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Phillips 66 Company 2 Circle K Store#1205 16470 Cambridge Street Lathrop,CA February 27 2002 of soil samples collected from GP-1 at 10 feet bgs reported maximum concentrations of TPHg and MtBE at 1,900 ppm and 0 31 ppm, respectively Laboratory analysis of grab groundwater samples collected from GP-1 contained concentrations of TPHg and MtBE of 52,000 ppb and 61 ppb, respectively (PEG, 1999) From August through September 1998, IT Corporation (IT) drilled and installed four groundwater monitoring wells (MW-1 through MW-4) to approximate depths of 26 to 28 feet bgs During the installation of well MW-4, the drill auger broke through a City of Lathrop water main releasing approximately 600,000 to 1,000,000 gallons of water Laboratory analysis of soil boring samples reported maximum concentrations of 6,800 ppm TPHG in MW-3-16' and 7 2 ppm MtBE in MW-2-11' Groundwater samples collected from newly installed wells contained maximum concentrations of TPHg and MtBE of 29,000 ppb (MW-1) and 4,000 ppb (MW-2), respectively (PEG, 1999) In December 2000, IT drilled and installed five groundwater monitoring wells (MW-5 through MW-9) to approximate depths of 24 feet bgs Laboratory analysis of soil samples reported maximum concentrations of TPHg and MtBE of 473 ppm (MW-9-10') and 0 119 ppm (MW-6-20'), respectively Groundwater samples collected from the newly installed wells reported maximum concentrations of TPHg and MtBE of 72,000 ppb (MW-6) and 750 ppb (MW-6), respectively (IT, 2001) • In March 1999, IT performed a Sensitive Receptor Survey and reported 12 wells within a 1/2-miles radius of the site The closest wells to the site are located approximately 0 15 mile west/southwest (upgradient) of the site The nearest downgradient wells are located approximately 0 3 northeast of the site (IT, 2001) Groundwater monitoring has been performed at the site since August 1998 In the fourth Quarter 2001, groundwater samples contained concentrations of TPHg in excess of 10,000 ppb in wells MW-1, MW-5, MW-6, MW-7, and MW-9 The highest concentrations of benzene and MtBE reported in MW-7 at 780 ppb and in MW-6 at 660 ppb Groundwater flow was to the northeast with a gradient of approximately 0 001 ft/ft Depth to groundwater ranged from 12 50 (MW-9) to 14 32 (MW-3) feet bgs (GR, 2001) PROPOSED SCOPE OF WORK Off-site assessment required to delineate hydrocarbon impacted groundwater to the north, east and west will be conducted in three phases the first phase will consist of drilling five Geoprobe° soil borings at the locations proposed on Figure 2, phase two will consist of drilling up to five additional step-out Geoprobe soil borings at the locations proposed on Figure 2 based on analytical results from the first phase of the project, and phase three will consist of installing up to five groundwater monitoring wells in locations determined to delineate groundwater from the prior two phases i • Site Safety Plan. As required by the Occupational Health and Safety Administration (OSHA) Standard "Hazardous Waste Operations and TOSCO!1205MKPLAN 1205