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Chevron Environmental Management Company Page 2 Chevron Station 9-3232 8660 Lower Sacramento Road Stockton California Jang 17 2003 shallow wells were advanced to approximately 46 feet bgs Upon completion of • drilling, a 2-inch diameter groundwater monitoring well was installed in each boring Data obtained from continuous cores of the deeper wells was used for shallow well construction The deeper wells were screened from 57-67 feet bgs (MW-4D) and 54-62 feet bgs (MW-5D and MW-6D) The shallow wells were screened from 30-45 feet bgs (MW-4 and MW-5) and 33-48 feet bgs (MW-6 and MW-7) Groundwater was first encountered at approximately 40 feet bgs in each of the boreholes Slug tests were also performed on the three onsite wells (MW-1 through MW-3) on November 1, 2001 A summary of field and laboratory procedures followed during these activities is included as Attachment B The results of the drilling and testing are described below • Subsurface Conditions. Two sandy horizons at approximately 5-20 and 55-65 feet bgs are over and underlain by silt with clay to lean clay horizons Groundwater was first encountered at approximately 40 feet bgs Boring logs for the new wells are included as Attachment C • Soil Sampling and Analysis. Ten to thirteen soil samples were collected from each of the deep borings and submitted for laboratory analysis Soil analytical results are summarized in Table 1 Analytical reports and chain-of-custody documentation is included in Attachment D Samples submitted for chemical analysis were analyzed for total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethyl- benzene and xylene (BTEX), methyl tertiary butyl ether(MtBE), di-isopropyl ether (DIPE), tertiary-amyl methyl ether(TAME), ethyl tertiary-butyl ether (EtBE), tertiary-butyl alcohol (TBA), ethylene dibromide (EDB), 1,2 dichloroethane (1,2- DCA), methanol, and ethanol Benzene was detected in three of the soil samples at concentrations ranging from 0 0052 milligrams per kilogram (mg/kg) (MW-4D) at 60 feet below ground surface (bgs) to 0 017 mg/kg (MW-4D) at 65 feet bgs MtBE was detected in one soil sample at a concentration of 0 0010 mg/kg (MW-4D) at 60 feet bgs • Monitoring Well Development and Sampling. The newly installed monitoring wells were developed by Gettler-Ryan(GR) on April 24 and 25, 2002, as part of the second quarter 2002 monitoring and sampling event A total of ten wells were sampled and analyzed for TPHg, BTEX, MtBE, TBA, EtBE, TAME, DIPE, and ethanol Groundwater analytical results, laboratory analytical reports, chain-of- custody documentation, and field notes for the event are documented in GR's Second Quarter Event off4prd 24 and 25 2002 and May 14, 2002, dated June 21, 2002 (Attachment E) • Well Surveying and Groundwater Gradient Interpretation. A state-licensed surveyor surveyed the newly installed wells to known vertical and horizontal datum Depth to groundwater measurements, groundwater gradient, and flow direction are 1 1Chevron1932321REPORTSI9-3232 2-4-02 MW SA doe