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1117 Lone Palm Avenue, Suite B <br /> Modesto, CA 95351 <br /> www atc-enviro com <br /> 209 579 2221 <br /> A S S O C I A T E S I N C Fax 209 579 2225 <br /> April 15, 2003 RDE� ��� <br /> 54 62605 0001APR 17 <br /> 2003 <br /> ENVIRONMENT HEALTH <br /> PERMIT/SERVICES V 4 <br /> Ms Vicky MacCartney T <br /> UA <br /> San Joaquin County 4`Y) V <br /> Environmental Health Department <br /> 304 E Weber Street, Third Floor <br /> Stockton, California 95202 <br /> Subject Monitoring Report - Fourth Quarter 2002, Former Thiemann's Service Station, <br /> 106 West Second Street, Ripon, California <br /> Dear Ms MacCartney <br /> This report presents the results of quarterly groundwater monitoring and sampling performed in <br /> October 2002 by ATC Associates Inc at Former Thiemann's Service Station The site is located <br /> at 106 West Second Street in Ripon, California (Figure 1) Sampling was performed to monitor <br /> the distribution of petroleum hydrocarbons in groundwater at the site and to determine the <br /> groundwater flow direction and magnitude of the hydraulic gradient in the uppermost aquifer <br /> SITE HISTORY <br /> In March 1991, three underground storage tanks (USTs) were removed from the site Analysis of <br /> soil samples collected from the excavation indicated that high concentrations of petroleum <br /> hydrocarbons were present in soil beneath the tanks Groundwater was not encountered in the <br /> excavation The location of the former USTs is shown on Figure 2 <br /> In July 1993, a subsurface investigation was conducted at the site to determine the extent of <br /> petroleum hydrocarbons present in soil and to determine if groundwater had been impacted The <br /> investigation included drilling eight soil borings and collection of soil samples Three of the <br /> borings were completed as shallow groundwater monitoring wells (MW-1, MW-2 and MW-3) <br /> Analysis of soil samples indicated that the main concentration of petroleum hydrocarbons in soil <br /> occurred from approximately 10 feet below ground surface (bgs) to the groundwater surface at a <br /> depth of approximately 29 feet bgs and within a radius of 35 feet from the former UST pit <br /> In August 1993, wells MW-1, MW-2, and MW-3 were monitored and sampled Analytical <br /> results showed that wells MW-2 and MW-3 contained detectable levels of petroleum <br /> hydrocarbons in the groundwater MW-1 had no measurable concentrations of petroleum <br /> w Iwordpro1626051quart[y14QR-2442 doc I <br /> ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS <br />