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<br /> S ECOR �.
<br /> i
<br /> Ms. Vicky McCartney
<br /> September 15, 2003
<br /> Page 2
<br /> Between December 3, 4 and 10, 1992, RESNA performed a preliminary site assessment for BP by
<br /> drilling four exploratory soil borings (B-1 through B-4) to total depths of 31.5 to 36.5 feet bgs and
<br /> converting them to Groundwater Monitoring Wells MW-1 through MW-4. Wells MW-1 and MW-2
<br /> were installed on the southeast and northwest corners, respectively, of the USTs;Well MW-3 was
<br /> installed on the west end of the northern dispenser island and Well MW-4 was installed between the
<br /> former waste oil tank and the new waste oil tank. Laboratory analytical results for soil detected
<br /> maximum concentrations of benzene at 0.1200 ppm (S-21.3-62), toluene at 0.0200 ppm (S-20.0-131),
<br /> ethylbenzene at 0.0180 ppm (S-21.3-132), and total xylenes at 0.0240 ppm (S-21.3-132). Gasoline
<br /> range total petroleum hydrocarbons (TPHg) and diesel range total petroleum hydrocarbons (TPHd)
<br /> were not detected above laboratory detection limits. Laboratory analytical results for groundwater
<br /> detected maximum concentrations of TPHg at 2,200 parts per billion (ppb, MW-1), benzene at 120
<br /> ppb (MW-2), toluene at 15 ppb (MW-1), ethylbenzene at 1.0 ppb (MW-2), and total xylenes at 24 ppb
<br /> (MW-2). TPHd was not detected above laboratory detection limits (RESNA, 1993).
<br /> In March 1994, Alisto Engineering (Alisto) conducted a supplemental subsurface investigation by
<br /> drilling and installing three groundwater monitoring wells (MW-5 through MW-7) to total depths of 31
<br /> to 32 feet bgs. Groundwater Monitoring Well MW-5 was installed on the northeast corner of the Vp a�
<br /> r property, Well MW-6 was installed in an alleywo Ked Drive, and MW-7 was installed on the
<br /> north side of West Hammer Lane.—Laboratory analysis of soil samples detected maximum
<br /> concentrations of benzene at 0.13 ppm (MW-5-16'), toluene at 0.67 ppm (MW-6-16'), and total
<br /> i xylenes at 0.015 ppm (MW-5-,16'). TPHg and TPHd were; not detected above laboratory detection
<br /> limits (EMCON, 1994).
<br /> On November 22, 1994, EMCON conducted a supplemental site assessment to establish baseline
<br /> subsurface conditions during the transfer of ownership of the property from BP to Tosco. The
<br /> investigation consisted of collecting two grab soil samples (TD-2 and TD-3) below the eastern fuel
<br /> dispensers at 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 total depth
<br /> of 1.7 feet bgs. Soil and hydropunch groundwater samples were collected and analyzed from borings
<br /> THP-1 and THP-2. Laboratory analysis of soil samples TD-2 and TD-3 detected maximum
<br /> concentrations of TPHg at 2,100 ppm (TD-2), toluene at 3.5 ppm (TD-3), ethylbenzene at 18 ppm
<br /> (TD-3), and total xylenes at 110 ppm (TD-3). TPHd, oil range total petroleum hydrocarbons (TPHo),
<br /> and benzene were not detected above laboratory detection limits. Laboratory analysis of soil
<br /> samples from borings THP-1 and THP-2 detected maximum concentrations of TPHd at 1 ppm
<br /> (THP1 S-10) and benzene at 0.03 ppm (THP@S-15). TPHg, TPHo, toluene, ethylbenzene, and total
<br /> i xylenes were not detected above laboratory detection limits. Laboratory analysis of groundwater
<br /> samples from borings THP-1 and THP-2 detected maximum concentrations of TPHg at 6,900 ppb
<br /> (THP2W-21), TPHd at 840 ppb (THP2W-21), benzene at 1,900 ppb (THP2W-21), and total xylenes
<br /> at 77 ppb (THP2W-21). TPHo, benzene toluene, ethylbenzene, and Halogenated Volatile Organic
<br /> Compounds (HVOC's)were not detected above laboratory detection limits (EMCON, 1994).
<br /> In February 1995, Alisto conducted baildown testing to determine aquifer properties beneath the site.
<br /> V Pumping occurred from well MW-1, generating approximately 1.5 feet of drawdown at an extraction
<br /> rate of 6 gallons per minute (gpm). Alisto concluded that the rapid recovery may be due to the sand
<br /> unit encountered in the lower portion of well MW-1, and may not be representative of the material in
<br /> the saturated zone (Alisto, 1995). Revised calculations of hydrogeologic parameters were submitted
<br /> in October 1995. Resulting hydraulic conductivity (K) values for wells MW-1, MW-2, and MW-5
<br /> i ranging from 2.25x10 to 8.68x10-5 centimeters per second (cm/s) were within the lower range of
<br /> i expected K values associated with the soil types encountered beneath the site (1 to 1x10-5 cm/s,
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