Gateway BP(1.1)-CS 900828 ALBERT H. HALFF ASSOCIATES, INC.
ENGINEERS · SCIEXTISTS · SURVEYORS
DALL4$' ARLINGTON' CHICAGO' FORTWORTH FI[ [ COP f
.z.6'6 %0'~--~'¢,'ES- =..-".ZA 3~ ',-'E · E'~,-LAS. -EXAS 75_326
2'-:'73~-009z
August 28, 1990
AVO 10564
City of Coppell /qb/a- ,.
Department of Public Works
Coppell, Texas 75019
col. k 2 d
Att: Ms. Shore Daneshmand, P.E.
Acting Ci, En~neer
Re: Gateway Business Park- Phase I
Storm Sewer ~e 'A'
Dear Ms. Daneshmand: ~'~
Please find enclosed ~ e~bit ~ustratMg the upstream end of Sto~ Sewer Line 'A'
crossMg Cotton Road. ~e Sto~ Sewer pipe at station 7+43.77 was const~cted 1.56 feet
lower than the proposed ~ade. We have dete~ined four solutions to this problem.
1) Remove the storm sewer pipe and re-lay the pipe from Station 7+00 to
Station 7 + 43.77.
This solution is not desirable due to the proposed sanitary sewer has
already been installed and further excavation in this area would resuk in a
wider trench section for the pipe.
v,,,~2) the channel section match this towline.
Regrafle
to
This solution is undesirable in that it would increase the slope of the
channel which in turn increases the velocities.
3) Extend the pipe on a 10.9% grade for three (3) pipe joints to match the
existing channel towline and construct a standard headwall.
4) Slope the headwall invert and add five (5) linear feet of Rock Rip Rap to
match the towline.
-~a,.S~.C=.-_--..2:.. ¢;:.;E= =ESC~=r£Es . _AI~Z Z---. E~T.='-."E':- * '-'Y', ',~ =:-- * : '- ';l a E ', '¢ -z '.-:-- · S-=~2--.2':'.-
.5-2 .El %C- * ~_5Ea_ PZ'S- Ct, ',3 E"~~--t-1 .3 = 5, . r, ?. . .? - --_ SE',E ',3 A':C '/ZF= '.3
_a,.ZEC-'F_= aF2--EZT~;E · :%a,,',
ALBERT H. HALFF ASSOCIATES, INC.
ENGINEERS · SCIENTISTS · SURVEYORS
Both solutions 3 and 4 will adequately solve the grade discrepancy. The Contractor
has stated a preference for the fourth alternative presented above.
The Owner has been informed of this solution and is in agreement. Please note that
these headwalls and the channel are temporary and are to be maintained by the Owner.
The fourth alternative presented does have one advantage in that it will allow for more
grade when this pipe system is extended to Gateway Blvd.
We are presenting alternative number 4 as our recommended solution for your
approval. We would sincerely appreciate your prompt action in this matter in order that this
construction may proceed.
Thank you for your time and consideration in this matter. If you have any questions,
please contact me.
Very truly yours,
ALBERT H. HALFF ASSOCIATES, INC.
.:~/ / /
Patrick L. Acker, P.E.
/jj
cc: Mr. Larry Davis, City of Coppell
Mr. Bill Jones, L.H. Lacy
Mr. Wayland Threadgill, Catellus Development Corp.