Lake Park-CS 910927 Federal Emergency Management Agcnc¥
Washin~on, D.C. 20472 B~ Enginee~ng
FILE
The Honorable Mark Wolfe Case No.: 91-06-36R
Mayor of the City of Coppell Community: City of Coppell,
P.O. Box 478 Dallas and Denton Counties,
Coppell, Texas 75019 Texas
Community No.: 480170
Dear Mayor Wolfe:
This is in reference to a February 8, 1991 letter from Ma. M. Shohre
Daneshmand, P.E., Acting Coppell City Engineer, concerning the Flood Insurance
Study (FIS) for your community. In her letter, Ma. Daneshmand requested that
the Federal Emergency Management Agency (FEMA) issue a conditional Letter of
Map Revision (LOMR) for the proposed Lake Park addition along Denton Creek
from approximately 1.5 miles downstream of Denton Tap Road to approximately
1.0 mile downstream of Denton Tap Road.
With her letter, Ms. Daneshmand submitted an undated technical report prepared
by Dan M. Dowdey & Associates, entitled Lake Park Addition. Coppell. Texas.
This report contained a written description of the project; HEC-2 hydraulic
models represent£ng ex£st£ng and proposed conditions for the 10-, 50-, 100-,
and 500-year floods and floodway for Denton Creek dated October 11, 1990; maps
delineating the 100-year floodplain and floodway for existing and proposed
conditions; and plotted stream cross sections representing the proposed
project. With an April 12, 1991 letter, Mr. William A. Anderson, P.E., of Dan
M. Dowdey Associates, submitted an annotated Flood Insurance Rate Map (FIRM)
panel for the City of Coppell depicting the location of the proposed project.
In response to our July 9, 1991 letter requesting additional data,
Mr. Anderson submitted the following data prepared by Dan M. Dowdey &
Associates:
· Plotted cross sections and valley storage calculations dated
October 1990 for the proposed project entitled Valley Storage
Sections. Lake Park Addition.
Plan entitled ~roposed Lake. Lake Park Addition, dated March 1990.
· Plan entitled Section Locations, Lake Park Addition, dated March
1990.
In addition, a Certification of Fill Compaction form dated September 4, 1991
was submitted certifying that fill involved with the proposed Lake Park
addition will be placed in compliance with National Flood Insurance Program
(NFIP) regulations Subparagraph 65.5(a)(6). Fees necessary to process this
case (a total of $850.00) have been received.
2
Currently, a revised FIS and FIRM are being prepared for the City of Coppell,
hereinafter referred to as the preliminary FIS and FIRM. In an August 1, 1991
letter to you, we stated that the preliminary FIS and FIRM, which will be
based on a comprehensive restudy of all the community's streams by Morrison
Hydrology/Engineering, Inc. (earlier work on this restudy was prepared by
Kimley-Horn and Associates, Inc.), would be sent to the community for review
near the end of September 1991. However, due to delays in receiving correct
corporate limits information, we now anticipate that the preliminary FIS and
FIRM will be issued near the end of October 1991. The preliminary FIS and
FIRM will modify lO0-year water-surface elevations and special flood hazard
areas in the vicinity of the proposed project. It was, therefore, necessary
for the aforementioned proposed conditions HEC-2 models, submitted in support
of the proposed Lake Park addition, to be compatible with the analyses used to
develop the preliminary FIS and FIRM for the City of Coppell.
The proposed project involves placing fill in the south overbank of Denton
Creek for the construction of 91 single-family residential lots and a 1.3-
acre undeveloped tract. Associated with this proposed subdivision are
modifications to an existing lake just west of the subdivision. These
proposed modifications to the lake will provide additional storage to contain
the local stormwater runoff from the subdivision. Although portions of the
proposed project are within the floodway shown on the currently effective FIRM
for the City of Coppell, dated February 15, 1984, and on the revised FIRM that
will become effective on October 16, 1991, the proposed project will be
located entirely within the floodway fringe of Denton Creek to be shown on the
preliminary FIS and FIRM.
