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ATTACHMENT A
<br /> SUMMARY OF PREVIOUS INVESTIGATION
<br /> Chevron 9-2396, 25651 Highway 99 North, Acampo, CA
<br /> On August 25, 1993, one used oil underground storage tank (UST) and one heating oil UST
<br /> were removed from the site One soil sample was collected from beneath each of the USTs
<br /> The heating oil UST soil sample contained no analytes above the laboratory method
<br /> reporting limit The used oil UST soil sample contained no analytes above the method
<br /> reporting limit, with the exception of chromium at a concentration of 29 milligrams per
<br /> kilogram (mg/kg), lead at a concentration of 7 mg/kg, zinc at a concentration of 44 mg/kg,
<br /> and nickel at a concentration of 21 mg/kg
<br /> On December 15, 1993, one 10,000 gallon, two 6,000 gallon, and one 3,000 gallon single
<br /> walled steel USTs and associated product piping were removed from the site The USTs
<br /> appeared to be in good condition, with no visible holes observed Approximately 1,000
<br /> cubic yards of soil was removed to facilitate the installation of the three new 12,000-gallon
<br /> USTs Laboratory analytical results for the soil samples contained Iow levels (1 9 mg/kg to
<br /> 410 mg/kg) of total petroleum hydrocarbons quantified as gasoline (TPHg), benzene (0 008
<br /> mg/kg to 0 11 mg/kg), toluene (0 009 mg/kg to 6 7 mg/kg), ethylbenzene (0 008 mg/kg to 6 9
<br /> mg/kg), and xylenes (0 009 mg/kg to 46 mg/kg)
<br /> On June 24 and July 28, 1994, water samples were collected from the domestic water supply
<br /> well located near the Frontage Road, west of the pump islands Analytical results contained
<br /> no detectable concentrations of TPHg, and benzene, toluene, ethylbenzene, and xylenes
<br /> (BTEX) above the laboratory report limit on either sampling event
<br /> On April 26 and April 27, 2001, SECOR supervised Cascade Drilling of Rancho Cordova,
<br /> California in drilling three soil borings (SB-1, SB-2, and SB-3) to approximately 79 feet
<br /> below ground surface (bgs) One soil boring (SB-1) was placed adjacent to the gasoline
<br /> USTs, one boring (SB-2) was placed between the fuel facilities and the on-site domestic well,
<br /> and one boring (SB-3) was placed near the former used oil UST Two soil samples and one
<br /> groundwater "grab" sample were submitted from each soil boring for chemical analysis of
<br /> TPHg, BTEX, fuel oxygenates, and total lead Fuel oxygenates include tert-butyl alcohol
<br /> (TBA), MtBE, di-isopropyl ether(DIPE), ethyl tert-butyl ether (EtBE), tert-amyl methyl
<br /> ether (TAME), ethanol, 1-2 dichloroethane (1-2 DCA) and ethylene dibromide (EDB)
<br /> TPHg and BTEX were analyzed using the DHS/LUFT method, fuel oxygenates were
<br /> analyzed using EPA Method 8260A, and lead analysis was performed using EPA 6000/7000
<br /> series None of the soil samples contained chemical concentrations above the laboratory
<br /> method-reporting limit
<br /> The groundwater "grab" samples were analyzed for TPHg, BTEX, fuel oxygenates, and total
<br /> lead Groundwater "grab" samples collected from boring SB-1, near the former USTs, and
<br /> SB-3, near the existing pump islands, were reported to contain low-levels of toluene ranging
<br /> from 0 617 to 0 893 µg/L and xylenes ranging from 1 17 to 148 µg/L A single detection of
<br /> MtBE in the groundwater "grab" sample collected from SB-1 was reported at a concentration
<br /> . of 13 0 µg/L
<br /> No chemical constituents above the laboratory method reporting limit were reported in the
<br /> water sample collected from the on-site domestic well
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