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ATC Associates Inc <br /> 1117 Lone Palin Avenue,Suite B <br /> VQ Modesto, California 95351 <br /> 209-579.2221 <br /> ' Fax 209-579-2225 <br /> a s s o c i a r e s i N c <br /> July 8, 2005 HrMlGETIED <br /> 54149810001 JUL 2005 <br /> Ms Margaret Lagono ENVIRONMENT HEMA <br /> San Joaquin County, Environmental Health Division pERMITOMAGEs <br /> 304 E Weber Street, Third Floor <br /> Stockton, California 95202 <br /> Subject Groundwater Monitoring Report Second Quarter 2005 and Closer Addendum, <br /> N& S Irrigation 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 1, 2005 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 the <br /> 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 to <br /> 30 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 <br /> the presence of petroleum hydrocarbons Results are summarized in ATC's Summary Report of <br /> Subsurface Investigation, dated January 14, I998 <br /> On July 13, 1998, a geologist from ATC supervised the advancement of four soil borings 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 MW 1, MW2, and MW3 were completed as <br />