St Joseph-CS001127A
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November 27, 2000
FREESEoNICHOLS
Mr. Kenneth M. Griffin, P.E.
Director of Engineering and Public Works
City of Coppell
255 Parkway
P. O. Box 478
Coppell, Texas 75019
Re:
Computation of Flood Storage for a 2 Acre Site South of Sandy Lake Road and
East of McArthur Blvd. In the Elm Fork of the Trinity River Floodplain in
Coppell, Texas
Dear Mr. Griffin:
We are pleased to provide this report to identify the required storage compensation
needed to fill a 2-acre site to one foot above the 100-year design floodplain as determined
from the 100-year and Standard Project Flood (SPF) as computer by the Corps of
Engineers and reviewed by the Federal Emergency Management Agency (FEMA), and
currently awaiting final approval to calculate storage compensation. The storage
compensation allows a 15% reduction in 100-year flood storage and a 20% reduction in
the Standard Project Flood (SPF).
The drawing on the following page shows the site.
Freese and Nichols, Inc. · Engineers · Environmental Scientists · Architects
1701 North Market Street · Suite 500 LB 51 · Dallas, Texas · 75202
214-920-2500 · Fax 214-920-2565 · www.freese.com
Using the new floodplain information the existing and developed volumes of storage
were calculated. They are as follows:
lO0-year existing condition volume
SPF existing condition volume
100-year existing condition allowable volume
SPF existing condition allowable volume
N/A above 100-year
3.32 acre feet
N/A above lO0-year
2.66 acre feet
100-year proposed condition volume
SPF proposed condition volume
N/A above 100-year
0.92 acre-feet
Required storage mitigation 100-year
Required storage mitigation SPF
N/A above 100 year
1.74 acre feet
If this area is developed after the new FEMA information is finalized no storage
compensation will be required since the area will be outside the 100-year floodplain.
We have been coordination this information with all parties involved. Now that the
information is complete' this project can be finalized.
Let me know if we can provide additional information.
Sincerely,
FREESE AND NICHOLS, INC.
Ronald W. Morrison, P.E., C.F.M.
Drainage Discipline Leader
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