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1117 Lone Palm Avenue, Suite B <br /> i Modesto, CA 95351 <br /> www atc-enviro cam <br /> ft -At2095792221 <br /> A s s o e r A T E s e N e �r t4 i q-,r' Fax 209 579 2225 <br /> 04 MAY 20 PH 12; 34 YL <br /> 0jr too <br /> { <br /> December 2, 2003 6-0 <br /> 54 62605 0001 <br /> Ms Vicky McCartney <br /> San Joaquin County <br /> Environmental Health Department <br /> 304 E Weber Avenue, Third Floor <br /> Stockton, California 95202 <br /> Subject Monitoring Report - Fourth Quarter 2003, Former Thlemann's Service Station, 106 West Second <br /> Street, Ripon, California <br /> Dear Ms McCartney <br /> This report presents the results of quarterly groundwater monitoring and sampling performed in October <br /> 2003 by ATC Associates Inc at the former Thiemann's Service Station The site is located at 106 West <br /> Second Street in Ripon, California (Figure 1) Sampling was performed to monitor the distribution of <br /> petroleum hydrocarbons in groundwater at the site and to determine the groundwater flow direction and <br /> 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 soil <br /> samples collected from the excavation indicated that high concentrations of petroleum hydrocarbons were <br /> present in soil beneath the tanks Groundwater was not encountered in the excavation The location of the <br /> former USTs is shown on Figure 2 <br /> In July 1993, a subsurface investigation was conducted at the site to determine the extent of petroleum <br /> hydrocarbons present in soil and to determine if groundwater had been impacted The investigation <br /> included drilling eight soil borings and collection of soil samples Three of the bonngs were completed as <br /> shallow groundwater monitoring wells (MW-1, MW-2 and MW-3) Analyses of soil samples indicated <br /> that the greatest concentration of petroleum hydrocarbons in soil occurred from approximately 10 feet <br /> below ground surface (bgs) to the groundwater surface at a depth of approximately 29 feet bgs and within <br /> a radius of 35 feet from the former UST pit <br /> In August 1993, monitoring wells MW-1, MW-2, and MW-3 were monitored and sampled Laboratory <br /> analytical results indicated that wells MW-2 and MW-3 contained detectable levels of petroleum <br /> hydrocarbons in the groundwater The sample collected from MW-I was reported to contain no measurable <br /> concentrations of petroleum hydrocarbons A quarterly groundwater monitoring and sampling program was <br /> initiated in March 1994 <br /> s Ienvironmenta11626051quartly14QR-2003 doe I <br /> ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS <br />