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�VO 1117 Lone Palm Avenue, Suite B <br /> Modesto, CA 95351 <br /> www atc-enviro corn <br /> 209 579 2221 <br /> Fax 209 579 2225 <br /> A S S O C I A T E S I N C <br /> April 15, 2003 <br /> APR 172003 <br /> 54 62605 0001 <br /> ENVIRONMEN r HEALTH (�� �a�a�`''' A <br /> PERMIT/SERVICEStA <br /> Ms Margaret Lagorio <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> 304 E Weber Street, Third Floor � t �l�y � � <br /> Stockton, California 95202 , <br /> 1V�� 1 � J11a� <br /> Subject Monitoring Report - Third Quarter 2002, Former Thiemann's Service Station, 106 ti <br /> West Second Street, Ripon, California <br /> Dear Ms Lagorio <br /> This report presents the results of quarterly groundwater monitoring and sampling performed in <br /> July 2002 by ATC Associates Inc at Former Thiemann's Service Station The site is located at <br /> • 106 West Second Street in Ripon, California (Figure 1) Sampling was performed to monitor the <br /> 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\word pro1626051yuartlyl3QR-2002 doc I <br /> ENVIRONMENTAL, GEOTECHNICAL AND MATERIALS PROFESSIONALS <br />