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In January 1997, Advanced GeoEnvironmental (AGI) advanced six soil borings (132 through 137)
<br /> in the vicinity of the northern and southern USTs areas and one boring (131) in the vicinity of
<br /> 1 former septic ]each lines for the purpose of soil and grab groundwater sample collection. Total
<br /> petroleum hydrocarbons as diesel (TPHd) was reported in one of the soil samples collected from
<br /> a depth of approximately six feet below ground surface (bgs) near the southern UST pit at a
<br /> concentration of 1,000 milligrams per kilogram (mg/kg). In grab groundwater samples from
<br /> both UST areas, concentrations of TPHd, total petroleum hydrocarbons as gasoline (TPHg), and
<br /> methyl tertiary butyl ether (MTBE) up to 320,000 micrograms per liter (µg/L), 2,700 µg/L, and
<br /> 95 µg/l, (EPA 8020), respectively, were reported. Results of this investigation were summarized
<br /> in AGI's Preliminary Site Assessment Report, dated January 24, 1997.
<br /> In February and October 1998, the USTs, product piping, and fuel dispensers were removed and
<br /> replaced during site renovation activities. Avalon Environmental Consultants (Avalon)
<br /> conducted compliance soil sampling beneath the southern single UST on February 23, 1998, and
<br /> beneath the three northern USTs on October 9, 1998. Concentrations of TPHd, benzene, and
<br /> MTBE were reported in soil samples collected from a depth of approximately 10.5 feet bgs at
<br /> maximum concentrations of 660 mg/kg, 0.88 mg/kg, and 0.46 mg/kg, respectively. Results of
<br /> this investigation cited in this report (included on Tables 2 and 3) were obtained from the
<br /> original laboratory report and hand-written notes taken by Avalon and SJCEHD staff(no report
<br /> was available to Stratus at the time this document was prepared).
<br /> In November 1998, Avalon advanced and collected soil and grab water samples from fifteen
<br /> additional soil probe borings in the vicinity of the former northern (GP-1 through GP-7) and
<br /> southern (GP-8 through GP-15) UST areas. Analytical results of soil samples collected from
<br /> �`✓ both areas indicated relatively little overall impact (although two of the twenty-one samples
<br /> contained concentrations of TPHd and MTBE of 200 and 0.064 mg/kg, respectively). In grab
<br /> water samples, concentrations of TPHd, benzene, and MTBE of up to 11,000, 16, and 1,700
<br /> µg/L, respectively, were reported in samples collected from both the northern and southern
<br /> former UST areas. Results of this investigation were summarized in Avalon's Phase II
<br /> Environmental Assessment of Soil and Groundwater Report, dated December 5, 1998.
<br /> In February 2000, Avalon installed six on-site groundwater monitoring wells (MW-1 through
<br /> MW-6) screened across the water table (Sand A) to depths of about twenty feet bgs. Results of
<br /> this investigation were summarized in Avalon's Phase II Groundwater Assessment, dated
<br /> March 20, 2000. A quarterly groundwater monitoring and sampling program was implemented
<br /> at the site at this time: Analytical results of the first several rounds of groundwater sampling of
<br /> the newly installed wells indicated MTBE concentrations in the range of 1,800 to 2,800 µg/L in
<br /> i
<br /> wells MW-1 and MW-2.
<br /> In January 2001, Avalon advanced four soil probe borings (GP-1 through GP-4) along the
<br /> northern property boundary and six soil probes (GP-5 through GP-10) on the adjacent property to
<br /> the north to evaluate the lateral downgradient extent of the dissolved-phase MTBE plume.
<br /> Analytical results of this investigation indicated the presence of detectable levels of MTBE at all
<br /> ten of the on- and off-site locations, with a maximum MTBE concentration of 2,600 µg/1 (in
<br /> GP-8). Results of this investigation were summarized in Avalon's Phase II Environmental
<br /> Assessment of Soil and Groundwater Report, dated April 15, 2001.
<br /> �f Page 7 STRATUS
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