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(. 1117 Lone Palm Avenue, Suite B <br /> ` a Modesto, CA 95351 <br /> r http Ilwww atcassociates corn <br /> 209 579 2221 <br /> . A s s O C t A T 8 8 1 N C Fax 209 579 2225 <br /> July 5, 2005 <br /> 54 14981 0001 <br /> Ms Margaret Lagorio <br /> San Joaquin County, Environmental Health Division <br /> 304 E Weber Street, Third Floor <br /> Stockton, California 95202 <br /> Subject Groundwater Monitoring Report - First Quarter 2005, N & S Irrigation Property, 215 <br /> West Main Street, Ripon, California <br /> Dear Ms Lagorio <br /> This report presents the results of quarterly groundwater monitoring and sampling performed on <br /> March 2, 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 petroleum <br /> hydrocarbon concentrations in the groundwater at the site <br /> BACKGROUND INFORMATION <br /> iIn 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 /> Ager 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 of Additional 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 MWI, MW2, and MW3 were completed as two- <br /> inch monitoring wells One soil sample from each boring was collected and after the groundwater <br /> monitoring wells were developed one groundwater sample was collected from each well Soil and <br /> groundwater samples contained detectable concentrations of petroleum hydrocarbons Results are <br /> summarized in ATC's Summary Report ofAdditional Subsurface Investigation, dated June 1, 1999 <br /> ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS <br /> s lenvironmenta11149811Reportsll QR-D5 doc ] <br />