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Work Plan tor Site Assessment <br /> 1022 Frontage Road,Ripon, California <br /> C A M B R I A July 25, 2006 <br /> evaluate the extent of hydrocarbon-impacted soil and to determine if groundwater beneath the site was <br /> impacted. A total of approximately 1,180 tons (600 cubic yards)of hydrocarbon-impacted soil was <br /> removed from the site and disposed of at Forward Landfill in Stockton, California. <br /> j 0� �►S <br /> May to August 1999: Between May and gust 1999,GE oversaw the advancement of soil borings <br /> B 1 through B 16,hydropunch borings BP17 and BA and the installation of groundwater monitoring <br /> wells MW-1 through MW-5. Based on the analytical results, it was determined that the greatest <br /> hydrocarbon-impact to soil was in the area immediately adjacent to the former USTs at 20 ft bgs. <br /> Hydrocarbon-impacted soil appeared to be limited to a depth of approximately 30 ft bgs. The highest <br /> TPHg concentration was detected in the 20 foot sample from boring B5(1,300 mg/kg)and the highest <br /> TPHd concentration was detected in the 20 foot sample from boring B4(8,200 mg/kg). The highest <br /> r <br /> benzene concentration was detected in the 20 foot sample from boring B4(2.6 mg/kg). The highest <br /> methyl tertiary-butyl ether(MTBE)concentration was detected in the 10 foot sample from boring B 1 <br /> (12 mg/kg). Grab groundwater samples were collected from borings B2,B5,B14,HP17,and HP18. <br /> Dissolved-phase hydrocarbons extended S6rth and west of the former USTs. TPHg and benzene <br /> norms <br /> concentrations appeared to attenuate east and mouth of the former USTs (AGE, 1999). The highest <br /> dissolved-phase TPHd, TPHg, benzene, and MTBE were detected at concentrations of 580,000; <br /> 23,000;370;and 2,900µg/L,respectively,in boring B2 located on the south side of the former USTs. <br /> r,V-I Y1101 <br /> March 2002: In March 2002,AGE oversaw the installation of groundwater monitoring well MW-9 <br /> d �!�� and extraction well EW-1. Well EW-1 was installed in preparation for an aquifer pump test. Soil <br /> J samples collected from the pilot boring for well MW-9 at 15,20,25,and 30 ft bgs were submitted to <br /> the laboratory for analysis. No soil samples collected from boring EW-1 were submitted to the <br /> laboratory for analysis. TPHg was detected in soil samples collected from boring MW-9 at 20,25 and <br /> 30 ft bgs at concentrations of 260,0.36 and 0.24 mg/kg,respectively. No benzene was detected in any <br /> of the soil samples analyzed. MTBE was detected in samples collected from boring MW-9 at 15,25, <br /> and 30 ft bgs at concentrations of 0.016,0.54,and 0.27 mg/kg,respectively. TPHd was only detected <br /> in the 20 ft sample of boring MW-9at a concentration of 800 mg/kg. <br /> June 2002: In June 2002,AGE conducted a 48-hour groundwater extraction pilot test to assess the <br /> characteristics of the aquifer and its response to groundwater extraction. The test was performed on <br /> extraction well EW-1 screened from 16 to 36 ft bgs. A maximum drawdown of 9.76 feet was <br /> measured in extraction well EW-1 while pumping at a constant rate of 6 gallons per minute(gpm). A <br /> maximum drawdown of 0.40 feet was observed in observation MW-1,located 20 feet from extraction <br /> well EW-1. The transmissivity and hydraulic conductivity of the shallow aquifer were calculated at <br /> 1,000 ftz/day and 0.175 cm/sec,respectively. Additional details are presented in AGE's November 6, <br /> 2002 Well Installation and Groundwater Aquifer Pumping Test Report. <br /> 4 <br />