Lake Park-CS 910709 Federal Emergency Management Agency
o . ~ Engineering
Case ~o.: 9[- 6-36[
Mr. William A. Anderson, P.E. Community: City of Coppel~,
Dan M. Dowdey & Associates Dallas County,
16250 Dallas Parkway, Suite 100 Texas
Dallas, Texas 752A8 Community No.: 480170
Dear ~r. Anderson:
!!i This is in response to the request for a conditional Letter of Map Revision
::: (LOMR) for Lake Park Addition in the City of Coppell, Texas, dated February 8,
1991. Our March 12, 1991 letter co you re~ardinE chis request indicated chat
additional data might be required to complete our review of the request. The
:..: data required to complete our review is listed on the enclosure.
The required data should be submitted Co the address below,'within 30 days of
the date of this letter.
Dewberry & Davis
8401 Arlin~ton Boulevard
Fairfax, Virginia 22031
Attention: Mr. Joseph Chapman
Management En~ineerins and Technical
Services Division
The case number referenced above should be included on any correspondence
re~ardin~ the reques=. Further ac=ion on Che request has been suspended
pendin§ rece£pC of che addiCtonal da=a.
Please note Chat the initial fee already submitted is the minimum charge for a
review of this type. Additional costs could be required upon completion of
our review and prior co issuance of a conditional LOMR, dependin~ on the
complexity of the required review. You will be notified of the estimated
total processin§ cost if tC is anticipated that, due to the extent of the
review required, the total cost will exceed $1,500. In that situation, our
review would be suspended pendin~ written authorization from you to proceed.
Also note that the initial fee of $560.00 already submitted will only be
applied Co chis request if we receive the required additional data within 90
days of the date of this letter. After 90 days, the request will be treated
as an original submittal and will be subject to all submittal/payment proce-
dures, includin~ the initial fee.
2
If you have any questions concerning FEMA policy, or the National Flood
Insurance Program in general, please call Hatthew B. Miller of our Head-
quarters staff in Washington, D.C., at (202) 646-3461.
Sincerely,
William R. Locke
Chief, Risk Studies Division
Federal Insurance Administration
Enclosure
cc: The Honorable Mark Wolfe, Mayor of the City of Coppell Ms. M. Shohre Daneshmand, P.E., Acting City Engineer
Mr. Ronald W. Morrison, P.E., Morrison Hydrology/Engineering, Inc.
Mr. Art Whitney, Dan M. Dowdey & Associates
Case No.: 91-06-36R
Community: City of Coppell,
Dallas County,
Texas
Community No.: 480170
Additional Data Required Co Support a
Conditional Letter of Map Revision Request
JOL 9 t991
Requescor: Mr. gilliamA. Anderson, P.E. Dace:
Currently, a revised Flood Insurance Study (FIS) and Flood Insurance Rate Map
(FIRM), hereinafter referred Co as the preliminary FIS and FIRM, are bein~
processed for the City of Coppell. The preliminary FIS and FIRM will modify
Base (lO0-year) Flood Elevations (BFEs) and Special Flood Hazard Areas (SFHAs)
in the vicinity of the proposed Lake Park Addition as shown on the FIRM Chat
will become effective October 16, 1991. lc Es therefore necessary for the
HEC-2 hydraulic models for Denton Creek, submitted in support of the proposed
Lake Park Addition, to be compared with the data used Co prepare the pre-
ltmtnary FIS and FIRM in order Co ensure that the analyses used to determine
potential effects on flood hazards of the Lake Park Addition are adequate and
compatible with the analyses beins used Co develop the preliminary FIS and
FIRM. The HEC-2 models submitted in support of this request were primarily
based on the models for Den=on Creek beins used to prepare the preliminary FIS
and FIRM.
However, before the Federal Emersency Management Asency can complete the
review of the effects of the proposed Lake Park Addition alons Denton Creek,
the followin~ issues must be resolved:
1. The revised existing conditions HEC-2 models for Denton Creek
contained in the submitted technical report entitled Lake Park
Addition. CoDDell. Texas, which was prepared by Dan M. Dowdey &
Associates, contain cross section numbers 24400 and 25770. These
sections were not included in the May 1, 1990 HEC-2 models for
Denton Creek prepared by Kimley-Horn and Associates, Inc. (KHA),
which are being utilized Co prepare the preliminary FIS and FIRM.
In order for us Co review the effects of the proposed project,
three models are required: a duplicate extscins conditions model
exactly dupltcacins the input data from the May 1, 1990 KHA
models, a revised existins conditions model tncorporaCin~ the
additional cross sections (24400 and 25770) through the project
area, and a proposed conditions model represenCin~ the proposed
project. Therefore, co complete the data necessary Co support
this request, models exactly duplicacin~ the input from the Hay 1,
1990 KHA models must be submitted.
2. Also, in the revised existing conditions HEC-2 models contained in
the submitted report, the lO0-year natural water-surface eleva-
tions at cross section numbers 29610 and 30570 from the 10-, 50-,
100-, and 500-year (multiple profile) run do not match the 100-
year unencroached water-surface elevations from the floodway run.
The multiple profile model and floodway model should be revised so
that the 100-year water-surface elevations agree at every cross
section.
3. The proposed fill associated with the Lake Park Addition will not
encroach in the floodway for Denton Creek that will be shown on
the preliminary FIP, H, but does encroach into the current regula-
tory floodway. However, the associated proposed improvements to
the existing lake upstream of the Lake Park Addition will encroach
into both the preliminary and regulatory floodways. This en-
croachment results in 100-year water-surface elevation increases
of 0.02 foot at cross section number 25770 and 0.22 foot at CROSS
section number 26830, when compared to the revised existing
conditions models. ~hen proposed encroachments within the
floodway result in any increase in flood levels of the base (100-
year) flood, the following items must be submitted, in accordance
with Section 65.12 of the National Flood Insurance Program (NFIP)
regulations.
o an evaluation of alternatives that would not result in a BFE
increase, demonstrating why these alternatives are not
feasible;
o documentation of individual legal notice to any property
owners impacted by the increased BFEs; and
o certification that no structures insurable under the NFIP
are located in areas that would be impacted by the increased
BFE.
In lieu of submitting the above items in accordance with Section
65.12 of the NFIP regulations, your project may be revised so that
the proposed 100-year water-surface elevation increases are
eliminated, if this option is pursued, HEC-2 models representing
the revised project showing no increases in the 100-year water-
surface elevation when compared to the revised existing conditions
model must be submitted.