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V 1117 Lone Palm Avenue, Suite B <br /> s 0 Modesto, CA 95351 <br /> www atc-enviro com <br /> 209 579 2221 <br /> Fax 209 579 2225 <br /> A S $ O C I A T E B 1 N C <br /> October 18, 2004 <br /> 54 14981 0001 0 C T 1 9 2094 <br /> Ms Margaret Lagono ENVIR010EN i HEALTH <br /> San Joaquin County, Environmental Health Division PERM;`SERV1rES <br /> 304 E Weber Street, Third Floor <br /> Stockton, California 95202 <br /> Subject Groundwater Monitoring Report - Second Quarter 2004, N & S Imgation <br /> Property, 215 West Main Street, Ripon, California <br /> Dear Ms Lagono <br /> This report presents the results of quarterly groundwater monitoring and sampling performed on <br /> June 4, 2004 by ATC Associates Inc (ATC) at the site located at 215 West Main Street, Ripon, <br /> California (Figure 1) Monitoring was performed to determine groundwater flow direction and <br /> the hydraulic gradient in the uppermost aquifer Sampling was performed to monitor dissolved <br /> petroleum hydrocarbon concentrations in the groundwater at the site <br /> BACKGROUND INFORMATION <br /> . In March 1990, one 1,500-gallon unleaded gasoline underground storage tank (UST), one <br /> unleaded gasoline UST of unknown size, and associated piping and dispensing equipment were <br /> removed and transported off-site Laboratory analyses of soil samples collected from beneath the <br /> former 1,500-gallon UST location indicated the presence of detectable concentrations of total <br /> petroleum hydrocarbons Discoloration of the soil and a petroleum hydrocarbon odor were noted <br /> in the field After the tanks were removed, the areas of the former tanks were backfilled <br /> On November 14, 1997, a geologist from ATC supervised the advancement of two soil borings <br /> to 30 feet below ground surface (bgs) Analytical results of soil samples indicated the presence <br /> of petroleum hydrocarbons One groundwater sample was collected from each boring at the <br /> depth groundwater was first encountered, approximately 30 feet bgs Groundwater samples j <br /> indicated the presence of petroleum hydrocarbons Results are summarized in ATC's Summary <br /> Report of Subsurface Investigation, dated January 14, 1998 <br /> On July 13, 1998, a geologist from ATC supervised the advancement of four soil bonngs to 26 to <br /> 31 feet bgs Analytical results of soil samples indicated the presence of petroleum hydrocarbons <br /> One groundwater sample was collected from each boring at the depth groundwater was first <br /> encountered Groundwater samples indicated the presence of petroleum hydrocarbons Results <br /> are summarized in ATC's Summary Report of Additional Subsurface Investigation, dated <br /> September 9, 1998 <br /> On February 18, 1999, a geologist from ATC supervised the installation of three groundwater <br /> monitoring wells from 39 to 41 feet bgs Soil borings MW1, MW2, and MW3 were completed as <br /> two-inch monitoring wells One soil sample from each boring was collected and after the <br /> ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS <br /> S lenvironmental1149811Reportsl2QR-04 doc 1 <br />