Alexander Ct-CS070622
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Ken Griffin - RE: Grapevine Creek! Alexander Court LOMR Review
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From:
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Attachments:
"Mike Boyd" <mboyd@ndmce.com>
"'Ken Griffin'" <kgriffin@ci.coppel1.tx.us>
6/22/2007 12:02 PM
RE: Grapevine Creek! Alexander Court LOMR Review
"Brad. Pickering (E-mail)..<brad.pickering@kimley-hom.com>
Temp00596.PDF
Ken,
I sent a revised study back to K-H that addresses their comments earlier this month (I thought you had been
copied on the transmittal). Brad Pickering has said that they would have the second review completed by the
26th. Attached is a copy of the transmital letter for your files. Thanks, Mike Boyd
-----Original Message-----
From: Ken Griffin [mailto:kgriffin@ci.coppell.tx.us]
Sent: Friday, June 22, 2007 10:55
To: Mike Boyd
Cc: Paula Crocker
Subject: Fwd: Grapevine Creek/Alexander Court LOMR Review
Mike
Could you provide a status update on revisions to the flood study? Plans are in on the project and
I would to make sure that all outstanding items are moving forward.
Thanks
Ken Griffin
>>> Ken Griffin 5/3012007 12:55 PM >>>
Mike
The review letter from Kimley-Horn for the Alexander flood study is attached.
Please make necessary changes. It probably would be quicker to work directly with K-H.
Ken Griffin, P. E.
Director of Engineering/Public Works
972-304-3686
kgriffi1].@Gi.QQJ)n~IIJx,l.Js
>>> <brad.pickering@kimley-hom.com> 5/2312007 5:01 PM >>>
Ken:
As discussed this afternoon with Nadia Dahab, attached are KHA's comments for the Grapevine Creek
LOMR application for Alexander Court, dated April 26, 2007, prepared by Nathan D. Maier Consulting
file://C:\Documents and Settings\rbrother\Local Settings\Temp\XPgrpwise\467BBA4CCity... 1/812008
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Engineers, Inc. If you have any questions regarding the attached comments, please do not hesitate to give
us a call.
Thank you,
Brad W. Pickering, EIT (IN), CFM
Kimley-Horn and Associates, Inc.
12700 Park Central Drive, Suite 1800
Dallas, TX 75251
p: (972) 776-1781
f: (972) 239-3820
e: brad.pickering@kimley-horn.com
file://C:\Documents and Settings\rbrother\Local Settings\Temp\XPgrpwise\467BBA4CCity... 1/8/2008
~DM
NATHAN D. MAIER
CONSULTING ENGINEERS, INC.
June 10,2007
Mr. Brad W. Pickering, EIT (IN), CFM
Kimley-Horn and Associates, Inc.
12700 Park Central Drive, Suite 1800
Dallas, TX 75251
Re: Letter of Map Revision (LOMR)
Grapevine Creelc/Alexander Court
NDMCE Project No. 07-03-026
KHA No.: 0613124008
Dear Mr. Pickering:
This is in response to your letter dated May 23, 2007 regarding the above referenced LOMR request. We
have addressed each of the items requested in that letter and have made revisions to the submittal
accordingly. Here are provided your comments in bold with our responses following.
Item 1: The MT -2 Form 2, page 1 of 2, states that the upstream tie-in of the study is at cross
section 27620. Cross section 27900 has been added to the revised existing conditions model and
is not included in the effective model. Revise the forms to reflect an effective tie-in upstream of
the model modifications.
The MT -2 Form 2 has been modified to reflect the effective cross-section 30130 as the tie-in cross
section.
Item 2: Revise the Floodplain Work Map to include the benchmarks and vertical datum used for
the on-ground survey.
An updated copy of the Floodplain Work Map with benchmarks and vertical datum used for the on-ground
survey is included as part of this package.
Item 3: The water surface elevations table in the report text is not consistent with the modeling
output for the effective floodway HEC-RAS model. Revise the report to be consistent with the
modeling output.
The water surface elevation table in the report has been modified to be consistent with the Effective
Floodway HEC-RAS modeling output.
Item 4: Revise the Location Map to reflect the boundaries of the LOMR submittal.
The Location Map has been reviewed to include the boundaries of the LOMR submittal. An updated copy
is included in this package.
Item 5: Cross section 22600, the location of the downstream effective tie-in, is not shown on the
Floodplain Work Map. Revise the Work Map to show this cross-section.
The Work Map has been revised to include cross-section 22600.
Two Park Lane Place / 8080 Park Lane / Suite 600 / Dallas. Texas 75231 / (214) 739-4741
Item 6: The sum of reach lengths for the HEC-RAS revised conditions model does not match the
sum of reach lengths in the FEMA effective model. Revise the reach lengths in the revised
conditions model or explain the discrepancy.
Channel lengths vary slightly due to the more detailed topographic information in the area. The sum of
channel reach lengths in the revised conditions model is a total of 11.0-ft larger than the sum of the
channel reach lengths in the effective model. Such a small difference should not significantly impact the
results obtained.
Item 7: The report text states that Manning's 'n' values were taken from the effective model, but
they vary from the effective model at multiple locations. Revise the model to be consistent with
the effective modeling or justify the proposed Manning's "n' values.
The revised conditions model Manning's 'n' values have been modified to be consistent with the effective
model. This change affected the resulting water surface elevations. An updated water surface elevation
summary table and a copy of the modified computer run are also included in this revision.
Item 8: Property owner notification is required by NFIP regulation 65.7(b)(1) due to the f100dway
revision. The notices must include the extent of revision, the changes to the f1oodway, and
contact information for any interested parties.
Property owner notifications will be sent once the City approves the results obtained by this study, and a
final submittal to FEMA is done.
Item 9: Revise the legend on the Floodplain Work Map to reflect revised existing conditions and
not proposed conditions.
The Floodplain Work Map legend has been modified and an updated copy has been included in this
package.
Item 10: Future development adjacent to the subject reach shall respect both the 100-year fully
developed and FEMA effective floodplain boundaries.
The plat being approved has set the minimum finished floor elevations to be the higher of 2-ft above
FEMA, or 1-ft above the fully developed.
Don't hesitate to contact me at (214) if you have any questions regarding the information listed above.
Thank you for your assistance.
P: (214) 739-4741
F: (214) 739-5961
E: oiohnson@ndmce.com
Cc: Ken Griffin, P.E.