Villages C P3&4-CS 900129 .... 214-462-0022
January 29, 1990 _
R80
Mr. William H. Wallace ' ' '
Nathan D. Maier Consulting Engineers
Three North Park X SD
8800 N. Central Expwy., Suite 300 --- ,
Dallas, Texas 75231 BDO
BCB
RE; Villages of Coppell
NDM Job No. 84-10054 ~ FILE
Dear Mr. Wallace:
We are in receipt, of your request for City of Coppell approval on
the attached January 26, 1990 letter.
.Please note that the City of Coppell as the Floodplain
Administrator monitors and reviews any floodplain activities to
assure that each activity is in compliance with FIS, FIRM and
Coppell's Floodplain Management Ordinance. Presently Mr. Morrison
is finalizing the FIS report to be submitted to FEMA along with
his work on completing the Carl Anderson planning work.
We are aware of the Reconnaissance Study that you have advised our
Consultant of and specifically that the City of Carrollton, et al
are already using it. Our Consultant is in the process of
reviewing that study and preparing recommendations to this office.
The Carl Anderson work is being conducted under a study started
some years ago and is not intended to be necessarily an update to
the FEMA FIS and FIRM nor a canned program and/or information that
can be used to allow a private.design engineer to adopt it without
question, nor to utilize the data and information for not only
current design purposes, but to be used at some future date when
other data, information and rules and regulations might be in
place.
We are receptive to assisting the development community the best
way(s) possible, but to make instantaneous decisions on matters of
this complexity without knowing the full impact on the future of
the City of Coppell's floodplains is not appropriate. Likewise,
to have the City of Coppell provide you with "supporting data for
the correct floodplain elevation" is at the least, inappropriate
and we cannot approve conditions that might change in the future
when the applicant is processing the tract through the City
approvals.
As at anytime in dealing with the Federal Flood Insurance Program,
private design engineers are to use the best available data and
information for the design of developments that they are retained
to do. That information is made available to you. Ron Morrison
has not been authorize to release any information on the behalf of
City of Coppell.
The 452.00 elevation highlighted on your enclosures appears to be
in agreement with the City's September 1989 report by Ron Morrison
for the 100 FIS Base flood elevations. That report has been
forwarded to FEMA, but there are still some outstanding issues to
be addressed before FEMA accepts and approves that work and
information. However, it is your prerogative whether to use it or
not.
As I understand these two tracts were already filled under the City
of Coppell and FEMA guidelines at a previous time. I do not have
that information in hand at this time. Please forward that
information to us. That would include FEMA approval letters.
Local residents have placed on the record that drainage patterns
were changed when this land was filled. That needs to be assessed.
We will review whatever you present for your clients and that you
assure under the licensing laws and practice of engineering in the
State of Texas, but please be explicit in your transmittal letter
as to what is being depicted on your attachments identifying
numerically quantities elevations, etc and how they were
determined. We are available to discuss this further with you at
anytime. Thank you.
Sincerity, ,..,/:
//, .~i ty Engihee~ ,/
RRDIbb
xc: Shohre Daneshmand, Civil Engineer
Ron Morrison, Kimley-Horn
Ed Toole, III, The Brooks Companies
WALLACE. RRD
CONSULTING ENGINEERS, INC.
January 26, 1990
Mr. Russell Doyle
City of Coppell
P.O. Box 478
Coppell, Texas 75019
Re: Villages of Coppell
NDM Job No.: 84-10-054
Dear Mr. Doyle:
Enclosed are topographic and boundary maps for two tracts of 23.8393 and 17.1386 acres located in the
City of Coppell, Texas. Marked in red on these maps are the 100-year flood limits for the following.
A. Ultimate floodplain elevation for the Elm Fork Trinity River, based on the existing condi-
tions hydraulic model from the Reconnaissance Study, with future discharges based on
ultimate watershed urbanization. ~
B. The higher of the ultimate 100-year water surface or the effective FIS elevation on
-Denton Creek, based on data provided by Mr. Ronald Morrison.
We are being asked to certify that these data are correct and accepted by the City of Coppell. This
information is required to evaluate the feasibility of purchase of this property and to develop engineering
costs.
We respectfully request a written response from the City of Coppell as to the validity of these data. Due
to pressing time constraints, the written response needs to be provided within the next week. If it is
determined that these data are not correct, then we will need the City to provide supporting data for the
correct floodplain elevations.
We are anxious to resolve this issue so that upcoming deadlines can be met. We will assist the City in
any way possible to expedite this matter.
Sincerely,
NATHAN D. MAIER
William L. Wallace, P.E.
WLW/rdp
Three NorthPark/aB00 N. Central Expwy./Suite 300/Dali&s, Texn~ 75231/(214) 739-4741
NATHAN D. MAIER
March2'1990 og~t
Mr Russell oyl75019 . . ....
o[ our Fobrua~ lg, 1000, repod' cdn~ornin~ tho oxistin~ flood-
plain eondifion~ with re~po~ to tho Villa~,~ o{ Ooppoll, Phaso Ill. ~oso revl~ion~ ~re providod duo to
rovision~ in h~drauli, modol~ [or thls area. ~o [ollowin~ ~ummari~os tho revi~lon~ with respo~ to tho
individual floodin~
Elm FQ~ Tdni~ Riv0r
~e recent study submlffed to the Ci~ of Coppell by Ron Mo~lson sho~ an existing hydraulic model
for the Elm Fo~ which is based on the ongoing Reconnaissance Study for the Co~s of Engineem. ~e
repoA also provides an ultimate conditions model, which agrees with our repoA of Februa~ 16, 1990.
Table 1 summarizes the 10~year water sudaces for ~th of these hydraulic models.
TABLE 1,
Elm Fork Trinity River
EXISTING ULTIMATE
CROSS RECONNAISSANCE 100-YEAR
SECTION MODEL ELEVATION
1000+40 447.09 447.59
1030+60 448.49 448.97
1060+80 451.52 451.95
Flrst floors of residences will now be based on two feet above the new existing condition since this ele-
vation will control. The floodplain limits shown on the attached maps show the limits of the ultimate
floodplain elevation along the perimeter of the property as shown in Table 1,
Denton Creek
The recent study submitted to the City of Coppell also provides revised hydraulic models for Denton
Creek. Table 2 provides a summary of the new existing conditions and ultimate discharges with exist-
lng hydraulic sections,
Three NorthPark/8800 N. Central Expwy./Suite 300/Dallas, Texas 75231/(214) 739-4741
Mr, Russell Doyle
March 2, 1990
Page 2
TABLE 2
Denton Creek
REVISED
CROSS 100-YEAR ULTIMATE
SECTION EXISTING 100-YEAR
ELEVATION ELEVATIONS
18440 452.12 452.38
19330 452.25 452.51
19930 452.25 452.51
21560 452.39 452.67
22370 452.58 452.90
23800 452.98 453.38
24700 453.45 453.92
25530 453.67 454.16
First floor elevations will be established at 2 feet above the revised existing 100-year elevations pro-
vided in Table 2, since these elevations will still control. The attached maps provided with this letter
show a floodplain delineation based on' the ultimate flood elevation provided In Table 2.
Please supplement our previous report with these revised data. Since Mr. Mo~rlson will be reviewing
this report, I have taken the liberty to send hlm a copy of ~his letter and maps.
If you have any questions concerning this data, please fell free to call me.
Sincerely,
NATHAN D. MAIER
CONSULTING ENGINEERS, INC.
.... · ~ ~J~'~ ~ /8'
William L Wallace, P,E,
WLW/sJg
Enclosures
cc:. Mr. Ronald Morrison