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/ 1 <br /> s� 1117 Lone Palm Avenue, Suite B <br /> Modesto, CA 95351 <br /> www ate-enviro cam <br /> j } 209 579 2221 <br /> A S S O C I A T E S I N G � k5►r �('�(4( �k � }�1HEALI11 Fax 209 579 2225 <br /> �,IT Si.}L <br /> September 5, 2003 03 SES' 4 0 PM I ` v� Z '�' v� � �rhy'1 <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 - Second Quarter 2003, Former Thiemann's Service Station, <br /> 106 West Second Street, Ripon, California <br /> Dear Ms McCartney <br /> This report presents the results of quarterly groundwater monitoring and sampling performed in <br /> April 2003 by ATC Associates Inc at the 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 /> Analyses of soil samples indicated that the greatest concentration of petroleum hydrocarbons in <br /> soil occurred from approximately 10 feet below ground surface (bgs) to the groundwater surface <br /> at a depth of approximately 29 feet bgs and within 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 <br /> Laboratory analytical results indicated that wells MW-2 and MW-3 contained detectable levels of <br /> petroleum hydrocarbons in the groundwater The sample collected from MW-1 was reported to <br /> contain no measurable concentrations of petroleum hydrocarbons A program of quarterly <br /> • groundwater monitoring and sampling was initiated in March 1994 <br /> NN lwordpro1626051quartly12QR-2003 doe I <br /> ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS <br />