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MEMO FOR RECORD
08/26/03
DAA JOB NO. 03-039
TO:
Terry Holmes
(via e-mail)
FROM:
William A Anderson, PE
RE:
Bethel Road Estates Floodplain
Rhonda Hurst and I met with Mr. Ken Griffin, PE, City Engineer for Coppell this morning, The
purpose of the meeting was to discuss the floodplain limits for the above referenced land
There are three situations that may exist at any given 1 OO-year event
CASE 1: Grapevine Creek flowing at the FEMA regulated flow and elevation, Based on this
condition, the 1 OO-year water surface on the east and north side of Lot 2, Block 1 is
494,0,
cASE 2: Grapevine Creek flowing less than the 100-year flood event, with Stream G-1 flowing
at a 1 OO-year event Based on this condition, the 1 OO-year water surface on the east
side of Lot 2, Block 1 is 489,85 and gradually rises to 493,88 at the northwest corner of
Lot 2, Block 1, This is based on a Goodwin Marshall LOMR dated 1992 (Not reflected
on the FIRM Map),
CASE 3: The Ultimate 1 OO-year water surface for Stream G-1 is 498:t, Mr. Griffin doesn't
regulate this 100-year event based on a horizontal location, He is concerned about
the height of the water surface, thus this condition often controls the minimum finish
floor as in this case, The minimum finish floor for Lot 2, Block 1 should be 499,0
OPTION 1: The FIRM Map needs to be changed to reflect the natural topographic contours
that are associated with the 494 elevation, This is referenced to as a Letter of Map
Amendment Under this case, no actual reclamation is occurring, only the map will
eventually be changed,
OPTION 2: Obtain the most current "effective model" from FEMA for Grapevine Creek and
Stream G-1. This requires sending an information request form to the FEMA
Library to get the most current Hydraulic Model for Grapevine Creek and Stream
G-1. Based on the models obtained, the model is revised to reflect a starting water
surface, which takes into consideration the backwater effect of Grapevine Creek as
shown on the FIS FIRM profile.
In addition, if any reclamation is attempted, Mr. Griffin will require that 85% of the existing valley
storage be retained (i.e. replace cut and fill situations to balance said valley storage.
Once a reclamation plan is completed, submit to FEMA a Letter of Map Revision (LOMR).
C\Documenl. and Scttings\kgriffinCITY _COPPELL\Local Scllings\TempOfRrY Internet Files\OLKI'i9\Bclnel Rd Estates Fluodplain Memo 8-26-3 waa.doc
From: "Rhonda Hurst" <rhurst@daa-civil.com> [rhurst@daa-civil.com] on behalf of "Rhonda Hurst" <rhurst@daa-
civil.com>
Sent: Thursday, September 11,20035:06 PM
To: "Ken Griffin P. E." <kgriffin@ci.coppell.lx.us>
Subject: Bethel Rd Estates Floodplain Memo 8-26-3 waa.doc
Ken,
Attached is the memo that Bill sent to Terry after we met with you. We
spoke with Terry yesterday and he said that he has discussed this issue with
you as well. Please let me know what option you and Terry discussed and how
you directed him to proceed. Thank you for this time in this matter.
Rhonda Hurst
9/1 1/2003