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Well Abandonment and Soil and Groundwater Investigation Work Plan
<br /> US Can-Welty Road September 2007
<br /> Stained soil and hydrocarbon odor was observed in borings GMX-1, GMX-3,and GMX-6 at depths
<br /> ranging from 15.5 to 51.5 feet bgs. TPH quantified as crude oil(TPHc)was detected in soil at a
<br /> concentration of 10,000 mg/kg at 37 feet bgs at GMX-3,and eight PAHs were detected at concentrations
<br /> ranging from 0.007 to 0.55 mg/kg.
<br /> No TPHd,TPHg,PAHs,or BTEX were detected in the groundwater sample collected form WFSMW-1.
<br /> TPHg and TPHd were detected in the groundwater sample from boring GMX-6 at concentrations of 110
<br /> and 92 µg/L,respectively.
<br /> Geomatrix concluded that TPHd in down-gradient groundwater samples was either non-detect or below
<br /> WQOs. The presence of TPHg,benzene,and naphthalene in the GMX-6 was likely from the adjacent
<br /> former gasoline station and not from the OVP or TAOC pipelines.
<br /> Soil and Groundwater Investigation(Geomatrix,2002). On May 20 and 21,2002,Geomatrix
<br /> advanced three soil borings(GMX-8,GMX-9, and GMX-IB)from which soil and groundwater samples
<br /> were collected and tested by a laboratory,to further assess the extent of affected soil and groundwater.
<br /> TPHc was detected in soil of GMX-8 at concentrations of 8,000 at 5 feet bgs and 1,200 mg/kg at 55 feet
<br /> bgs,and at a level of 5,100 mg/kg in GMX-1B at 30 feet bgs. Benzene was detected only in GMX-8 at a
<br /> concentration of 0.067 mg/kg at 55 feet. Toluene was detected in all samples,ranging to 0.58 mg/kg.
<br /> Ethylbenzene 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-IB at 30 feet bgs. Various PAHs were reported in the GMX-8 sample collected at 55
<br /> feet bgs,and in the GMX-1B sample collected at 30 feet bgs.
<br /> Off-Site Soil and Groundwater Investigation (Geomatrix,2003). Because the RWQCB requested
<br /> additional off-site assessment,Geomatrix on August 4 and 5,2003 advanced three off-site soil borings
<br /> (GMX-10,GMX-11,and GMX-12)and obtained soil and groundwater samples for analytical testing.
<br /> TPHc was detected in the soil sample from boring GMX-12 collected at 41.5 feet bgs at a concentration
<br /> of 15,000 mg/kg. Benzene,toluene,and xylenes were also detected in soil of GMX-12.TPHd was
<br /> detected in groundwater samples collected from GMX-10, GMX-11,and GMX-12 at concentrations of
<br /> 210,3,600,and 110 µg/L,respectively. Geomatrix recommended that a search of California Department
<br /> of Water Resources(DWR)files be conducted to identify water wells within 2,000 feet of the site.
<br /> Soil and Groundwater Investigation (SAIL,2005). On March 14 through 16,2005, SAIC supervised
<br /> the drilling of four soil borings(SB-13, SB-14, SB-15,and SB-17)and the installation of one
<br /> groundwater monitoring well(MW-5),to further assess the extent of affected soil and groundwater at the
<br /> site. Additionally,DWR files were searched to identify water wells within 2,000 feet of the site.
<br /> No TPHc,TPHg,BTEX,or MTBE was detected in the soil samples from SB-13, SB-14,and SB-15,
<br /> except 120 mg/kg TPHc in SB-14 at 1 foot bgs. TPHc,TPHg,ethylbenzene,and xylenes were detected
<br /> in SB-17 at a depth of 42 feet bgs at concentrations of 6,700, 510,0.2,and 2.9 mg/kg. Low levels of
<br /> PAHs 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 depths of 1 and 5 feet bgs.
<br /> TPHg,BTEX, or MTBE were not detected in grab groundwater samples from SB-13 and SB-14. TPHd
<br /> was detected in these samples at concentrations up 450 and 200 pg/L,and several PAHs were also
<br /> reported for groundwater samples from SB-13 and SB-14. TPHd,TPHg,benzene,naphthalene and
<br /> phenanthrene were detected in the grab groundwater sample from SB-17 at concentrations of 150,000,
<br /> 480,0.6, 0.2,and 0.1 µg/L,respectively.
<br /> To define the vertical extent of affected soil off site, SAIC collected one soil sample from boring SB-15 at
<br /> 47 feet bgs. TPHc,TPHg, BTEX, or MTBE were not detected in this soil sample and thus,the vertical
<br /> extent of affected soil has been defined at this depth.
<br /> In April 2004, SAIC searched DWR files,and three domestic wells were located within the 2,000-foot
<br /> search radius. One of the domestic wells was located up gradient of the former pipeline ROW, and two
<br /> are located cross gradient,approximately 1,000 feet and 1,500 feet away. The well completion reports
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