FS9902-CS 990303
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Kimley-Horn
and Associates, Inc.
March 3, 1999
Ken Griffin, P.E.
Director of Engineering and Public Works
City of Coppell
P.O. Box 478
Coppell, TX 75019-4409
Coppell, TX
Re: Review of CLOMR and CDC submittal for The Elm Fork of the
Trinity River at Beltline Road
Dear Mr. Griffin:
We have completed our initial review of the Flood Study in Support of a
Conditional Letter of Map Revisionfor the Elm Fork of the Trinity River at
Beltline Road in Coppell, Texas prepared by Morrison Hydrology Engineering,
Inc. dated December 1998. Our review comments, which are summarized below
are divided into two categories: General and CDC.
The following are general comments regarding the CLOMR submittal:
1. A site plan has not been included in the CLOMR submittal. When plans are
submitted to the City, they should be checked to match the conditions and
topography of the hydraulic modeling runs.
2. Please include larger scale workmaps with topography and floodplain and
floodway limits for the resubmittal to the City.
3. Please confirm the manning's n values used in the study. Heavy trees and
grass areas were mentioned in the report. Was a composite n value used in
some sections? Were the bank stations set at breakpoints in vegetation or
based on elevation? Please provide more detailed information.
4. Will the owner be maintaining the grass swale? If so, this should be signed
off on the plans submitted to the City.
5. The existing condition HEC-2 model with ultimate flows ends at Section
100040 while the proposed condition model ends at 106080. Please include
these additional sections in the existing condition model and show results in
the summary tables.
6. Please complete and submit the latest FEMA forms. These can be
downloaded from: www.fema.gov
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TEL 972 770 1300
FAX 972 239 3820
c~: f(0V'v ~F f/7/ a ttj 1336
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Suite 1800
12700 Park Central Drive
Dallas, Texas
75251
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Kimley-Horn
and Associates, Inc.
Mr. Ken Griffin, March 3, 1999, Pg 2 of 2
7. Please include all HEC-2 models on diskette.
8. Please explain the storage compensation pond. Was the storage pond
topography included in the model? Is this an on-line or off-line pond?
Please include more information.
Further comments may be provided on the CLOMR submittal once the requested
information is submitted.
The following comments pertain to the CDC application:
I. The City should be copied on the transmittal form for the CDC application to
US ACE, FEMA, TNRCC, NCTCOG, and all other cities, counties, and
agencies required.
2. For Part 2, #3, please include the cross-section where the US converges (0
feet change). You may reference and include the table provided in the
CLOMR submittal.
3. The CDC application cannot be approved until a site plan is submitted.
Very truly yours,
KIM LEY -HORN AND ASSOCIATES, INC.
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Suzanne Sheaffer
Project Manager
SMS/fas
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