CF-Cozby Library-CS 940520 (4)May 20, 1994
REVISED
Mr. Jim Bullock
F & S Partners, Inc
3535 Travis, Suite//201
Dallas, Texas 75204-1497
RE: W.T. Cozby Public Library
Coppell, Texas
Dear Mr. Bullock:
In accordance with your request of March 16, 1994, we are pleased to provide our
recommendations regarding the influence of the water level in the lake on the proposed
sub-drain system and building pad.
We are provided with information that the normal water surface elevation of the lake
immediately south of the proposed library site is at 460.0 feet and the 100 year water
surface elevation is at 463.8 feet. The current design calls for a finish floor elevation
of 467.0, with five (5) feet of below slab select fill and a sub-drain system about five (5)
feet below the finish floor elevation. The sub-drain system is currently designed to drain
to the lake using gravity, by way of an existing storm drain at the southwest corner of
the proposed building. Based on current design, the sub-drain system is to be founded
at about elevation 462.0 feet, which is below the 100 year water surface elevation. This
leaves potential for water in the lake backing up through the gravity drain pipe and
saturating the select fill and underlying expansive subgrade.
Mr. Jim Bullock
May 20, 1994
Page Two
Based on the above information, we recommend the following alternatives be considered
to reduce potential for water ponding under the building:
1. Raising the finish floor elevation and subdrain elevation so that the subdrain
system is above the 100 year water surface elevation.
2. Connecting the sub-drain system to a suitable sump pump and pumping the water
to the lake rather than utilizing the existing storm drain. Provisions for prevention
of backflow throughout the system should be made. This would allow the finish
floor elevation to remain at 476.0.
3. Lowering the water elevations in the lake. This would allow the finish floor
elevation to remain at 476.0.
We further recommend a minimum horizontal distance between the lake and building pad
of ten (10) feet. If this cannot be maintained, consideration may need to be given to a
three (3) foot wide clay wall, slurry wall or other suitable water barrier between the lake
and the building pad.
We trust the information provided above is sufficient for your use at this time. If you
have any questions, please do not hesitate to contact our office.
Sincerely,
GEE Consultants, Inc.
Gary G. Huang, Ph.D Richard W. Gee, P.E.
Project Manager President
GGH:RWG/lej
cc: Gary Sieb -- City of Coppell
Mike Sherpinskas -- Diversified Construction Services, Inc.
Ayres Associates
Brockette Davis Drake, Inc.