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Chevron Products Comp-iny 6 Chevron Station 99-5775 301 W Kettlemin Lane Lodi c A �. August 25 2000 Monitoring data from July 2000, indicates depth to water in shallow zone wells ranging from 55 to 57, and from 56 to 59 feet bgs in deeper zone wells Groundwater flow direction is currently to the west in the shallow zone wells at an apps oximate gradient of 0 005 and is currently to the southwest in deeper zone wells at an approximate gradient of 0 003 HYDROCARBON PRIMARY AND SECONDARY SOURCES Primary Source The primary source of gasoline hydrocarbons and fuel oxygenates in soil and groundwater at the subject site was from the former USTs In August 24, 1998, the primary source was removed Secondary Source — Soil Around Former USTs Maximum concentrations of petroleum hydrocaibons and fuel oxygenates in soil are located in the vicinity of the former USTs adjacent to extraction well EX -1 and vapor extraction wells VE -1 through VE4 The vertical extent of TPHg, BTEX, and MtBE in the area of the former USTs extends to approximately 65 feet bgs as indicated trom analytical results from EX -1, VE -1 through VE -4, and soil borings SB -2 and SB -3, with the exception of trace concentrations (0 0078 mg/kg benzene and 0 24 mg/kg MtBE) at a depth of 72 feet bgs in SB -1 Estimated areas of TPHg, Benzene, and MtBE impacted soils are shown on Figures 13, 14, and 15, respectively The area below the eastern end of the middle gasoline UST was excavated from 14-1/2 to 16 feet bgs, and a second sample was collected Concentrations of TPHg and MtBE were reported as 880 mg/kg and I 1 mfr kg, respectively Benzene was not ieported in this sample On August 31, 1998, the area below the eastern end of the middle gasoline UST was over -excavated from 16 to 22 5 feet bgs Soil samples collected from the base and the eastern wall of the excavation were reported to have concentrations of TPHg, benzene, and MtBE at 2,300 mg/kg, 4 1 mg/kg, and 330 mg/kg, respectively SUMMARY OF REMEDIAL FEASIBILITY TESTING Soil Vapor Extraction Feasibility Testing Soil vapor extraction (SVE) feasibility testing was conducted by G -R on April 6, 13, 19, 27, and May 4, 2000 G -R extracted soil vapor from wells VW- I and VW -2 using a VR Systems III internal combustion vapor extraction system Based upon the results of the SVE feasibility testing G -R estimated an SVE radius of influence of 60 feet (G -R, July 14, 2000) Vapor samples were collected from the influent and effluent vapor streams on each of the five test days Reported influent TPHg concentrations ianged from 3,600 to 26,000 mg/m3 077 41991 043/FRP