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SI 1 Chevron Environmental Management Company Page 2 Chevron Station 9-8264 3775 Tracy Boulevard Tracy,California Janua 17 2003 at one onsite location (CPT-2) and three offsite locations (CPT-1, CPT-3, and CPT-4) to assess soil stratigraphy and to collect discrete groundwater samples (Figure 2) Each CPT boring was monitored continuously for soil behavior and pore pressure to approximately 30 to 35 feet below ground surface (bgs) Based on pore pressure and on lithologic information collected from the CPT logs, one to two depth-discrete groundwater samples were collected at each boring location Soil samples were also collected from the borings CPT-1 and CPT-3 Upon completion, the borings were filled with grout from the bottom up and finished to surface grade with either asphalt or concrete depending on the pre-existing surface material A summary of the field and laboratory procedures which were followed during these activities is presented in Attachment B The findings of this assessment are summarized below • Subsurface Conditions. Review of the CPT logs indicated the stratigraphy at CPT-I, CPT-2, and CPT-4 is comprised mainly of sand or a sand mixture to an approximate depth of 12 feet bgs From 12 feet bgs to the bottom of these borings the soil lithology is comprised mainly of silt/clay mixtures The log from CPT-3 indicates a predominately silt mixture with some clay to the total depth of the boring at 30 feet bgs Groundwater was generally encountered at approximately 14 feet bgs CPT logs are included in Attachment C • Soil Analytical Results. Soil samples were collected from CPT-1 and CPT-3 at 9 and 8 5 feet bgs, respectively, and submitted for chemical analysis to a California state-certified laboratory for the presence of total petroleum hydrocarbons quantified as diesel (TPHd), total petroleum hydrocarbons quantified as gasoline (TPHg),benzene, toluene, ethylbenzene, 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), ethyl dibromide (EDB), 1,2 dichloroethane (1,2- DCA), ethanol, and methanol Laboratory analytical reports and chain-of- custody documentation are presented as Attachment D Methanol was reported in the soil sample from CPT-3 at 8 5 feet bgs at a concentration of 0 37 milligrams per kilogram (mg/kg) No other analytes were detected above the laboratory method detection limits • Groundwater Analytical Results. Groundwater samples were submitted to a California state-certified laboratory and analyzed for the presence of TPHg, TPHd, BTEX, and the fuel oxygenates MtBE, DIPE, TAME, EtBE, TBA, EDB, 1,2-DCA, methanol, and ethanol One to two depth-discrete groundwater samples were collected from each of the borings in the identified water-bearing zones at approximately 14 and 24 feet bgs and submitted for chemical analysis Groundwater analytical results are summarized in Table 1 Groundwater chemical concentrations are shown graphically in Figure 3 Laboratory analytical reports and chain-of-custody documentation are presented as •>� Attachment D I 1Chevron1982641REPORTSICPT siteassessment doe