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i <br /> �✓ Y,, <br /> Work Plan for Additional Site Assessment <br /> Jimco Truck Plaza <br /> CAM B R ]I A 1.022 Frontage Road <br /> Ripon, California <br /> May 18, 2005 <br /> 3.0 PREVIOUS INVESTIGATIONS <br /> Below is the chronology of site assessment, feasibility testing and interim remedial activities at the <br /> site. Historical soil and groundwater analytical data are presented in Tables 1 and 2,respectively. <br /> October 1996: In October 1996, AGE drilled 3 borings (B-14 through B-16) along the southern <br /> border of the site. These borings were part of AGE's delineation of a hydrocarbon plume originating <br /> from the adjacent Ripon Farm Services property, located south of the site. TEC Accutite collected <br /> split soil and grab groundwater samples on behalf of Olympian Oil. Total Vetroleum hydrocarbons as <br /> 8�'F@2o'�1.9 mglR� ) 815aa ho =i7oo. glh1 o <br /> diesel(TPHd)was detected only in boringaB 15 at 20 ft bgs at a concentration ofmilligrams per <br /> kilogram(mg/kg). Total petroleum hydrocarbons as gasoline(TPHg)was detected in all-tl�borings <br /> Wf 240r any <br /> at concentrations ranging from 0,8T to W mg/kg. Benzene wa"detected inhborings 9 ars 44 t— <br /> cenGe}tratian .Grab groundwater samples were collected from <br /> borings B14 and B16. Dissolved-phase TPHd, TPHg, and benzene were detected at maximum <br /> 51400 2Yo a A/D <br /> concentrations of 13,000 13 A9B; and micrograms per liter (µg2), respectively, in boring B14 <br /> located near the southern.site boundary. V v s��o✓'r <br /> May 1998: In May 1998, AGE oversaw the installation of.groundwater monitoring wells MW-6, <br /> MW-7,and MW-8.These wells were intended to assess the extent of a hydrocarbon plume related to <br /> the adjacent Ripon Farm Services property located south of the site. A 20 ft bgs soil sample was <br /> collected from each of the well pilot borings. TPHd was detected in each sample and concentrations <br /> ranged from 1.1 to 490 mg/kg. The highest TPHd concentration detected was from the pilot boring <br /> for well MW-6. No benzene was detected in any of the soil samples. The only sample analyzed for <br /> TPHg was from the pilot boring for well MW-7 and TPHg was detected at a concentration of 6 mg/kg. <br /> June 1998: In June 1998 Walton Engineering Walton of West Sacramento California removed six <br /> J g g( ) , <br /> fuel dispenser islands and associated piping. Soil samples collected by Grayland Environmental <br /> (Grayland)of Davis,California during the fuel dispenser and product piping removal activities(FDI <br /> through FD6,PL1 through PL4)confirmed that soil beneath the site had been impacted primarily by <br /> TPHd and TPHg to a lesser extent. <br /> July 1998: In July 1998, Walton removed old product piping and installed a new UST, ten <br /> dispensers, and new product piping to connect the new dispensers with the new UST and existing <br /> ASTs. Soil samples collected by Grayland during the product piping removal activities(PL-7 through <br /> pL-q-;P17)confirmed that soil beneath the site had been minimally impacted by TPHd. <br /> 3 <br />