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1117 Lone Palm Avenue, Suite 201
<br /> YA Modesto, California95351
<br /> 209-579-2221
<br /> Fax : 209-579-2225-2225
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<br /> ASSOCIATE 8 1 N C .
<br /> feet below ground surface (bgs). The excavation was limited to the north by the on-site building. The
<br /> confirmation samples collected from the base of the over-excavation still contained elevated
<br /> concentrations of volatile organics. The over-excavated soil was disposed of at Forward Landfill
<br /> near Stockton, California.
<br /> I
<br /> On June 30 and July 1 , 1997, Smith Technology personnel supervised advancement of seven soil
<br /> borings, SBI through S137, at the site to depths ranging from approximately 40 to 45 feet bgs to
<br /> investigate the horizontal and vertical extent of petroleum hydrocarbon soil and groundwater
<br /> contamination. Three of the soil borings were completed as groundwater monitoring wells and two of
<br /> the soil borings were completed as vapor extraction wells. On July 3, 1997, the monitoring wells
<br /> were developed and sampled for petroleum hydrocarbons along with the adjacent property owner' s
<br /> well (CW). The samples from MWl, MW2, and MW3 contained concentrations of total petroleum
<br /> Ij hydrocarbons as gasoline (TPHg) and benzene ranging from 3 ,200 micrograms per liter (ug/1) to
<br /> 130,000 ug/I and 920 to 11 ,000 ug/1, respectively. Field activities and analytical results were detailed
<br /> in Smith Technology' s Summary Report dated September 17, 1997 .
<br /> On March 24 and 25, 19983 ATC personnel supervised advancement of seven soil borings, (ASB1 ,
<br /> MW4, MW5, MW6, MW7, S138, and S139) at the site to depths ranging from approximately 26. 5 to
<br /> 62 feet bgs. These borings were advanced to : 1 ) evaluate the horizontal and vertical extent of
<br /> petroleum hydrocarbon impacted soil and groundwater; 2) evaluate and refine soil stratigraphy; and
<br /> 3) install groundwater monitoring wells (MW4, MW5 , MW6, and MW7) within the uppermost
<br /> aquifer. Groundwater samples collected from MW5, MW6, and MW7 contained elevated
<br /> concentrations of TPHg and benzene. Field activities and analytical results were detailed in ATC' s
<br /> Summary Report of Subsurface Investigation, dated August 14, 1998 .
<br /> In November 1999, ATC personnel supervised the advancement of three soil borings, SB9A, SB 10,
<br /> 1 and SB 11 . SB 10 and SBI I were advanced to 46 feet bgs using hollow stem auger techniques and
<br /> SB9A was advanced to 65 feet bgs using continuous core methods. Field activities and analytical
<br /> results were detailed in ATC ' s Summary Report of Groundwater and Soil Investigation, dated July
<br /> 16, 1999,
<br /> In March 2000, ATC personnel performed a vapor extraction and air sparge pilot test at the site. The
<br /> purpose of these tests was to evaluate vapor extraction and air sparging as viable remedial options for
<br /> impacted soil and groundwater at the site. Specifically this included evaluation of whether vapor
<br /> extraction could sufficiently capture air sparge off-gas, evaluation of short-term VOC flux rates, and
<br /> collection of data to design a vapor extraction/air sparge system. The results of the pilot test are
<br /> detailed in ATC' s Vapor Extraction and Air Sparge Pilot Test Results and Feasibility Study at the
<br /> Farmer Property, 610 North Hunter Street, Stockton, California, dated November 2, 2000.
<br /> In December 2001 , an ATG geologist supervised the advancement of five soil borings to depths of
<br /> approximately 42 feet bgs and two soil borings to depths of approximately 26 feet bgs. Three of the
<br /> seven soil borings were completed as groundwater monitoring wells. Of the remaining borings, two
<br /> were completed as SVE wells, and two as AS wells. Field activities and analytical results were
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