Specs

Proposed Bridgestone April 20, 2011
NWC of Vance St. & W. Center Ave. PSI Project No. 532281
Lakewood, Colorado Page 5 of 15
movements in the pavement area. As an alternative to overexcavation and replacement,
the subgrade may be chemically treated with lime. If potential movement of less than 3
½ inches is required in pavement areas, PSI recommends that lime treatment of the
subgrade be performed.
Below, we provide recommendations for the depth of overexcavation and type of
replacement soil for the proposed parking area and the amount of potential movement
that can be expected.
Pavement Subgrade
Depth of Overexcavtion
Below Final Subgrade
Elevations
3 feet
3 feet
Replacement Soil
Moisture Conditioned,
Compacted On-Site Soils
Moisture Conditioned,
Compacted Import Non-
Expansive Soils
Potential Movement
5 inches
3 ½ inches
1 ½ feet Lime Treated Subgrade ¼ inches
The owner should perform a cost analysis for each overexcavation recommendation and
choose which method and depth of excavation would be the most economical for each
of the proposed alternatives.
Overexcavation and replacement for the proposed building and parking areas should
extend 2 feet horizontally beyond their limits. The areas that are excavated and will
receive structural fill should be graded to drain before fill placement to prevent water
from being trapped.
Once the areas below the parking area have been overexcavated, the existing site soils
should be proofrolled to identify areas of loose soils prior to placement of moisture
conditioned, compacted soils (either on-site or imported). The proofroll should be
conducted with a loaded tandem-axle dump truck or similar pneumatic-tired equipment
with a minimum weight of 15 tons and a maximum weight of 25 tons.
If the on-site excavated soils are re-used as moisture conditioned, compacted structural
fill, it should be noted that the moisture content of the existing soils should be maintained
throughout the construction process. The soils should not be allowed to dry excessively
and should be replaced as compacted structural fill as detailed in the Section 5.3 below.
If the soils are allowed to dry after placement, it will need to be removed and replaced.
Some of the soils encountered at this site are considered sensitive to changes in
moisture content. Controlling the moisture content variation of a soil will reduce its
tendency to undergo changes in volume. In this regard, we recommend that positive site
drainage be provided to reduce infiltration of surface water around the perimeter of the
concrete anchors and beneath exterior concrete slabs.