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Appendix C:Previous Environmental Activities
<br /> not detected in the soil samples analyzed. The presence of TPHg,benzene, and naphthalene in
<br /> GMX-6 was likely from the adjacent former Union Oil Service Station, and not from the former
<br /> Old Valley Pipeline(OVP)or Tidewater Associated Oil Company (TAOC)pipelines.
<br /> GEOMATRIX 2002 SOIL AND GROUNDWATER INVESTIGATION'
<br /> On May 20 and 21, 2002, Geomatrix advanced three soil borings (GMX-8, GMX-9, and
<br /> GMX-1B) at the site to further assess the extent of affected soil and groundwater. TPHc were
<br /> detected in soil from GMX-8 at concentrations of 8,000 mg/kg at 5 feet bgs and 1,200 mg/kg at
<br /> 55 feet bgs, and at 5,100 mg/kg in GMX-1 B at 30 feet bgs. Benzene was detected only in
<br /> GMX-8 at a concentration of 0.067 mg/kg at 55 feet bgs. Toluene was detected in all samples at
<br /> concentrations ranging from 0.006 to 0.58 mg/kg. Ethylbenzene concentrations ranged to
<br /> 0.87 mg/kg in GMX-8 at 55 feet bgs. Xylenes were reported up to 2.1 mg/kg in GMX-1B at
<br /> 30 feet bgs. Various PAHs were reported in the GMX-8 sample collected at 55 feet bgs, and in
<br /> the GMX-1B sample collected at 30 feet bgs.
<br /> GEOMATRIX 2003 OFF-SITE SOIL AND GROUNDWATER INVESTIGATION10
<br /> The Central Valley RWQCB requested additional off-site assessment, and Geomatrix
<br /> subsequently advanced three off-site soil borings(GMX-10,GMX-11, and GMX-12)between
<br /> the former HPP-BTR pipelines and Welty Road. TPHc were detected at a concentration of
<br /> 15,000 mg/kg in the soil sample from GMX-12 collected at 41.5 feet bgs. Benzene, toluene, and
<br /> total xylenes were also detected in soil from GMX-12. TPHd were detected in groundwater
<br /> samples collected from GMX-10, GMX-11, and GMX-12 at concentrations of 210, 3,600, and
<br /> 110 pg/L,respectively. Geomatrix recommended that a search of California Department of
<br /> Water Resources (DWR) files be conducted to identify water wells within 2,000 feet of the site.
<br /> SCIENCE APPLICATIONS INTERNATIONAL CORPORATION (SAIC) 2005 SOIL
<br /> AND GROUNDWATER INVESTIGATION"
<br /> On March 14 through 16, 2005, SAIC advanced of four soil borings (SB-13, SB-14, SB-15, and
<br /> SB-17) and installed one groundwater monitoring well(MW-5)to further assess the extent of
<br /> affected soil and groundwater in the area of the former HPP-BTR pipelines. Additionally, DWR
<br /> files were searched to identify water wells within 2,000 feet of the site.
<br /> TPHc, TPHg, BTEX, and methyl tertiary butyl ether(MTBE)were not detected in the soil
<br /> samples from SB-13, SB-14, and SB-15, except for 120 mg/kg TPHc detected in SB-14 at 1 foot
<br /> bgs. TPHc, TPHg, ethylbenzene, and xylenes were detected in SB-17 at 42 feet bgs at
<br /> concentrations of 6,700, 510, 0.2, and 2.9 mg/kg,respectively. Minor concentrations of PAHs
<br /> were detected in all of the borings. Laboratory results indicated non-detect or low concentrations
<br /> of TPHc, TPHg, BTEX, and PAHs in soil at SB-17 from 1 and 5 feet bgs.
<br /> TPHg, BTEX, and MTBE were not detected in grab groundwater samples from SB-13 and
<br /> SB-14. TPHd were detected in these samples at concentrations of 450 and 200 gg/L,
<br /> 8. Central Valley RWQCB,2007. Water Quality Control Plan(Basin Plan)for the Sacramento River Basin and the San
<br /> Joaquin River Basin,4th ed. October.
<br /> 9. Geomatrix,2002. Report of Soil and Groundwater Investigation, US Can/Welty Road, Vernalis, California. August.
<br /> 10.Geomatrix,2003. Report of Off-site Soil and Groundwater Investigation, US Can/Welty Road, Vernalis, California.
<br /> November.
<br /> 11.SAIC,2005. Soil and Groundwater Investigation Report and Second Quarter 2005 Monitoring and Sampling at
<br /> US Can—Welty Road,35275 Welty Road, Vernalis, California. October.
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