W Sandy Lk Addn-CS040818CO??ELL
August 18, 2004
Mr. B. David Littleton, P.E.
Halff Associates
8616 Northwest Plaza Drive
Dallas TX 75225
RE: West Sandy Lake Road Addition, Lot 1 Block 1
Construction Plan Review Comments
Dear Mr. Littleton:
The City of Coppell has reviewed the referenced plans and has the following comments to offer:
Cover Sheet -
1. The Existing Tree Plan and Existing Tree legend are not necessary for our review and should
be removed from the sheets submitted as the civil set.
Minor Plat-
1. See the comments that were sent back on the Early Grading Permit set. There are several
easement issues that still need to be addressed.
Erosion Control Plan -
1. Again, there were comments made on the Early Grading set, refer to those comments for
erosion control sheets.
Grading Plan -
1. There are some easement call-outs that need to be removed from these sheets, per the plat
comments.
2. There is a good deal of grading being shown on the adjacent private property, you'll need
some sort of written agreement from the adjacent property owner giving permission to grade.
3. There is some concrete work on the channel that appears to be on the adjacent property; that
will need to be addressed with an agreement as well.
4. There are a few places where the comment "Grade to Drain" is included; make sure there is
enough topo, and that drainage will actually occur where you indicate it.
5. Turn off the numbers for the tree survey for this set as it causes some confusion.
Drainage Area Map -
1. The offsite drainage "A" labeled with 161 cfs saying it is based on a study performed by
Halff Associates dated June 5, 2004, I don't have a copy of that study in the file. There is a
document dated June 25 that indicates 161 cfs but neither of those match plans for the Sandy
9478 ~ COPPELL IX 7SOI9 ~ TEL 972/462 0022 ~ FAX 972/304 3673
2
Lake Road drainage design being prepared by Teague, Nall& Perkins which shows
approximately 422 cfs entering the site through the proposed drainage structure. That needs
to be conveyed through the proposed channel to the appropriate outfall.
Storm Drain Channel -
1. The Q100 needs to be based on fully developed conditions, both upstream of your site, and
for your site.
2. We need to see some cross-sections of the channel at various locations including typical
sections, there are several elements that begin and end. It appears there is a "pilot channel"
at the bottom of the channel - what is that made of?. Several places at the outfall from the
onsite drainage it appears that riprap crosses the pilot channel. Is that a proposed design or
have I misread the intention?
3. We need clarification on how the 6-inch concrete riprap on the slope is going to be
constructed; it may be helpful to see typical sections.
4. Make sure the double 8' x 4' box culverts under the drive across the channel are sized for
fully developed conditions. There are no computations contained here for the box culverts.
5. Again, any grading or construction activity on the adjacent private property needs to be done
by written agreement with that property owner.
Storm Drain Plans -
1. Do we need some kind of culvert under the driveway that accesses SH 1217
shown, make sure that drainage patterns in that area are not disturbed.
Nothing is
Storm Sewer Profiles -
1. Show all utility crossings including water and sewer lines.
Water and Wastewater Plan -
1. End the public water line with a blow-off rather than just a plug.
2. Connect your sewer line to the existing line in Sandy Lake Road rather than to the line on the
adjacent property.
3. The crossing of Sandy Lake Road with your waterline should be performed by boring rather
than open cut.
4. Has any consideration been given to two 45° bends rather than a 90° bend in a couple of
locations in your water main?
There are several other comments contained in this set you may want to consider. Please make
the necessary changes and submit these marked-up plans and two sets of revised plans to the
City for review. If you have any questions, please contact this office at your convenience.
Sincerely,
Keith R. Marvin, P.E.
Civil Engineer
Office Phone: (972) 304-7044
Fax: (972) 304-3570