Coppell/121 Off Pk 3-CS070312T H E C I T Y O F
COPPELL
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March 12, 2007
Konstantine Bakintas, P.E.
BHB Engineering & Surveying
309 W. Seventh St, Suite 500
Fort Worth, TX 76102
RE: Coppell / 121 Business Park Lot 3, Block 1
Dear Mr. Bakintas:
The City of Coppell has reviewed the plans submitted for Coppell/121 Business Park and has the
following comments to offer:
General Comments -
1. Before the sanitary sewer, storm drain and water lines are extended west from your site,
easements filed with the county should be provided to the City of Coppell.
Sheet 2 -
2. Please provide the thickness of pavement and the subgrade proposed for this project. If you
are not proposing to stabilize the subgrade, then a letter requesting a waiver of the lime
stabilization requirements should be provided to my office. Also, if you request a waiver, the
required thickness of the paving should be increased by one inch or the strength increased to
at least 4000 psi.
Sheet 3 -
3. Drainage Areas 'A' & 'B' should be subdivided into sub-basins to show what area actually
goes to what pickup point. Without the sub-basins, it is difficult to determine where you are
proposing to pickup the off-site water.
4. The 'c' factor for Drainage Area 'B' should be at least .9.
5. The time of concentration for Drainage Area 'B' should be a maximum of 10 minutes.
6. All designs are 100-year, only. The 5-year and 10-year calculations can be removed from the
plans. Also, we do allow the use of Hydro 35, in lieu of TP40.
7. There are several other minor comments on this sheet that also need to be addressed.
255 PARKWAY * P. O.BOX 9478 * COPPE LL TX 75019 * TEL 972!462 0022 * FAX 972/304 3673
2
Sheet 4 -
8. It appears that you are doing a substantial amount of grading to the west of your site.
However, no Erosion Control Plan has been provided with this set of construction plans.
Please comment on how you are proposing to grade off-site, let that water go across the
graded land onto your west parking lot, and proceed in a southerly direction to the storm
drain system without carrying a substantial amount of silt.
9. Based on your drainage plan, it appears that you are allowing all the off-site water to the west
to drain into your parking lot and then proceed south. You should consider unplugging the
proposed 27" RCP at your west property line and building a headwall and providing
appropriate grading to direct the water to that headwall. Obviously, this will require
additional erosion control measures.
Sheet 5 -
10. Please provide information on the size of the two drainage laterals that connect to the
proposed 27" RCP. Note: I referred to the drainage system as a 27" because that is what is
shown on the profile on Sheet 7. However, the notes on this sheet call it out as a 30" RCP.
Please clarify and correct.
11. The line for the FDC should be 4 inches, per our standard details, not 6 inches as shown.
Sheet 6 -
12. The maximum spacing for valves on an 8" water line is 500 feet. The extension of the 8"
water line from Lot 2, Block 1 to the west is approximately 970 feet. You should provide an
8" valve at approximate Sta. 5+00.
Sheet 8 -
13. On Detail 2, you show a Swale on the backside of the proposed wall. Please comment on
how the water is going to get from that proposed Swale on the backside of the wall to your
property where it is suppose to be picked-up and placed into the drainage system.
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,
~~
Kenneth M. G iffin, P.E.
Director of Engineering/Public Works
Office: 972/ 304-3686
Fax: 972/ 304-7041
Kgriffin@ci.coppell.tx.us