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Chevron Products Company 2
<br />�cb Chevron Service Station#9-2033 08 West Charter Wa Stockton Cahfomia Janua 18 2001
<br /> I
<br /> butanol, di-isopropyl ether(DIPE), ethyl tertiary-butyl ether(EtBE), tertiary-amyl
<br /> methyl ether(TAME), 1,2-dichloroethane, (1,2-DCA), 1,2-dibromo ethane (EDB),
<br /> ethanol, and methanol
<br /> In March 1995, Groundwater Technology installed three monitoring wells (MW-1, 2,
<br /> and 3) onsite to approximately 50 feet below ground surface (bgs), and one soil boring
<br /> (SB-1) to 35 feet bgs Soil analytical results indicated no detectable levels of TPHg in
<br /> soil bonngs for wells MW-1 and MW-2 Concentrations of TPHg in MW-3 soil were
<br /> reported at 3 8 and 250 milligrams per kilogram (mg/kg) at 25 and 35 feet bgs,
<br /> respectively Soil boring SB-1 test results indicated TPHg concentrations of 4 2 and 28
<br /> mg/kg at 30 and 35 feet bgs, respectively Generally, aromatic hydrocarbons including
<br /> benzene, toluene, ethylbenzene and xylene were reported for soil samples collected from
<br /> the 20 to 25-foot depth range near the former underground storage tank area (i e SB-1)
<br /> and in the 30 to 35 foot depth range, (i e MW-3) consistent with the first occurrence of
<br /> groundwater Metals analyses results for soil samples from MW-1 indicated
<br /> concentrations of chromium, lead, nickel and zinc at 23, 7 8, 21, 50 mg/kg (10 feet bgs)
<br /> and 31, 6 5, 42, and 59 mg/kg (35 feet bgs), respectively
<br /> Quarterly sampling of monitoring wells MW-1 through MW-3 has been performed
<br /> since May 1995 Dissolved concentrations of TPHg in MW-1 increased from 340 to
<br /> 5,900 micrograms per Liter (gg/L) during this period Dissolved benzene
<br />• concentrations in MW-1 have also increased from 67 gg/L in May 1995 to 1,100 gg/L
<br /> in August 1997 Review of MW-1 analytical results also suggests an increasing trend in
<br /> 1,2 dichloroethane (DCA) Analytical results for MW-2 have consistently indicated no
<br /> detectable concentrations of TPHg, BTEX, and MtBE Review of analytical results for
<br /> MW-3 suggests a decreasing trend of hydrocarbon concentrations between May 1995
<br /> and August 1997, from 44,000 µg/L to 7,100 µg/L TPHg, and 2,900 gg/L to 800 gg/L
<br /> benzene respectively
<br /> On September 9, 1996, Touchstone Developments oversaw the excavation and removal
<br /> of three USTs, three hydraulic hoists, product dispensers, and associated product lines
<br /> Soil samples collected from beneath the former USTs, hydraulic hoists, product piping,
<br /> and dispenser locations were analyzed for TPHg and BTEX Hydrocarbon
<br /> concentrations reported for soil samples collected from beneath the former southern
<br /> product island (P6)were 3,000 mg/kg TPHg, and 2 6, 20, 47, and 240 mg/kg BTEX
<br /> components, respectively, at 3 5 feet bgs On September 11, 1996, soils near the former
<br /> locations of the USTs,product dispensers, and product lines associated with these test
<br /> results were removed by excavation Results for additional samples collected and
<br /> analyzed following soil excavation suggest remnant hydrocarbon concentrations
<br /> underlying the former southern product island of 1,700 ppm TPHg and 3 2 ppm benzene
<br /> at 6 feet bgs, and 1,300 ppm TPHg and 14 ppm benzene at 7 feet bgs west of the
<br /> southern product island
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