Riverchase(6.3)-CS 941205Ken Griffin
City Engineer
city
255 Parkway Bird
Coppell, TX 75019
Dear Sir:
JOHN SCHOENTHALER
3913 Bobbin Lane
Addison, Texas 75244
(214) 392-2230
December 5, 1994
I am requesting a variance from the Subdivision Ordinance requiring lime stabilization
under the driveways and fn~ lanes associated with 1445 Riverside Drive (Kids R Kids).
Attached is a letter from Stan Tech Engineering Co. who did the soil testing at Riverchase
pl_n~, both for myself and Fehmi Karahan. The letter _~__t_~ that the lime stabilization will
reduce failure due to 'pumping' but otherwise is not needed. Since pumping is a function
of the vehicular loads to be expected and the vehicular loads to be expected are limited to
waste disposal trucks, light delivery trucks, and a school bus, lime stabilization is not
e~ to yield significant benefit.
Fehmi Karahan told me the City granted a variance for Riverchase Plaza Phase I
(Blockbuster et al.) paving and for the Tom Thumb development across the street. My
builder and engineer at Bucher, Willis and Ratcliff also question the ne~ for lime
stabilization since pumping is not expected to be severe.
Although I am not a paving expert, I have inspected the Tom Thumb paving and the
Riverchase Plaza paving and have seen no evidence of failure to date. Although this paving
is fairly recently installed, the decision to eliminate lime stabilization at my childcare
location seems to be a prudent one based on the advice I have been given. Please advise
your decision.
Thank you,
John Schoenthaler
21; November 1994
StanTech Job No. 169,L0029
Bucher, Willis and P,.~ttlLff
8140 Walnut Hill
Dallas, Texas 75231-4~50
Re; Kids R Kids It
Paving Reconuue~atlons
Coppell, Texas
Dear Mt'.. Anaya:
In accordance with your verbal request, gtanTech Engineerhtg Co. is .pleased to
provide this opinlon.'tetter regarding paving and base depths which revise the paving
recommendations presented in our Geotechnical Inv~tigatio~ R¢t~ort submitted 18 October
1994. Our original 'recommendation for rigid pavement was:
5 inches of jointed rehfforced Portland Cement Concrete (PCC) pavement (28-day
3rd point flexural modulus = 550 psi, or 28-day compression strength = 3000 psi)
NCTCOG Item 5.8.
4 inches of base material consisting of granular, free drahting, non-pumping soil,
N.C..TCOG lt~n 2.1.4 '(compacted to 950/0 of Standard Proctor density), or 6 inches
o~ me stabilized subgrade per NG'rCOG Item 4.6 (use a lime application rate of 24
pounds per squme' yard).
These recommendations were based on a 30-year design life,
Mr. John Schoenthaller, Kids B. Kids owner/develOper, requesfed our periiiis~ion to
omii the base material cons/sting of either 4 inches of granular soil or 6 inches of lime-
stabilized soil, No compensation for the omlsston of the base material ~vas discusifi'dl We
explained that this change would still provide sufficient strength to supPSrt the antiCiPated
loads for some period of ttme, but that the useful service llfe of the pavement would be
compromised, and that higher maintermnce costs over the life of the pavement should be
anticipated. The reason is flint the subgrade soil is fine-grained and will be a "ptunplng"
25 November 1994
StanTeeh Job No. 1694-0029
Mr. Pete Anaya, P.II.
material. In our experience, loss of subgrade support due to pumping is the primary mode
of failure in similar '.pavements in similar uses in thi~' area.
The owner may omit the ~inch granular subbase or 6-inch llme stabilized soil. It
is our recommendation that the natural soil in the pavement area should be scarified to a
depth of 6 inches mid recompacted to 95% of Standard Proctor density.
We trust this; opinion letter provides the information you need. If you have any
questions, or need more information, please call the undersigned at (214)631-4372.
Very truly yours, ~
Stax Tech FaS/neeri Co.
TOTRL P.I~.