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December 8, 1992
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City of Coppell
P.O. Box 478
Coppell, TX 75019
Attn: Mr. Ken Griffin, P.E., City Engineer
Re: Sandy Knoll/Shadowcrest Drainage Improvements
Dear Ken:
Attached please find a copy of the letter fi'om Gibson & Associates requesting approval
to substitute 2 inches of additional concrete in place of 6 inches of lime stabilization for the street
paving on the above referenced drainage improvement project. Halff Associates has allowed this
type of substitute previously. Hove'ever, a recommendation/analysis by a geotechnical consultant
was required prior to approval. The drainage problems (flooding over the top of curb) within this
subdivision were caused by subgrade movements which flattened and reversed slopes.
Geotechnical testing was not included in the engineering services contract for this project,
therefore we have no particular information about the soils in this area, nor an avenue to ask for
a geotech's recommendation. If the City of Coppell wishes to pursue this alternative further,
llalff Associates recommend> that the City require a submittal from a qualified geotechniczd
engineer which states that this would be an equal design.
In addition, Gibson & Associates requests altem:tte permission to substitute 6 inches of
cement treated base in lieu of the lime stabilization. This alternative would provide the same
thickness of stabilized material as the lime stabilization called for in the construction plans.
Assuming that there would be no increase in cost of construction, this would be the preferable
alternative.
Please feel free to call if you have any questions or comments.
Yours very truly,
ALBERT lt. HALFF ASSOCIATES, INC.
Jean Hansen, P.E.
/sn
c: Garrth Campbell, City of Coppell
11210 Ryll~relt
P, O. 9ox 600679
Belch Springs, Texas
75180.0579
214/5S7,1199
FAX 5~7.1552 '.
· A$90 tATI:$, INC.
November 20, 1992
Mr. Garreth Campbell.
City of Coppell
P.O. Box 478
Coppell, Texas 75019
Re: Sandy Knoll/Shadowcrest
Drainage Improvements
Dear Sir:
We propose to substitute two (2) additional inches of concrete
paving in lieu of the 6" lime stabilization that was specified.
We believe this would be an equal design and would save the City
time and money. The savings would be as follows:
l) Two extra inches of concrete
1,194 SY @ $5.00/sy $5,970.00
2) Delete lime stab on Shadowcrest
334 SY @ $15.00/~y (5,010.00)
3) Delete lime on Shadowcrest
4.5 Tons @ $100.00/ton ( 450.00)
4) Delete lime stab. on Woodhurst
860 SY @ $10 00/sy (8,600.00)
s)
Delete lime on Woodhurst
11.6 Tons @ $100.00/ton
(1,160.00~
Net Savings:S(9,250.00)
Also by eliminating thc lime stabilization, this would save two to
thr~e weeks on time, pre~enting less construction inconvenience for
the citizens.
However, if the City chooses not to select this proposal, we
request permission to substitute 6" cement treated base for the
lime stabilization. Though this would not represent a cost
savings, it will save several days on time.