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Chevron Products Company Page 2 Chevron Station 9-1452 334 East Main Street Ripon,California June 11 2002 Geoprobe borings advanced during the previous site assessment. Copies of the Geoprobe boring logs are included in Attachment B. The soil borings were advanced using 8-inch hollow stem augers to approximately 40 feet bgs in the shallow borings and 52 to 56 feet bgs in the deep borings. Data obtained from continuous cores of the deeper borings and lithologic data obtained from the previously advanced Geoprobe borings were used in the design of the wells. Upon completion of drilling, a 2-inch diameter groundwater monitoring well was installed in each of the borings. Field and laboratory procedures are included in Attachment C. The results of the drilling and sampling are described below: • Subsurface Conditions. Silty sand to sand was encountered in each of the borings to the total explored depth of approximately 56 feet bgs. Groundwater was measured at approximately 31 feet bgs in MW-3 prior to drilling operations and encountered prior to the first soil sample taken (at approximately 40 feet bgs) in each of the deep borings. Boring logs and well construction details are included in Attachment D. • Soil Sampling and Analysis. Four to five soil samples were collected from each of the deep soil borings and submitted to a California certified laboratory for chemical analysis. Soil analytical results are summarized in Table 1. A copy of the laboratory analytical report and chain-of-custody documentation is included in Attachment E. Soil samples submitted for chemical analysis were analyzed for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, and xylenes (BTEX), and the fuel oxygenates methyl tertiary butyl ether(MtBE), di-isopropyl ether(DIPE), tertiary amyl methyl ether(TAME), ethyl tertiary butyl ether (EtBE), tertiary butyl alcohol (TBA), 1,2-dibromoethane (EDB), and 1,2 dichloroethane (1,2- DCA), methanol, and ethanol. Methanol was detected in all of the soil samples at low concentrations ranging from 1.6 milligrams per kilogram (mg/kg) in the sample from MW-5D at 41.5 feet bgs to 3.6 mg/kg in the sample from MW-7D at 38 feet bgs. MtBE was detected in one sample at a concentration of 0.0020 mg/kg in the sample from MW-5D at 51 feet bgs. • Groundwater Analytical Results. The newly installed wells were developed and sampled by Gettler-Ryan (GR) in conjunction with the first quarter 2002 groundwater monitoring and sampling event. Groundwater samples were submitted to a California certified laboratory and analyzed for the presence of TPHg, BTEX, the fuel oxygenates MtBE, DTPE, TAME, EtBE, TBA, EDB, 1,2 DCA, and methanol, ethanol. Groundwater analytical results are summarized in Table 2. A copy of the laboratory analytical report and chain-of-custody documentation are included in Attachment E. Copies of GR's well development field data sheets are included in Attachment F. Groundwater chemical concentrations are shown graphically in Figure 3. MtBE was detected in five groundwater samples at concentrations ranging from 8 micrograms per liter (µg/l) in the sample from MW-6D to 8,200 µg11 in the sample I\Chevron1914521REPORTSI9-1452 2002 MW SA.doc