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Chevron Products Company 1 Former Chevron Station 9-5775, 301 W Kettleman Lane, Lodi, CA July 24,2000 • 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 The area beneath the eastern end of the middle gasoline UST was excavated from 14 5 to 16 feet bgs, and a second sample was collected Concentrations of TPHg and MtBE were reported as 880 mg/kg and 11 mg/kg, respectively Benzene was not detected in this sample On August 31, 1998, the area beneath 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 contain concentrations of TPHg, benzene, and MtBE at 2,300 mg/kg, 4 1 mg/kg, and 22 mg/kg, respectively Soil analytical data is also shown on cross-section A -A' (Figure 3) Historical soil analytical data is included as Attachment B Extent of Dissolved Petroleum Hydrocarbons in Groundwater Concentrations of dissolved petroleum hydrocarbons and fuel oxygenates in shallow groundwater from May 25, 2000 are illustrated on Figures 6, 7, and 8 Maximum concentrations of benzene and MtBE were reported in well EX -1 at concentrations of 19,000 ug/l, and 350,000 ug/l, respectively A maximum concentration of TPHg was reported in monitoring well MW -3 at a reported concentration of 1,390 ug/l • The lateral extent of the shallow groundwater hydrocarbon plume is defined by wells MW -7, - 8A, -10A, -12A, and -13 Definition of the shallow hydrocarbon plume in the direction of the municipal well is defined by monitoring well MW- IOA Historical groundwater analytical data is included as Attachment C • No detectable concentrations of dissolved petroleum hydrocarbons and fuel oxygenates were reported in the deeper groundwater zone (from July 12, 2000 data — initial sampling) with the exceptions of MtBE in wells MW -5B and MW -1 OB at concentrations of 160 ug/1 and 5 2 ug/l, respectively, and ETBE in well MW -5B at a concentration of 14 ug/l Additionally, ethanol was reported in wells MW- 1OB and MW -12B at concentrations of 1,400 and 2,000 ug/l, respectively Since Chevron has no record of using ethanol onsite and since these detections were reported only in offsite wells, these detections are thought to be anomalous or may be indicative of an offsite source Groundwater Mass Balance Calculations Estimates of the total mass of TPHg, benzene, and MtBE have been calculated based on the developed area isocontours (Figures 10 through 12) Mass balance calculations for soil and groundwater are presented in Attachment L Assumptions used for this mass estimate are listed below 077 41991 04319-5775PAR doc