We have reviewed the submitted technical information and determined that the
proposed project meets the minimum floodplain management criteria of the NFIP.
If the proposed Lake Park addition is completed as proposed, a revision to the
preliminary FIS and FIRM would be warranted. This revision would result in
both increases and decreases in computed 100-year water-surface elevations
(ranging from 0.22 foot higher to 0.75 foot lower) for Denton Creek through
the project area to Denton Tap Road. This revision would also show a narrower
lO0-year floodplain for Denton Creek in the fill area.
This determination is based on the 100-year flood discharges computed in the
preliminary FIS for your community, and does not consider subsequent changes
in watershed characteristics that would tend to increase flood discharges.
The development of this project and other projects upstream could result in
increased flood discharges, which, in turn, could result in increased lO0-
year flood elevations. Future restudies of your community's flood hazards
would take into account the cumulative effects of development on flood
discharges and could, therefore, establish higher 100-year flood elevations in
this area.
3
This conditional LOMR is based on minimum floodplain management criteria
established under the NFIP. Your community is responsible for approving all
proposed floodplain development, including the project upon which this request
is based, and for ensuring that permits required by Federal or State law have
been received. State and community officials, based on knowledge of local
conditions and in the interest of safety, may set higher standards for
construction or may limit development in floodplain areas. If the State of
Texas or the City of Coppell has adopted more restrictive or comprehensive
floodplain management criteria, those criteria take precedence over the
minimum NFIP requirements.
Upon completion of the proposed Lake Park addition, your community should
request a revision to the FIS and FIRM. The revision request must include the
following data:
1. Evidence of compliance with NFIP regulations Paragraph 65.4(b),
which states that 'all requests for changes to effective maps must
be made in writing by the community's Chief Executive Officer
(CEO) or an official designated by the CEO. Should the CEO refuse
to submit such a request on behalf of another party, FEMA will
agree to review it only if written evidence is provided indicating
the CEO or designee has been requested to do so."
2. 'As-built' plans of the Lake Park addition certified by a regis-
tered professional engineer.
3. Revised HEC-2 hydraulic analyses and floodplain mapping if the
'as-built' condition deviates from the proposed condition.
4. Certification that the 'as-built' complies with Subparagraph
65.5(a)(6) of the NFIP regulations, as previously discussed.
We have enclosed a copy of Part 65 of the NFIP regulations, which further
describes the nature and extent of the material needed to support a request to
revise a FIS and FIRM. Compliance with the criteria outlined in this document
will expedite FEMAts review process, thus allowing the FIS and FIRM for your
community to be revised as appropriate.
Should you have any questions regarding this matter, please do not hesitate to
contact the Chief, Natural and Technological Hazards Division of the Federal
Emergency Management Agency in Denton, Texas, at (817) 898-5127 or Matthew B.
Miller of our Headquarters staff in Washington, D.C., at (202) 646-3461.
Sincerely,
William R. Locke
Chief, Risk Studies Division
Federal Insurance Administration
Enclosure
cc: Ms. M. Shohre Daneshmand, P.E.
Mr. William A. Anderson, P.E.
Mr. Erv A. Meyer, P.E., Nathan D. Maier Consulting Engineers, Inc.
Mr. Ron Morrison, P.E., Morrison Hydrology/Engineering, Inc.
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FIRM
FLOOD INSURANCE RATE MAP
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STREET INDEX
CiTY OF
COPP£LL,
DALLAS AND DENTON COUNTIES
MAP LOCATOR DIAGRAM
*05D-
'PANEL NOT PRiNTED-NO SPECIAL FLOOD HAZARD
AREAS
COMMUNITY-PANEL NUMBER
480170 0010 D
MAP REVISED:
OCTOBER 16, 1991
Federal Emergency Management Agency