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Chevron Products Company Page 2 Chevron Service Station 9-9840,4344 Waterloo Road,Stockton,California September 20,2001 approximately 70 feet bgs Soil samples were generally collected every 15 feet bgs and submitted for chemical analysis Based on pore pressure and on lithologic information collected from the CPT logs, one depth-discrete groundwater sample was collected from each of the borings Soil and groundwater samples were analyzed for the presence of total petroleum hydrocarbons quantified as gasoline (TPHg), benzene, toluene, ethylbenzene, xylenes (BTEX), and the fuel oxygenates methyl tertiary butyl ether (MtBE), tertiary butanol (TBA), di-isopropyl ether(DIPE), ethyl tertiary-butyl ether(EtBE), tertiary-amyl methyl ether (TAME), ethanol, and methanol Upon completion, the borings were filled with grout from the bottom up and finished to surface grade with asphalt Field and laboratory procedures are presented as Attachment B The findings of this assessment are summarized below • Subsurface Conditions. Review of the boring logs and CPT profiles suggests silt mixtures with clay and/or clay mixtures with silt comprise the stratigraphy to an approximate depth of 70 feet bgs at all CPT locations Groundwater was generally encountered at approximately 68 feet bgs at the boring locations CPT logs are included as Attachment C • Soil Analytical Results. Three to four soil samples were collected from each of the borings Soil analytical results are summarized in Table 1 Soil analytical data are presented graphically in Figure 2 Laboratory analytical reports and chain-of custody documentation are presented as Attachment D Soil samples from CPT-1 through CPT 5 and CPT-8 did not contain any of the analytes • above the laboratory detection limits Soil samples from CPT-6 contained xylenes at a concentration of 13 milligrams per kilogram (mg/kg) at 15 feet bgs, and MtBE at a concentration of 11 mg/kg at 50 feet bgs Soil samples from CPT-7 contained TPHg at a concentration of 2 0 mg/kg at 45 feet bgs, benzene at 53 mg/kg at 45 feet bgs, ethylbenzene at 130 mg/kg at 45 feet bgs, xylenes at 550 mg/kg at 45 feet bgs, and MtBE at 32 mg/kg and 24 mg/kg at 45 feet bgs and 60 feet bgs, respectively • Groundwater Analytical Results. Groundwater samples were collected from the identified water-bearing zone or depth intervals showing distinct pore pressure One depth-discrete groundwater sample per boring was submitted for analysis Groundwater analytical results are presented in Table 2 Groundwater analytical results are presented graphically in Figure 3 Certified analytical report and chain-of-custody documentation are presented as Attachment D TPHg was detected in three groundwater samples at concentrations ranging from 0 11 micrograms per liter (µg/L) in CPT-4 at 68 feet bgs to 0 26 µg/L in CPT-5 at 68 feet bgs Benzene was detected in three groundwater samples at concentrations ranging from 0 69 µg/L(CPT-6 at 68 feet bgs)to 3 0 µg/L (CPT-5 at 68 feet bgs) MtBE was detected in four groundwater samples at concentrations ranging from 0 88 µg/l, (CPT-3 at 68 feet bgs) to 78 µg/L(CPT-6 at 68 feet bgs) TAME and TBA were detected in CPT-6 at 68 feet bgs at concentrations of 3 3 µg/L and 26 µg/L, respectively i 1 1Chevron1998401REPORTS199840 CPT SA&WPFSA(4 wells)doc