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Q I II
<br /> I
<br /> •CVVIY I
<br /> A S S O C I A T E S INC
<br /> On July 3, 1997, the monitoring wells were developed and sampled for petroleum hydrocarbons
<br /> along with the adjacent property owner's well (CW) The samples from wells MW1, MW2, and
<br /> MW3 contained concentrations of total petroleum hydrocarbons as gasoline (TPHg) and benzene
<br /> ranging from 3,200 parts per billion (ppb) to 130,000 ppb and 920 to 11,000 ppb, respectively
<br /> Field activities and analytical results were detailed in Smith TechnoIogy's Summary Report
<br /> dated September 17, 1997
<br /> On March 24 and 25, 1998, ATC personnel supervised advancement of seven soil borings,
<br /> ASB1, MW4, MW5, MW6, MW7, S138, and S139, at the site to depths ranging from
<br /> approximately 26 5 to 62 feet bgs at the project site to 1) evaluate the horizontal and vertical
<br /> extent of petroleum hydrocarbon impacted soil and groundwater, 2) determine and define soil
<br /> stratigraphy, and 3) install groundwater monitoring wells (MW4, MW5, MW6, and MW7)
<br /> within the uppermost aquifer Groundwater samples collected from wells MW5, MW6, and
<br /> MW7 contained elevated concentrations of TPHg and benzene Field activities and analytical
<br /> results were detailed in ATC's Summary Report of Subsurface Investigation, dated August 14,
<br /> 1998
<br /> In November 1999, ATC personnel supervised the advancement of three soil borings, S139A,
<br /> SB 10, and SB 1 I Borings SB 10 and SB 11 were advanced to 46 feet bgs using hollow stem
<br /> auger techniques and boring SB9A was advanced to 65 feet bgs using continuous core methods
<br /> Field activities and analytical results were detailed in ATC's Summary Report of Groundwater
<br /> 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
<br /> The purpose of these tests was to evaluate vapor extraction and air sparging as viable remedial
<br /> options for impacted soil and groundwater at the site and to determine whether vapor extraction
<br /> could sufficiently capture air sparge off-gas, to determine short-term volatile organic compound
<br /> (VOC) flux rates, and to collect data to design an vapor extraction/air sparge system The results
<br /> 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, 6.10 North Hunter Street, Stockton, California, dated
<br /> November 2, 2000
<br /> SAMPLING ACTIVITIES
<br /> On June 11, 2001, ATC Associates personnel collected groundwater samples from monitoring
<br /> wells MWI through MW7 and CW The locations of the monitoring wells are shown on Figure
<br /> 2 Prior to collection of groundwater samples, the depth to water, pH, electrical conductivity,
<br /> and temperature were measured in the monitoring wells and recorded A minimum of three well
<br /> casing volumes was purged from each well prior to sampling The wells were allowed to recover
<br /> and samples were collected from each well using dedicated disposable bailers Groundwater well
<br /> purge and sample logs are contained in Attachment 1
<br /> w 1625Wquart1yl2gr-2041 doc 2
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