Villages of CC 4-CS 921015Request for variance for use of subgrade stabilization for Villages of Cottonw~ Creek
The dev/~opers of Villages of Cottonwood Creek Phase IV has requested that the City waive the
req~tnent for subgrade stabilization for this project. The Subdivision Ordinance states that if
thefPIJfor the soil is between 6 and 12, then the requirements for stabilization can be waived.
It ~ states that upon a recommendation from a soils engineer familiar with the soils in the area,
that the requirements for subgrade stabilization can also be waived. The soils firm of
conducted sixteen (16) soil samples on this job. Of the sixteen, fourteen fell outside the
range of six to twelve and were also outside the limits of what would be streets. Only two fell
within that range. However, the soil consultant still made a recommendation that the subgrade
requirement be waived. Because so many of the soil samples fell outside this range and because
no type of cement or lime series testing was performed to determine the benefits of stabilization
to the soil, I informed the developers' engineer that the City could not support a recommendation
for waiving the subgrade stabilization requirement.
I informed the developers' engineer that additional floor samples should be taken from the street
area and that lime or cement series testing should be performed on those soil samples to
determine the benefit of the lime or cement.
Based on the lime/cement series testing, it does show that there will be some benefit to the soil
by stabilizing. Therefore, even though the developer is requesting waiving this requirement, it
is staffs position that the subgrade should be stabilized with cement, for the soil is sandy in
nature and with lime, for the soil is more clay in nature.
Staff would be available to discuss this with the City Council.
subgrage
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Y-75•1107. FINAL PLAT
1 16 cllSO'I.•
VILLAGE at COTTONWOOD CREEK
2 <6(SAND) p
3 6 •� IEINC RIPLAY r SECTION S.I AND•MOCK r OI
4 <6(SAND)) VILLAGE OF COTTONWOOD CREEK
<6(SAND) Ar�„� SECTION I!
grapAlle 6 <6(SAND) '"{('
<6(SAND) �•• l s EELNC..•es•ACRES TRACT( ra•(ors)
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9 <6(SAND) 1n: iri• ... -' TIOYIl c rOLLANI MUMMY ABSTRACT NO. •••
7 10 0 n is1 � CITY•/COMMA.DALLAS COUNTY. TOMS
12 15 M!M 1►�
13 <6(SAND) o(rAU a.rn¢n srR((r ro I +
MI!VOILA CONSTRUCTION rRE NSLSON CORroDAAON
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SIL1{ILTY[ASEI[MT «•n Rvu.,MP r
LECAIRM IMP
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Additional Streets and Alley_~G~]=ements.
1. Streets and alleys shall be platted and
constructed in accordance wi%_h the Thoroughfare
Plan of the Comprehensive Plan or other plans
approved by the City Council, and shall conform
to the following requirements:
a. lhe subgrade on all streets and alleys
shall be thoroughly compacted and proof-
roiled as required. Subgrode material
with o plasticity index of less than 6 or
greater than 12 shall be stabilized with
hydrated lime, unless recommended other-
wise by a soils engineer.
Fill material when tested in accordance
with ASTN D-698/THD T-99 shall be in lifts
compacted to 95~ of theoretical density
with a moisture content within 3, of
optimum moisture.
In lieu of the above subgrade requirements
the recommendations of a soils engineering
firm familiar with local conditions may be
substituted.
Appendix A
15