A profile shall be given showing critical
elevations that control the function and capacity of the facility, and one or more cross -sections shall
be provided to indicate the general grading of the facility. A typical example of a schematic plan for
a simple detention basin is shown in Figure 3.18.
c. Details — detail drawings shall be provided for the outlet control structure(s), flumes, weirs, and all
other structures associated with the facility.
d. Landscaping -Vegetation shall be shown consistent with the accepted Landscape Plan, either on
the Schematic Plan or as a separate drawing.
3. Exhibit C Operations and Maintenance Plan -Specific maintenance tasks shall be defined for each element
of the facility. Maintenance tasks specific to the facility shall be described in simple terms consistent with
nomenclature contained in the Schematic and Landscape plans. An inspection and maintenance frequency
shall be established for each task.
4. Exhibit D Maintenance Checklist -A checklist consistent with the Operations and Maintenance Plan shall be
provided for the use of future owners in performing routine and special maintenance tasks. This list shall
describe work required and frequency in language that is easy to understand and specific for the facility to
be maintained. This form will be completed by the Owner and submitted to the City annually as part of a
regular self -inspection program. See Inspection Checklist for Simple Detention Basin Form CFW-6 for an
example checklist for a simple detention basin. In some cases, this example checklist can be used as is
and included in Exhibit D.
Additional guidance for facility maintenance is provided in the iSWM Technical Manual, for several types of
stormwater controls. The engineer must certify that the construction has been completed in accordance with the
general plans and Schematic Plan. After approval of construction by the City, an engineer is expected to provide
guidance to the owner's representative in implementing the accepted maintenance program and to co-sign the first
annual inspection after the construction. A checklist for preparing a Stormwater Facility Maintenance Agreement is
provided by the City and shall be completed and submitted with the SWFMA application.
City of Fort Worth Stormwater Criteria Manual 128
EL. = 700 B
7a0
E c6— 698
fist
A I 6ss Q�C0 q
t � � co � � CR
EL. = 696 695.5 �
L. = 695,9 N 10.0'
16.0.` 66.5' 16:0' 20A'
696
698 697
EL. = 699 E I I
699 •- II �
700 OaQ
CD10.0' i I—jMQ
700 I I�•N
699
698
697 EL. = 698.8
696
695
EL. = 695.32
EL.. = 695.28
B
.PLAN VIEW
N.T.S.
101-0° i 0'-00
EL. = 700 100 Yr. WSEL = 699.0 EL. = 700
1 4 1.0% 1 1 4
EL. = 696 EL. = 696
EL. = 695.9 SECTION A A- EL. = 695.6 EL. = 695
N.T.S.
90`-00 EL = 700
EL = 698.8 EL. = 699 100 Yr. WSEL=,699.0
1 4 — 1.0% - 1 EL = 700
3S LF CF L. = 695.5 EL. = 696
24° RCP SD
EL = 695 @ o.fi__; SECTION B-B EL. = 695.8
N.T.S.
Figure 3.18 Typical Detention Pond Exhibit B — Example
City of Fort Worth Stormwater Criteria Manual 129
3.12 Plan and Document Preparation Requirements
Plans and documents submitted for review by the Infrastructure Plan Review Center or for a Grading Permit shall
include, but not be limited to, the following:
Cover sheet, Genera[ Requirements and Drafting Standards:
• All cover sheets for Developer projects shall comply with the current version of the cover sheet template
promulgated by the City's Infrastructure Plan Review Center (IPRC).
• For Developer projects, the current version of the title block promulgated by the City's Infrastructure
Plan Review Center (IPRC) shall be used.
• Full size drawings shall be submitted on 22" x 34" for both paper and electronic submissions.
• A copy of the recorded (or proposed) Final Plat or Draft Horizontal Control Plan of the project area must
be included in the construction plans for Developer projects.
• Contact Information -- Contact information for the City Project Manager; DigTess electric, gas, and
communication utilities shall be included in the City Standard General Notes as set forth in the City's
Standard Construction Specifications and Details. Telephone numbers for any other entities affected
by the project, including but not limited to the Texas Department of Transportation (TxDOT) or a railroad
company must be included in the General Notes.
• Fort Worth standard symbols and abbreviations must be used in construction plans. Refer to Section
8.3 (Water and Wastewater Main Plan and Profile Sheet Requirements) and Section 8.4 (Standard
Abbreviations) for standard abbreviation and drafting symbols.
• All construction plans shall be submitted in black ink. Colored construction plans are not allowed.
General Plan View, Design & Layout:
• All construction plans shall be sealed by a Professional Engineer licensed by the State of Texas
• Label existing, proposed, and future utilities and/or provide line type legend
• Existing contours and existing features shall be dashed or other utility line type and shaded back
• Proposed contours and proposed features shall be of a solid or other utility line type and bold
• Existing contours must extend a minimum of 20' outside project boundary or to an appropriate tie-in
• Provide and label existing file numbers for existing storm drain infrastructure. File numbers to be
obtained from existing infrastructure plans.
• Show and label proposed drainage infrastructure in plan and profile view consistent with calculations
• Retaining walls are not permitted in public right of way, drainage easements (unless approved via an
encroachment agreement), or floodplain easements
• Retaining walls adjacent to public facilities (ROW, easements) must be designed to TX DOT standard
and included in the IRPC or private plan set
• Add relevant notes as supplied by staff based on submitted plans such as erosion control notes or
return to existing grade notes.
Grading and Drainage Plan & Profile:
• Show and label temporary or interim controls needed for phasing of storm drain systems for phased
subdivisions such as temporary outfall channels, temporary headwalls, and temporary drop inlets.
• Storm line mains/channels must be presented in plan and profile view on the same sheet
• Storm laterals can be presented on one overall sheet
• Plan view horizontal scale must be 1"=40', vertical scale V=4'
• When water or sewer mains or laterals cross storm drains, a minimum clearance of 2 feet as measured
from the outside diameter of each pipe shall be maintained.
• Water and sanitary laterals may not be located directly under inlet or junction boxes. A minimum of two
(2) feet of horizontal clearance is required between laterals and outer edge of boxrunction
• All easements for a channel must include the entire depth of the channel and 5' beyond top of bank on
both sides
City of Fort Worth Stormwater Criteria Manual 130
• Private storm infrastructure must be labeled or otherwise denoted as private
• Pipe profiles shall include pipe size, length, slope, flow line elevations, and 100-year HGL shown and
labeled, headwater and tailwater shown and labeled for culverts, design frequency, headwall/end
section callout, flow rate and velocity specified
• Channel profiles shall include lining type, existing and proposed centerline, proposed right and left top
of bank, slope and 100-year water surface elevation, design flow, and velocity. Outfall details, drop
structures, and energy dissipaters, shall be labeled and construction details shall be provided.
The source of starting tailwater shall be stated on hydraulic tables. Hydraulic grade lines for plans,
profiles and tables must be consistent at all locations.
• Upstream and offslte bypass for the current phase of Development shall be accounted for in the bypass
column of hydraulic tables.
• Channel cross section(s) must be provided to show compliance with minimum channel requirements
per Section 3.8.4
• Provide cross section for roads and alleys with relevant calculations (flow, velocity, depth, n, etc.)
• Grade to drain callouts are not acceptable
Label top of curb elevations along street and around cul-de-sacs/elbows
• Finish pad elevations must be shown to document minimum finish floor elevation compliance with
section 3.11 (min 2' above 100 year fully developed water surface)
• Show directional flow arrow on lots
• Label each lot grading type on the lot or provide a chart indicating the lot grading type
• Lot grading type detail(s) shall be provided
• Phased lot grading must be designed such that new construction will not increase runoff to existing
homes
• Superelevation or pavement warping may not be used in lieu of inlets at low points.
• Flumes in lieu of inlets are not permitted, inlets shall be used to drain streets.
Floodplain, Easements, & Labels:
Delineate and label floodplain and floodplain easement on all civil plan sheets. Floodplain label shall
include a reference to the Floodplain Development permit number, Flood study number for FEMA
floodplains, or SWM number for non -regulatory floodplains.
Finish pad elevations must be shown to document minimum finish floor elevation compliance with
Section 3.11 (min 2' above 100 year fully developed water surface)
Retaining walls are not permitted in public right of way, drainage easements (unless a waiver is
approved in conjunction with an encroachment agreement), or floodplain easements.
Erosion & Sediment Control Plan:
• Existing and proposed contours with labels and flow arrows must be shown on the erosion control plan
• Existing and proposed storm infrastructure must be shown on Erosion Control Plans
• City genera[ Erosion Control Notes shall be added to the City Notes sheet
• A legend showing Erosion and Sediment Control measures must be provided
• The SWPPP location near the construction exit must be shown and labeled.
• A silt fence must be located at the toe of graded slopes
• Limits of disturbance, including off -site areas that will be disturbed and natural features to be protected
within the disturbed areas, must be shown on the plan sheet
• Location, details, and notes for erosion controls must be provided
• Location, details, and notes for waste controls (toilets, demolition material, and other potential sources
of pollution) must be shown on the plan sheet.
• BMP Design Calculations for erosion, sediment, and waste controls must be shown on the plan sheet
• Inspection and maintenance notes must be provided on the plan sheet.
City of Fort Worth Stormwater Criteria Manua[ 131
Sequence of BMP installation based on sequence of construction phases must be provided on the plan
sheet.
• Schedule and phasing of temporary and permanent stabilization on different area of the site must be
shown on the plan sheet.
• Temporary structures that will be converted into permanent stormwater controls must be shown on the
plan sheet.
• Sites draining 10 or more acres must use sediment traps or ponds
• Top soils must be banked on site. If top soils are not banked on site, then comments describing the
provisions being made for soil amendments must be included on the plan sheet.
• All plan sheets must be prepared by an engineer
• All erosion and sediment control plans must comply with Chapter 4 of this Manual
Drainage Area Maps:
• Project boundaries must be shown.
• Topography must be shown with 1 or 2 foot contour intervals. For areas more than one square mile, 5
or 10 foot contour intervals must be used.
• The map must be labeled with USDA hydrologic soil types or a separate soils map must be provided
• Perennial or intermittent stream centerlines must be shown.
• FEMA floodplains, studied floodplains, floodp[ain easements and open channels must be delineated
on the map.
• Locations of wetlands, damns and impoundments must be shown.
• Roads, buildings and other impervious areas must be shown on the map.
• Locations and size major utility lines and easements must be shown on the map.
• Location, size, and City File Number for existing stormwater conveyance systems such as storm drains,
inlets, catch basins, channels, swales, and areas of overland flow must be shown on the map.
• Locations and dimensions of channels, bridges, or culvert crossings must be shown on the map.
• Delineation of watershed boundaries with flow arrows must be shown on the map.
• Offsite drainage areas must be delineated on the map.
• Time of concentration calculations for each area and lag time calculations for hydrograph methods
must be shown on the map.
• The longest flow path for each drainage area must be shown on the map.
• A computation table showing drainage areas, runoff coefficients or curve numbers, time of
concentration or lag times, rainfall intensities and peak discharges for the 1, 5, and 100-year storms,
for existing, proposed and ultimate conditions must be shown. The collection design point for each
drainage area must also be shown
• The location of all site outfalls or where runoff leaves the site must be shown
• Zoning and land use must be shown on the map.
• Changes to watershed boundaries must be identified on the map.
• Composite calculations for runoff coefficients or curve numbers must be shown on the map.
• The entire Zone of Influence must be delineated.
• Downstream constrictions with runoff controls must be shown.
• Drainage area maps for existing, proposed and ultimate conditions must be provided. When the project
is a multi -phase project, an overall drainage area map with all phases labeled must be provided.
• Proposed stormwater facilities with private maintenance (including private storm drains) must be
provided. If detention is proposed, the volume required must be shown
• Drainage area map basin labels shall be consistent with hydrologic and hydraulic calculations tables
• Basins must be identified using an icon with the ID code and Area (flow rate may also be included)
City of Fort Worth Stormwater Criteria Manual 132
to — ARLA
DRAINAGE AREA la
I.00 ice'ACRES
Construction Details
• All detail sheets provided in the construction plan set shall be comprised of at least one detail and a
maximum of eight details to ensure that the details are not too small and all details are legible. This is
dependent on the orientation and size of each detail.
• Provide only applicable details in accordance with the City Standard Construction Details related to the
project.
• A backfill, embedment and surface detail assembly for all storm drain mains and laterals to be
constructed shall be provided on the construction plans.
Provide a customized and engineered (sealed) construction detail for any non-standard installations
such as specialized junction structures, or otherfeatures that the City does not provide a standard detail
for.
City of Fort Worth Stormwater Criteria Manual 133
4 Stormwater Construction Criteria
This chapter presents an integrated approach for reducing the impact of stormwater runoff from construction
activities on downstream natural resources and properties. The purpose is to provide design criteria for temporary
controls during construction that protect water quality by:
Preventing soil erosion;
Capturing sediment on -site when preventing erosion is not feasible due to construction activities; and
Controlling construction materials and wastes to prevent contamination of stormwater.
Temporary controls to protect water quality are known as Best Management Practices (BMPs). The design of the
BMPs is to be coordinated with and done at the same time as the Drainage Study and Construction Plans.
Construction BMPs complement and work with the site grading and drainage infrastructure.
Erosion Control BMPs are designed to minimize the area of land disturbance and to protect disturbed soils from
erosion. Protection can be accomplished by diverting stormwater away from the disturbed area or by stabilizing the
disturbed soil. Erosion control BMPs are most important on disturbed slopes and channels where the potential for
erosion is greatest. The design of erosion control BMPs must be coordinated with related grading, drainage and
landscaping elements. (e.g. channel armoring, velocity dissipaters, etc.)
Sediment Control BMPs are temporary structures or devices that capture soil transported by stormwater. The
BMPs are designed to function effectively with the site drainage patterns and infrastructure. An effective design
ensures that the sediment control BMPs do not divert flow or flood adjacent properties and structures. Some types
of permanent drainage structures, such as retention basins, can also be designed to function as a sediment control
BMP during construction.
Material and Waste Control BMPs prevent construction materials and wastes from coming into contact with and
being transported by stormwater. These BMPs consist of a combination of notes to direct contractors and temporary
construction controls.
