Specs

Proposed Bridgestone April 20, 2011
NWC of Vance St. & W. Center Ave. PSI Project No. 532281
Lakewood, Colorado Page 2 of 15
any of the noted information is incorrect, please inform us so that we may amend the
recommendations presented in this report, if needed.
3.0 SUBSURFACE INFORMATION
The following sections provide information relating to subsurface conditions in the area
of the proposed addition. The geology section is based upon the, “Geologic Map of the
Greater Denver Area, Front Range Urban Corridor, Colorado” by Donald E. Trimble and
Michael N. Machette, dated 1979 and information relating to subsurface conditions
within the property gathered from our current field study.
3.1 Site Geology and Geologic Hazards
The site is located on the high plains approximately 25 miles east of the foothills of the
Rocky Mountains. Based on the United States Geological Survey (USGS) “Geologic
Map of the Greater Denver Area, Front Range Urban Corridor, Colorado” by Donald E.
Trimble and Michael N. Machette, 1979, the majority of the site is mapped as being
underlain by the Early Tertiary and Late Cretaceous age Denver and Arapahoe
Formations. The Denver and Arapahoe Formations consist of sandstone, mudstone,
claystone and conglomerate and is characterized by andesitic materials.
3. 2 Subsurface Conditions
As part of PSI’s evaluation of this site, PSI drilled 9 exploratory borings, 5 within the building
pad and 4 within the parking lot, at the subject site as indicated on Figure 2, the Boring
Location Map. The borings were drilled to approximate depths of 20 feet below existing
grades within the proposed building area and to approximate depths of 10 feet below the
existing grades in the parking areas. The borings were advanced using a CME-55 truck
mounted drill rig equipped with 4-inch diameter, solid-stem, continuous-flight auger. Soil
samples were recovered at selected depths during drilling with the truck-mounted drill rig
using a Modified California Barrel Sampler (inside diameter- 2.0 inches and outside
diameter- 2.4 inches) driven by a 140-lb. weight free falling 30 inches. The number of
blows required to drive the sampler 12 inches is designated as the penetration resistance
(N-value, blows per foot) and provides an indication of the consistency of cohesive soils
and the relative density of granular materials. While the procedure is similar to that
employed in the Standard Penetration Test (ASTM D1586), the penetration resistance
obtained using the California barrel sampler is generally higher than that obtained using the
standard split spoon sampler.
An engineer from our office observed the drilling of our borings and logs were prepared of
the encountered conditions. Individual logs of the borings are presented on Figures 3
through 11. It should be noted that the subsurface conditions presented on the boring logs
are representative of the conditions at the specific locations drilled. Variations may occur
and should be expected across the site. The stratification represents the approximate
boundary between subsurface materials and the transitions may be gradual and indistinct.
Water level information, if encountered, obtained during our field operations is also shown
on the boring logs.
3.2.1 Subsurface Profile
In general, the overburden soils consisted of light brown to dark brown, moist, very stiff
to stiff sandy clay and clayey sand. The overburden material was found overlying