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Appendix B: Previous Environmental Activities
<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 Hunter Container site to further assess the extent of affected soil and
<br /> groundwater. TPHc were detected in soil from GMX-8 at concentrations of 8,000 mg/kg at
<br /> 5 feet bgs and 1,200 mg/kg at 55 feet bgs, and at a level of 5,100 mg/kg in GMX-1B at 30 feet
<br /> bgs. Benzene was detected only in GMX-8 at a concentration of 0.067 mg/kg at 55 feet bgs.
<br /> Toluene was detected in all samples, ranging from non-detect to 0.58 mg/kg. Ethylbenzene
<br /> concentrations ranged to 0.87 mg/kg in GMX-8 at 55 feet bgs. Xylenes were reported up to
<br /> 2.1 mg/kg in GMX-1B at 30 feet bgs. Various PAHs were reported in the GMX-8 sample
<br /> collected at 55 feet bgs, and in the GMX-1B sample collected at 30 feet bgs.
<br /> GEOMATRIX 2003 OFF-SITE SOIL AND GROUNDWATER INVESTIGATIONS
<br /> The RWQCB requested additional off-site assessment, and Geomatrix subsequently advanced
<br /> three off-site soil borings (GMX-10, GMX-11, and GMX-12)between the former HPP pipelines
<br /> and Welty Road. TPHc were detected at a concentration of 15,000 mg/kg in the soil sample
<br /> ' from GMX-12 collected at 41.5 feet bgs. Benzene, toluene, and total xylenes were also detected
<br /> in soil from GMX-12. TPHd were detected in groundwater samples collected from GMX-10,
<br /> GMX-11, and GMX-12 at concentrations of 210, 3,600, and 110 µg/L, respectively. Geomatrix
<br /> recommended that a search of California Department of Water Resources (DWR) files be
<br /> conducted to identify water wells within 2,000 feet of the site.
<br /> SAIC 2005 SOIL AND GROUNDWATER INVESTIGATIONIo
<br /> On March 14 through 16, 2005, SAIC supervised the advancement of four soil borings (SB-13,
<br /> SB-14, SB-15, and SB-17) and the installation of one groundwater monitoring well (MW-5) to
<br /> further assess the extent of affected soil and groundwater in the area of the former HPP pipelines.
<br /> Additionally,DWR 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-detectable or low
<br /> concentrations 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 [Ig/L,
<br /> respectively. Several PAHs were also detected in groundwater samples from SB-13 and SB-14.
<br /> TPHd, TPHg, benzene, naphthalene, and phenanthrene were detected in the grab groundwater
<br /> sample from SB-17 at concentrations of 150,000, 480, 0.6, 0.2, and 0.1 µg/L, respectively.
<br /> 8. Geomatrix,2002. Report of Soil and Groundwater Investigation, US CanlWelty Road, Vernalis, California. August.
<br /> 9. Geomatrix,2003. Report of Off-site Soil and Groundwater Investigation, US CanlWelty Road, Vernalis, California.
<br /> November.
<br /> 10.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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