The iSWM Construction Criteria are the minimum requirements for temporary controls during construction and are
adopted and incorporated herein by reference. The state permit and requirements for stormwater discharges
associated with construction activities must also be followed. More information on state requirements is provided in
Section 4.2,
4.1 Applicability
The City has established requirements for controlling construction runoff for all land disturbance activities, even
where there is less than 1.0 acre of disturbed surface.
Construction activities shall comply with the SWPPP requirements in the effective TPDES General permit relating
to Stormwater Discharges from Construction Activities, of the Stormwater Pollution Control Ordinance and the
appropriate federal (Environmental Protection Agency) and state (Texas Commission on Environmental Quality)
regulations. When the ordinance and applicable regulations are in conflict, the most stringent requirements shall
apply.
See Appendix D (Sediment and Erosion Control Guidelines for Small Sites).
4.2 Introduction
The City requires the use of temporary controls during construction to prevent or reduce the discharge of sediment
and other pollutants from the construction site. The temporary controls are known as Best Management Practices
(BMPs). BMPs may be activities, prohibitions, maintenance procedures, structural controls, operating procedures
and other measures to prevent erosion and control the discharge of sediment and other pollutants.
Construction BMPs fall into three general categories: Erosion Control, Sediment Control, and Material and Waste
Control. The first category prevents erosion, and the second catches soil from erosion that does occur. It is generally
more effective and less expensive to prevent erosion than to treat turbid runoff. Material and waste controls are for
other sources of stormwater pollutants on a construction site.
City of Fort Worth Stormwater Criteria Manual 134
The following priorities shall be applied to the selection of construction BMPs:
• Retain native topsoil and natural vegetation in an undisturbed state by incorporating natural drainage
features and buffer areas into the site design.
Limit the area of disturbance and vehicle access to the site.
• Limit the extent of clearing operations and phase construction operations to minimize the area disturbed
at any one time.
• Stabilize disturbed areas as soon as possible (not at the end of construction), particularly in channels
and on cuttfill slopes.
• Minimize the disturbance of steep slopes during construction, and minimize slope length and
steepness.
• Coordinate stream crossings and minimize the construction of temporary stream crossings.
• Provide sediment controls, including but not limited to perimeter controls, where stormwater discharges
will occur from disturbed areas.
• Prevent tracking of sediment off -site through the establishment of stabilized construction entrances and
exits.
• Control sediment and other contaminants from dewatering activities.
• Control discharges of construction materials and wastes.
4.2.1.1 State Requirements
In addition to the City requirements outlined in this chapter, land disturbing activities must comply with the Texas
Commission on Environmental Quality (TCEQ) requirements under General Permit Number TXR150000,
commonly referred to as the "Construction General Permit." This permit contains requirements for a Stormwater
Pollution Prevention Plan (SWPPP), state and local notifications, and installation, maintenance, and inspection of
best management practices on construction sites. The Water Quality Technical Manual contains information for
preparing a SWPPP. However, compliance with the Construction General Permit is beyond the scope of this Manual
and is the sole responsibility of the construction site operator(s).
4.3 Criteria for BMPs during Construction
The Erosion Control Plan shall include the following:
• Topography.
• Limits of all areas to be disturbed by construction activity, including off -site staging areas, utility lines, batch
plants, and spoil/borrow areas.
• Location and types of erosion control, sediment control, and material and waste control BMPs;
• Construction details and notes for erosion control, sediment control, and material and waste control BMPs.
• Inspections and maintenance notes.
• All items listed in Section 3.12
BMPs and notes shall be provided for all the elements listed in this Section, unless site conditions render an element
not applicable. BMPs shall be selected and designed according to the technical criteria in the Construction Controls
Technical Manual. Site data gathered and analyzed in Step 1 of the integrated Development Process shall be the
basis for selecting BMPs.
The minimum design storm for temporary BMPs is the 2-year, 24-hour duration storm event. Design calculations
for all BMPs shall be included in the construction plans.
Plans for temporary BMPs shall be prepared by a Certified Professional in Erosion and Sediment Control (CPESC),
a licensed Professional Engineer or registered Landscape Architect in the State of Texas who has documented
experience in hydrology and hydraulics and erosion and sediment control.
It is the responsibility of the engineer to design appropriate BMP's for each site. If the most appropriate BMP is not
in the NCTCOG BMP Manual, the engineer shall submit calculations and references for design of the BMP to City.
City of Fort Worth Stormwater Criteria Manual 135
4.3.1 Erosion Controls
Erosion control is first line of defense and the primary means of preventing stormwater pollution. They shall be
designed to retain soil in place and to minimize the amount of sediment that has to be removed from stormwater
runoff by other types of BMPs. Fact Sheets for different types of Erosion Control BMPs are in the iSWM Technical
Manual.
4.3.1.1 Limits of Disturbance
On the iSWM Construction Plans, clearly show the limits of the area to be disturbed and the area in acres draining
to each outfall.
Design Criteria:
• Minimize the disturbance of steep slopes.
• Constrain the disturbed area to the minimum necessary to construct the project.
+ Include the contractor's staging area, borrow/spoil area, utilities and any other areas on or off site that
will be disturbed in support of the construction activity.
• Specify construction fencing or similar protective measures to prevent disturbance of natural drainage
features, trees, vegetative buffers and other existing features to be preserved.
4.3.1.2 Slope Protection
Slope protection shall be provided for disturbed or cut/fill slopes that are one vertical on three horizontal (3H:1V) or
steeper, fifty (50) feet in length or longer, or on highly erodible soils. Show the location and type of BMPs to be used
on the plans.
Design Criteria:
• Where feasible, add notes that prohibit disturbing the slope until final site grading.
• Where a stabilized discharge point is available, provide temporary berms or swales to direct stormwater
away from the slope until the slope is stabilized.
• Check dams shall be used within swales that are cut down a slope.
• Temporary terraces, vegetated strips or equivalent linear controls shall be specified at regular intervals
to break-up slopes longer than fifty (50) feet until the slope is stabilized.
• Specify final stabilization measures to be initiated within 14 days of completing work on the slope.
• Hydromulch is prohibited for slope stabilization unless the slope is one vertical on five horizontal
(5H:1V) or less.
4.3.1.3 Channel Protection
Show the location and type of BMPs used to prevent the erosion of channels, drainage ways, streambanks, and
outfalls until permanent structures and final stabilization measures are installed.
Design Criteria:
• Provide temporary energy dissipaters at discharge points.
• If final channel stabilization consists of vegetation, anchored erosion control blankets, turf reinforcement
mats, or an equivalent BMP that is resistant to channel flow shall be installed until the vegetation is
established.
• If the BMPs include check dams, velocity dissipaters or other structures that extend into the channel,
the BMPs shall be designed by a licensed engineer to function under the flow conditions produced by
the design storm. The engineer shall verify that the BMPs will not divert flow or cause flooding of
adjacent properties and structures.
• Specify final stabilization measures to be initiated within 14 days of completing work on the channel.
City of Fort Worth Stormwater Criteria Manual 136
4.3.1.4 Temporary Stabilization
Portions of a site that have been disturbed but where no work will occur for more than 21 days shall be temporarily
stabilized as soon as possible, and no later than 14 days from cessation of work, except when precluded by
seasonal and conditions or prolonged drought.
Temporary stabilization shall consist of providing a protective cover, without large bare areas, that is designed to
reduce erosion on disturbed areas. Temporary stabilization may be achieved using the following BMP's: temporary
seeding, soil retention blankets, fibrous mulches, hydra -mulches and other techniques that cover 100% of the
disturbed areas until final stabilization can be achieved or until further construction activities take place.
Design Criteria:
• Stabilization measures shall be appropriate for the time of year, site conditions, and estimated duration
of use.
• Stabilization BMPs shall be provided for soil stockpiles.
4.3.1.5 Final Stabilization
Final stabilization practices shall be specified for disturbed areas that are not covered by buildings, pavement or
other permanent structures upon completion of construction. Final stabilization measures shall be coordinated with
the site's landscaping plan.
Design Criteria:
• Final stabilization shall be specified to start within fourteen days of completing soil disturbing activities.
• if space is available, top soil shall be stockpiled during construction and distributed onto the surface of
disturbed areas prior to final stabilization.
• If top soil has not been stockpiled, soil amendments (compost, fertilizer, etc.) shall be specified with the
final stabilization measures.
• Final stabilization measures must provide a perennial vegetative cover with a uniform density of 70%
of the native background vegetative cover or equivalent permanent measures (riprap, gabion, or
geotextiles).
• Hydra -mulch will not be allowed in vegetated swales, channels or other drainage ways. BMPs may
remain in place during stabilization; however, BMPs shall be removed after stabilization is achieved.
The plan for final stabilization shall be coordinated with the permanent BMPs in the SWPPP and with
the landscaping plan, if applicable.
• Include notes requiring temporary BMPs be removed within 30 days of establishing final stabilization.
• A Notice of Termination (NOT) must be filed in accordance with the TCEQ TPDBS General Permit
TXR15000, usually within 30 days after final stabilization of operational control. All parties that
submitted a NO[ shall submit a NOT within 30 days after final stabilization is established. When the
owner of a residential subdivision transfers ownership of individual lots to builders before final
stabilization is achieved, the SWPPP shall include controls for each individual lot in lieu of final
stabilization. These controls shall consist of stabilization of the right-of-way and placement of structural
BMPs at the low point of each individual lot or equivalent measures to retain soil on each lot during
construction. Additionally, the builder must submit a valid NOI before or NOT can be submitted by the
owner.
4.3.2 Sediment Controls
Sediment control BMPs shall be designed to capture sediment on the site when preventing erosion is not feasible
due to on -going construction activity. Sediment control BMPs and their locations shall be designed to change with
the different phases of construction as site conditions and drainage patterns change. Sediment controls for the
initial phase of construction shall be installed before any site disturbing activities begin. Fact Sheets for different
types of Sediment Control BMPs are in Section 3.0 of the Construction Controls Technical Manual.
City of Fort Worth Stormwater Criteria Manual 137
4.3.2.1 Sediment Barriers
Sediment barriers may be linear controls (silt fence, compost socks, sediment logs, wattles, etc.), check dams,
berms, sediment basins, sediment traps, active treatment systems and other structural BMPs designed to capture
sediment suspended in stormwater.
Design Criteria:
• Sediment barriers shall be designed to treat the volume of runoff from the design storm.
• Sediment barriers are not required for areas of the site that are undisturbed.
• If linear controls are used as the only sediment barrier for a project, the linear control shall be provided
at a rate of 100 linearfeet per quarter -acre of disturbed area. A series of linear controls may be needed
throughout the site and are not limited to the perimeter.
• Linear controls shall not be used across areas of concentrated flow, such as drainage ditches, swales
and outfalls.
• A sediment basin shall be provided where stormwater runoff from 10 acres or more of disturbed area
flows to a common drainage location, unless a basin is infeasible due to site conditions or public safety.
The basin shall be designed for the volume of runoff from the total area contributing (on -site and off -
site) to the common drainage location, not just the volume from the disturbed portion of the contributing
area. Stormwater diversion BMPs may be used to divert stormwater from upslope areas away from and
around the disturbed area to minimize the design volume of the sediment basin.
• Both existing topography and graded topography shall be evaluated when determining if 10 acres or
more discharges to a common location.
• if a sediment basin is infeasible on a site of 10 acres or more, a series of smaller sediment traps and/or
linear controls shall be provided throughout the site to provide an equivalent level of protection.
• Permanent detention and retention basins may be used as a sediment basin during construction if all
sediment is removed upon completion of construction.
4.3.2.2 Perimeter Controls
A linear BMP shall be provided at all down slope boundaries of the construction activity and side slope boundaries
where stormwater runoff may leave the site. Linear sediment barriers may be used to satisfy the requirement for
perimeter controls.
4.3.2.3 Storm Drain Inlet Protection
Storm drain inlet protection shall not be used as a primary sediment control BMP unless all other primary controls
are infeasible due to site configuration or the type of construction activity. Inlet protection is intended to be a last
line of defense in the event of a temporary failure of other sediment controls.
Design Criteria:
• The operator will be expected to diligently monitor storm conditions and to remove inlet protection when
there is a risk of flooding.
• Inlet protection shall only be specified for low point inlets where positive overflow is provided.
• Drainage patterns shall be evaluated to ensure inlet protection will not divert flow or flood the roadway
or adjacent properties and structures.
4.3.2.4 Construction Access Controls
BMPs shall be provided to prevent off -site vehicle tracking of soil and pollutants.
Design Criteria:
Limit site access to one route during construction, two routes are allowed for linear projects.
Design the access point(s) to be at the upslope side of the construction site. Do not place the
construction access at the lowest point on the construction site.
Specify rock stabilization or an equivalent BMP for all access points.
City of Fort Worth Stormwater Criteria Manual 138
Include notes requiring soil tracked onto public roads be removed at a frequency that minimizes site
impacts and prior to the next rain event, if feasible.
Using water to wash sediment from streets is prohibited.
4.3.2.5 Dewatering Controls
Water pumped from foundations, vaults, trenches and other low areas shall be discharged through a BMP ortreated
to remove suspended soil and other pollutants before the water leaves the site. The plans shall include notes that
prohibit discharging the water directly into flumes, storm drains, creeks or other drainage ways. Where state or local
discharge permit requirements exist for the pollutant(s) suspected of being in the water, the plan shall include the
discharge permit conditions.
4.3.3 Material and Waste Controls
Notes shall be placed on the iSWM Construction Plan for the proper handling and storage of materials and wastes
that can be transported by stormwater. At a minimum, notes shall be provided for the materials and wastes in Table
4.1. Additional notes and BMPs shall be provided if other potential pollutants are expected to be on -site.
Construction details shall be provided when necessary to ensure proper installation of a material or waste BMP.
All material and waste sources shall be located a minimum of fifty (50) feet away from inlets, swales, drainage ways,
channels and waters of the U.S., if the site configuration provides sufficient space to do so. In no case shall material
and waste sources be closer than twenty (20) feet from inlets, swales, drainage ways, channels and waters of the
U.S.
City of Port Worth Stormwater Criteria Manual 139
Table 4.1 Requirements for Materials and Wastes
Material or
Requireritents
Waste
Sanitary
Sanitary facilities shall be provided on the site, and their location shall be shown on the iSWM
Facilities
Construction Plan. The facilities shall be regularly serviced at the frequency recommended by
the supplier for the number of people using the facility.
