Coppell/121 Off Pk 3-CS070403o Q o
Baird, Hampton 8 Brown, Inc. ~ Q ° Engineering ~ Surveyin
Mr. Kenneth M. Griffin, P.E.
Director of Engineering! Public Works
255 Parkway Blvd.
Coppell, TX 75019
RE: Coppell/ 121 Office Park Lot 3, Block 1
Mr. Kenneth Griffin:
We are in receipt of the City's review comments, have revised the engineering plans accordingly and offer
the following responses:
General Comments -
1. The sanitary sewer and storm drain lines were shortened and, as shown, do not cross the
property line but extend past the proposed pavement, facilitating future extension. We
acknowledge that the 20' Offsite Utility Easement, to be filed with Denton County, shall be
provided to the City of Coppell prior to construction. The easement has been enclosed for your
review.
Sheet 2 -
2. A note has been added to the Site Paving Plan indicating the proposed pavement section;
enclosed is our letter requesting a waiver of the lime stabilization.
Sheet 3 -
3. In accordance with the comment, the drainage area was subdivided to indicate the runoff to the
two proposed curb inlets; also, the drainage calculations have been revised to reflect this
analysis.
4. The 'C' factor for Drainage Area B (now 61, B2 & B3) has been increased to 0.9.
5. The time of concentration for Drainage Areas 61 through B3 have been decreased to 10 min.
6. Only the design calculations for the 100 year frequency storm are shown and we have elected to
use the TP40.
7. To clarify, we are proposing to construct the chamfered drive on the west side to avoid easement
dedication and to promote proper traffic flow around the building, as the drive is intended, until
future development. This is consistent with the previous phase.
Sheet 4 -
8. An Erosion Control Plan has been provided that indicates the use of Silt fences, straw bale dikes,
and erosion control blankets with hydromulch to mitigate erosion in accordance with the EPA
guidelines.
9. Primarily, all the property west of our site currently drains south to existing grate inlets within the
TXDOT Right of Way. The revised drainage analysis indicates the area (62) draining to the
proposed curb inlet at the southwest corner of our site and the expected offsite runoff to this inlet
is only around 4 cfs.
Sheet 5 -
10. The proposed storm drain line is a 27" RCP and the sheets have been coordinated to indicate
this.
920 South Main Street, Old Main Place Suite 190, Grapevine, Texas 76051, www.bhbinc.com
Main: 817-338-1277, Office: 817-251-8550, Fax: 817-251-8810, Email: mail@bhbinc.com
Mr. Kenneth Griffin
April 3, 2007
Page 2 of 3
11. The line for the FDC has been reduced to 4 inches.
Sheet 6 -
12. An 8" gate valve has been added to the 8" water line at station 5+00
Sheet 8 -
13. The revised Drainage Analysis shows the areas (A1 & A2) that will drain to the swale behind the
retaining wall and we are proposing to capture this flow with 3 - 2' x 2' grate inlets. The grate
inlets are shown on the Grading & Drainage Plan.
Please feel free to contact us for further clarification.
Thank you,
BHB Engju~erin 8~ Surveying
~~/
Joshua Pettijohn,
Civil EIT
BHB Engineering ~ Surveying
4
Konstantine a In as, P.E.
Vice President
Enclosed: (1) Letter for Waiver of Lime Stabilization
(1) 20' Utility Easement Documents
(1) Original Marked-up Set
(2) Full Size Set of Revised Engineering Plans
920 South Main Street, Old Main Place Suite 190, Grapevine, Texas 76051, vrww.bhbinc.com
Main: 817-338-1277, Office: 817-251-8550, Fax: 817-251-8810, Email: mail@bhbinc.com