SITE INFORMATION AND CORRESPONDENCE

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J&L Market • - 3 - • 8 May 2013 8125 S. EI Dorado St., French Camp San Joaquin County significantly and full scale ozone remediation was not implemented. However during the last scheduled monitoring event in June 2011, eighteen months after the ozone pilot study, groundwater concentrations increased significantly at JLM5 (north of the station building) to levels approaching the pre-remediation levels of 2009 at JLM13. Additional groundwater monitoring was conducted to determine if a new USTs release had occurred. By March 2012, there was no evidence of a new release (included reviews of inventory reconciliation and USTs system sensor logs, and no reported drive-off spill) as concentrations were declining in JLM5 over two sampling events. The June 2011 spike in groundwater concentrations was attributed to groundwater rising and contacting residual soil contamination present at 20' bgs under the station building, due to the extremely wet 2010/2011 winter that caused water levels to rise onsite to the highest water levels recorded since groundwater monitoring began in 2002. Also note that monitoring well JLM5 is actually much closer to the station building than depicted in Figure 3, and the over-excavation to 30' below ground surface (bgs) was above the water table in 1995. Groundwater monitoring was suspended in March 2012 with staff concurrence, pending submittal of closure documents. Risk Assessment Two soil results (Figure 2) for TPHg (over-excavation confirmation sample P-15, 4,200 mg/kg west wall of excavation at 12.5' bgs, and the 2001 boring JLM2, 1,300 mg/kg at 20' bgs, Figure 2), taken in November 1995 and November 2001, respectively, exceeded the San Francisco Bay Regional Board Environmental Screening Levels (ESLs) for gross contamination and direct contact. P-15 and JLM2 were located below typical construction worker exposure depth. In February 2003, weathered TPHg was detected at JLM9 (8.2 mg/kg at 17' bgs) in a slanted boring under the station building. Even though the station is an active fueling facility that is exempt from a vapor intrusion evaluation under the low risk closure policy (LTCP), a soil gas survey was not required for closure, prior to implementation of the LTCP. Based on nearly 18 years since over-excavation removed the majority of soil contamination down to 30' bgs, with the depth to groundwater in excess of 20' bgs, and with the open bay construction of the station, there is a low threat of potential vapor intrusion due to residual soil and groundwater contamination. The groundwater plume is well defined both vertically and laterally (Figure 13). The plume is stable and has remained onsite, TPHg and BTEX have significantly declined at JLM5, and 1 , 2-DCA is declining very slowly at JLM13. Nearby domestic and irrigation supply wells are not threatened by the release. Groundwater concentrations will continue to decline, with Water Quality Goals estimated to be reached in 28 years. Sensitive Receptor Survey A 2011 sensitive receptor survey (ATC Figures 4 and 5, and Table 3) identified approximately 48 domestic supply wells and 5 public supply wells located within 2,000' of the Site. The four nearest wells are 200' to the northeast (domestic) and the southeast (domestic), and 400' to the north (irrigation) and to the east-northeast (domestic) of the Site. None of the wells are threatened by the petroleum hydrocarbons release at this Site.