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Appendix B:Previous Environmental Activities
<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 concentrations were detected in these samples at 450 and 200 µg/L, respectively.
<br /> Several PAHs were also detected in groundwater samples from SB-13 and SB-14. TPHd, TPHg,
<br /> benzene, naphthalene, and phenanthrene were detected in the grab groundwater sample from
<br /> SB-17 at concentrations of 150,000, 480, 0.6, 0.2, and 0.1 gg/L, respectively.
<br /> SAIC collected one soil sample from SB-15 at 47 feet bgs to define the vertical extent of affected
<br /> soil off site. TPHc, TPHg, BTEX, and MTBE were not detected in this soil sample, and thus the
<br /> 1 vertical extent of affected soil was defined at this depth.
<br /> SAIC searched DWR files in April 2004 and identified three domestic wells located within
<br /> 2,000 feet of the former HPP-BTR pipelines adjacent to the Hunter Container facility. One of
<br /> ' the domestic wells was located up gradient of the former pipeline alignments, and two were
<br /> located cross gradient, approximately 1,000 feet and 1,500 feet away. The well completion
<br /> reports indicated two domestic wells were constructed with minimum sanitary seals extending to
<br /> ' 20 feet bgs. The well completion report of the third well did not indicate a seal depth. One
<br /> industrial well may be located in the vicinity of the Site,but the exact location was unspecified.
<br /> Municipal or agricultural water-supply wells were not identified during the DWR search, but two
<br /> ' wells were described on well completion reports as public wells and were located at the Site.
<br /> One well is sealed from the surface to 150 feet, and the other to 200 feet. The DWR search did
<br /> not yield records of domestic wells down gradient(east)of the Site.
<br /> 1 SAIC concluded that the data collected during this and previous investigations indicated that
<br /> residual petroleum had affected soil between 5 and 42 feet bgs in the vicinity of SB-17, MW-1,
<br /> ' SB-1, SB-2, SB-3, B-1, B-4 through B-7 (MW-2), GMX-3, GMX-8, GMX-1B, and GMX-12. In
<br /> SB-17, clay and sandy layers below 37 feet bgs appeared to be the most affected. The lateral
<br /> extent of affected soil appeared to be delineated towards the south, west,north, northeast, and
<br /> 1 east. However, the lateral extent of affected soil southeast of the former OVP and TAOC
<br /> alignments and SB-17 was not fully characterized. The area northeast of GMX-6 had likely been
<br /> affected by a refined-fuel plume as a result of a leaking UST at the former Union Oil Service
<br /> ' Station at the eastern corner of Welty Road and Highway 33. The service station operated from
<br /> 1972 to the mid 1980s.
<br /> SAIC 2007 MONITORING WELL DESTRUCTION EVALUATION
<br /> ' In September 2007, SAIC used the following criteria to evaluate historical groundwater
<br /> monitoring well sampling analytical results to determine whether monitoring wells may be
<br /> 1 destroyed:
<br /> 1. COPCs in a well must be less than WQOs and San Francisco Bay RWQCB
<br /> Environmental Screening Levels (ESLs) 13 for at least last four sampling events; or
<br /> ' 13.San Francisco Bay RWQCB,2008 Screening for Environmental Concerns at Sites with Contaminated Soil and Groundwater
<br /> (Interim Final). May.
<br /> B-5
<br /> SAIE
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