Trash and
Show the location of trash and debris storage on the iSWM Construction Plan. Store all trash
Debris
and debris in covered bins or other enclosures. Trash and debris shall be removed from the
site at regular intervals. Containers shall not be allowed to overflow.
The amount of chemicals and hazardous materials stored on -site shall be minimized and
limited to the materials necessary for the current phase of construction. Chemicals and
hazardous materials shall be stored in their original, manufacturer's containers inside of a
Chemicals
shelter that prevents contact with rainfall and runoff. Hazardous material storage shall be in
and
accordance with all Federal, state and local laws and regulations. Storage locations shall have
Hazardous
appropriate placards and secondary containment equivalent to 110% of the largest container
Materials
in storage. If an earthen pit or berm is used for secondary containment, it shall be lined with
plastic. Containers shall be kept closed except when materials are added or removed.
Materials shall be dispensed using drip pans or within a lined, bermed area or using other
spillloverflow protection measures.
On -site fuel tanks shall be provided with a secondary enclosure equivalent to 110% of the
Fuel Tanks
tank's volume. If the enclosure is an earthen pit or berm, the area shall be lined with plastic.
Show the location of fuel tanks and their secondary containment on the iSWM Construction
Plan.
An area shall be designated on the iSWM Construction Plan for concrete wash -out. A pit or
Concrete
bermed area, lined with plastic, or an equivalent containment measure shall be provided for
Wash -out
concrete wash -out water. The containment shall be a minimum of 6 C>= for every 10 CY of
Water
concrete placed plus a one (1) foot freeboard. The discharge of wash -out water to drainage
ways or storm drain infrastructure shall be prohibited.
Hyper -chlorinated water shall not be discharged to the environment unless the chlorine
Hyper-
concentration is reduced to 4 ppm or less by chemically treating to dechlorinate or by on- site
chlorinated
retention until natural attenuation occurs. Natural attenuation may be aided by aeration. Water
Water from
with measurable chlorine concentration of less than 4 ppm is prohibited from being discharged
Water Line
directly to surface water. It shall be discharged onto vegetation or through a conveyance
Disinfection
system for further attenuation of the chlorine before it reaches surface water. Alternatively,
permission from the sanitary sewer operator may be obtained to discharge directly to the
sanitary sewer.
Vehicle/Equip
Vehicle and equipment washing is prohibited on the site unless a lined basin is provided to
ment Wash
capture 100% of the wash water. The wash water may be allowed to evaporate or hauled -off
Water
for disposal.
Lime or other chemical stabilizers shall be limited to the amount that can be mixed and
Soil
compacted by the end of each working day. Stabilizers shall be applied at rates that result in
Stabilizers
no runoff. Stabilization shall not occur immediately before and during rainfall events. Soil
stabilizers stored on -site shall be considered a hazardous material and shall meet all the
requirements for chemicals and hazardous materials.
Concrete
Slurry from concrete cutting shall be vacuumed or otherwise recovered and not be allowed to
Saw -cutting
discharge from the site. If the pavement to be cut is near a storm drain inlet, the inlet shall be
Water
protected by sandbags or equivalent temporary measures to prevent the slurry from entering
the inlet.
City of Fort Worth Stormwater Criteria Manual 140
4.3.4 Installation, Inspection and Maintenance
The iSWM Construction Plan shall include details and notes that specify the proper installation, inspection and
maintenance procedures for BMPs. The BMPs for the initial phase of construction must be implemented before
starting any activities that result in soil disturbance, including land clearing. Notes shall indicate the sequence of
BMP installation for subsequent phases of construction.
Notes on the iSWM Construction Plan shall indicate the frequency of inspections and the areas to be inspected.
Inspections shall include:
• Inspecting erosion and sediment controls to ensure that they are operating correctly;
• Inspecting locations where vehicles enter or exit the site for evidence of off -site tracking;
• Inspecting material and waste controls to ensure they are effective; and
• Inspecting the perimeter of disturbed areas and discharge points for evidence of sediment or other
pollutants that may have been discharged.
Erosion, sediment, and material and waste controls shall be repaired, replaced, modified and/or added if inspections
reveal the controls were not installed correctly, are damaged, or are inadequate or ineffective in controlling their
targeted pollutant.
Notes for maintenance of BMPs shall require the removal of sediment from BMPs when the sediment reaches half
of the BMP's capacity or more frequently. Sediment discharged from the site shall be removed prior to the next rain
event, where feasible, and in no case later than seven days after it is discovered. Upon completion of construction,
sediment shall be removed from all storm drain infrastructure and permanent BMPs before the temporary BMPs
are removed from the site.
Refer to Section 3.11 for further information on maintenance agreements.
City of Port Worth Stormwater Criteria Manual 141
5 References
City of Fort Worth Public Works Department, Storm Water Management Design Manual, March 2006 Fort Worth,
Texas.
City of Fort Worth Public Works Department, Storm Drainage Criteria and Design Manual, December 10, 1967,
amended June 1, 1975, December 17, 1986, and September 20, 1994, Fort Worth, Texas.
Harris County Flood Control District, October 2009, Policy, Criteria and Procedure Manual for Approval and
Acceptance of Infrastructure, Houston, Texas.
Integrated Stormwater Management Criteria Manual for Site Development and Construction, December 2009,
NCTCOG, Arlington, TX
integrated Stormwater Management Planning Technical Manual, 2010 Edition, Revised September 2014.
NCTCOG, Arlington, TX.
integrated Stormwater Management Program Guidance: Dam Safety and Water Rights, 2010 Edition, Revised April
2010. NCTCOG, Arlington, TX.
integrated Stormwater Management Water Quality Technical Manual, 2010 Edition, Revised September 2014.
NCTCOG, Arlington, TX.
integrated Stormwater Management Hydrology Technical Manual, 2010 Edition, Revised September 2014.
NCTCOG, Arlington, TX.
integrated Stormwater Management Hydraulics Technical Manual, 2010 Edition, Revised September 2014.
NCTCOG, Arlington, TX.
integrated Stormwater Management Site Development Controls Technical Manual, 2010 Edition, Revised
September 2014. NCTCOG, Arlington, TX.
integrated Stormwater Management Construction Controls Technical Manual, 2010 Edition, Revised September
2014. NCTCOG, Arlington, TX.
integrated Storm Water Management Landscape Technical Manual, 2010 Edition, Revised September 2014.
NCTCOG, Arlington, TX.
Texas Department of Transportation, October 2011, Hydraulic Design Manual, Austin, Texas.
U.S. Army Corps of Engineers, August, 1992, Design and Construction of Grouted Riprap, ETL 1110-2- 334.
U.S. Army Corps of Engineers, July 19911June 1994, Hydraulic Design of Flood Control Channels, EM 1110-2-
1601.
U.S. Department of the Interior Bureau of Reclamation , Hydraulic Design of Stilling Basins and Energy Dissipaters,
March 1978, Engineering Monograph No. 25
City of Fort Worth Stormwater Criteria Manual 142
Appendix A - Checklists and Forms
The checklists and forms provided in Appendix A are intended as examples and a starting point. The latest
checklists and forms shall instead be downloaded from the City's website or obtained from the SIDS team by
emailing your request to SDS(a)fortworthtexas.gov
The checklists and forms shall be periodically updated by City staff to provide better guidance to applicants or other
refinements. Applicants shall use the most recent version of checklists and forms. Checklists and forms shall be
used as described with the manual and submitted with the corresponding applications.
Appendix A includes the following example forms:
Form CFW-1 Drainage Study Checklist
Form CFW-2 Flood Study Checklist
Form CFW-3 Culvert Hydraulics Documentation Checklist
Form CFW-4 Bridge Hydraulics Documentation Checklist
Form CFW-5 Preliminary and Final Dam Maintenance and Emergency Action Plan
Form CFW-6 Inspection Checklist for Simple Detention Basin
Form CFW-7 Request for Waiver from City of Fort Worth - Stormwater
Form CFW-8 Engineer's Checklist for Stormwater Facility Maintenance Agreement
Form CFW-9 Grading Permit Application
Form CFW-10 Final Grading Certificate
Form CFW-11 Certificate of Compliance City Flood Risk Areas
City of Fort Worth Stormwater Criteria Manual 143
FORT WORTH:
DRAINAGE STUDY CHECKLIST
DEVELOPMENT SERVICES
INFRASTRUCTURE DEVELOPMENT
STORAhVATER DEVELOPMENT SERVICES (SDS)
SDS(dfortworthtexas.ctov
200 Texas St, Fort Worth, TX 76102
Project Information:
Name:
Submittal Date:
Location:
Site ! Plat Area (ac):
Description:
Disturbance Area (ac):
Land Use:
Construction Start Date
Owner Information:
Engineer Information:
Name:
Name:
PE No.:
Company:
Firm:
Firm No.:
Phone:
Phone:
Additional Design Contact:
Email:
Email:
Name:
Address:
Address:
Phone:
Email:
This Drainage Study Is submitted for the purpose of supporting the following development applications (check all that apply):
Single -Phase Preliminary Plat
Multi -Phase Preliminary Plat
Concept Plan (Multi -Phase) Infrastructure Plan Review
IDGrading Permit
❑
Final Plat
❑
Zone A (only) Flood Study ❑ Update To Previous Study
—20 —0
Attachments:
Sealed Report or Technical Memo
Drainage Area Maps
El
Hydrologic Analysis Hydrologic Model Files
Pre & Post Project Maps
El
Offsite Drainage Area Map
Land Use Maps Soils Maps
Downstream Assessment
El
Hydraulic Analysis
Hydraulic Model Files Hydraulic Work Maps
Detention Pond Checklist
El
Culvert Hydraulics Checklist
Bridge Hydraulics Checklist Dam Maintenance & FAP
Record Drawings
El
Previous Applicable SWMP
Other (list):
y�ljraii
City of Fort Worth Storrnwater Criteria Manual 144
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Item Description Yes No NIA Comments, Clarifications and Description
2. Planning and Data Collection
a. List and reference previous drainage studies, iSWM Plans
or watershed plans that considered the project area.
b. Note the source and date of contour or topography
information (2015 UDAR contours freely available from
the CFW GIS website).
c. Is there known or suspected flooding or erosion
downstream of the project? (If yes, describe and identify)
d. Are.there any known or suspected downstream
constrictions such as undersized culverts?
e. Are there any FEMA floodplains that require a flood study,
CLOMR, LOMR, etc. If yes, list and reference any
existing studies.
f. Are there any known or suspected wetland areas,
mitigation areas, waters of the US, or other natural habitat
features that may require consideration, 404 permit, -
nationwide permit, or state or federal permit?
g. Are there any existing impoundments or dams that could
be, or become, subject to TCEQ permitting?
h. Are there any existing environmental concerns that would
require special treatment or design consideration (e.g. fuel
station, vehicle maintenance, auto recycling, illegal dump
sites, industrialfacilities, etc.)?
3. Does this project provide opportunities,for Low Impact
Design? If yes, then describe.
a. Preserve floodplains, streams, drainage patters, natural
storage, or steep slopes?
b. Preserve trees, natural vegetation, wetlands, or other
natural features?
c. Drain runoff to pervious or vegetated areas?
d. Utilize natural drainage systems (without erosion) Instead
of storm drain systems.
e. Reduce pavement, minimize impervious cover or use
alternative materials
4. Pre -Development Conditions Map
a. Project boundaries
b. Aerial photo representing existing conditions
(imagery captured within 5 years of submission)
CFW-1
City of Fort Worth Stormwater Criteria Manual 146
Item Description
c. Perennial and intermittent streams
d. Delineate effective FEMA floodplains
e. Delineate wetlands and natural habitat areas
f. Location of dams and impoundments
g. Existing roads, buildings and other impervious features
h. Existing major utilities, pipelines and easements
I. Existing stormwater conveyance systems, including:
overland flow, storm drains, inlets, catch basins, channels,
swales, culverts, bridges
S. Post -Development Map
a. Limits of clearing and grading
b. Proposed street and lot layout (SFR)
c. Site plan (buildings, facilities, parking lot, etc.)
d. Construction phasing plan
e. Location and size of proposed storm drains and other
stormwater controls (e.g. ponds)
f. Proposed dams or ponds subject to TCEQ requirements
g. Proposed FEMA floodplain limits
S. Pre -Development Drainage Area Maps shall include:
a. Project boundaries
b. Existing topography (1 or 2 foot contour Interval, 5 or 10
foot for areas more than one square mile)
c. USDA hydrologic soil types (or separate soils maps)
d. Perennial or intermittent stream centerlines
e. Delineate FEMA floodplains, studied floodplains,
floodplain easements and open channels
f. Location of wetlands, dams and Impoundments
g. Existing roads, buildings and other impervious areas
h. Locations and size major utility lines and easements
Yes No NIA Comments, Clarifications and Description
CFW-1
City of Fort Worth Stormwater Criteria Manual 147
Item Description Yes No NIA Comments, Clarifications and Description
1. Location, size, and City File Number for existing
stormwater conveyance systems such as storm drains,
Inlets, catch basins, channels, swales, and areas of
overland flow
J. Locations and dimensions of channels, bridges, or culvert
crossings
k Delineation of watershed or drainage area boundaries,
with correctly orientated flow arrows
I. Delineate offsite drainage areas (1 or 2 foot contour
interval, 5 or 10 foot for areas more than one square mile)
m. Contours extend.beyond project limits and offsite drainage
areas to ensure the entire watershed has been delineated
n. Delineate longest flow path each drainage area
o. Provide time of concentration calculations for each area
and lag time calculations for hydrograph methods.
p. Computation table showing drainage areas, runoff
coefficients or curve numbers, time of concentration or lag
times, rainfall intensities and peak discharges for the 1, 5,
and 100 year storms. include a column to identify the
collection point for each drainage area.
q. Location of all site outfalls or where runoff leaves the site
r. Delineate entire zone of influence and identify analysis
points.
s. Existing zoning and land use
t. Composite calculations for runoff coefficients or curve
numbers
u. Drainage area and analysis point labels consistent with
hydrologic and hydraulic calculations tables
7.. Post -Development Drainage Area Maps shall include:
a. Project boundaries
.b. Existing and proposed topography (1 or 2 foot contour
Interval, 5 or 10 foot for areas more than one square mile)
c. USDA hydrologic soil types (or separate soils maps)
d. Perennial or intermittent stream centerlines
e. Delineate FEMA floodplains, studied floedplains,
floodplain easements and open channels
CFW-1
City of Fort Worth Stormwater Criteria Manual 148
Item Description
f. Location of wetlands, dams and impoundments
g. Roads, buildings and other impervious areas
h. Locations and size major utility lines and easements
I. Location, size, and City File Number for existing
storrnwater conveyance systems such as storm drains,
inlets, catch basins, channels, swales, and areas of
overland flow
J. Locations and dimensions of channels, bridges, or culvert
crossings
k Delineation of watershed or drainage area boundaries,
with flow arrows
I. Delineate offsite drainage areas (1 or 2 foot contour
interval, 5 or 10 foot for areas more than one square mile)
m. Contours extend beyond project limits and offsite drainage
areas to ensure the entire watershed has been delineated
n. Delineate longest flow path each drainage area
o. Provide time of concentration calculations for each area
and lag time calculations for hydrograph methods.
p. Computation table showing drainage areas, runoff
coefficients or curve numbers, time of concentration or lag
times, rainfall intensities and peak discharges for the 1, 5,
and 100 year storms, for existing, proposed and ultimate
conditions. Include a column to identify the collection point
for each drainage area.
q. Location of all site outfalls or where runoff leaves the site,
including labels with prelpostlultimate discharges.
r. Proposed and ultimate zoning and land use
s. Identify changes to watershed boundaries
t Composite calculations for runoff coefficients or curve
numbers
u. Delineate entire zone of influence acid identify analysis
points.
v. Show downstream constrictions with runoff controls
w. When the development is a multi -phase project provide an
overall drainage area map with all phases labeled,
x. Proposed stormwater facilities with private maintenance
(includes private storm drains, if detention is proposed,
provide volume required)
Yes No MIA Comments, Clarifications and Description
CFW-1
City of Fort Worth Stormwater Criteria Manual 149
Item Description
y. Drainage area and analysis point labels consistent with
hydrologic and hydraulic calculations tables.
