HomeMy WebLinkAboutIR 8461 INFORMAL REPORT TO CITY COUNCIL MEMBERS No. 8461
To the Mayor and Members of the City Council January 28, 2003
Page 1 of 2
SUBJECT: REPORT ON FRENCH LAKE DAM AND DRAINAGE STRUCTURE
AT CANDLERIDGE PARK
On Monday afternoon, December 2, 2002 the Parks and Community Services Department was notified
that the French Lake earthen dam was leaking and seeping at the pipe outlet and wing walls. Initial
PACS and T/PW staff assessment concluded that the dam integrity was threatened. Immediate action
was taken to lower lake levels in order to relieve pressure on the earthen dam. In the following days, City
forces from TPW, PALS, and the Water Department closely monitored water levels while staff moved
forward in obtaining technical assistance from a local consulting firm, Freese and Nichols, Inc. (FNI), to
determine the probable cause of dam seepage and develop a short term plan to protect the dam from
further deterioration.
During the following week, City staff conducted several on-site meetings with FNI to verify the probable
cause of dam degradation. Soil borings were taken to determine the extent of voids created. Upon
analysis of the soil boring samples, it was concluded that the probable cause of dam seepage was the
result of subsurface lateral water movement through sand bedding underneath the dam drainpipe. This
has created voids by which subsurface water has traveled from the lake water body and exited through
both the pipe joints and rock rip rap at the outfall structure. FNI recommended that a diversion channel
be constructed as quickly as possible within the dam spillway area to maintain lake water levels below
the base of the earthen dam. T/PW personnel completed the construction of the diversion channel on
December 17, 2002.
In consultation with the City Attorney's Office and with the approval of the City Manager's Office, staff
concluded that the City should move forward in design and reconstruction of the dam to protect the
structural integrity of the dam and to protect the public health and safety of the local neighborhood and
downstream areas. Because of the possible threat to public health and safety, the situation at French Lake
was determined to be exempt from the competitive bid requirements.
Preliminary cost estimates provided by FNI for the geotechnical, hydraulic& hydrology analysis, local
revision of floodplain map, and engineering design fees is approximately $113,000. The basic dam
repair, which requires excavation and removal of the existing intake structure and drainage outlet, the
construction of a new intake structure and outlet to allow for necessary flow capability during storm
events, a reworking of the existing stone wall at the pedestrian bridge and raising the spillway area totals
approximately $271,797. Additional costs have been or will be incurred by City forces (T/PW
construction of the diversion channel and dam reconstruction inspection / project management costs) and
these costs are estimated at $31,669. The estimated funding needed to cover the design and construction
costs to repair and reconstruct the French Lake Dam is approximately$416,466.
FNI has completed hydraulic studies, dam design parameters, preparation of a specific scope of services
and fee estimate and has provided conceptual plans and material quantities in order for staff to select
bidders and solicit bids for dam reconstruction. Staff will evaluate bids and select a contractor in
February 2003 and commence construction in March 2003. Completion would occur in June 2003,
contingent on weather conditions.
ISSUED BY THE CITY MANAGER FORT WORTH, TEXAS
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INFORMAL REPORT TO CITY COUNCIL MEMBERS No. 8461
To the Mayor and Members of the City Council January 28, 2003
Page 2 of 2
SUBJECT: REPORT ON FRENCH LAKE DAM AND DRAINAGE STRUCTURE
AT CANDLERIDGE PARK
Given that this situation was unforeseen, there are no funds earmarked for this project. Due to the
potential for flooding that the current condition presents, it is the staffs recommendation to move
forward with rebuilding the dam. The appropriate funding source for this project is the Capital Projects
Reserve Fund and would require an appropriation of$ 416,466.
Unless the City Council directs otherwise, staff will proceed with awarding a contract to rebuild the dam.
An M&C ratifying the design contract with Freese and Nichols, Inc. and appropriating funds for design
and engineering services will be presented to the City Council for approval as early as the Council agenda
of February 11, 2003. Upon solicitation and review of construction bids in early February 2003, an
additional M&C will be submitted for award of construction contract and appropriation of funds in late
February or early March 2003.
Should you have any questions, please feel free to contact Richard Zavala at (817) 871-5711 or Joe
Paniagua at (817) 871-6191.
Cli 4tlyl n a g e r
ISSUED BY THE CITY MANAGER FORT WORTH, TEXAS