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Chevron Products Company Page 2 Chevron Service Station 9-9840,4344 Waterloo Road,Stockton,California September 25,2002 groundwater monitoring well was installed in each boring Field and laboratory procedures are included in Attachment B The results of the assessment activities are described below • Subsurface Conditions. Silty clay to clayey silt was encountered in all of the borings to approximately 60 feet bgs Below that, a sandy silt to silty sand was encountered to the total depth explored of approximately 75 feet bgs Groundwater was first encountered at approximately 67 feet bgs Boring logs and well construction details are included in Attachment C • Soil Sampling and Analysis. Two soil samples were collected from each of the bonngs (capillary fringe and bottom) and submitted to a state-certified laboratory for chemical analysis Samples submitted for chemical analysis were analyzed for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, xylenes (BTEX) and the fuel oxygenates methyl tertiary butyl ether (MtBE), di- isopropyl ether(DIPS), tertiary amyl methyl ether(TAME), ethyl tertiary butyl d ether(ELBE), tertiary butyl alcohol (TBA), ethylene dibromide (EDB), 1,2 dichloroethane (1,2-DCA), methanol, and ethanol A copy of the laboratory analytical reports and chain-of-custody documentation are included in Attachment D TPHg was detected at a concentration 5 0 milligrams per kilogram g/kg) in the soil sample from MW-6 at 65 feet bgs o other analytes were detected above their . respective laboratory detection limits • Groundwater Analytical Results. The newly installed wells were developed and sampled on May 10, 2002 Depth to water measurements were also collected from all seven groundwater monitoring wells Samples submitted for chemical analysis were analyzed for TPHg, BTEX, MtBE, DIPE, TAME, EtBE, TBA, EDB, 1,2 DCA, methanol, and ethanol Analytical data for the three pre-existing wells can be found in Gettler-Ryan's (G-R) second quarter 2002 monitoring and sampling report dated June 20, 2002 A copy of the laboratory analytical report and chain-of- custody documentation are included in Attachment D A copy of well development field data sheets are included in Attachment E MtBE was detected in the groundwater sample collected from well MW-4 at 2 micrograms per liter (µg11) No other analytes were detected above their respective method detection limits Groundwater monitoring and analytical data are summarized in Table 1 • Monitoring Well Survey and Groundwater Gradient Interpretation. The newly installed wells were surveyed along with the three previously installed wells to 0 01- foot accuracy relative to mean sea level (MSL) Based on depth to water readings taken during the sampling of the new monitoring wells, groundwater flow was to the east/northeast at a gradient 0 0026 foot per foot (Figure 3) • 11Chevron1998401REPORTSI9-9840 MW SA 2002 doe