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' v 1117 Lone Palm Avenue, Suite B <br /> Modesto, CA 95351 <br /> www atc-enviro com <br /> ' Fax 209 579 2225 <br /> V92095792221 <br /> A 8 $ O C I A T E S I N G <br /> May 3, 2004 ID C F <br /> 54 14981 0001 <br /> 1 Ms Margaret Lagorio MAY 0 6 2004 <br /> San Joaquin County, Environmental Health Division ENVIRONMENT HEALTH <br /> 304 E Weber Street, Third Floor PERMIT/SERVICES <br /> Stockton, California 95202 <br /> Subject Interim Remedial Action and Groundwater Monitoring Report - Fourth Quarter 2003, <br /> N & S Irrigation Property, 215 West Main Street, Ripon, California <br /> ' Dear Ms Lagorio <br /> This report presents the results of groundwater extraction activities conducted from July 8 to <br /> ' December 4, 2003, and quarterly groundwater monitoring and sampling performed on December 8, <br /> 2003, by ATC Associates Inc (ATC) at the site located at 215 West Main Street, Ripon, California <br /> (Figure 1) Groundwater extraction at monitoring well MW1 was conducted in an attempt to reduce <br /> ' petroleum hydrocarbon concentrations in groundwater in the vicinity of MW I (Figure 2) Quarterly <br /> groundwater monitoring and sampling was performed to determine groundwater flow direction and <br /> the hydraulic gradient m the uppermost aquifer, and to monitor dissolved petroleum hydrocarbon <br /> concentrations in the groundwater at the site The groundwater extraction activities were conducted <br /> �) in general accordance with ATC's letter Workplan for Interim Remediation, dated May 7, 2003 <br /> ' BACKGROUND INFORMATION <br /> In March 1990, one 1,500-gallon unleaded gasoline underground storage tank (UST), one unleaded <br /> gasoline UST of unknown size, and associated piping and dispensing equipment were removed and <br /> ' transported off-site Laboratory analyses of soil samples collected from beneath the former 1,500- <br /> gallon UST location indicated the presence of detectable concentrations of total petroleum <br /> hydrocarbons Discoloration of the soil and a petroleum hydrocarbon odor were noted in the field <br /> ' 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 to 30 <br /> ' feet below ground surface (bgs) Analytical results of soil samples indicated the presence of <br /> petroleum hydrocarbons One groundwater sample was collected from each boring at the depth <br /> groundwater was first encountered, approximately 30 feet bgs Groundwater samples indicated the <br /> presence of petroleum hydrocarbons Results are summarized in ATC's Summary Report of <br /> Subsurface Investigation, dated January 14, 1998 <br /> On July 13, 1998, a geologist from ATC supervised the advancement of four soil borings to 26 to 31 <br /> feet bgs Analytical results of soil samples indicated the presence of petroleum hydrocarbons One <br /> groundwater sample was collected from each boring at the depth groundwater was first encountered <br /> Groundwater samples indicated the presence of petroleum hydrocarbons Results are summarized in <br /> ATC's Summary Report ofAddilional Subsurface Investigation, dated 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 MW 1, MW2, and MW3 were completed as <br /> ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS <br /> s leovironmentai1149811ReportsAQR-03 doe I <br />