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<br /> Philhps 66 Company 2
<br /> Circle K Store#1205 I6470 Cambndge Street,Lathrop,CA July 16 2002
<br /> iof soil samples collected from GP-1 at 10 feet bgs reported maximum concentrations of
<br /> TPHg and MtBE at 1,900 ppm and 0 31 ppm, respectively Laboratory analysis of grab
<br /> groundwater samples collected from GP-1 contained concentrations of TPHg and MtBE
<br /> of 52,000 ppb and 61 ppb, respectively (PEG, 1999)
<br /> From August through September 1998, IT Corporation (IT) drilled and installed four
<br /> groundwater monitoring wells (MW-1 through MW-4) to approximate depths of 26 to
<br /> 28 feet bgs During the installation of well MW-4, the drill auger broke through a City
<br /> of Lathrop water main releasing approximately 600,000 to 1,000,000 gallons of water
<br /> Laboratory analysis of soil boring samples reported maximum concentrations of 6,800
<br /> ppm TPHG in MW-3-16' and 7 2 ppm MtBE in MW-2-11' Groundwater samples
<br /> collected from newly installed wells contained maximum concentrations of TPHg and
<br /> MtBE of 29,000 ppb (MW-1) and 4,000 ppb (MW-2), respectively (PEG, 1999)
<br /> In December 2000, IT drilled and installed five groundwater monitoring wells (MW-5
<br /> through MW-9) to approximate depths of 24 feet bgs Laboratory analysis of soil
<br /> samples reported maximum concentrations of TPHg and MtBE of 473 ppm (MW-9-10')
<br /> and 0 119 ppm (MW-6-20'), respectively Groundwater samples collected from the
<br /> newly installed wells reported maximum concentrations of TPHg and MtBE of 72,000
<br /> ppb (MW-6) and 750 ppb (MW-6), respectively (IT, 2001)
<br /> In March 1999, IT performed a Sensitive Receptor Survey and reported 12 wells within
<br /> a'/z-miles radius of the site The closest wells to the site are located approximately 0 15
<br /> mile west/southwest (upgradient) of the site The nearest downgradient wells are
<br /> located approximately 0 3 northeast of the site (IT, 2001)
<br /> Groundwater monitoring has been performed at the site since August 1998 In the
<br /> fourth Quarter 2001, groundwater samples contained concentrations of TPHg in excess
<br /> of 10,000 ppb in wells MW-1, MW-5, MW-6, MW-7, and MW-9 The highest
<br /> concentrations of benzene and MtBE reported in MW-7 at 780 ppb and in MW-6 at 660
<br /> ppb Groundwater flow was to the northeast with a gradient of approximately 0 001
<br /> ft/ft Depth to groundwater ranged from 12 50 (MW-9) to 14 32 (MW-3) feet bgs (GR,
<br /> 2001)
<br /> On June 5 and 21, 2002 SECOR performed a Geoprobe assessment in order to delineate
<br /> hydrocarbons in the soil and groundwater down gradient and cross gradient of the site
<br /> Nine Geoprobe borings were completed to approximately 15 feet bgs Groundwater
<br /> depths ranged from 9 7 feet bgs in boring GP-2 to 12 1 feet bgs in boring GP-4 Soil
<br /> and groundwater samples were analyzed for TPHg, benzene, toluene, ethylbenzene,
<br /> total xylenes (collectively BTEX), MtBE, di-isopropyl ether(DIPE), tert-amyl butyl
<br /> ether (TAME), ethyl-tert butyl ether (ETBE), tert-butyl alcohol (TBA), ethanol, 1,2-
<br /> dicloroethane (1,2-DCA), and 1,2-dibromoethane (EDB) bye EPA Method 826013,
<br /> single run Laboratory analysis Soil samples collected at the capillary fringe were
<br /> analyzed and all analytes were reported below laboratory reporting limits Laboratory
<br /> analysis of groundwater samples reported maximum concentrations of TPHg, benzene,
<br /> and MtBE of 17,000 ppb (GP-1), 170 ppb (GP-2), and 230 ppb (GP-8), respectively
<br /> TOSCO/1205/WKPLAN1205 Addendum
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