ST9902-CS121025 (2)
Halie Hernandez
From:Andrew Luce <ALuce@TNPINC.com>
Sent:Thursday, October 25, 2012 11:07 AM
To:Keith Marvin
Cc:Kyle A. Bennett; Mike Jones
Subject:RE: City of Coppell Drainage requirement
Attachments:Drainage Calculations.pdf
Keith,
th
On October 15, Kyle Bennett of TNP had a phone conversation with Mike Garza regarding the drainage and dry lane
requirements for both Freeport Parkway and Sandy Lake Road. During that conversation Mike mentioned that both
Freeport (in the interim 4-lane and ultimate 6-lane design) and Sandy Lake needed to be designed with a dry lane in
both directions during the 100-yr storm as they were both arterials for the City of Coppell.
Due to the flat grades for the majority of Sandy Lake Rd. from S. Coppell Rd. to Denton Tap (-0.50% from Summer Place
to Oak Trail, 0.50% Oak Trail to Arbor Manor) the amount of water that can be carried in the gutter is greatly reduced.
To maintain one dry lane, the gutter flow depth is reduced to 0.24’. This results in 2.52 cfs capable of being carried in
the outside lane. In the 100-yr storm, for a drainage area with a runoff coefficient of 0.65, this correlates to an inlet
being required for every 0.44 acres of runoff, for a runoff coefficient of 0.90, an inlet for every 0.32 acres of runoff. See
attached for calculations.
The previous submittal for Sandy Lake Rd. was based on a maximum depth of gutter flow to be the top of curb. If the
one dry lane requirement is followed, the number of inlets required would increase by two to three times as much.
Would you prefer to reduce the dry lane requirement from the full 12’ lane to perhaps 6’-8’ or continue to follow the
same criteria as the last submittal where the maximum depth of gutter flow is the top of curb?
If you would like to meet or call to discuss this further, please let me know and I can meet at your convenience.
Thanks,
Andrew
Andrew Luce, P.E.
Project Manager
1100 Macon Street
Fort Worth, Texas 76102
817.336.5773 Main
817.665.8208 Direct
817.336.2813 Fax
aluce@tnpinc.com
From: Kyle A. Bennett
Sent: Tuesday, October 09, 2012 11:41 AM
To: kmarvin@coppelltx.gov; Michael Garza (MGarza@coppelltx.gov)
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Cc: Mike Jones (mjones@tnpinc.com); Andrew Luce; Chris Schmitt; Casey McBroom
Subject: City of Coppell Drainage requirement
Keith and Mike,
We have a question regarding the City of Coppell’s requirement for drainage. My understanding is that the City of Dallas
Drainage Design Manual is to be used. In their manual, the following statement is made regarding gutter flow / inlet
location.
“Inlets shall be placed to ensure that the 100-year flow in a street does not exceed top-of-curb elevation, and
that encroachment into the travelway does not violate the dry lane requirements given in part 3.1.3 of this
section.”
Section 3.1.3 gives the following chart regarding the dry lane requirement:
Street Classification Allowable Encroachment
Minor Arterial and lower classification Maximum depth of 6” or top of curb
Principal Arterial One lane of traffic in each direction must remain open
We have two separate conditions for our projects, so we wanted to clarify the requirements.
Freeport South Parkway
Currently, the interim condition will be built, which is a 4-lane divided roadway.
o
Can we design the drainage so that in the ultimate condition (6-lane divided roadway) the dry lane
o
rd
requirement will be met by the inside (3) lane that will be built in the future or does the interim
condition need to have a dry lane?
Sandy Lake Road
The ultimate condition is being built, which is a 4-lane divided roadway.
o
Do we need to design the drainage to meet the dry lane requirement, meaning the inside two lanes will
o
be dry?
I apologize if you have given us this information before, but I cannot find any documentation on which direction we
should go. Let me know if you have any questions or comments. Thank you.
Kyle A. Bennett, P.E.
Project Manager
17304 Preston Road, Suite 1340
Dallas, Texas 75252
214.461.9867 Phone
214.587.5629 Mobile
214.461.9864 Fax
kbennett@tnpinc.com
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