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1 <br /> ' Working To Restore Nature <br /> 1710 Main Street <br /> Escalon, CA 95320 <br /> Phone (209) 838-3507 TRIRD QUARTER 1994 <br /> ' FAX (209) 838-3509 GROUNDWATER MONITORING REPORT <br /> Former Thiemann's Service <br /> ' Ripon, California <br /> INTRODUCTION <br /> tThis report presents the results of quarterly groundwater monitoring and sampling performed <br /> in September 1994 by RESNA Industries Inc. (RESNA) at Former Thiemann's Service. The <br /> ' site is located at 106 West Second Street 1n 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 /> 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 /> approximately 29 feet bgs and within a radius of 35 feet from the former UST pit. <br /> t <br /> In August 1993, wells MW-1, MW-2, and MW-3 were monitored and sampled Analytical <br /> ' 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 /> ' 150078NQUARTLYUQR-1994 FNL <br />