FS0001-CS010810NDM NATHAN D. MAI ER
CONSULTING ENGINEERS, INC.
August 10, 2001
Mr. Ken Griffin, P.E., City Engineer
City of Coppell / Engineering Development
255 Parkway Boulevard / P.O. Box 478
Coppell, Texas 75019
RE: Holmes Tract, North of Sandy Lake, West of Denton Creek
Response to second Review, NDM Job # 9810102
Dear Mr. Griffin:
By transmittal letter dated March 7, 2001 we submitted a revised CLOMR and CDC application
for the Estates of Denton Creek, a 31.6-acre tract that fronts on the northerly line of Sandy
Lake Road and west of Denton Creek. At the City's request, Kimley-Horn and Associates
(KHA) provided a second review of the submittal by letter dated March 20, 2001. The letter
was set up to show the KHA comments from the previous NDM submittal.
Following is a response to KHA CLOMR comments:
1. Comment cleared.
2. Comment cleared.
3. Comment cleared.
4. KHA comment: The included FEMA MT-1 Form 3 outlines criteria for fill compaction and
erosion control in the FEMA lO0-year floodplain. It is suggested that this information be
required on the grading plan for the site.
NDM report Exhibit 3 is a post-project Floodplain Work Map that is intended to show the
limits of the 100-year floodplain after construction. Some spot minimum elevations are
shown but no future grading is shown. This plan is not intended to be a grading plan but
rather a general guide for the future grading plan that will be included in the construction
plans. When the construction plans are prepared the applicable compaction requirements
will be on the grading plans or the project specifications. Additionally, the creek bank
erosion plan will include either gabions or steel piling along the sloping bank of Denton
Creek. The specific details have not been designed at this phase of project permitting.
NDM feels that this comment does not apply to the CLOMR application. At this point in the
permitting process FEMA only requires the completed MT-1 Form 3.
5. KHA comment: The Post-Project Conditions Work Map shows a portion of the multiple lots
wi//be located in the FEMA floodplain. It is suggested that the engineer be made aware of
Subdivision Regulation Appendix C, Section/I. 5 aYb covering access to this floodplain area
for maintenance and provide for this access via easements or other means.
As stated by KHA in the "Suggestion stands" comment, this item does not pertain to the
CLOMR submittal. The floodplain work map is a concept plan only which will be refined
with the development plans and final platting process.
NDM feels that this comment does not apply to the CLOMR application.
Two NorthPark / 8080 Park Lane / Suite 600 I Dallas, Texas 75231 I (214) 739-4741
6. Comment cleared.
7. Comment cleared.
8. This KHA comment pertains to the HEC-2 Denton Creek model that is contained in the
report. This model was developed at the City's request and contains the authorized release
discharge from Grapevine Lake and a bank high discharge (approximately 2-year
frequency). These discharges were modeled to look at the channel velocities as an aid in
designing future erosion protection for the creek bank adjacent to the subdivision. This
model was included to show the FEMA reviewer the calculated velocities along Denton
Creek for review purposes only.
As shown on the effective FIRM, the effective FEMA model for Denton Creek begins about
3000 feet north of the project north property limits. Any discharges that exceed the top of
bank in the creek along this northerly reach will overflow into the Elm Fork floodplain. The
Elm Fork is the only controlling water surface elevation at the project location.
NDM feels that this comment does not apply to the CLOMR application.
9. Comment cleared.
10. Comment cleared.
The summary comment by KHA on the CLOMR review is that the CLOMR report is
substantially complete for submittal to FEMA. This is understood by NDM that the application
and drainage report (dated January 2001) as submitted with the March 7 transmittal is
acceptable to be submitted to FEMA for processing without any further modifications.
Following is a response to KHA CDC comments:
1. Comment cleared.
2. KHA noted that the FEMA and CDC models were slightly different. NDM obtained both
models from the Corps of Engineers. NDM duplicated the models as received from the
CORPS, did not modify either model, nor feel that we are at the discretion to change
adopted baseline modeling. Standard CDC Form Part 2, page 2 is changed to reflect the
upstream boundary 97919 channel velocity.
3. Comment cleared.
4. (New Comment) Several Exhibits in the application were incorrectly labeled as the East
Fork rather than the Elm Fork Trinity. This has been corrected and new exhibits submitted
with this transmittal.
These changes should bring the CLOMR and CDC applications to be acceptable so that
processing through FEMA and the CDC program can proceed.
Sincerely,
NATHAN D. MAIER
CONSULTING ENGINEERS, INC.
Michael H. Boyd, P.E. /
Executive Vice President
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