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16 well locations are shown on Figure 2 On July 3, 1997, the monitoring wells were developed and sampled
<br /> for petroleum hydrocarbons along with the adjacent property owner's well (CW) The samples from
<br /> MW 1, MW2, and MW3 contained concentrations of total petroleum hydrocarbons as gasoline (TPHg)
<br /> and benzene ranging from 3,200 micrograms per liter (ug/1) to 130,000 ug/1 and 920 to 11,000 ug/1,
<br /> respectively Field activities and analytical results were detailed in Smith Technology's Summary Report
<br /> dated September 17, 1997
<br /> ' On March 24 and 25, 1998, ATC personnel supervised advancement of seven soil borings, (ASB1,
<br /> MW4, MW5, MW6, MW7, SB8, and SB9) at the site to depths ranging from approximately 26 5 to 62
<br /> feet bgs These borings were advanced to 1) evaluate the horizontal and vertical extent of petroleum
<br /> ' hydrocarbon impacted soil and groundwater, 2) evaluate and refine soil stratigraphy, and 3) install
<br /> groundwater monitoring wells (MW4, MW5, MW6, and MW7) within the uppermost aquifer
<br /> Groundwater samples collected from MWS, MW6, and MW7 contained elevated concentrations of TPHg
<br /> ' and benzene Field activities and analytical results were detailed in ATC's Summary Report of
<br /> Subsurface Investigation, dated August 14, 1998
<br /> In November 1999, ATC personnel supervised the advancement of three soil borings, SB9A, SB 10, and
<br /> SBI 1 SB 10 and SBI 1 were advanced to 46 feet bgs using hollow stem auger techniques and SB 9A was
<br /> advanced to 65 feet bgs using continuous core methods Field activities and analytical results were
<br /> ' detailed in ATC's Summary Report of Groundwater and Soil Investigation, dated July 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 volatile organic
<br /> compound (VOC) flux rates, and collection of data to design a vapor extraction/air sparge system The
<br /> results of the pilot test are detailed in ATC's Vapor Extraction and Air Sparge Pilot Test Results and
<br /> Feasibility Study at the Farmer Property, 610 North Hunter Street, Stockton, California,dated November 2,
<br /> 2000
<br /> In December 2001, an ATC 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 were
<br /> completed as SVE wells, and two as AS wells Field activities and analytical results were detailed in
<br /> ATC's Final Remediation Plan, Farmer Property, 610 North Hunter Street, Stockton, California, dated
<br /> ' March 27,2002
<br /> Additionally, in December 2001, an ATC geologist supervised the advancement of five Geoprobe
<br /> borings, SB 12 to SB 16 to a depth of approximately 25 feet bgs Three additional offsite borings were
<br /> advanced to depths of approximately 42 feet bgs and completed as groundwater monitoring wells, MW8
<br /> through MW 10 Field activities and analytical results were detailed in ATC's Offsite Subsurface
<br /> Investigation Report, dated April 24, 2003
<br /> QUARTERLY GROUNDWATER MONITORING ACTIVITIES
<br /> On May 12, 2005, ATC personnel collected groundwater samples from MW1 through MW10, VW1,
<br /> VW2, and CW The locations of the monitoring wells are shown on Figure 2 Prior to collection of
<br /> ' groundwater samples, the depth to water (DTW) was measured in the wells The pH, electrical
<br /> conductivity, and temperature were measured in groundwater purged from the monitoring wells, and
<br /> JP
<br /> visual observations regarding turbidity were recorded A minimum of three well casing volumes was
<br /> purged from each well prior to sampling The wells were allowed to recover and samples were collected
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