ST9902-CS130611C011 Kimley -Horn
and Associates, Inc.
June 11, 2013
Sent via email
Mr. Kenneth M. Griffin, P.E.
Director of Engineering/Public Works
City of Coppell
255 Parkway
Coppell, TX 75019
ST- 9c, -0z.g
Re: Sandy Lake Road and Freeport Parkway
Cottonwood Branch
Conditional Letter of Map Revision
Dear Mr. Griffin:
Kimley -Horn and Associates, Inc. (KHA) is in receipt of the Conditional Letter of
Map Revision submittal for Sandy Lake Road and Freeport Parkway, prepared by
Teague Nall and Perkins, Inc. (TNP), dated March 2013. KHA has reviewed the
documents for adherence to the City of Coppell Floodplain Management Ordinance
and National Flood Insurance Program regulations. KHA offers the following
comments based on a review of the above referenced documents.
The CLOMR submittal prepared by TNP ties into the preliminary FIRM
panel. KHA understands the CLOMR will not be submitted to FEMA;
however, the applicant should be aware that a LOMR submittal will need to
be based on the FIRM information that is effective at the time the LOMR is
prepared. Depending on schedule, the information provided in this CLOMR
submittal may need to be revised to tie into the current effective FIRM
panel.
The response provided by TNP indicates they anticipate the project will
comply with the Endangered Species Act; however, no documentation was
provided to support this statement. The applicant should provide evidence
that the proposed project is in compliance with the Endangered Species Act.
KHA recommends TNP obtain concurrence from the U.S. Fish and Wildlife
Service.
The proposed improvements result in increases in water surface elevation
for both ultimate and existing watershed conditions.
The water surface elevations summary tables in the report and on the
workmaps are inconsistent with HEC -RAS output.
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TEL 972 770 1300
FAX 972 2393820
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12750 Merit Drive
Suite 1000
Dallas, Texas
75251
EM „ Kimley -Horn
and Associates, Inc.
Mr. Kenneth M. Griffin, P.E.
June 11, 2013
Page 2
5. The proposed improvements result in an increase in erosive channel velocity.
6. Floodway encroachments at several cross sections remain within the channel
bank stations.
7. Contrary to the statements included in the report and on the workmap, the
Freeport Parkway crossing does not provide the required freeboard.
8. Separate workmaps should be prepared for existing and proposed conditions
for clarity purposes.
9. The proposed condition HEC -RAS model does not appear to be consistent
with the proposed improvements at cross section 12868.
10. Cross section labeling on the Freeport Parkway workmap is incorrect. The
cross section labels should be revised.
11. The proposed condition HEC -RAS model does not appear to be consistent
with the proposed improvements at cross section 9590.
12. Proposed condition floodplain delineations are not consistent with the
topographic information shown on the workmaps. Floodplain delineations
should be verified.
13. The floodplain delineation downstream of Sandy Lake Road encroaches on
an existing residence that does not appear to be shown in the floodplain per
the current effective FIRM panel. The applicant should be aware that a
LOMR, based on the currently proposed floodplain delineation, will place
this residence in the FEMA effective floodplain and may result in a
mandatory requirement for the homeowner to purchase flood insurance. TNP
should verify survey information in this area to determine if this residence is
located in the floodplain and revise the floodplain delineation if necessary.
COPKimley -Horn
and Associates, Inc.
Mr. Kenneth M. Griffin, P.E.
June 11, 2013
Page 3
The applicant should revise the Conditional Letter of Map Revision submittal based
on the above comments and resubmit to the City of Coppell for further review. The
applicant should include a written response to each comment as part of the
resubmittal package. KHA may offer additional comments as a result of a technical
review of the revised submittal.
Please don't hesitate to give me a call at 972 - 776 -1781 if you have any questions or
comments regarding this letter.
Sincerely,
KIMLE Y-HORN AND ASSOCIATES, INC.
Brad W. Pickering, P.E., CFM
Associate
Cc: Mr. Niraj A. Acharya, P.E., CFM; Teague Nall and Perkins, Inc. (via email)