8. Hydrologic Analysis
a. Analysis methodology and Inputs conform to Chapter 3.4
and relevant sections of the NCTCOG iSWM Technical
Manuals.
b. Selected hydrologic methods per Table 3.4
c. Runoff coefficient and curve numbers per Table 3.5
d. On site existing conditions per actual land use, not zoning
e. Offsite conditions modelled as existing land use for
comparison of pre- and post -development conditions
f. Entire watershed (onsite and offsite areas) modelled per
zoning or land use, which ever yields the highest peak
discharge, for ultimate conditions hydrology.
g. Ultimate conditions hydrology used for easement and
stormwater facility sizing
h. Unit hydrograph analysis performed using acceptable
software package and models files provided.
1. Modified Rational Method, if selected, was calculated
using the equations described in the NCTCOG Hydrology
Technical Manual, and not using a software package.
j. The hydrologic analysis and downstream assessment Is
carried to, or beyond, the zone of influence based on the
10% rule of thumb. This is required even when detention
is provided (except for the specific small site waiver).
k Hydrologic work map was provided and shows model
basins and routing.
1. Junctions or calculation nodes provided at critical analysis
points (e.g. at outfalls, culvert crossings, ponds, etc.)
m. Reach modelling approaches applied per criteria manual
and standard modelling conventions
n. Pre- and post -development modelling Include onsite
storage (e.g. upstream of a road culvert) and floodplain
storage to determine impacts of any watershed storage
loss that result from the development
o. Where a project discharges to more than one outfall,
provide a corresponding analysis for each outfall
p. Include mitigation design and analysis.
Yes No NIA Comments, Clarifications and Description
CFW-1
City of Fort Worth Stormwater Criteria Manual 15D
Item Description Yes No NIA Comments, Clarifications and Description
q. All applicable hydrologic condition analyses, including but
not limited to: existing; proposed, proposed with mitigation
if applicable, and ultimate. A mull -phased development
would include an additional condition for eachi phase.
r. Rainfall depths per NCTCOG iSWM Hydrology Technical
Manual.
s. A summary results and comparison table was provided,
and Includes all junctions and design storms.
t. Analysis fora Zone. A floodplain includes all applicable
design storms and complies with FEMA guidelines.
9. Hydraulic Analysis
a. Analysis methodology and inputs conform to Chapter 3.8
and other relevant sections of the Stormwater Criteria
Manual, the NCTCOG iSWM Technical Manuals, and
applicable references (e.g. HEC-RAS manual).
b. Standard modelling conventions are adhered to (e.g.
ineffective flow'areas at culverts, cross -sections
perpendicular to flow, bank stations contained well inside
the floodplain, etc.)
c. For 1D-analysis, Manning's n per Table 3.15, Table 3.16
and other relevant technical references.
d. Proposed multi -barrel culverts designed with one of the
barrel flow lines at the stream centerline, and other barrels
set higher to establish a single low flow drainage,path
e. Provide a hydraulic work map including, but not limited to:
aerial imagery, cross sections, inundation limits, stream
centerline, structures, flow change locations; labels,
proposed easement limits, etc.
f. Provide a summary table that correlates cross -sections to
hydrologic nodes or add hydrologic nodes to RAS
workmap
g. Analysis considers appropriate tail water and effect of
coincidental peaks
h. Analysis sizes all driveway culverts and demonstrates that
roadside ditch design meets design standards.
i. Mixed flow regime analysis is included if Froude
number(s) is 0.9 or above (supercdtica[ flow check).
j. Analysis shows compliance with all applicable design
criteria in Chapter 3.8.
k Analysis shows compliance with all No Adverse Impact
criteria throughout the entire Zone of Influence
CFW-'I
City of Fort Worth Stormwater Criteria Manual 151
Yes No NIA
Item Description
I. Results summaries for all design storms and watershed
conditions are tabulated. comparison of pre- and post-
M. summary tables include a comps
development conditions at all cross sections and critical
locations. feted
n. Culvert and bridge hydraulics checklists are romp
and attached for all proposed hydraulic structures-
and
Where a project dischan3es t ys s for each outfallttall, —
re than.an
provide a corresponding was performed for a and the results,
p. A dam breach anance plan
l in and EAP are attached --
dam maintenance p
q. Drainage structure sizes anti
easement
w ment delineations
(ultimate conditions 1Q0-Y ondin minimum finished
r. Flood elevations and corresponding
and proposed lots
floor elevations for all potentially _
(ultimate conditions 1oo-year flow)
Any other information pertinent to the preparation and
i di plat and
comments, Clarifications and Description
s. documents. inc u ng _ — —
review of project �--
construction plans. radon or rseview of a drainage
standards,study, please
For additional infOrmation about the requlrements,
criteria, or policies that appiy.ta the Prep$ and a licable
refer to the relevant Partirns of the CF. W ordinances, Policies and Stamtwater Criteria Manual, NCTCOQ Technical Manuals, P
tions,
engineering tecfrnical Publica
appendices were prepared
resented on the checklist, report, and attachments is correct
that.this drainage study and all attached and referenced exhibits, documents a aPP
l certify ante of this plan by the City of Fort Wow does not waive
under my responsible Supervision s4r+d derstareidin�at anlaccept
to the best of my knowledge,
nowledg . specific waiver request was submitted and approved.
any City standards or requirements unless a
Date:
Signed: Firm No:
Name:
CFW-1
City of Fort Worth Stormwater Criteria Manual
152
FORT WORTH :
TRANSPORTATION & PUBLIC WORKS DEPARTMENT
STORMWATER MANAGEMENT
2CC Texas St, Fort Worth. TX 76102
Project Information:
Name:
Location:
Description:
Stream Name
Owner Information:
Name:
Company:
Phone:
Emaif:
Address:
Engineer Information:
Name:
Firm:
Phone:
Email:
Address:
FLOOD STUDY SUBMITTAL FORM
Submitflood study model requests to FLOODPLAIN MANAGEMENT group
Floodplain@fortworthtexas gov
Pre -Submittal meetings are required before submitting flood studies,
coordinated by STORMWATER DEVELOPMENT SERVICES (SDS)
SDS@fortworthtexas.gov
Submit Flood Studies to yourfirm's SIM360 folder, coordinated by SDS.
Once Flood Study is accepted, submit Floodplain Development Permit
application to SDS through Accela for approval
Submittal Date:
FIRM Panel:
SFHA Flood Zone Type:
Pre -Sub Meeting Date:
PE No.:
Firm No.
Additional Design Contact:
Name:
Phone:
Email:
This Flood Study is submitted in support of the following (check all that apply): Floodplain Development Permit
Letter of Map Revision (LOMR) Conditional Letter of Map ❑ Letter of Map Amendment ElCorridor Development
Revision (CLOMR) (LOMA) Certificate (CDC)
Pre -Project Flood Study (LOMR to Letter of Map Revision ❑ Conditional Letter of Map Revision ElCFW Project
be submitted after construction) based on Fill (LOMR-F) based on Fill (CLOMR-F) (City funded)
Attachments:
Sealed Report or Technical Memo
El Hydrologic Work Maps
El Annotated FIRM
CDC Application
Hydrologic Analysis
❑ Hydrologic Analysis Tables
El Proposed/As-Built Plans
WOTUS Delineation
Hydrologic Model Files
Hydraulic Work Maps
El Reference Study(s)
404 Permit
Hydraulic Analysis
Hydraulic Analysis Tables
Property Owner Notification
TxDOT Permit
Hydraulic Model Files
Geo-referenced GIS/CAD files
ESA Compliance
❑ O&M Plan (detention
basin, dam, berm levee)
CFW-2
City of Fort Worth Stormwater Criteria Manual 153
e Re\oaf\°r"s
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add�°nat the reio chnica! p abed iom,at\o 4.& fie oft �S 5ubfri\it
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FORT WORTH
O
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Stormwater
Management
CULVERT HYDRAULICS DOCUMENTATION CHECKLIST
Project:
Date
Road,
Watershed',
Si ream
Type of work.-
FEMA considerations (Detailed or Approx. Study?):
Culvert location:
Culvert size $ shape'.
Calvert material:
Fill height:
Skew angle.
Hydrologic method used Hydrograph
USGSShtion
Other (specify)
Design frequency (yrs):
Drainage area
Channel ana€ysis_
Channel slope (mlm)
N values (channel)
100 Yr Proposed discharge (cfs):
f 00-Year Fully developed discharge - Q ,m (cis):
100 Yr Proposed taibrrater (ft)-
100-Year Fully developed tailwater (ft):
100 YR Proposed headwater (ft).
100-Year Fully developed headwater (ft):
Allowable hghwater (ft)
100 Yr Proposed velocity thru bridge (fps).
100-Year Fully developed velocity thru bridge (fps),
Design unconstricted velocity (fps)
100-Year unoonstricted velocity (fps)
% Flow overtopping road for Q,on:
Height of water over road for 01 D (ft):
Est. overtopping frequency (years):
Headwater computation method' THYSYS-CULVERT HEC-RAS" HEC 2 Other
`Required by CFW
Comparison with existing hydrauhC condition:
Meets FEVIA requirements Yes
No NIA
Outlet velocity excessive -yes -No
Outlet protectionlcontrol:
Safety end treatment:
Comments'
Form CFW-3
City of Fort Worth Stormwater Criteria Manual 155
FORT WORTH
°c
Stormwater
t0anagemtnt
BRIDGE HYDRAULICS DOCUMENTATION CHECKLIST
Project:
Date:
Road:
Watershed:
Stream:
Type of work:
FEMA considerations (Detailed or Approx_ Study?)
Bridge Length:
Pier Configuration:
Bridge Width:
Bridge Love Chord and Roadbed Elev,:
Hydrologic Method Used: Hydrograph Only
Gauged - USGS Station
Other
Design Frequency (yrs):`
Drainage Area:
Channel Dimensions:
Channel sope(ft'ft):
N value:
DESIGN
PROPOSED
100 YR
EXISTING
100 YR
PROPOSED
1 D0 YR
FULLY DEVELOPED
STATION
Q
crs
V
(fps)
WSEL
1t
Q
rf
V
f
WSEL
{ft
a
efs
V
(fps
WSEL
ft
Q
cis)
V
(fps)
WSEL
ft
EXET
FULL V
BRIDGE
APPR
(GONSTR)
APPR
(UNCONS)
Headwater computation method: HEC-RAS OTHER
Bridge/Roadway overtopping: Yes No
Overtopping Frequency(years):
% Flow overtopping road:
Height of water over road(ft):
Existing Bridge Length(ft):
Meets FEMA requirements:
Yes No N!A
Type of Bridge Rail:
Skew:
Abutment protection (rock riprap, etc):
Comments:
"Complete for cases where "design frequency' (such as TxDOT structures) may be different than 100-year
Form CFW-4
City of Fort Worth Stormwater Criteria Manua! 156
FORT WORTH
TRANSPORTATION AND PUBLIC WORKS DEPT
STORMWATER MANAGEMENT
1. Project Information
A. Name of Development
C. Dam Name, Number or Tributary
E. Name of Owner:
G. Owner Contact Name.
1. Owner Address
PRELIMINARY AND FINAL a ti
DAM MAINTENANCE AND = �t Stormrmwa#er
EMERGENCY ACTION PLAN warrn,rnr
Please attach additional sheets as necessary for comments and descriptions.
Fold all sheets to 8%" x 11"or 9" x 12" and bind with a clip.
B_ Case No:
D. Date:
F. Telephone No
N. E-mail:
J Engineer's Name: K. Texas P E, No:
L. Engineering Firm: M. Telephone No.:
N. Engineer Address: O. E-mail:
2. Dam Summary Information (Item H not required for Preliminary Submittal)
Adam that meets the TCEQ guidelines must be registered with the TCEQ, have a breach analysis, hazard assessment. and emergency action:
plan per 30 TAC §299.
A. Dam height" (feet):
B. impoundment surface area (acres): For City Use Reviewer: Date:
C. Watershed size (acres): Accepted Not Accepted Case No.:
D Approx. impoundment volume (acre-feet): Comment
'Height measured from the crest of the dam to the bottom of the outfall channel
Form CFW-5
City of Fort Worth Stormwater Criteria Manual 1 F-
Page 2 of 3
E Who will own and maintain dam (HOA, Citypark, eta)?
