PA9702-CS 981117 214 739 0095
11/17/98 TUE 16:34 FAX 214 739 0095 HALFF ASSOC 0 001
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mks • 8616 Northwest Plaza Drive
H alff Associates, Inc. Dallas,Tex (214)3466200
Fax (214) 739 -0108
ENGINEERS • ARCHITECTS • SCIENTISTS • PLANNERS • SURVEYORS
FAX TRANSMITTAL
TO: Ken Griffin, PE DATE: November 17, 1998
AVO: 16521
•
FAX #: 972/304 -3570 PROJECT: Andrew Brown Park East LOMR
FROM: Walter Skipwith, PE
Email wskipwith@halff.com # OF PAGES 5 (including cover sheet)
❑ URGENT COPY TO FOLLOW BY MAIL:
p PLEASE REPLY D YES 0 NO
FOR REVIEW
ITEMS SENT: ► j
I Letter
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COMMENTS:
Ken:
We need some direction on the Andrew Brown Park East project. Originally, this was to be a Letter of Map
• Revision based on the existing CLOMR. With the Recreation Center site plan changes, the project has blossomed
somewhat into a flood plain reclamation feasibility study, which needs to be completed quickly to keep the
Recreation Center construction on schedule. At the same time, other parts of the Park Master Plan are not
complete or even scheduled for construction in the near future and a new Denton Tap Road bridge is under
construction but not included in the CLOMR. It may be a good idea to revise the project scope to address some of
these problems. Please review the attached letter and let me know what you think.
SIGNED:
NOTE: The comments on and attachment to this cover sheet are intended only for the use of the individual or entity to which it is
addressed, and may contain information that is privileged, confidential. and exempt from disclosure under applicable law. if the reader
of this message is not the intended recipient, or the employee or agent responsible for delivering the message to the Intended recipient.
you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited. If you have received
this communication in error, please notify us immediately by telephone and retum the original to us, at the above address, via the U. S.
Postal Service. Thank you.
11/17/98 TUE 16:34 FAX 214 739 0095 HALFF ASSOC 0002
8616 NORTHWEST PLAZA DRIVE
.0111 8616 TEXAS 75225
um
Halff A (214) 346 -6200
1111111111 FAX (214) 739.0095
ENGINEERS • ARCIIIT1 U1S • SCIENTISTS
I, PLANNERS • SURVEYORS
r November 17, 1998
AVO 16521
Mr. Kenneth M. Griffin, P. E.
;;; Assistant City Manager/ Director of Public Works
!' City of Coppell
255 Parkway Blvd.
Coppell, Texas 75019
Re: Revisions to the project scope of work.
Letter of Map Revision (LOMR) Submittal.
Andrew Brown Jr. Park (East).
Dear Mr. Griffin:
The services that we are providing to the City of Coppell, as part of the Andrew Brown Jr. Park
(East) Letter of Map Revision (LOMR) Submittal project, are increasingly deviating from the
original scope of work that was approved by the City of Coppell on August 8, 1997. This is
r primarily due to a revised Aquatic and Recreation Center Site Plan. This letter outlines a revised
scope of work to fit the changing project requirements and better serve the needs of the City in its
efforts to meet the construction deadlines of the proposed Aquatic and Recreation Center on the
t e park site.
'' At the request of the City and in the course of coordination with Brinkley Sargent Architects , our
efforts up to now have focused on analyzing various site plan alternatives for the proposed Aquatic
and Recreation Center in the CLOMR hydraulic model. Effective coordination of this change
required meetings with the Architect/Engineer team and the City of Coppell. In addition, wetland
issues raised by the new site plans were clarified.
This is in contrast to the original scope of work which consisted of
1. collecting final grading plans for the various site improvements in the park,
2. surveying spot elevations at each site,
3. comparing the surveyed data with the grading plan on which was based the 1992
Conditional Letter of Map Revision ( CLOMR) submittal to the Federal Emergency
Management Agency (FEMA),
4 comparing the as -built improvements with the data of the Fully Developed (Ultimate)
Landuse hydraulic model that was prepared in conjunction with the CLOMR submittal,
5. comparing the same improvements to the two (2) Existing Landuse hydraulic models
included in the CLOMR submittal, the lloodway model and the natural or multiprofile
model,
i l 6. and finally the preparation of a LOMR submittal to FEMA.
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ARCHITECTURE • LANDSCAPE ARCHITECTURE • PLANNING
a 11/17/98 TUE 16:35 FAX 214 739 0095 HALFF ASSOC el 003
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7_ All phases of the work included a maximum of one (1) coordination meeting with the
City of Coppell and one (1) final signatures meeting.
