FS9901-CS000125· -- Halff Associates
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8616 NORTHWEST PLAZA DRIVE
DALLAS, TEXAS 75225
(214) 346~200
FAX (214) 739-0095
January 25, 2000
AVO 17669
Laura Bittner
Michael Baker Jr., Inc.
3601 Eisenhower Avenue, Suite 600
Alexandria, Virginia 22304
RE: Request for a Conditional Letter of Map Revision for Windsor Estates and DeForest Court
on Denton Creek in the City of Coppell, Dallas County, Texas
Case No: 00-06-276R
Dear Ms. Bittner:
Halff Associates, Inc. has reviewed the comments which were made about the above mentioned
case number and would like to make the following comments about our findings.
We attempted to extend the floodway models upstream to include Cross-sections 23800
through Cross-section 28870 as suggested (Issue 2) using the current effective models
received by Halff (May 1999) from Mr. Venkataiah Venkatraj with the FEMA Project
Library. In the process of delineating the flood plain and floodway in the areas suggested
(Issue 1), the effective flood plain and floodway model and current FIRM mapping were
found to be in conflict. It appears that we either have an incorrect floodway model for
this area or the current effective Flood Insurance Rate Map (preliminary per July 30,
1999) is incorrect. Also, the 100-year flood plain appeared to be contained within the
channel compared to what was shown on the current effective FIRM (fight overbank
area). The difference is possibly due to the use of 1998 City of Coppell topography for the
area for delineations or to not having the correct effective flood plain model for this area.
We were unable to resolve these differences.
Copies of the CLOMR have been submitted to the Cities of Carrollton and Lewisville for
their review. Once we receive their letters of community aclcnowledgement, we will
forward to you.
It seems unfair to make a downstream owner responsible for correcting mapping and/or model
problems well upstream in the area of cross-section 23800. The client's proposed site
modifications are far enough downstream to have a negligible effect on the flood plain and
floodway in the upstream area.
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Ms. Laura Bitmer
Michael Baker Jr., Inc.
January 25, 2000
Page 2
If you have any questions or comments, please feel free to contact me at (214) 346-6220 or
Russell Erskine at (214) 346-6225.
Sincerely,
HALFF ASSOCIATES, INC.
Walter E. Skipwith, P.E.
Vice-President
CC:
Mr. Kenneth M. Griffin, P.E.
Director of Public Works
City of Coppell