F. Was dam previously registered and/or inspected by TCEQ? When?
G. TCEQ impoundment size classiliicaffon.(30 TAC §299.12): Exempt Small Intermediate Large
H. Hazard Assessment (from 6.B. below per 30 TAC §299.13): N/A Low Significant High
3. Attachments
Water Rights Permit (where applicable)
Breach Analysis (where applicable)
Emergency Action Plan (final submittal)
Yes No NIA Comments and Descriptions
4. State Water Rights
In accordance with texas Water Code §11, all surface impoundments not used for domestic or livestock purposes must obtain a
water rights permit from the TCEQ. For proposed City -owned dams, a completed permit, orwritten documentation from TCEQ stating
that a permit is not required, must be submitted prior to final acceptance by the City.
Has water rights permit been obtained or applied fort (For
proposed City -owned dams, attach permit correspondence)
5. Dam and Pond Site Map(s), showing:
A. Proposed and existing contours, with recent aerial
B. Existing and proposed FEMAfloodplain limits
C. Street and lot layout around dam and inundation area
D. Contributing watershed (reduced scale if necessary)
E. Hydrologic calculations for Q100 and PMF
F. Location, size and capacity of proposed spillway _
G. Conceptual or final spillway and erosion protection design
Form CFW-5
City of Fort Worth Stormwater Criteria Manual 168
Page 3 of 3
Yes No NIA Comments and Descriptions
6. Dam Breach Analysis —Attach and Include: (Required for Final Submittal only, for dams -meeting the guidelines in Chapter
3.8.4 for Detention Structures in this manual).
A. Breach analysis for "sunny day", "barely overtopping" or
Q100, and Probable Maximum Flood (PMF) conditions
B. Hazard Assessment based on potential for loss of life
or property damage in breach/non-breach comparison _
C. Emergency Action Plan per current City standards
1 certify that this Conceptual Stormwrater Management plan, including this checklist, required
attachments, and additional comments, was prepared under my responsible supervision and that
the information presented on this checklist and attachments is correct'to the best of my knowledge.
1 also understand that an acceptance of this plan by the City does not waive any City standards or
requirements unless a specific waiver request has been submitted and accepted.
Signed Date
(seal) A
Print Name:
Form CFW-5
City of Fort Worth Stormwater Criteria Manual 159
FolzH
INSPECTION CHECKLIST FOR SIMPLE DETENTION BASIN
Facility Name:
Basin/Pond Number: Inspected By:
Type of Inspection: Annual
Basin Conditions:
Facility Agreement Number:
Date:
Quarterly . Mcntriy , Routine , or Storm Event . (# days since event
1. Is there standing water or wet spots?
2 Does sides or bottom show signs of erosion, settling, cracking, etc?
3 Does dam or emergency spillway show signs of erosion, settling,
cracking, or other problems?
4. Is there evidence of animal burrowing in dam?
5 Is there evidence of changes in shape or volume of basin?
6 Igo vegetated areas need mowing?
7. Are there trees or woody growth in dam?
& Are there areas that need to be re -vegetated?
9. Is there any accumulation of silt, trash, debris or litter in the basin?
1D. Are there any other basin maintenance activities needed?
Structural Components:
1, Are pipes, channels. trash racks, etc. free of obstructions?
2. Are pipes. spillway or trash racks in need of repair?
3. Is the low flow or trickle channel in need of repair?
4. Is the outfali channel in need of repair?
5. Are there any other structural maintenance activities needed?
Plan for correcting deficiencies:
Yes
No
Comments
Yes_
No
Comments
Yes_
No _
Comments
Yes_
No —Comments
Yes_
No
Comments
Yes_
No _
Comments
Yes_
No
Comments
Yes
No
Comments
Yes_
No —Comments
Yes—
No
_ Comments
Yes_
No _
Comments
Yes_
No _
Comments
Yes
No
Comments
Yes_
No
Comments
Yes_
No
Comments
Form CFW-S
Sign at ure:
Date:
City of Fort Worth Stonmwater Criteria Manual I Is
5tormwate
Owners Representative
FORT WORTH
ago
Frxf LVrcth
Stormwater
�,,ement
REQUEST FOR WAIVER
FROM CITY OF FORT WORTH - STORMWATER
Submitted by: PhoneEmail:
Company: Date:
Proposed Project Description
Name
Type:
Location (include map)
Existing Condition (show information on map or drawing)
CFWMaintained Facilities:
Existing Right -of -Way for CFW facility,
Topography.
Other Pertinent Data Related to Variance Request:
Waiver Request
Specific criteria you want to vary
Explain why the criteria needs to be varied or is not applicable:
Explain how the basis for the criteria will be satisfied:
List attachments supporting waiver request {preliminary design report excerpt, construction drawings.
calculations photographs. map, etc
Justification of Decision:
Notes:
Waiver Decision: Accepted rl Denied ❑
Reviewer Signature: Date:
Form CFW-7
City of Fort Worth Stormwater Criteria Manual
rORTWORTH ENGINEER'S CHECKLIST FOR STORMWATER r,Ytw,Yth Cli
FACILITY MAINTENANCE AGREEMENT Stormwater
.-i nagement
Transportation and Public Works Dept. Please attach additional sheets as necessary for comments and
Stormwater Management descriptions. Fit all sheets to$'/" x 11".
ORGANIZATION
INFORMATION
1. Company (Applicant)
Address:
2. Contact's Information-
3. Execution Information:
Contact Name
Signatory's Name
Mailing Address
Mailing Address
Telephone Number(s)
Telephone Numbers;
Email
Email
4. Property Location:
i Nato If the property has not been addressed, please enter the legal description)
5. Associated Plat Numbers:
(Note: if request is related to multiple plat applications, please list each individually)
6. Associated Building Permit Numbers:
(Note: i['request is related to multiple permits, please list each individually)
7. Associated iiSWM Master Numbers:
AGREEMENT&. ATTACHMENT INSTRUCTIONS
If the property owner is a corporation, the agreement must be signed by the President or a Vice -President of the company. If a
partnership, the agreement must be signed by the managing partner. If the applicant is a sole proprietor, he/she signs the agreement
on behalf of him or herself. Additionally, for corporations and partnerships, a copy of the Articles of Incorporation, showing signature
authority for whoever signs the agreement must also be submitted (Note: Applicants may also submit a board resolution or power of
attorney authorizing an agent or assign to sign on behalf of the property owner. The agreement must be completely felled out and three
copies submitted to the Planning and Development Department. Signatures on all three agreement drafts must be original and
notarized. Lastly, please submit a copy of the deed for the noted property.
NOTE: Agreement and all attachments should be submitted on 8 yz" x 11".
Form CF'W-8
City of Fort Worth Stormwater Criteria Manual 162
WA CommentsiQescolons
Mn
Yes
CC°
ndard a9�eme�,tarm pr°wd� by
a 1.m�n9ffl� ant —Ste an �p,cjied)
peps ti
, legal Qescnp
titDtt"A . ds d mimed as
Metes and � Wtth seal aifocea
Sa�eYo�s q�wir�,
B 'praw age Ea�me
ached'!
Plat- mt[ons t
`8�,gt9nP' acevi[� [Plan schevicl
3. Exhces�9n�lwwuons pjcamp[epetena ucfionptan�
A4 gee cow eats .
auo lan � ce wal egg,, ed ctumi etern
hem
9 rePared [n a . orlon show[ng cnticat stru dead`! [abated
p ,Plan View
n� are
uctural e[eme owing
Gritil str terms sect[an sh
intalmman $lon91tud[��w[Lbelevat�ans•
ing m e and
� Profile in�'��urai ele � show $4Z
all cnt�ca[ st
toss sec6onsasneeded en 9'h" x 11A,
genQml gm sutd be submitted �� owls.[ ands
NOTE: Att �i,emabs�n �r aFpn'ved plan tp�achedl
hands�ng d {+t�tntenance
q OPzrationsanGf'xcat\an5: wood'lpl AS-
4, Exhib Hance SPe weeds and
A R+�'ne ghaln a needed to control cturat elements•
1 Mowing l tram l
2. Tmsh rem Hance.
3 pad�tionatmal �et1t�es
6 Non todme Maude ,tabilrLa'ton' e6 more of area is
1. Banff reRau a en
Revegetat�on - reAu[red wh
2 unprotected•
Glty of fOTONO th
tormwater Griteria Manual
Pa eZat3
163
Yes
No
NIA
3. Sediment removal from the detentionfretention facility when:
• Detention basin —when water depth is reduced 25%
or more, or basin does not drain within 72 hours.
❑
❑
❑
• Retention pond —when water depth is 4' or less.
❑
❑
Sediment trapslfarebay—when depth is reduced
by 50% or more,
❑
❑
❑
4. Structural repair/replacement for all damaged or deteriorated
trickle trash
❑
❑
❑
structures, channel, rack, etc.
6. Mechanical equipment repairs.
❑
H
H
6. Other maintenance Activities.
5. Mchlbit I'D" -Maintenance Checkllst *
A. Covers ordinary needs, in layman terms.
❑
B. Structural components labeled consistent with Schematic Plan.
❑
❑
*See attached Inspection Checklist for Detention Basin
Comments/Descrlptlons Page 3 of 3
NOTE: All Exhibits should be submitted on 8 ." x 11".
certify that this Stormwater Facility Maintenance Agreement, checlist, required attachments, and additional
comments, was prepared under my responsible supervision and that the information presented on this checklist
and attachments is correct to the best of my knowledge. I also understand that an acceptance of this plan by the
City does not waive any City standards or requirements unless a specific waiver request has been submitted and
approved
(seal) I Print Name;
Form CFW-8
City of Fort Worth Stormwater Criteria Manual 164
FORT WORTH °
Fort Wcx th
S#ormwater
GRADING PERMIT APPLICATION Management
Applicant to Complete Sections I through VII Belaw• Permit No.
Questionnaire For: Commercial Construction or Grading activities.
What Type of Grading Permit is being applied for? (circle one) EARLY FINAL
Note A Final Commerciaf Grading Permit is required even if an Early Grading Permit is obtained.
I. Identification:
Project Name:
Project Location:
Owner:
Name: e-mail:
Address, Phone:
Contractor:
Name:
Address:
Emergency Telephone No.: e-mail:
II. Do you have an approved iSWM Plan? (circle one) yes no
An iSWM Plan (integrated Storm Water Management Plan) may have been approved if a Plat,
Infrastructure Plans, or a Unified Residential Plan has been approved after March 2006.
If yes provide caseiplan number(s), if known:
SWM SWPPP
Plat Urhan Forestry Plan
DOE Number Unified Residential Development Plan
VII. Signature of Applicant or Authorized Agent:
Signature:
Name:
Name of Company:
Address:
Phone No.:
VIII. Conditions of Approval
Approval is contingent upon compliance with City grading and development requirements
including drainage, floodplain management, urban forestry and construction runoff control. A site
grading plan sealed by an engineer is required for all land disturbances of 1.0 acre or more.
City Action:
Reviewer Date
Accepted 1 Not Accepted Comments
Qll
City of Fort Worth Stormwater Criteria Manual 165
FORT WORTH
o�Fort worth
5tarmwater
Management
FINAL GRADING CERTIFICATE
Effective Date Case No. (From Early/Final Grading Permit)
This certification is required after construction and grading activities are complete and prior to Certificate
of Occupancy being issued.
OWNERf DEVELOPER/ PERMITTEE INFORMATION
Project Name
Project Location
Project Description
OwnerlDevelo per/Permittee
Address
Phone No, e-mail
DESIGN PROFESSIONAL OR CONTRACTOR (Responsible Party)
Name
Address
Phone No. e-mail
LicenseiGertificate No Expiration Date
To the best of my knowledge and personal inspection, the above described project has been constructed
in substantial compliance with the plans dated as accepted by the City of Fort Worth AND
temporary BMPs have been removed
Signature_
Printed Name
Form CFW-10
Date
(Seal)
City of Fort Worth Stormwater Criteria Manual 166
FORT WORTH
Transportation & Public Works
Stormwater Management
200 Texas Street, Fart Worth, TX 76102
CITY FLOOD RISK AREAS
CERTIFICATE OF COMPLIANCE
STORMWATER DEVELOPMENT SERVICES (SDS)
S DS@ fo rt W ortht a xas .gov
The certificate must be completed for all development located within the City Flood Risk Areas (Ci that have a land
disturbance of less than one acre. Submittals must also include the Project Boundary Map showing the CFRA and proposed
project.
PROJECT• •
Project Name:
Site/Plat Area (acres):
Project Address:
Land Disturbance Area (acres):
Description of Project:
Property Owner Name:
Engineering Company:
Surveying Company:
Contact Name/Representative:
Contact Name:
Contact Name:
Property Owner Address:
Engineer Address:
Surveyor Address:
Property Owner Email:
Engineer Email:
Surveyor Email:
Property Owner Phone Number:
Engineer Phone Number:
Surveyor Phone Number:
CFRA INFORMATION
What is the Design Flood Flevation {DFE) for this property?
How was the DFE determined?
How will you mitigate flood risk?
l7 City provided engineering study
0 Elevate Structure to DFE
❑ Independent engineering evaluation performed
❑ Floodproofing {attach additional details)
per the Stormwater Criteria Manual
Type:
❑ Other:
Briefly explain how any potential adverse impacts were addressed. (Additional pages may be attached if needed.) See Texas
Water Code, Chapter 11, for more information on the State law prohibiting development on a properryfrom creating adverse
drainage impacts on others.
CERTIFICATION
I certify that the above referenced information and supporting analysis were prepared under my responsible supervision and is
correct to the best of my knowledge. I also understand that an acceptance of this certificate by the City of Fort Worth does not
waive any City standards or requirements unless a specific waiver request was submitted and approved.
Typed Name/Title:
Texas P.E. License Number:
Seal/Stamp:
Signature of Engineer:
Date:
CFW-CFKA Certificate Compliance —Draft
CFW-11
11PaIe
City of Fort Worth Stormwater Criteria Manual 167
Appendix B: Stormwater Computer Models
B.1 Introduction
Stormwater management is becoming increasingly complex. The simple notion of collecting runoff and sending it
efficiently to the nearest stream is being replaced with considerations of stormwater quantity and quality control,
infrastructure management, master planning and modeling, financing, complaint tracking, and more. Information
needs are critical to a successful local program. North Central Texas communities need to both invest in and be
aware of new and emerging technologies that can provide the ability to collect, organize, maintain and effectively
use vast amounts of data and information for their community's stormwater management activities.