The original budget for the tasks listed above totaled $18 , The original scope of work
specifically excluded hydrology, hydraulic modeling of Cottonwood Creek, and Denton Creek
hydraulic analysis related to revised park site plans. These items were included in the original
I scope because they were not thought to be required at the time.
t Because it has become apparent that construction in the park will not be accomplished for several
months, preparation of a LOMR submittal for the entire park is premature. A proposed pond
enlargement and a proposed fill at the east end of the park have not been constructed. This state of
lack of completion has rendered a hydraulic analysis of the impact of the Aquatic and Recreation
Center design rather difficult, as the CLOMR model works as a whole, with all the improvements
in place. The impacts of each individual site improvement have never been analyzed separately.
As previously suggested, one approach would be to prepare a new CLOMR submittal for the
Aquatic and Recreation Center only, to avoid the problems mentioned above and still ascertain that
• the Center design does not cause any rises in the hydraulic models. However such a submittal may
be unnecessary, expensive and time consuming. It may be confusing for FEMA to deal with two
CLOMR's and later on two LOMR's for the same site improvements. When contacted, FEMA
confirmed that such an effort was unnecessary to satisfy their requirements. FEMA does expect
construction to proceed in phases. This approach would '* also make it very hard for the
Architect/Engineer team to meet their December 1998 deadlines.
,, 2K ,
Therefore we suggest that the LOMR submittal preparation be postponed until all the construction
in the park is complete, and that the scope of work of the current project be modified to meet the
needs of the City and of the designing team. We think that the revised work plan should consist of
two phases.
First, we suggest that hydraulic analysis for the proposed Aquatic and Recreation Center proceed as
part of the preparation of a Floodplain Development Permit application, based on current
conditions per the latest 1998 topographic mapping, using discharges for Fully Developed Landuse
conditions. Such an effort would isolate in a hydraulic model the impact of the Aquatic and
1 , :° Recreation Center construction. Because of deadlines, this work needs to be completed as soon as
possible. The end product of Phase One would be a letter report from Halff Associates, Inc. to the
City of Coppell certifying that the proposed Center design does not cause rises in base flood levels
outside of the park and that the design is roughly consistent with the intent of the 1992 CLOMR
submittal. It would include exhibits such as a water surface elevation comparison table, a channel
velocity comparison table, a valley storage analysis, a site plan and copies of the hydraulic models
developed. Expected costs may vary depending on how many iterations need to be performed to
satisfy a no -rise condition for Fully Developed Landuse hydraulics. The following estimate
11/17/98 TUE 16:35 FAX 214 739 0095 HALFF ASSOC @1004
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presumes that only one such iteration will be necessary, additional iterations can be billed
r separately as an added task.
1
The second phase of the project would analyze the impact of all the park improvements, proposed
and as -built (including the Denton Tap Road bridge upstream of the park that is under
construction), on all pertinent hydraulic models for Dcnton Creek. The models analyzed will be the
one Fully Developed Landuse model and the two Existing Condition models that were analyzed in
the CLOMR submittal. The end product of Phase Two would be a letter report to the City, with
pertinent exhibits and attachments, that would include, if appropriate, recommendations on
additional mitigation necessary to satisfy the City's Floodplain Management Ordinance and
FEMA's LOMR requirements. Those models could be used eventually as a base for the LOMR as-
built models. Phase Two analysis could be postponed until all construction is complete and the
LOMR application is being prepared.
Please refer to the attached Exhibit A for a detailed list of the tasks and costs involved. Phase One
will be accomplished promptly to allow the Architect/Engineer team to meet their December 1998
deadlines. Phase Two will be completed within the next three months.
t
,,
Please take the time to call me at 214346 -6226 if you have any further questions or comments
regarding this suggested change of scope of services_ You may also reach Mr. Walter Skipwith at
, 214- 346 -6220.
Y ,
Sincerely,
HALFF ASSOCIATES, INC.
/ ii.-t() 6u7
Sabine Borgnet - Harris, EIT
enclosures
1
cc Brad Reid, Park Planning and Landscape Manager, City of Coppell
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11/17/98 TUE 16:36 FAX 214 739 0095 HALFF ASSOC 0 005
�:' Halff Associates
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Exhibit A
Estimated Fees
Revised Scope of Work
for the Andrew Brown Jr. Park (East)
Final Letter of Map Revision (LOMB) Project
in the City of Coppell, Texas
Al
for the City of Coppell.
c :
AVO 16521
November 17, 1998
Task Budget
Phase I - Aquatic and Recreation Center
I. Completed work as of 11/15/98 $5,000
II. Flood Plain Development Permit, Including Fully Developed Landuse Hydraulics $7,600
Al
4
Lump Sum Total, Phase I: 812,600
Phase II - Comprehensive Flood Plain Analysis for Andrew Brown Jr_ Park (East)
I. Fully Developed Landuse Hydraulics $3,600
II. Existing Landuse Hydraulics $2,500
III. Letter Report $3,100
Lump Sum Total, Phase II: 89,200
Lump Sum Total, Phases I and II: $21,800
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