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` Working To Restore Nature <br /> 1710 Main Street <br /> Escalon, CA 95320 <br /> Phone: (209) 838-3507 <br /> FAX: (209) 838-3509 FOURTH QUARTER 1994 <br /> GROUNDWATER MONITORING REPORT <br /> Former Thiemann's Service <br /> Ripon, California <br /> Lo INTRODUCTION <br /> This report presents the results of quarterly groundwater monitoring and sampling performed <br /> in December 1994 by RESNA Industries Inc. (RESNA) at Former Thiemann's Service. The <br /> a. <br /> site is located at 106 West Second Street in Ripon, California (Plate 1). Sampling was <br /> performed to monitor the distribution of petroleum hydrocarbons in groundwater at the site. <br /> Monitoring was performed to determine the groundwater flow direction and the hydraulic <br /> gradient in the uppermost aquifer. <br /> BACKGROUND <br /> In March 1991, three underground storage tanks (USTs) were removed from the site. <br /> Analysis of soil samples collected from the excavation indicated that high concentrations of <br /> petroleum hydrocarbons were present in soil beneath the tanks. Groundwater was not <br /> encountered in the excavation. The location of the former USTs is shown on Plate 2. <br /> L- 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. <br /> This included drilling eight soil borings and collecting soil samples. Three of these borings <br /> were completed as shallow groundwater monitoring wells (MW-1, MW-2 and MW-3). <br /> Analysis of soil samples indicated that the majority of petroleum hydrocarbons in soil were <br /> present from about 10 feet below ground surface (bgs) to groundwater at a depth of <br /> w 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 /> LW results showed that MW-1 had no measurable concentrations of petroleum hydrocarbons in the <br /> groundwater. Wells MW-2 and MW-3 contained detectable levels of petroleum hydrocarbons. <br /> A program of quarterly groundwater monitoring and sampling was begun in March 1994. <br /> �c <br /> 1500781QUARTLYI4QR-1994.doc <br /> i... <br />