There is a great deal of computer software that has been developed based on the intensive research effort in urban
hydrology, hydraulics and stormwater quality. Computer models use the computational power of computers to
automate the tedious and time-consuming manual calculations. Most models also include extensive routines for
data management, including input and output procedures, and possibly including graphics and statistical
capabilities.
Computer modeling became an integral part of storm drainage planning and design in the mid-1970s. Several
agencies undertook major software developments and these were soon supplemented by a plethora of proprietary
models, many of which were simply variants on the originals. The proliferation of personal computers in the 1990s
has made it possible for virtually every engineer to. use state-of-the-art analytical technology for purposes ranging
from analysis of individual pipes to comprehensive stormwater management plans for entire cities.
In addition to the simulation of hydrologic and hydraulic processes, computer models can have other uses. They
can provide a quantitative means to test alternatives and controls before implementation of expensive measures in
the field. If a model has been calibrated and verified at a minimum of one site, it may be used to simulate non -
monitored conditions and to extrapolate results to similar ungauged sites. Models may be used to extend time series
of flows, stages and quality parameters beyond the duration of measurements, from which statistical performance
measures then may be derived. They may also be used for design optimization and real-time control.
A local staff or design engineer will typically use one or more of these pieces of software in stormwater facility
design and review, according to the design objectives and available resources. However, it should be kept in mind
that proper use of computer modeling packages requires a good knowledge of the operations of the software model
and any assumptions that the model makes. The engineer shall have knowledge of the hydrological, hydraulic and
water quality processes simulated and knowledge of the algorithms employed by the model to perform the
simulation.
B.2 Types of Models
In urban stormwater management there are typically three types of computer models that are commonly used:
hydrologic, hydraulic and water quality models. There are also a number of other specialty models to simulate
ancillary issues (some of which are sub -sets of the three main categories) such as sediment transport, channel
stability, lake quality, dissolved oxygen and evapotranspiration, etc.
B.2. 1 Hydrologic Models
Hydrologic models attempt to simulate the rainfall -runoff process to tell us "how much water, how often." They use
rainfall information or models to provide runoff characteristics including peak flow, flood hydrograph and flow
frequencies. Hydrologic models can be either:
• Deterministic -- giving one answer for a specific input set, or
• Stochastic -- involving random inputs giving any number of responses for a given set of parameters;
• Continuous — simulating many storm events over a period of time, or
• Single Event — simulating one storm event;
City of Fort Worth Stormwater Criteria Manual 168
Lumped — representing a large area of land use by a single set of parameters, or
Distributed — land areas are broken into many small homogeneous areas each of which has a complete
hydrologic calculation made on it.
B.2.2 Hydraulic Models
Hydraulic models take a known flow amount (typically the output of a hydrologic model) and provide information
about flow height, location, velocity, direction, and pressure. Hydraulic models share some of the differing
characteristics of hydrologic models (continuous vs. single event) and add the following:
• One-dimensional — calculating flow information in one direction (e.g. downstream) only, or
• Multi -dimensional — calculating flow information in several dimensions (e.g. in and out of the channel
and downstream);
• Steady — having a single unchanging flow velocity value at a point in the system, or
• Unsteady — having changing flow velocities with time;
• Uniform — assuming the channel slope and energy slope are equal, or
• Non -uniform — solving a more complex formulation of the energy and momentum equations to account
for the dynamic nature of flows.
For most problems encountered in hydraulics, a simple one-dimensional, steady model will work well. But if the
volume and time distribution of flow are important (for example, in a steeper stream with storage behind a series of
high culvert embankments) an unsteady model is needed. If there is a need to predict with accuracy the ebb and
flow of floodwater out of a channel (for example in a wide, flat floodplain where there are relief openings under a
road) then a 2-dimensional model becomes necessary. If pressure flow and the accurate computation of a hydraulic
grade line are important, an unsteady, non -uniform model with pressure flow calculating capabilities is needed.
B.2.3 Water Quality Models
The goal in water quality modeling is to adequately simulate the various processes and interactions of stormwater
pollution. Water quality models have been developed with an ability to predict loadings of various types of
stormwater pollutants.
Water quality models can become very complex if the complete cycle of buildup, wash -off and impact are
determined. These models share the various features of hydrologic and hydraulic models in that it is the runoff flow
that carries the pollutants. Therefore, a continuous hydrologic model with estimated pollution concentrations
becomes a continuous water quality pollution model. Water quality models can reflect pollution from both point and
nonpoint sources.
Water quality models tend to have applications that are targeted toward specific pollutants, source types or receiving
waters. Some models involve biological processes as well as physical and chemical processes. Often great
simplifications or gross assumptions are necessary to be able to model pollutant accumulations, transformations
and eventual impacts.
Detailed short time increment predictions of "pollutographs" are seldom needed for the assessment of receiving
water quality. Hence, the total storm event loads or mean concentrations are normally adequate. Simple
spreadsheet -based loading models involve an estimate of the runoff volume which, when multiplied by an event
mean concentration, provide an estimate of pollution loading. Because of the lack of ability to calibrate such models
for variable physical parameters, such simple models tend to be more accurate the longer the time period over
which the pollution load is averaged. An annual pollutant load prediction may tend toward a central estimate, while
any specific storm prediction may be grossly in error when compared to actual loadings because antecedent
conditions vary widely from week to week. Simulation models have the ability to adjust a number of loading
parameters for calibration purposes and can simulate pollution accumulation over a long period. They can then
more reliably predict loadings for any specific storm event.
City of Fort Worth Stormwater Criteria Manual 169
While calibration data is not always needed in hydrologic or hydraulic models for an acceptably accurate answer,
in water quality models the non -calibrated prediction is often off by orders of magnitude. Water quality predictions
are not credible without adequate site -specific data for calibration and verification. However, even without
specifically accurate loading values relative effects of pollution abatement controls can be tested using uncalibrated
models.
B.2.4 Computer Model Applications
Stormwater computer models can also be categorized by their use,or application:
Screening -level models are typically equations or spreadsheet models that give a first estimate of the magnitude
of urban runoff quality or quantity. At times this is the only level that is necessary to provide answers. This is true
either because the answer needs to be only approximate or because there is no data to justify a more refined
procedure.
Planning -level models are used to perform "what if' analysis comparing in a general way design alternatives or
control options. They are used to establish flow frequencies, floodplain boundaries, and general pollution loading
values.
Design -level models are oriented toward the detailed simulation of a single storm event for the purposes of urban
stormwater design. They provide a more complete description of flow or pollution values anywhere in the system of
concern and allow for adjustment of various input and output variables in some detail. They can be more exact in
the impact of control options, and tend to have a better ability to be calibrated to fit observed data.
Operational models are used to produce actual control decisions during a storm event. They are often linked with
SCADA systems. They are often developed from modified or strongly calibrated design models, or can be
developed on a site -specific basis to appropriately link with the system of concern and accurately model the
important physical phenomena.
B.3 Summary of Acceptable Models
Computer models can be simple, representing only a very few measured or estimated input parameters or can be
very complex involving twenty times the number of input parameters. The "right" model is the one that: (1) the user
thoroughly understands, (2) gives adequately accurate and clearly displayed answers to the key questions, (3)
minimizes time and cost, and (4) uses readily available or collected information. Complex models used to answer
simple questions are not an advantage. However, simple models that do not model key necessary physical
processes are useless.
There is no one engineering model or software that addresses all hydrologic, hydraulic and water quality situations.
Design needs and troubleshooting for watershed and stormwater management occur on several different scales
and can be either system -wide (i.e., watershed) or localized. System -wide issues can occur on both large and small
drainage systems, but generally require detailed, and often expensive, watershed models and/or design tools. The
program(s) chosen to address these issues shall handle both major and minor drainage systems. Localized issues
also exist on both major and minor drainage systems, but unlike system -wide problems, flood and water quality
solution alternatives can usually be developed quickly and cheaply using simpler engineering methods and design
tools.
Table B.1 lists several widely used computer programs and modeling packages which are approved by the City for
the specific uses listed in the Table.
For the purposes of this table, major drainage systems are defined as those draining to larger receiving waters.
These are typically FEMA-regulated streams, or lakes or reservoirs. Minor drainage systems are smaller natural
and man-made systems that drain to the more major streams. Minor drainage systems can have both closed and
open -channel components and can include, but are not limited to, neighborhood storm sewers, culverts, ditches,
and tributaries.
City of Fort Worth Stormwater Criteria Manual 170
Table B.1 Stormwater Modeling
Programs and Design Tools
IVEajor
System
Modeling
'Mirior-
'System
-Modeling
-
Hydrologic'
Features
: _ _
.Hydrau,fic
Features £
-Water ..
Quality
Features
Unsteady
glow
2-D'
�Flow�
SoftwareNydrology
HEC-1 1
X
X
HEC-HMS
X
X
PondPack
X
X
X
StormCAD
GEOPAK
X
X
X
SWFHYD 1
X
X
n
Hydraulics Software
HEC-RAS
X
X
X
X
InfoWorks SD
X
X
X
X
X
X
X
XPSWMM
X
X
X
X
X
X
EPA SWMM
X
X
X
X
X
X
ICPR
X
X
X
X
X
Water Quality Software
HSPF
X
X
X
BASINS
X
X
X
X
QUAL2K
X
X
X
s
Design Tools
Macral ( Gabion
Channels
X
X
X
GeowacWlN (Gabion
Retaining Walls)
X
X
X
HY8 (Culverts and
Energy Dissi ators
X
X
X
CulvertMaster
X
X
FlowMaster
X
X
' Only where model currently exists
171
Appendix C -- City of Fort Worth Miscellaneous
Details and Specifications
CA Straight Drop Spillways
Overview The three parts of a straight drop spillway (see Figure C.1) are:
• Upstream draw down reach
• Drop opening
Downstream hydraulic jump reach
The drop structure shall be constructed of steel sheet piling. Reinforced concrete lining and
riprap shall be placed upstream and downstream of the drop structure for erosion and scour
protection.
Design Criteria Design criteria for straight drop spillways are:
• Comply with general design criteria for all transition control structures as described
in the "General Design Criteria" below.
• Design steel sheet piling to prevent bending or rotating.
• Coat steel sheet piling in accordance with industry standards to reduce rusting and
scaling.
• Use concrete lining on the entire cross-section upstream and downstream of the
drop.
• Tie the concrete lining to the steel sheet piling drop structure.
• Use a minimum six (6) inch thick slab on the downstream concrete lining due to the
impact load and potential severe turbulence.
• Determine length of concrete lining upstream and downstream of the drop.
• Include twenty (20) feet of riprap at the ends of the concrete slope paving to
decrease flow velocities and protect the concrete toe from scour (see Section 3.9
Stone Riprap Design)
• Materials and installation shall conform to City construction specifications.
General Design General design criteria for transition control structures are:
Criteria Design for a range of flows and tailwater conditions up to and including the 1%
exceedance event. At a minimum, the structure shall be designed for 1-, 5-, and
100-year storms.
• Conduct a geotechnical investigation to assist with design of the structure.
• Locate transition control structures where flow is straight. Avoid channel bends and
high turbulence areas.
• Provide structural erosion protection where maximum velocities are exceeded
upstream and downstream of the transition control structure and where the
hydraulic jump occurs.
• For drop structures in lateral channels at the confluence with the receiving channel:
o Locate the drop just inside the ultimate right-of-way of the receiving channel.
o Design the hydraulic jump to occur before it enters the receiving channel.
City of Fort Worth Stormwater Criteria Manual 172
A
-comfete Lining
Top at Bank
• .. • �•. • ,
SteE1 '4y-•
ShcetPting
:.e ••`
2a min.
Top Of Bonk
- e
• a ; ' • ' 4,
Riprap
o- .
mtn.
e
•..;
. •� . ■
V1/3
g •a '
PLAN VIEW
d •
.� .
A
[Upstream Drcw pawn Reach
oownstraam UtydrouGc lump Reach
Notuml g=nd
d
d
PROFILE VIEW
SECTION A —A
POLICY, TYPICAL STRAIGHT DROP
CMTERIA, &
u,,;,cm PROCEDURE
tl•■d[o lg�d MANUAL DATE:ICU5104 I
Figure C.1 Typical Straight Drop
City of Fort Worth Stormwater Criteria Manual 173
C.2 Baffled Chutes
Overview Baffled chutes are used to dissipate energy at abrupt changes in channel flowline and
require no tailwater to be effective. They are generally selected over straight drop
spillways for larger drop heights and where lateral channels drop into main channels.
Baffle blocks prevent undue acceleration of the flow as it passes down the chute. Since
the flow velocities entering the downstream channel are low, no stilling basin is needed.
A generic baffled chute is shown in Figure C.2.
Design Criteria Design criteria for baffled chutes:
• Comply with minimum design criteria for all transition control structures in
the previous General Design Criteria.
• Use concrete lining on the entire cross section for the structure.
• Include twenty (20) feet of riprap at the upstream end of the concrete lining
to decrease flow velocities and protect the concrete toe from scour (see
Chapter
• Use an applicable structural and hydraulic design methodology for baffled
chutes.
Use fully developed watershed conditions for establishing the design flow
rate to avoid rebuilding the baffled chute as the watershed develops.
City of Fort Worth Stormwater Criteria Manual 174
a
4 ••
••. • i • N
Riprap
See "Hydraulic Design of Stilling Basins and Energy Dissipators' Engtneering Monograph No- 25,
U.S. Department of the interior, Bureau of Redamalon,1984.
POLICY,
CRITERIA, & BAFFLE BLOCK DROP
�� PROCEDURE
llwdfa�ralt1L MANUAL
DATE: 1015f04
Figure C.2 Baffle Block Drop
City of Fort Worth Stormwater Criteria Manual 175
Appendix D -- Sediment and Erosion Control
Guidelines for Small Sites
SEDIMENT AND EROSION CONTROL GUIDELINE FOR SMALL SITES
As a builder, you are responsible for controlling soil and sediment on your job site during construction. This fact
sheet provides some general guidelines that may be used for sites that involve construction activity that disturbs
less than one acre of soil and are not required to obtain a Construction Stormwater Permit, but have the potential
to discharge sediment and other non-stormwater discharges prohibited by city ordinance.
