FIRM-931111 (2)�4 Federal Eimergency Management Agency
Washington, D.C. 20472
Summary of Additional Data Required to Support a
Conditional Letter of Map Revision (CLOMR)
Case No.: 93- 06 -267R Date: NOV i 11%3
Requester: Mr. Kenneth M. Griffin, P.E. Community No.: 480170
Community: City of Coppell, Texas
The issues listed below must be addressed by you before we can continue the
review of your request.
1. The submitted existing conditions (Pre - project) and proposed conditions
HEC -2 models for Grapevine Creek (10 -, 50 -, 100 -, 500 -year, and 100 -year
floodway) considered a divided flow between Cross Sections 4.5 and 6
(i.e., main channel and by -pass channel) even though there is no
physical separation between the two branches during any of the 10 -, 50 -,
100 -, and 500 -year storm discharges. In order to make a better
determination as to the base (100 -year) flood elevations along this
reach, please submit: HEC -2 models (10 -, 50 -, 100 -, 500 -year, and
100 -year floodway) for existing and proposed conditions modeling this
reach without dividing; or splitting the discharge.
2. The starting water - surface elevations for the 10- and 50 -year storms at
Cross Sections 27400 (downstream tie -in) are 492.09 feet and 494.08 feet
respectively. However, the submitted existing conditions model
considered elevations of 490.84 feet and 493.20 respectively. Please
provide a revised existing conditions model which resolves these
discrepancies.
3. The model requested in Items 1 and 2 above should include a complete
input and output listing.
4. Please submit a revised work map showing all the cross sections used in
the models requested in Item 1 above.
The required data are to be sent directly to our Technical Evaluation
Contractor at the following; address:
Michael Baker Jr., Inc.
3601 Eisenhower Avenue
Suite 600
Alexandria, Virginia 22304
(703) 960 -8800
Attention: Mr. David P. Preusch, P.E.
For identification purposes, the case number referenced above must be
included on all correspondence.