Park, Peter-CS 961227 CONSULTING ENGINEERS. INC.
December 27, 1996
Mr. Kenneth M. Griffin, P.E.
Director of Public Works / City Engineer
City of Coppell
P.O. Box 478
Coppell, Texas 75019
Subject: Elm Fork Trinity River Floodplain Reclamation
18.9 acre Sandy Lake Road Property
Dear Mr. Griffin:
We are in receipt of your letter dated December 18, 1996 regarding the project cited above.
Your two review comments contained in that letter are addressed below.
The 0.01 foot increase in 100-year water surface elevation at stream station 938+ 10 occurs
for the Flood Insurance Study (FIS) condition. The City of Coppell (City) Floodplain
Management Ordinance permits as much as a one foot increase in water surface elevation
for the FIS base flood. The Design Base Flood is defined in the ordinance as the condition
resulting from occurrence of the 100-year storm on a fully developed watershed. This is the
condition for which an increase in base flood elevation is prohibited by the City ordinance.
This is the scenario evaluated in the study report pertaining to Application for Corridor
Development Certificate. Results embodied in that report illustrate zero increase in Design
Base Flood elevations as a consequence of the reclamation for the 18.9 acre Sandy Lake
Road Property. Compliance with the City ordinance is therefore achieved. It is quite
common for a floodplain modification to result in no increase in water surface elevation for
one discharge yet to exhibit an increase for a different discharge.
IConstruction plans for the improvement of Sandy Lake Road by Dallas County indicate theX~
swale across the 18.9 acre Sandy Lake Road Property will be abandoned and not used to~
receive any storm sewer discharges. An Interim Grading Plan has been devised toJ
accommodate the flow directed toward the swale until such time that the improve~t Sandy
Lake Road storm sewer system has been constructed. A ditch will be constructed from the
upstream end of the existing swale on the north side of Sandy Lake Road to the proposed
cut area on the east side of the property. A copy of the Interim Grading Plan is enclosed.
When the storm sewer system has been constructed, the southern portion of the site will
then be regraded to match the Grading Plan as originally submitted.
Three NorthPark / 8800 N. Central Expwy. / Suite 300 / Dallas, Texas 75231 / (214) 739-4741
Mr. Griffin
12..'27."96
Page 2
This is hopefully adequate information such that City approval for the CLOMR Request will
result. The previous letter indicates that you have initiated the CDC review process by the
other agencies involved. Enclosed is a check for $3100 payable to the National Flood
Insurance Program for the Federal Emergency Management Agency (FEMA) review fee. On
page four of the Reuision Requester and Community Official Form in Appendix C of the
report, please mark through the $640 entry and indicate the new fee amount. The
appropriate community official signature should also be provided at the bottom of this page.
Please note that the floppy disk with the HEC-2 input files for CLOMR Request provided to
you with the initial submittal in August should be included with the submittal to the FEMA.
To expedite the FEMA review process, we suggest that you send the package for the
CLOMR Request directly to FEMA Headquarters and simply copy the Region VI Office with
your transmittal. For your convenience, the applicable addresses are provided below.
Send the entire package for the CLOMR Request to'
Federal Emergency Management Agency
Mitigation Directorate
Hazard Identification and Risk Assessment Division
500 C Street, SW
Washington, D.C. 20472
Send a copy of the transmittal letter to:
Mr. Jack B. Quarles, P.E.
Federal Emergency Management Agency
Region VI - Federal Center
800 North Loop 288
Denton, Texas 76201
We ask that you also supply us with a copy of your transmittal letter to the FEMA. Thank
you for your assistance.
Sincerely,
NATHAN D. MAIER
CONSULTING ENGINEERS, INC.
Mark D. Walter, P.E.
enclosures