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<br /> Former Countryside Market,Stockton, California
<br /> Feasibility Study and Interim Remedial Action Plan May 20,2013
<br /> ethylbenzene, and total xylenes at concentrations of 14,000 mg/kg, non-detect (<0.005 mg/kg), 37
<br /> mg/kg, 78 mg/kg, and 340 mg/kg, respectively. The excavation was backfilled with clean stockpiled
<br /> soil and clean pea gravel (UEC, 1995).
<br /> In August 2001, two soil borings (CM-1 and CM-2) were completed on I Site at locations shown on
<br /> Figure 2. Boring CM-1, located between the dispenser island and the former USTs, was advanced to
<br /> 90 feet bgs. Boring CM-2, located approximately 25 feet south of CM-1, was completed to a depth of
<br /> 50 feet bgs. During the completion of boring CM-1, groundwater was encountered at a depth of
<br /> approximately 90 feet bgs. TPHg was detected above the laboratory reporting limit in all eight soil
<br /> samples collected from baring CM-1, including a maximum concentration of 15,000 mg/kg in the
<br /> sample collected from 50 feet bgs. Boring CM-2 yielded TPHg above the laboratory reporting limit in
<br /> one of four analyzed soil samples at a concentration of 590 mg/kg in the sample collected from 50
<br /> feet bgs (UEC, 2001).
<br /> During the August 2001 environmental investigation, one grab groundwater sample was collected
<br /> from boring CM-1 and analyzed for TPHg, BTEX compounds, MtBE, tertiary butyl alcohol (TBA),
<br /> diisopropyl ether (DIPE), ethyl tertiary butyl ether(EtBE), tertiary amyl m hyl ether(TAME), EDB, and
<br /> 1,2-dichloroethane (1,2-DCA). TPHg, BTEX compounds and TBA were letected at concentrations of
<br /> 62,000 micrograms per liter (Ng/L), 5,500 pg/L, 10,000 pg/L, 2,900 pg/l., 8,300 pg/L, and 230 pg/L,
<br /> respectively (UEC, 2001). No other analytes were detected above tie corresponding laboratory
<br /> reporting limits. Soil and groundwater analytical results are presente in SGI's Site Investigation/
<br /> Fourth Quarter 2012 Groundwater Monitoring and Sampling Report, date i February 8, 2013.
<br /> A Site investigation was completed during the fourth quarter 2011 and first quarter 2012. The
<br /> investigation included the installation of five monitoring wells (MW-1 through MW-5), a sensitive
<br /> receptor survey, and domestic well sampling. Petroleum hydrocarbons were detected in monitoring
<br /> wells MW-1, MW-2 and MW-5, and 1,2-DCA was detected in the domestic well located at 10967
<br /> Copperopolis Road. No other compounds were detected above the laboratory Method Reporting
<br /> Limit in any of the domestic wells, although benzene was detected at a J-flag value of 0.22 pg/L
<br /> (i.e., above the laboratory Method Detection Limit) in the domestic wells located at 10757 and 10967
<br /> Copperopolis Road. The results are presented in SGI's Site In estigation Report and Site
<br /> Investigation Work Plan, dated July 16, 2012.
<br /> In response to the domestic well sampling results, SGI installed a w llhead treatment system at
<br /> 10967 Copperopolis Road during late November and mid-December 20 2. The system includes two
<br /> 200 pound granular activated carbon vessels and isolation valves to al ow for carbon filtration back
<br /> washing. System installation details and related sampling activities are provided in SGI's Wellhead
<br /> Treatment Memorandum, dated February 22, 2013.
<br /> SGI completed another Site investigation during the fourth quarter 2012 that included the installation
<br /> of two additional monitoring wells (MW-6 and MW-7), and the collection of grab groundwater samples.
<br /> Results of the investigation activities helped to define the horizontal extent of the petroleum
<br /> F..,bllAy S"&I P_Te Fh.l.dx 2-2 The Source Group,Inc.
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