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S E C 0 R
<br /> Aim
<br /> Ms Victoria L McCartney
<br /> • March 3, 2005
<br /> Page 2
<br /> Between December 3 and 10, 1992, RESNA performed a preliminary site assessment for
<br /> BP by drilling four exploratory soil borings (B-1 through B-4) to total depths of 31 5 to 36 5
<br /> feet bgs and converting them to wells MW-1 through MW-4 Wells MWA and MW-2 were
<br /> Installed on the southeast and northwest corners of the USTs, respectively Well MW-3
<br /> was Installed on the west end of the northern dispenser Island, and well MW-4 was Installed
<br /> between the former waste oil UST and the new waste oil UST While gasoline range total
<br /> petroleum hydrocarbons (TPHg) and diesel range total petroleum hydrocarbons (TPHd)
<br /> were not detected above laboratory detection limits, maximum concentrations of benzene
<br /> (0 12 ppm, S-21 3-62), toluene (0 0200 ppm, S-20 0-131), ethylbenzene (0 0180 ppm, S-
<br /> 21 3-132), and total xylenes (0 0240 ppm, S-21 3-82) were detected in soil Maximum
<br /> concentrations of TPHg (2,200 parts per billion [ppb], MW-1), benzene (120 ppb, MW-2),
<br /> toluene (15 ppb, MW-1), ethylbenzene (1 0 ppb, MW-2), and total xylenes (24 ppb, MW-2)
<br /> were detected In groundwater TPHd was not detected In groundwater above laboratory
<br /> detection limits (RESNA, 1993)
<br /> In March 1994, Alisto Engineering (Alisto) conducted a supplemental subsurface
<br /> Investigation by drilling and installing three groundwater monitoring wells (MW-5 through
<br /> MW-7) to total depths of 31 to 32 feet bgs Benzene, toluene, and total xylenes were
<br /> detected in soil at maximum concentrations of 0 13 ppm (MW-5-16'), 0 67 ppm (MW-6-16'),
<br /> and 0 015 ppm (MW-5-16') TPHg and TPHd were not detected in soil above laboratory
<br /> detection limits (EMCON, 1994)
<br /> • On November 22, 1994, EMCON conducted a supplemental site assessment to establish
<br /> baseline subsurface conditions during the transfer of ownership of the property from BP to
<br /> Tosco The Investigation consisted of collecting two grab soil samples (TD-2 and TD-3)
<br /> below the north and south dispensers, drilling of two soil borings (THP-1, THP-2) to total
<br /> depths of 26 5 feet bgs, and the drilling and installation of vapor extraction well VW-1 to a
<br /> total depth of 17 feet bgs Soil and Hydropunch®groundwater samples were collected and
<br /> analyzed from borings THP-1 and THP-2 Laboratory analysis of soil samples TD-2 and
<br /> TD-3 confirmed the presence of maximum concentrations of TPHg at 2,100 ppm (TD-2),
<br /> toluene at 3 5 ppm (TD-3), ethylbenzene at 18 ppm (TD-3), and total xylenes at 110 ppm
<br /> (TD-3) TPHd, oil range total petroleum hydrocarbons (TPHo), and benzene were not
<br /> detected above laboratory detection limits Laboratory analysis of soil samples from
<br /> borings THP-1 and THP-2 Indicated maximum concentrations of TPHd at 1 ppm (THP1 S-
<br /> 10) and benzene at 0 03 ppm (THP@S-15) TPHg, TPHo, toluene, ethylbenzene, and total
<br /> xylenes were not detected above laboratory detection limits Maximum concentrations of ,
<br /> TPHg, TPHd, benzene, and xylenes were reported in groundwater at 6,900 ppb (THP2W-
<br /> 21), 840 ppb (THP2W-21), 1,900 ppb (THP2W-21), and 77 ppb (THP2W-21) TPHd,
<br /> benzene toluene, ethylbenzene, and Halogenated Volatile Organic Compounds (HVOC's)
<br /> were not detected above laboratory detection limits (EMCON, 1994)
<br /> i
<br /> In February 1995, Alisto conducted balldown testing to determine aquifer properties
<br /> beneath the site Pumping occurred from well MW-1, generating approximately 1 5 feet of
<br /> drawdown at an extraction rate of 6 gallons per minute (gpm) Alisto concluded that the
<br /> rapid recovery may be due to the sand unit encountered in the lower portion of well MW-1,
<br /> and may not be representative of the material in the saturated zone (Alisto, 1995) Revised
<br /> calculations of hydrogeologic parameters were submitted In October 1995 Resulting
<br /> hydraulic conductivity (K) values for wells MW-1, MW-2, and MW-5 ranging from 2 25x10
<br /> 1 1ConocoPhdlips\Retad Sdes1111931QMR14QMR04 Final doc
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