Alexander Ct-CS070821CZ—" Kimley -Horn
and Associates, Inc.
August 21, 2007
Mr. Kenneth M. Griffin, P.E.
Director of Engineering/Public Works
255 Parkway Boulevard
Coppell, TX 75019
RE: Ultimate Condition Study Review
Grapevine Creek/Akwander Court
KffA No.: 063124008
Dear Mr. Cmffm:
Kimley -Horn and Associates, Inc. (KHA) has performed the first review of the
Grapevine Creek Ultimate Conditions Study for Alexander Court, dated August
2007, prepared by Nathan D. Maier Consulting Engineers, Inc. ( NDMCE).
KHA reviewed the document for adherence to currently published City of
Coppell drainage design guidelines. KHA recommends that NDMCE address the
following items:
1. The flow change locations used in the ultimate conditions study are
inconsistent with the flow change locations in the City -Wide Storm Water
Management Study for the City of Coppell, dated January 1991, prepared
by Albert H. Halff Associates, Inc. Revise the flow change locations to
be consistent with the Halff study or explain the discrepancy.
2. The known starting water surface elevation used for the ultimate
condition profile is inconsistent with the City-Wide Storm Water
Management Study for the City of Coppell. Revise the starting water
surface elevation to be consistent with the Halff study or explain the
discrepancy.
3. The mapped top width at cross section 27540 does not reflect the HEC-
RAS model output. Revise the foodplain delineation at this cross
section to be consistent with the HEC -RAS model.
4. Revise the Floodplain Work Map to show the entire studied reach, the
extent of the model cross sections, and the cross section labels.
5. The Floodplain Work Map or report should include a water surface
elevation table showing the ultimate condition water surface elevation
for each lot to be used to set the minimum finished floor elevation.
■
suite 1800
12790 Park Central Drive
Dallas, Texas
75251
■
TEL 972 770 1300
FAX 972 239 3820
��❑ Kimley -Horn
and Associates, Inc.
Mr. Kenneth M. Griffin, P.E.
August 21, 2007
Page 2 of 2
Please note that the ultimate condition floodplain delineation encroaches heavily
on several of the proposed lots. Should any grading be proposed within the
ultimate condition floodplain boundary, a proposed condition floodplain study
will need to be submitted to the City for review.
If you have any questions regarding the comments included in this letter, please
feel free to contact us at 972.770.1300.
Sincerely,
KEWZY -HORN AND ASSOCIATES, INC.
� Igexer 14 .
Steven D. Galloway, P.E., CFM Brad W. ickering, EIT, CFM
Cc: Michael Boyd, P.E.; Nathan D. Maier Consulting Engineers, Inc.
G: Vi YDRO\PROJECTS\631240081Alexanda Court120070821.doc