Magnolia Park-CS 860421Federal
Emergency Management
Washington, D.C. 20472
April 21, 1986
Mr. Mark W. Roberts, P.E.
Jack R. Davis & Associates, Inc.
3535 Travis Street, Suite 100
Dallas, Texas 75204
Dear Mr. Roberts:
This is in reference to a letter dated February 25, 1986, an
submitted by Mr. Ed Powell, P.E., City Engineer for the City
Texas, and forwarded to us by our Region VI office. In his
requested that the Federal Emergency Management Agency (FEMA
ditional Letter of Map Revision (LOMR) for a proposed projec'
the construction of swales and the placement of fill within ~
the Denton Creek floodplain immediately upstream of Denton T~
FEMA has initiated a reimbursement procedure to allow for th,
costs associated with the review of conditional LOMRs, there]
expenses to the general taxpayer. The initial fee for this
$400.00. This fee must be received by FEMA in order to cont.
Please provide the total initial fee within 30 days of the d~
letter. Payment should be in the form of a check or money ol
to the United States Treasury and should be submitted by Regl
Return Receipt Requested, to the following addressz
Federal Emergency Management Agency
Federal Insurance Administration
Office of Risk Assessment
Technical Operations Division
500 C Street, S.W., Room 422
Washington, DC 20472
ATTENTION MR. CHARLES A. LINDSEY
The case number referenced above should be included on your
order for identification purposes.
Please note that the initial fee is the minimum charge for a
type; additional costs could be required upon completion of
prior to issuance of a conditional LOMR depending on the nat
quired review. You will be notified of the estimated total
it is anticipated that, due to the extent of the review requ
cost will exceed $1,500. In that situation, our review woul
pending written authorization from you to proceed.
Following our initial review of the technical data submitted
letter, we identified several concerns with the HEC-2 hydrau
with the submitted mapping of this portion of the Denton Cre
The following concerns must be resolved prior to FEMAproces
ditional LOMR for the proposed project:
Agency
REPLY REFER TO:
iA-RA-RS (316A)
:ase #86-06-13R
technical data
of Coppell,
letter, Mr. Powell
issue a con-
which involves
portion of
p Road.
~ recovery of
)y reducing the
;ype of request is
Lnue our review.
~te of this
:der made payable
Lstered Mail,
=heck or money
review of this
)ur review and
ure of the re-
processing cost if
ired, the total
~ be suspended
with Mr. Powell's
lic models and
ek floodplain.
sing of a con-
2
Discrepancies were found between the mapping and th
model outputs. In particular, the map delineating
proposed 100-year flood and floodway boundaries doe
represent the output from the HEC-2 computer models
Discrepancies in water-surface elevations (WSELs)
Insurance Study (FIS) text and the existing conditi.
output were found. Reasons for these differences
mented.
The starting WSELs for the proposed conditions HEC-
be identical to the starting WSELs for the existing
model.
Standard HEC-2 modeling techniques suggest that cro:
oriented left to right, looking downstream; if a di
is used, it must remain constant throughout the mod,
the location of the encroachment station so it is c.
cross section orientation.
From our review of the technical data submitted, we also det.
following additional data would be required to continue proc.
The existing and proposed 100-year flood and floodw
to be delineated on both sides of the stream and sh.
these boundaries meet the existing upstream and dow
and floodway boundaries.
A copy of the input and output for the HEC-2 hydrau
senting the 10-, 50-, 100-, and 500-year natural fl.
should include a summary printout table 150.
Plotted water-surface profiles of the 10-, 50-, 100.
natural floods for the existing and proposed condit
4. A floodway data table for the 100-year encroachment
Please forward all supportive data, within 30 days of the da
to our technical evaluation contractor, Dewberry & Davis, 84
Boulevard, Fairfax, Virginia 22031, to the attention of Mr.
~ HEC-2 computer
the existing and
not adequately
tween the Flood
~ns HEC-2 computer
%ould be docu-
model should
conditions HEC-2
~s sections be
~ferent orientation
~1. Please check
)nsistent with the
~rmined that the
~ssing the request:
~y boundaries need
)uld show where
%stream flood
tic models repre-
)ods. This copy
-, and 500-year
tons model.
models·
=e of this letter,
)1 Arlington
?ernando Pasquel.
If you have any questions concerning FEMA policy, or the Nation
Insurance Program in general, please call the Chief, Natural an.
Hazards Division of the Federal Emergency Management Agency in l
at (817) 387-5811 or members of our Headquarters staff in Washi
(202) 646-2767.
Sincerely,
~Studies Di
Federal Insurance Administrat
cc: The Honorable Lou Duggan, Mayor of the City of Coppell
Mr. Ed Powell, P.E.
~1 Flood
Technological
)enton, Texas,
~gton, D.C., at
~ision
Lon