Billingsley-CS050720.il! Halff Associates
ENGINEERS · ARCHITECTS · SCIENTISTS
PLANNERS · SURVEYORS
8616 NORTHWEST PLAZA DRIVE
DALLAS, TEXAS 75225
(214) 346-6200
FAX (214) 739-0095
July 20, 2005
AVO 23186
Kenneth M. Griffin, P.E.
City of Coppell Engineering Dept.
255 Parkway Blvd.
Coppell, Texas 75019
RE: Billingsley Development / Floodplain Development Permit
(near southwest comer of Belt Line Rd / MacArthur Blvd)
Dear Mr. Griffin:
Thank you for expediting the review of the plans. The Drainage Area Map has been revised to
address inconsistencies from the Belt Line Rd plans. We have added additional information to
the Drainage Area Map to clarify drainage areas, where they drain to, and capacity of existing
outfall locations. The intent of the Drainage Area Map is to show allowable discharges and
discharge locations for a fully developed condition when the site is developed in the future.
Halff Associates has addressed your review comments of June 5, 2005, as follows:
On Drainage Area A-2, a runoff coefficient of 0.4 should be used, not 0.3. Also, the
Belt Line Rd plans show a portion of what you show as Drainage Area A-2 being
picked up by the inlet in Belt Line Rd. Your plans propose taking all of Drainage
Area A-2 in a pipe to the east and discharging it into a different drainage pipe.
Response: We have changed the runoff coefficient for drainage area A-2 to equal 0.4
instead of 0.3. Also, while the Belt Line Road Improvement plans show a portion of
area A-2 being picked up by the inlet in Belt Line Rd, the Belt Line Rd frontage
actually slopes 8-10' down to the TXU R.O.W. We added the storm drain line to
prevent the TXU R. O. W. from ponding.
The Belt Line Rd plans show a portion of Drainage Area A-5 going to the inlet in Belt
Line Rd.
Response: Drainage area A-8 has been sized to be conveyed by the inlet in Belt Line
Rd.
In two locations in the Drainage Area labeled A-5, there are ridge lines showing
drainage to break north and south. However, you are showing the entire Drainage
Area A-5 to go north. Please clarify.
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Ill Halff Associates
ENGINEERS · ARCHITECTS · SCIENTISTS
PLANNERS ° SURVEYORS
Kenneth M. Griffin, P.E.
City of Coppell Engineering Dept.
July 20, 2005
Page 2
Response: The new ridge location and drainage area map now agree.
The as-built plans for Valley Ranch Plaza show an additional 6.39 cfs draining to the
existing culvert system in Belt Line Rd. This will reduce the available capacity in that
pipe. The Belt Line Rd plans show that only 67.5 cfs was proposed to go into the
culvert on the south side of Belt Line Rd.
Response: The 6.39 cfs shown on the Valley Ranch Plaza as-built plans is part of
drainage area K-l(along with 5.61 cfs from the street equals 12 cfs) on the Belt Line
Rd plans, thus it does not count against the 67.5 cfs of drainage area K-2.
It is my understanding that there will be some changes associated with the grading
plans along the east side of the property based on comments from the City of Irving
related to fill above the existing 54" Irving water main and the 48" DWU water main.
Response: The grading plan has been revised to reflect pulling the proposed fill out
of easements. To maintain drainage, minor grading requiring less than I-foot of fill is
proposed.
If you have any questions, please call me at (214) 346-6244.
Sincerely,
HALFF ASSOCIATES, INC.
Mark W. McGraw, P.E.
Project Manager
Enc: Revised Floodplain Development Permit Drawings (2 Sets)
Returned City Comment Set