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Work Plan for Additional Site Assessment 1022 Frontage Road,Ripon,California CA M "B R I A July 25, 2006 the adjacent Ripon Farm Services property,located south of the site. TEC Accutite collected split soil and grab groundwater samples on behalf of Olympian Oil. Total petroleum hydrocarbons as diesel (TPHd) was detected only in boring *1315 at 20 ft bgs at a concentration of 1,300 milligrams per kilogram(mg/kg). Total petroleum hydrocarbons as gasoline(TPHg)was detected in all three borings at concentrations ranging from<0.5 to 160 mg/kg Benzene was detected in borings*1315 and*1316 at concentrations ranging from<0.005 to 0.11 mg/kg.Grab groundwater samples were collected from borings *B 14 and *B 16. The highest dissolved-phase TPHd;TPHg, and benzene were detected at concentrations of 15,000; 12,000; and 9 micrograms per liter (µg/L), respectively, in boring *B14 located near the southern site boundary. May 1998: In May 1998, AGE oversaw the installation of groundwater monitoring wells MW-6, MW-7, and MW-8 to assess the extent of a hydrocarbon plume related to the adjacent Ripon Farm Services property located south of the site. A 20 ft bgs soil sample was collected from each of the well pilot borings. TPHd was detected in each sample and concentrations ranged from 1.1 to 490 mg/kg. The highest TPHd concentration detected was from the pilot boring for well MW-6. No benzene was detected in any of the soil samples. The only sample analyzed for TPHg was from the pilot boring for well MW-7 and TPHg was detected at a concentration of 6 mg/kg. June 1998: In June 1998,Walton Engineering(Walton)of West Sacramento,California removed six fuel dispenser islands and associated piping. Soil samples were collected by Grayland Environmental (Grayland)of Davis,California during the fuel dispenser and product piping removal activities(FD 1 through FD6,PL1 through PL4). TPHd was only analyzed and detected in soil samples FD4 through FD6, and PL3 and PL4 at concentrations ranging from 3.3 to 13,000 mg/kg. TPHg was detected in six out of the 10 soil samples at concentrations ranging from 3.4 to 5,100 mg/kg. Benzene was detected in three out of the 10 samples at concentrations ranging from 0.022 to 0.12 mg/kg. July 1998: In July 1998,Walton installed a new gasoline UST,ten dispensers(eight diesel and two gasoline dispensers), and new product piping to connect the new dispensers with the new gasoline UST and existing diesel ASTs. September 1998: In September 1998,Walton removed three steel, single wall USTs, (7,500 gallon and 10,000 gallon gasoline USTs and one 12,000 gallon diesel UST),four additional dispensers,and i associated piping. Twenty four soil samples (T1 through T3,FD7 through FD10,and PL5 through PL17)were collected by Grayland during the UST,dispensers,and piping removal activities. TPHd concentrations ranged between<1.0 and 12,000 mg/kg(FD10).✓TPHg concentrations ranged between <1.0 and 1,500 mg/kg(T2n). Benzene concentrations ranged between<0.005 and 2.3 mg/kg(T3n). r As a result, Grayland Environmental recommended that additional assessment be conducted to 3