Creekview Add PD-CS 871218 NATHAN D. MAIER
CONSULTING ENGINEERS, INC.
Mr. Kevin Pieffer
Ginn, Incorporated
17103 Preston Road
Suite 100, LB 118
Dallas, TX 75248
December 18, 1987
Re: Creekvtew Variance
NDM No.: 87-6-062
Dear Mr. Peiffer:
Pursuant to our meeting of December 14, 1987, we provide you, the City
of Coppell and Mr. Carl Anderson, with this request for a variance to the new
floodplain ordinance for the Creekview project. We would like to be included
on the agenda for the January 12, 1988 council meeting.
Additional changes have been made to the plans and we have again changed
the hydraulic models to reflect additional compromise from those plans
previously submitted. From our December 7, 1987 letter, while not our
preference, we have incorporated channelization of the overbank along the west
end of the project and actually reduced the 100-year ultimate water surface
upstream from the site. Basic changes that were made to the December 7, 1987
hydraulic model, include widening the floodplain at sections 1.0, 22600, 3.0,
and 4.0, a distance of 20', 10', 10', and 10' , respectively by moving the fill
limit line back farther from the Creek, changed the fill boundary to a 3:1
sloped encroachment rather than a vertical encroachment, and lowering the
right overbank "n" value to account for un~rbrtmh clearin~ on the backside of
several of the lots. Tabulations of Water surface elevations and velocities
are enclosed for your review.
¢
At this point, we have taken all reasonable measures to co=ply with the
present ordinance. The fill licit boundazy on ~ost of the lots fronttn~ the
Creek has been reduced to a 'bare ainimu~', and will certainly lt~tt the
building alternatives on these lots. ~hile we mu~t ask for a varianCe due. to
some slight technical deviation~ to the ney ordinance, th~ perceived
alternative of channeltzatton through the residential ar~a is not thought to
be acceptable. :' ':~ ;:?ii:?!
Three NorthPark/8800 N. Central Expw¥./Suita 300/Dallao, Texae 75231/(214) 739-4741
Mr. Kevin Pieffer
December 18, 1987
Page 2
Working with you, John Kahrlsruher, Carl Anderson and Shohre Daneshmand,
we have together provided for some very significant improvements to the
previous models. These include:
Lowering water levels and velocities in certain parts of the study
reach up to 0.21 feet. Water levels increase up to 0.27 feet with
this project in certain areas, however, no existing structures will
be flooded. The maximum water surface increase with the enclosed
hydraulic model has been reduced from 0.42 (12/7/87 model) to 0.27
feet. Simtlarily, the maximum channel velocity increase has been
reduced from 0.82 to 0.56 feet per second. The velocity increases
generally occur at straight sections of the Creek (e.g. sections
1.0, 22600 and 4.0). The north overbank velocities along the toe of
slope of the existing homes, is generally 2.05 to 4.31 feet per
second, which is not erosive and should not threaten existing
structures.
Actually reducing ultimate 100-year flood waters upstream from
Denton Top Road by up to 0.20 feet.
The project will have no impact on the 2-year flood for ultimate
watershed build-out conditions.
Being in compliance with all FEMA regulations, and in compliance
with the City of Coppell ordinance in effect at the time the project
was conceived and largely designed.
Lots along the north side of Bethel Road will be filled by each home
builder and architect, only_ to the extent necessary to design a home. To this
end, maximum fill will not occur on most of the 26 lots alon~ Crapevine Creek,
especially since each owners ~otlvation will be the preservation of~he
trees that presently occupy most-of this area. As you ara aware,
however detailed, cannot account for these sit~ations, and conditions
surely be benefited by these accomzodations. The fill lfml~
of these lots has been revised Zo the absolute
sisnificant channelization of the Creek, loss o£ trees and
without requirin~ a major redesign of ~he atready approved final
Mr. Kevtn Pteffer
December 18, 1987
Page 3
We feel we have made every effort to achieve a workable solution, given
the status and timing of Creekvtew. The mitigating factors described above,
coupled with the fact that we are in compliance with federal (FEMA) criteria,
allows us to request your support of this request. Please feel free to call
should you have any questions regarding the new model or this request.
Sincerely,
NATHAN D. MAIER
K:/z'." "~ ' ~
Dennis L. Johnson, P.E.
DU/ld
cc: Carl Anderson
Shohre Daneshmand
OEC 2 I 198'1'
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NATHAN D. MAIER
CONSULTING ENGINEERS, INC.
Three NorthP&rk/8800 N. Central ExpwF./Sulle 300
Oallea, Texas 75231
(214)/739-474 I
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NATHAN D. MAIER
CONSULTING ENGINEERS, INC.
Three NorlhPatk/8800 N. Cenltal Fxpwy./Sulle 300
Della,, Texas 75231
(214)/739-4741
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