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Carol Dye - FW: Deforest Road Drainage in Coppell
5105-0 I
From:
To:
Date:
Subject:
"Quinn Spann" <qspann@gswwengineers.com>
<kgriffin@ci.coppell.tx.us>, <kmarvin@ci.coppell.tx.us>, <DBASKINS@ci.coppell.tx.us>
6/23/2008 3 :00 PM
FW: Deforest Road Drainage in Coppell
Ken, Keith and DiWanna,
Here is Halff's first report!
Quinn G. Spann, Jr., P.E.
Associate / Sr. Project Manager
GSWW, Inc.
11117 Shady Trail
Dallas, Texas 75229
972-620-1255 Ext 225
972-620-8028 Fax
From: Alvarez, Jeffrey [mailto:JAlvarez@Halff.com]
Sent: Monday, June 23, 2008 11 :01 AM
To: Quinn Spann
Cc: Skipwith, Walter; Chovan, Dennis
Subject: Deforest Road Drainage in Coppell
Quinn,
I have researched our files for the Deforest Court and Windsor Estates design plans and have found that the
starting HGL for the 36 inch RCP shown on the Deforest Court design plans on sheet PRF-1 relates to the water
surface elevation on Denton Creek resulting from the published Grapevine Lake's controlled reservoir release rate
of 2000 cfs. This water surface elevation was called out on the Deforest Court plans because it was thought that
having a localized 1 OO-year event over the Deforest CourtlWindsor Estates area while Denton Creek's water
surface elevation is also at its 1 OO-year flood stage is unlikely. Given this, using the controlled reservoir release
rate starting water surface elevation on Denton Creek is the minimum that should be used to start your HGL
calculations. However if a more conservative approach is to be taken, assuming Denton Creek is at 100-year
flood stage when the Deforest CourtlWindsor Estates peaks, then the 1 OO-year starting water surface on Denton
Creek should be used as shown on the Windsor Estates design plans.
We are also still investigating whether there is a new US Army Corps of Engineers study along Denton Creek and
if we can obtain a copy. That study may reflect different information than is discussed here. We will keep you
informed of what we can turn up from the Corps. Let me know if you have any further questions.
Jeffrey J. Alvarez, P.E. III HAL. FF
Project Manager . ...
HALFF ASSOCIATES, INC.
3801 Parkwood Blvd., Suite 500
Frisco, Texas 75034
Phone 214-618-4570
Fax 214-618-4574
www.halff.com
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