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S 3 <br /> Ld Geological 7ech4&S Itt& Page 2 <br /> Sinclair&Thompson Property <br /> Soil Gas Survey Report <br /> LW January 29,2007 <br /> • In general, the zone between 3 and 10-feet bgs is a silty-sand <br /> The degree of saturation in the vadose zone is anticipated to be less than 80% <br /> �. 1.2 Scope of Work <br /> ` The scope of work is outlined in the Active Soil Gas Investigation Work Plan dated August <br /> La 18, 2006. In summary GTI proposes: <br /> • Obtain borehole permits from SJCEHD <br /> ' • Advance up to six (6) soil gas probes to a depth of approximately 9-feet bgs in selected <br /> L. locations between the former UST location and the shop and house. <br /> 0 Collect and analyze the vapor samples for the following: <br /> 0 BTEX, TPH, MtBE, 1,2-DCA, and EDB <br /> La • Report the findings <br /> La 2.0 SUMMARY OF SITE BACKGROUND <br /> 2.1 Site Description and Location <br /> The Sinclair Trucking site (Property) is located in the southeast quarter of the northwest <br /> LN quarter of Section 7, T3S, R6E, related to the Mount Diablo B&M, on the United States <br /> Geological Survey (USGS) Topographic Map, Vernalis Quadrangle, California, 7.5 minutes <br /> series. A review of the USGS Topographic Map reveals that the elevation of this site is <br /> approximately 75 feet above mean sea level (AMSL). <br /> The Property is located on the gradually sloped floor of the northern San Joaquin Valley. The <br /> geologic composition of the area is characterized as fluvial deposits of the San Joaquin - <br /> Sacramento River delta system that overlay continental rocks and deposits derived from <br /> erosion of the Sierra Nevada Mountain Range located approximately 50 miles northeast of <br /> Modesto. <br /> The southwest tilting Sierra Nevada fault block underlies the northern San Joaquin Valley <br /> area. Overlying the consolidated rocks are unconsolidated sediments. The lower consolidated <br /> batholithic and metamorphic rocks are poorly transmissive; however the overlying <br /> sedimentary layers are often quite permeable_ These unconsolidated layers include <br /> Pliocene/Pleistocene age continental deposits, Pleistocene age lacustrine and marsh deposits, <br /> and Holocene older and younger alluviums and flood-basin deposits. <br /> L. 2.2 Summary of Site History <br /> On March 31, 198'; one steel 250-gallon underground storage tank (UST), used to supply <br /> leaded gasoline, was removed from the site. The SJCEHD inspection report indicated that <br /> corrosion was present on the UST and a petroleum odor was noticeable in the area of the tank <br /> removal. Subsequent laboratory soil analyses indicated the presence of petroleum <br /> La <br />