PERIMETER CONTROLS
Perimeter controls are used to capture sediment before it leaves the construction site. These types of controls
include vegetative buffers, silt fencing, sediment traps and sediment logs. Sediment traps are small stormwater
detention areas that allow sediment to settle out of runoff. A type of trap shown below (see sketch below) is called
a cut -back curb. Cut- back curbs are small traps used to pond water behind the curb and gutter system. Frequent
monitoring and maintenance of sediment traps is needed to ensure that deposited sediment doesn't reduce their
capacity.
INLET PROTECTION
The purpose of inlet protection devices is to reduce the amount of sediment carried into the storm drain system.
The device slows runoff and filters out sediment particles at the storm drain. Inlet protection devices are the last line
of defense for capturing sediment and shall only be used if no other control measures are adequate as they can
cause property damage due to flooding if not frequently inspected and maintained.
STABILIZED CONSTRUCTION EXIT
A stabilized construction exit is used to reduce the amount of sediment tracked from a site onto the street by vehicles
or equipment. A stabilized construction exit is typically made by creating a driveway from 1.5 inches or larger
aggregate on top of a geotextile mat located where vehicles or equipment exit the site.
TEMPORARY COVER
Temporary cover is used to reduce erosion and shall be applied immediately to areas where construction activity
has ceased and is not planned to resume within 21 days or to temporary stockpiles of materials stored on site.
Stockpiled material consists of gravel, sand, excavated soil, topsoil or any other similar material. These piles shall
never be placed where stormwater is conveyed (e.g., curb and gutter, drainage ditch). Temporary cover may be
obtained by planting fast-growing plants like rye, oats, or winter wheat, or it may be obtained by spreading straw,
wood chips, erosion control blankets or geotextile fabric over the area.
WASTE DISPOSAL
All waste and construction debris shall be properly stored to prevent spills, leaks or discharges and to protect it from
being carried away from the site by wind or water. All waste and debris shall be properly disposed of in compliance
with local, state and federal regulations.
CONCRETE WASH WATER
Concrete wash water must never be discharged or allowed to drain into the storm drain or adjacent properties.
Wash water disposal must be limited to a defined area of the site or to an area designated by the Developer for
cement washout. The area must be sufficient to contain all wash water and residual cement.
INSPECTIONS AND HOUSEKEEPING
To ensure your control measures are in good condition and working properly, they shall be inspected by Owner
weekly and after any storm event. Good housekeeping shall be practiced at all times. Housekeeping includes
cleaning and maintaining all erosion and sediment control devices, cleaning sediment off streets, and picking up all
debris that has been deposited off site by wind or water. Soil or sediment that has been deposited or tracked onto
any street shall be removed by the end of the day or before the next rain event.
City of Fort Worth Stormwater Criteria Manual 176
REMOVAL. OF EROSION CONTROLS
Erosion control devices shall remain in place and maintained until permanent vegetation is established. Once
permanent vegetation is established, the control measures can then be removed.
MUST
REGULARLY
MAINTAIN
CUTBACK
TRENCH ---
12" — 24"
DENSE
vEGATAI}ON
XIED.
REET
SECTION •UNDERCUT LOT
NOT TO- SOLE
City of Fort Worth Stormwater Criteria Manual 177
Appendix E -- Single Family Residential Lot Drainage
EA Lot Drainage Types
LOT GRADING TYPE B
DRAINAGE TO FRONT AND REAR LOT LINE
GENERAL NOTES:
1. EXCEPT AS NOTED, BUILDING PAD GRADING
TO BE PERFORMED BY HOUSE CONTRACTOR
AFTER COMPLETIONOF SUBDIVISION
IMPROVEMENTS.
2. ALL FINISH FLOOR ELEVATION SHALL BE
MINIMUM OF B" ABOVE THE HIGHEST GRADE
ADJACENT TO BUILDING PAD. SEE CURRENT
BUILDING CODE.FLOOR ELEVATIONS SHOWN
ARE BASED ON THE MINIMUM FRONT SETBACK.
ALL GRADING TYPE A & B LOT FINISH FLOORS
SHALL BE AT LEAST 1.0 FT. ABOVE THE ROAD
CROWN ALONG LOT FRONTAGE.
3. DRIVEWAY SLOPES BREAKS SHALL NOT EXCEED
AN ALGEBRAIC DIFFERENCE OF:14% WITHOUT
PROPER VERTICAL CURVE.
4. MEANDER SWALES AROUND SPECIMEN TREES AND
DO NOT DISTURB WETLAND VEGETATION.
LOT GRADING TYPE A
ALL DRAINAGE TO STREET
LOT GRADING TYPE C
ALL DRAINAGE TO REAR LOT LINE
Single Family Residential Lot Drainage Types (Federal Housing Administration, Land Planning Bulletin No. 3)
City of Fort Worth Stormwater Criteria Manual 178
E.2 Block Grading Types
(Source; Federal Housing Administration Land Planning Bulletin No. 3)
Block Grading Type 1 has a ridge along the rear lot lines and each lot is graded to drain surface water directly to
the street independent of other properties. It is the most simple and desirable type of block grading. Topography,
however, will often require other types of block grading types.
Block Grading Type 2 for a gentle cross -slope involves drainage of some surface water from lots of the high side of
the block across the lower tier of lots. Difficulties are not encountered, however, if slopes are gentle and if the water
always drains over short routes to the streets and does not concentrate or accumulate in volume at any point inside
the block.
Block Grading Type 3 for steep cross -slopes and Type 4 for a valley along rear lot lines require special provision
for block drainage and erosion control.
Erosion is controlled by provision of intercepting drainage swales in easements at the top of the rear lot incline or
at intermediate locations along it, and by treatment of the steep slope itself.
Drainage easements in Block Types 3 and 5 must have alignment, width, and improvements appropriate for the
expected use and maintenance. Assurance of a permanent outfall is essential. The easements must be permanently
established by proper legal methods, with continuous maintenance assured by public authority, property -owners'
association or individual owners, as appropriate to the situation. Walls, buildings and any other obstructions to
drainage flow, such as dense planting or tight fencing, must be legally prohibited in the easement area.
PRDTECTIYE SLOPES SIDE SRALE OR dtAlDI
REAR DRAINAGE SWJUS
t
a�
i � ! ..�►�
n-
i..—
-
.J 05
L07 02"398•TRE A LOT GRADING TYPE A
BLOCK GRADING TYPE .1: RIDGE ALONG REAR LOT LIMES
City of Fort Worth Stormwater Criteria Manual 179
REAR ORAIME SYALE DRAINAGE MID ROTECTIYE SLOPES
SIDE SYALE OR CYAIIEL REAR SLOPE
TO LOYER LOT
man." j
�f� [
1
LOT ROM WE A LOT GRAOIRG TY►E'E
BLOCK GRADING TYPE 2: 6ENTLE CROSS -SLOPE
REAR DRAIRAGE SHALES ORAIRAOE OI11DE
SIDE SYALE OR CHARM
ORAIYAO5
E g11ALE
ME SYALE OR CHANNEL
PROTECTIVE SLOPES r r
4y
»- POSSIBLE LOCATIOSS OF
REAR PRAMSE ElSERfl[TS
TO FROM ODTFALL
f
l
7
LOT OWING. TYPE A L07 GRADING TYPE C
BLOCK GRADING TYPE 3: STEEP CROSS -SLOPE
City of Fort Worth Stormwater Criteria Manual 180
City of Fort Worth Storrnwater Criteria Manua] 181
Appendix F - Stormwater Utility Fee Credit Policy
Includes:
Stormwater Utility Fee Credit Policy
Development Incentives and Integrated Design Point System
City of Fort Worth Stormwater Criteria Manual 182
Authority and Purpose
The City of Fort Worth (City) adopted an ordinance (No.16781) creating a Storm Water Utility (Utility)
in July 2006 to provide a stable and equitable funding for its storm water management program.
Developed properties are charged monthly storm water utility fees based primarily on the amount of
impervious area on a parcel of property. The ordinance establishing the Utility also gives the
Transportation and Public Works Director the authority in Section 12.5-343(C) to grant credits (Credits)
to rate payers who voluntarily use storm water quality management techniques or Best Management
Practices (BMPs) to offset the impact of their property on storm water runoff. These credits are applied
as percent discounts to regular monthly storm water fees.
A general scheme of granting credits was developed by citizen task force and presented to the City
Council for comment in 2008. The purpose of this Credit Manual is to set out the specific conditions that
must be achieved to qualify for Credits. Each credit listed below is given to encourage voluntary
practices which will benefit theStorm Water Management (S WM) program.
Eli ibili
It is infeasible to review, validate, and monitor practices at single-family residences. Therefore, only non -
single family properties are eligible for credits. Credits are awarded to the water bill account.
Types of Credits
Credits are available under the following BMP categories. The percentages reflect maximum possible
credit award.
1). Industrial Permit Compliance:
2). Detention Maintenance:
3). Zero Discharge:
4). Channel Protection Detention:
5). Water Quality Treatment:
6). Inlet Trash Collection:
7). Parking Lot Sweeping:
8). Student Education:
9). Adopt A -Creek:
10). Special Measures:
City of Fort Worth Stormwater Criteria Manual
10%
20%
80%
16%
25%
10%
Minimum 5%, maximum on case -by -case
10%
5%
Maximum on case -by -case
183
Conditions for Credit
The following general conditions apply:
• Credit is valid for a year, and will require yearly renewals;
• Deadline for annual renewals is March 31;
+ Credit applicant agrees to their facility being inspected;
• Annual self -inspection of facilities and reporting is required for renewal;
• A maintenance plan for credits associated with detention and retention ponds is required;
• Incomplete or untimely submission by renewal deadline will be automatically suspended for 3
months.
Administration of Credit Program
The Credit program will be administered as follows:
• The Engineering Manager or designee in SWM will be responsible for the overall administration
of the program;
• The Water Quality Engineer in SWM will be the point -of -contact for accepting, reviewing and
authorizing the individual credit application;
• Once credit is authorized, the application will be sent to SWM's Billing Section which will be
responsible for amending the account for change in storm water utility fees with the credit;
• Credit will be given to the applicant on the next billing cycle following receipt of completed
application.
Next, the individual Credit categories are discussed.
Industrial Permit Compliance (10% cred j§
Industrial facilities (Facility) in the City that are required by the Texas Commission on Environmental
Quality (TCEQ) to obtain coverage under the Multi -Sector General Permit (TXR050000) for storm water
discharge, or another applicable storm water general permit (1XG110000, TXG340000) or individual
permit, may be eligible under this category. Facilities with a No Exposure Certification (NEC) are also
eligible for the fee credit if compliance with all NEC requirements is maintained. The following
conditions apply for this category:
a). The Facility is in compliance with all applicable permit requirements;
b). Water quality testing results from permitting are consistently at or below their benchmark levels or
permitted effluent limits during each,sampling event. When results exceed benchmarks or effluent limits,
Appropriate actions, documented in the Storm Water Pollution Prevention Plan, must be taken to reduce
pollutant discharge. Continued elevated levels may result in suspension of Credit.
City of Fort Worth Stormwater Criteria Manual 184
c). Copies of the water quality testing results must be submitted to the SWM Water Quality Engineer
as and when they 6ccur.
d). A copy ofthe Facility's annual compliance inspection report and a copy of the Facility's Storm
water Pollution Prevention Plan (SWPPP) required by the permit.
Detention Maintenance Credit (20% credits
A maximum of 20% credit will be given to impervious areas draining into detention and retention pond
facilities which are maintained in accordance with a city approved maintenance plan. The owner of the
facilities must submit an annual self -report by the March 3 1 ' deadline.
Zero Discharge Credit (80% credit)
A credit of up to 80% will be given for impervious areas which drain to a retention pond that is designed
and operated to contain runofffrom a 100 year 24•hour storm without discharge from the property.
Retention pond with lower levels of service will be considered for a pro -rated credit. This credit is
intended for runoff thaes. stored in retention ponds for later re -use. A signed and sealed study by a
qualified engineer must be approved by SWMfor this credit to be granted. Property owners interested in
this credit should meet with SWM staffprior to engaging an engineer to perform the study to understand
the engineering analysis required to meet the qualifying standards.
Channel Protection Detention Credit (10% credit)
A 10% credit will be given for impervious areas draining to a detention or retention facility that is
designed to discharge a one year storm over 24 hours. The purpose of this control is to reduce the impact
of flows and velocities on channel banks and is normally associated with the City's iSWM development
standards. A signed and sealed study by a qualified engineer must be approved by SWM for this credit to
be granted. Property owners interested in this credit should meet with SWM staff prior to engaging an
engineer to perform the study to understand the engineering analysis required to meet the qualifying
standards.
Water Quality Treatment Credit (25% credit)
Up to 25% credit will be given for impervious areas draining to a water quality treatment control BMP
that on average annual basis removes.80% TSS or detains the 85s' percentile storm (I NJ over 24-hours.
A maintenance plan for the BMP is required. A signed and sealed study by a qualified engineer must be
approved by SWM for this credit to be granted. Property owners interested in this credit should meet
with SWM stafiprior to engaging an engineer to perform the study to understand the engineering analysis
required to meet the qualifying standards.
City of Fort Worth Stormwater Criteria Manual 185
Inlet Trash Collection L10% credit)
Up to 10% credit will be given for impervious areas draining to inlet BrO devices that are designed and
operated to collect fitter and sediment from minor flows of less than one year storm frequency. The inlet
BW devices should not pose additional flooding risks around the inlet area. Approval must be given for
the specific design of the fitting, including manufacturer's recommended maintenance and frequency.
Annual self -reporting is required.
Parking Lot Sweeping (Minimum 5%, maximum on case -by -ease basis)
The 5% credit will be given for a parking lot swept once weekly. More intense sweeping and cleaning in
environmentally sensitive areas may be eligible for higher levels of credit on a case -by -case basis.
Student Education (10%)
Up to 10% credit will be given to public or private 1{ 12 educational facilities where an average of one
hour/student of age appropriate storm water related teaching is provided each year. Eligible topics
include: flood protection, public safety and environmental stewardship and other subject material
approved by the City. A sample educational template is available from the SWM Water Quality
Engineer.
Adopt -A -Creek (5016)
Up to 5% credit will be given to qualifying organizations that commit to clean City waterways for trash.
