Cambridge Phase 1-CS 930922 DA .vl. DOWDEY AND ASSOCIATES, C.
CIVIL ENGINEERS
16250 DALLAS PARKWAY SUITE 100
DALLAS, TEXAS 75248
(214) 931-0694 FAX (214) 931-9538
September 22, 1993
Mr. Ken Griffin, P. E.
City Engineer
City of Coppell
255 Parkway boulevard
Coppell, Texas 75019
Re; Floodplain review for property
adjacent to Denton Creek and
North of Deforest Road
Dear Ken:
I received comments form Kimley-Horn and Associates, Inc. on
September 14, 1993 regarding the Flood Study submitted to you on
July 15, 1993. Their letter dated September 13, 1993 addresses
seven (7) concerns that they expressed.
I will attempt to offer additional information, see attached, and
an explanation for other comments.
~-1. Appendix A was reserved for the FEMA forms. I was awaiting a
review before I submitted the FEMA application. This
application is attached.
2. I noticed that the computer printouts had hole punches which
made it more difficult to read some of the "card
identification characters" however the reviewer should still
be able to identify the card since there are only 4 to 5
different input data cards involved. For submittal to FEMA,
I will revise the printing. I would appreciate your return of
our reports for this purpose.
· ~'~ I disagree with Mr. Maggiore's contention the "the storage
runs in the report do not correctly define volume storage."
I reviewed the X3 cards. The areas that Mr. Maggiore
indicated as ineffective flow were included in the volume
calculation. The X3 card allows all of the area under the
water surface to be included. This methodology is consistent
with your own models that we did not change.
4. We did not raise the "N" values on the NC cards. We used
0.035 for channel areas and 0.055 for flood plain area. If
there is a particular model that you can refer to I would
appreciate the input. Please understand that our flood study
was prepared for an area between Section 19930 area and
Section 22370. Any areas above and below this area were not
altered nor do we intend to make alterations there to.
5. Unless there was a clerical error, the study that Mr. Maggiore
reviewed included cross-sections.
6. The basis of our study was discussed in Section III hydraulic
analysis of the report. However to reiterate, the initial
basis of the study was a model prepared by Kimley-Horn,
specifically Mr. Ron Morrison, P. E.. The proposed models
affect an area within 300 feet in either direction of Section
21560. We relied on the City of Coppell Aerial Topographic
Map which is very recent, February 1993, for field topography
primarily because Kimley-Horn has a field cross section within
600 feet of our additional section. If the existing data is
not accurate, please acknowledge this. In addition, we field
checked the limit of the site as indicated in Figure No. 8,
which was field surveyed and reproduced from an autocad
process.
7. We obtained the Corridor Development Certificate Manual from
you. In the text of this CDC manual there was an application.
I am submitting this application for your processing purposes.
It is my understanding that the City Council has adopted the
concept at the CDC Process, however, they have not adopted the
ordinance which requires interaction with the various government
agencies defined in the CDC application.
If there are any additional concerns, I would appreciate discussing
the concern verbally to ascertain that the discrepancy is addressed
and to facilitate this process.
Sincerely,
WAA;jrb