FS9901-CS 991116REPLY TO
ATTENTION OF
DEPARTMENT OF THE ARMY
FORT WORTH DISTRICT, CORPS OF ENGINEERS
P.O. BOX 17300
FORT WORTH, TEXAS 76102-0300
November 16, 1999
Hydrology/Hydraulics Section
Mr. Kenneth Griffin
City Engineer
City of Coppell
P.O. Box 478
Coppell, Texas 75019
Dear Mr. Griffin:
The U. S. Army Corps of Engineers, Fort Worth District, was requested to perform a
preliminary technical review for project COP-070199-01, Windsor Estates, for purposes of
meeting the criteria as set forth in the Corridor Development Certificate (CDC) process. An
initial response to this request was made by letter dated September 3, 1999. The initial response
is hereby superseded by this final response.
As part of the technical report, extensive coordination was required between the Corps'
Regulatory Branch, Halff Associates, Inc. (the consultant), North Central Texas Council of
Governments, the Corps' Hydrology/Hydraulics Section, and your office. The determination of
appropriate criteria proved to be most challenging. The project was subject to three different
criteria: (1) CDC, (2) the 1988 Trinity River Regional Environmental Impact Record of
Decision, and (3) city ordinances.
The following paragraphs provide a summary of our findings:
(1) For purposes of meeting CDC criteria, valley storage associated with passage of the
100-year storm on the Elm Fork Trinity River is the primary concern. While the report did not
specifically address this issue, sufficient information was provided which confirmed that there
would be no net loss in valley storage available to the Elm Fork. Thus, this project meets the
CDC criteria as cited in version 2 of the CDC manual.
(2) According to Mr. Walter Skipwith of Halff Associates, the consultant for this project,
they determined that no jurisdictional areas would be effected. However, an official determi-
nation has not been made. No Section 404 permit would be required from the Corps' Regulatory
Branch if there are no discharges of dredged or fill material into waters of the United States.
Thus, the project was not subject to meeting the requirements contained in the Record of
Decision, which calls for no net loss in available valley storage during passage of the 100-year
storm on Denton Creek.
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(3) Additional information was obtained from the City of Coppell which indicates that
city ordinances require that the project meets the "no net loss in valley storage for the 100-year
storm" requirement, similar to the Record of Decision criteria cited above. It is our opinion that
the project, as proposed, does not fully meet this criteria. While cut and fill computations
support the consultant's claim that the on-site storage is slightly increased, the hydraulic model
indicates that the proposed project lowers upstream water surface elevations by approximately
0.05 feet. While this is a relatively small decrease, it results in a loss of at least 10 acre-feet of
valley storage during passage of the 100-year storm on Denton Creek. More precise numbers are
not available because the effects extend beyond the upstream limits of the model that was
provided.
I sincerely hope this review meets your need for assistance in making a final permitting
decision on this project. If you need additional information, please contact Mr. Elston Eckhardt
of my staff at 817-978-2222.
Sincerely,
Darrell R. Alverson, P.E.
Chief, Design Branch
Copy Furnished:
CESWF-EV-R
Mr. Walter Skipwith
Halff Associates, Inc.
8616 Northwest Plaza Drive
Dallas, Texas 75225
Mr. Jack Tidwell
North Central Texas Council of Governments
P.O. Box 5888
Arlington, Texas 76005-5888