Organizations are encouraged to participate in city-wide, cleanup efforts such as the Cowtown Great
American Cleanup event while earning credits from this category.
special mensures (maximum on case -by -case)
Recognizing that there may be measures for water quality improvement not identified in the previously
listed category, this category allows awarding credit for special measures that are supportive of broader
storm water management goals and objectives. These include measures that solve or improve water
quantity and quality concerns for which the City has encountered various feasibility constraints. Credit
under this category will be awarded on a case -by -case basis. In many cases, a signed and sealed study by
a qualified engineer must be approved by SWM for this credit to be granted. Property owners interested
in this credit should meet with SWM staff prior to engaging an engineer to perform the study to
understand the engineering analysis required to meet the qualifying standards.
City of Fort Worth Storrnwater Criteria Manual 186
No fees are required to submit an application for a storm water credit. The cost of administering this
program will be borne solely by SWM.
Application for Credits
All applicants must complete the attached Application for Storm Water Fee Credit. Industrial facilities
applying for the Industrial Permit Compliance credit must also complete the Supplemental Industrial
Permit information form. All required attachments indicated in the forms or specified above must be
included for the application to be considered complete.
The initial review of Storm Water Credit Applications will be completed within 60 days of the receipt of
the application form and required documentations.. The application forms will be checked for
completeness and accuracy. If deficiencies are found during the review, a deficiency letter or email will
be sent to the applicant. Upon receipt of required additional information, the review will resume and be
completed within 60 days of receipt of additional information. Upon qualifications, a letter or email will
be sent to the applicant notifying them of approval of the credit. The storm water utility fee reduction will
be applied to the next regular billing cycle.
Inspections
Upon application for a credit; the applicant shall grant the City a right -of -entry to inspect the site at any
.time to verify the information submitted and to confirm compliance with applicable program
requirements. If, after its review or inspection, the City finds the application to be inaccurate or the
facility to be out of compliance, the applicant will be notified in writing and given up to 45 days to correct
'the deficiency. The applicant must provide written documentation to the City within 45 days of the
original notice by the City that the facility is now meeting all program requirements along with evidence
that the deficiency has been corrected. If the deficiency is not satisfactorily corrected, the fee credit will
be terminated on the following billing cycle. The credit suspension will remain in effect a minimum of 6
months, after which time the facility may reapply for the fee credit. The reapplication must include
evidence that the deficiency has been corrected and that the facility has been in compliance with the
program requirements for at least 3 months prior to reapplication.
APPROVED:
Douglas W. Wiersig, F.E.
City of Fort Worth Stormwater Criteria Manual
Date
187
FORT WORTH Application for Storm Water Fee Credit
(Please Type or Print)
Check One: ❑ This is the first application for credit for this facility.
❑ This is a reapplication for renewed credit after a credit suspension.
'PART I
A I Facili :Information-
1. Facility Name:
2. Physical Address of Facility: (enter ins aces below)
Street Number.
Street Name:
Zip Code:
3. Mailing Address: Is mailing address same as above? ❑Yes ❑ irno, provide below
Street Number:
Street Name:
City:
State:
Zip Code:
_B �A - licant Contact Information _. ' _.. . _ _
1. Name:
2. Title:
3. Phone No.: ( ) Ext:
4. Fax No.: ( )
5. E-mail address:
C Credits applied for (check all that apply)
❑Industrial Permit Compliance (complete Supplemental Industrial Permit Information Fonn and
include all required attachments)
❑ Zero Discharge (submit drainage study by licensed Professional Engineer)
❑Detention Maintenance (submit approved Maintenance Plan)
❑ Channel Protection Detention (submit design and calculations sealed by Professional Engineer)
❑ Water Quality Treatment (submit design and calculations sealed by Professional Engineer)
❑Inlet Trash Collection (submit drainage map, inlet design details and manufacturer's
recommendations for operation and maintenance)
El Student Education (submit information regarding curriculum and student hours).
❑Adapt a Creek (submit information regarding proposed clean up project, including location of
creek or channel, date of activity, number of volunteers expected, and specific support by City
forces needed to accomplish project)
❑Parking Lot Sweeping (submit map and schedule showing areas and frequency of sweeping to be
accomplished)
CFW Storm Water Utility Fec-Credit Application
Page 6
City of Fort Worth Stormwater Criteria Manual 188
FORT WORTH Storm Water Fee Credit
Application
PART II Sienature and ADnroval I
I hereby stare that the inforrrratitra in this application, including all attachments and supplemental forms, is $rite to the best
of my brendedge and ackrrotrledge that any attempt to purposely supply irrcorrec► infonuarion may result in denial of
the credit application. I farther understand the review of the documenis submitted by me may rake rip to silly (60) days
to complete and that submissions which do riot contain rite correct information or that are otherwise incamplete will be
delayed air additional sirey (60) dais after the elate lire corrected or nrissing information is provided to the City.
Signature or Applicant Title bate
Submit application and all attachments to:
Case No. SW Act No.
City of Fort Worth
TPW S►onn IVaterManagernewDivision
1000 Throckmorton St. Credits approved: %
Fort Worth TX 76102
ATrN: Storm Water Utility Fee Review I Approved by Date
CF%V Storm Water MiLity Fee47rxdit Application
Page 7
City of Fort Worth Stormwater Criteria Manual 189
FORT WORTH Storm Water Fee Credit
Application
Supplemental Industrial Permit Information Form
A Permit Information
1. Facility Name:
(as listed on Nol or NEC)
2. TPDES Permit No.: 3. Primary SIC Code: 4. Industrial Sector.
5. Date Industrial Operations Began: 6. Date NOI or NEC Filed with TCEQ:
for Comm owncdgvrator
-B 1 Compliance with.Current TPDES Storm Water Permit
1. Have all schedules of the current permit relating to monitoring, training, implementation of Best
Management Practices (BMPs) and compliance with the Storm Water Pollution Prevention Plan
(SWPPP) been met for the preceding 12 month period?
-or-
For facilities with a No Exposure Certification, have all eleven of the no exposure requirements
been met for the preceding 12 month period?
❑Yes []No
If the answer is no, provide a summary description of the current permit requirement/schedule that
has not been met, cause for non -attainment, compliance schedule, and current efforts to complete
this activity (attach additional pages if necessary).
City of Fort Worth Stormwater Criteria Manual 190
FORT WORTH Storm Water Fee Credit
Application
Supplemental Industrial Permit information Form
C I Attachments _ All required attachments must be included for the application to be considered complete (not
required for facilities with No Exposure Certification).
ATTACHMENT 1 A copy of your Storm Water Pollution Prevention Plan: Include records for
spills, Best Management Practice (BMP) maintenance, training, employee
education, periodic inspections, and quarterly visual monitoring for the
previous 12 month period. A copy of the permit does not need to be
included.
ATTACHMENT 2 Most recent Annual Comprehensive Site Compliance Evaluation Report
ATTACHMENT 3 Annual Hazardous Metals Monitoring (Numeric Effluent Limitations)
Have you obtained a waiver from hazardous metals testing for all or a
portion of the metals and outfalls? Waivers may be obtained on a metal by
metal basis, or on an outfall by outfaIl basis.
❑ A waiver has been obtained for all metals at all outfalls.
Attach a copy of the signed waiver (form TCEQ-10425).
❑ A waiver has been obtained for only a portion of the metals and/or
outfalls.
Attach a copy of the signed. waiver (form TCEQ-10425) and a copy
of your most recent results.(use EPA form 3320-1).
❑ A waiver has not been obtained.
Attach a copy of your most recent results (use EPA form 3320-1).
ATTACHMENT 4 Benchmark Monitoring Report.
Not all facilities must conduct benchmark monitoring. No SIC codes in
Sectors I, P, R, V, W, X, Z, AB, AC, or AD require benchmark monitoring.
Is Benchmark Monitoring required for your facility? ❑Yes ❑No
If yes, attach a copy of your most recent Report of Benchmark Monitoring
Data submitted to TCEQ (Form TCEQ-20091).
City of Fort Worth Stormwater Criteria Manual 191
Point System
All sites that wish to receive City stormwater fee credits must provide on -site enhanced water quality protection.
Under the integrated Site Design Practice option, sites that accumulate a minimum number of points by
incorporating integrated Site Design Practices are considered to have provided enhanced water quality protection.
The point system is made up of three components:
1. The initial percentage of the site that has been previously disturbed sets the minimum requirement. This is
shown in the left-hand column of Table F.1.
2. A minimum required total of Water Quality Protection (WQP) points are needed to meet the basic water
quality criteria. This minimum is shown in the center column of Table F.1.
3. Optional additional points can be accumulated through additional use of Site Design Practices to be eligible
for developer incentives. Each developer incentive attained requires ten (10) additional Site Design Practice points
above the minimum required points as shown in the right-hand column of Table F.1.
As shown in Table F.1, the initial percentage of site disturbance sets the minimum required points necessary to
meet Water Quality Protection criteria. If a Developer wishes to go beyond this minimum then the number of
additional points required to attain specific development incentives is also given.
Table F.1 integrated Site Design Point Requirements
Percentage of Site (by Area) with
Natural Features Prior to
Proposed Development
Minimum Required Points
for Water Quality Protection
WQp
Additional Points Above
WQP for Development
Incentives
> 50%
50
10 points each
20 - 50%
30
10 points each
< 20%
20
10 points each
The minimum number of points required to achieve WQP, as shown in the center column of Table F.1, depends on
the proportion of undisturbed natural features that exist on the site before it is developed. It is assumed that
disturbing a site that has little previously disturbed area will cause more relative environmental impact than a site
that has already incurred significant site disturbance. Therefore, disturbing a "pristine" site carries a higher
restoration/preservation requirement.
For the purpose of this evaluation, undisturbed natural features are areas with one or more of the following
characteristics:
• Unfilled floodplain
• Stand of trees, forests
• Established vegetation
• Steep sloped terrain
• Creeks, gullies, and other natural stormwater features
• Wetland areas and ponds
The number of points credited for the use of integrated Site Design Practices is shown in Table F.2. To determine
the qualifying points for a site, the Developer must reference Table F.2 and follow the guidance for each practice in
the Planning Technical Manual.
Using the area of the site that is eligible for a practice as a basis, points are given for the percent of that area to
which the integrated Site Design Practice is applied. For example, if a planned site has four (4) acres of riparian
buffer and the Developer proposes to preserve two (2) acres, then the site would qualify for 50 percent of the 8
credit points for iSWM Site Design Practice 2 (Preserve Riparian Buffers), because 50 percent of the site design
City of Fort Worth Stormwater Criteria Manual 192
practice was incorporated. The actual points earned for iSWM Site Design Practice 2 would be 4 points (0.50 * 8
pts = 4 pts). To comply with water quality protection and to apply for site design credits, the Developer must submit
the completed table and associated documentation or calculations to the City.
The Water Quality Protection Volume requirement is encouraged but not mandatory in the City, except as may be
required by Tarrant Regional Water District for new facilities connecting directly with the Trinity River.
Table F.2 Point System for integrated Site Design Practices
iSWM
Practice Na.
Practice
Percent of
Eligible Area'
using
Practice_ _max.
Maximum
Points.
Actual Points
Earned
o
(/o practice used
oints
Conservation of Natural Features and Resources
1
Preserve/Create Undisturbed Natural Areas
8
2
Preserve or Create Riparian Buffers Where Applicable
8
3
void Existing Floodplains or Provide Dedicated Natural
Drainage Easements
8
4
void Steep Slopes
3
5
IMinimize Site on Porous or Erodible Soils
3
Lower Impact
Site Design
6
Fit Design to the Terrain
4
7
Locate Development in Less Sensitive Areas
4
a
Reduce Limits of Clearing and Grading
6
9
Utilize Open Space Development
8
10
Incorporate Creative Design (e.g. Smart Growth, LEED
,Design, Form Based Zoning)
8
Reduction of Impervious Cover
11
Reduce Roadway Lengths and Widths
4
12
Reduce Building Footprints
4
13
Reduce the Parking Footprint
5
14
Reduce Setbacks and Frontages
4
15
jUse Fewer or Alternative Cul-de-Sacs
3
16
Create Parking Lot Stormwater "Islands"
5
Utilization of Natural Features
17
Use Buffers and Undisturbed Areas
4
18
Use Natural Drainageways Instead of Storm Sewers
4
19
Use Vegetated Swale Design
3
20
Drain Runoff to Pervious Areas
4
Subtotal —Actual site points earned
100
Subtract minimum points required (Table F.1)
Points available for development incentives
Add 1 point for each 1 % reduction of impervious surface f
Total Points for Development Incentives
City of Fort Worth Stormwater Criteria Manual 193
Development Incentives
The Developer can use integrated Site Design Practice points in excess of the minimum required for water quality
protection to qualify for development incentives provided by the City. Additional points can be earned for
redevelopment sites. Each reduction of one (1) percent imperviousness from existing conditions qualifies for one
(1) site design point. The total points available for development incentives shall be calculated per Table F.2. Each
incentive requires ten (10) additional points above the minimum point required to meet water quality criteria, as
stated in Table F.1.
A list of available development incentives includes:
1. Narrower pavement width for minor arterials
2. Use of vegetated swales in lieu of curb and gutter for eligible developments
3. Reduced ROW requirements, i.e. Sidewalk/Utility Easements
4. Increased density in buildable area, floor area ratios, or additional units in buildable area
5. Expedited plans review and inspection
6. Waiver or reduction of fees
7. Local government public -private partnerships
8. Waiver of maintenance, public maintenance
9. Stormwater user fee credits or discounts
10. Rebates, local grants, reverse auctions
11. Low interest loans, subsidies, tax credits, or financing of special green projects
12. Awards and recognition programs
13. Reductions in other requirements
The Development Incentives and Integrated Design point system described above are not adopted by the City. City
development policies, however, encourage the incorporation of stormwater controls for achieving stormwater quality
goals through the acceptance of perpetual, limited maintenance of preserved streams and by affording flexibility in
placing stormwater quality treatment controls in land required for other purposes such as parks or commercial
landscape areas.
The City has adopted a stormwater fee credit system, which provides monthly fee discounts where BMP's are
provided. These include credits for the following structural BMP's:
Water Quality Controls-----25% credit
Channel Protection Detention-10% credit
• Detention Basins-5% credit for maintenance and annual self -inspection in accordance with Private
Maintenance Agreement
These credits apply to fees associated with impervious areas treated by these controls. Water quality and channel
protection controls must be designed in accordance with standards adopted in this manual.
City of Fort Worth Stormwater Criteria Manual 194