SWM-CS 990413 (4)APR-14-99 09 05 FROM: NCH ENGR ID: 9724380770 PAGE 2
■�� 8616 Norttivl W Ptaxe Drive
C.. Halff Associates, Inc. Da "�, ;4 ,
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ENGINEERS - ARCHITECTS • BCIENTWTs - PLANNERS • SURVEYORS
MEMORANDUM
TO: Curtis Inglis
D/FW Airport
FROM: D. David Littleton.
Erned: dlittleion®halt %com
SUBJECT: DIFW Drainage Guidelines
DAIS: April 13, 1999
AVO' 17582
PROJECT: Southwest Coppell
Drainage Study
Mr. Inglis, we met last month with'Tracy Thompson, Doug Bryan and Mike Pyles to discuss the existing drainage
patterns In the nord*nterty portion of airport property and Its erect on the Bethel Road drainage system in
Coppell. In an ongoing drak age study we air preparing on behalf of the City of Coppell and area property owners,
the "beat' aitemative for the area would call for storm water detention on properties that are yet to be developed.
The criteria recommended In the report for ttre sizing of determon facilities tmrits runoff from developed sites to not
exceed pre- dawelopment rate. The sites which would be subject to this proposed master drainage plan includes
airport property and two sites controlM by property owners in Coppell who are participating in the study. Some
existing developments in this part of Coppell have incorporated detention into their site drainage systanrs. This
concept will allow ivr better management of runoff and help control flooding along the tributary of Grapevine Creek
we arc atiacting.
Mr. Pyles and Mr. Bryan indiceted that the airport must control runoff to pre- development volumes and velocities.
We were refwmd to the airport Design Criterta Manual for clarification of this requirement
We reviewed the Design Crlterta Manual and conferred with Don Brock, one of our engineers working for the
airport, and were unable to determine if the airport will require detention in developments that may affect the
Bethel ROW drainage system and the tributary of Grapevine Creek. Can you please help clarify the airports
position regarding the potential for drainage detention In this area. Also, can you phase indicate other areas an
the airport property where drainage detention has been implemented.
Please call me to discuss this issue or to schedule a tirne when we can come over and visit with you regarding the
drainage requirements.
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