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During the Second Quarter 2009 monitoring event TBA was detected in wells MW-5 and MW-7 at concentrations of 23 µg/l, and 35 µg/L, respectively. The TBA concentrations reported in these wells during the May 2009 event are inconsistent with previous and subsequent monitoring event data, which reports TBA below the laboratory reporting limit. As such,TRC considers the TBA results from the Second Quarter 2009 monitoring event to be anomalous and not representative of Site groundwater. 4.0 WATER QUALITY OBJECTIVES No definitive cleanup goals have been established for TPH-d for this Site. The Central Valley Regional Water Quality Control Board (CVRWQCB) recommends (in Appendix A of the Tri- Regional Board Staff Recommendations for Preliminary Investigation and Evaluation of Underground Tank Sites) application of the USEPA Superfund Provisional Reference Dose of 56-140 µg/L as the water quality limit(CVRWQCB, 2004). This water quality objective is very conservative and intended to protect existing or potential sources of drinking water.According to the San Joaquin County Community Development Department(SJCCDD), the Site is zoned as "limited industrial", meaning the zone is not designated for residential use (SJCCDD, 1992). The groundwater directly beneath the Site is not likely to be used in the future as municipal or domestic supply water; therefore TRC proposes a less stringent water quality objective, as described below. The San Francisco Bay Regional Water Quality Control Board(SFRWQCB)developed Environmental Screening Levels(ESLs)to address environmental protection goals. The ESL for TPH-d in groundwater with the potential to be used for drinking water is 210 µg/L. The ESL for deep soil(i.e., soils encountered at depth greater than to fbg) is 83 mg/kg(SFRWQCB, 2008). These ESLs are proposed to be used as the water quality objectives and soil cleanup goals for the Site. Samples collected from Site wells were below the 210 µg/l,water quality objective for TPH-d (ESL) during the most recent sampling event; MW-5 was the only well reported to contain TPH-d above its laboratory reporting limit during this event( 170 µg/L; July 28, 2010). This concentration is below the recommended water quality objective for the Site. Furthermore, as noted in Figure 8, the projected level of TPH-d in this well is expected to diminish below the upper limit of the USEPA's range of provisional Reference Doses for Superfund sites (i.e., 140 µg/L) in a matter of a few months. The projection of diminished concentrations is consistent with historical trends, and is likely attributable to the implementation of remedial actions at the Site and to natural biodegradation processes active in the subsurface. Since, as summarized above, these Reference Doses are recommended as water quality limits in the Tri-Regional guidelines (CVRWQCB, 2004), it is concluded that water quality objectives have essentially been achieved at this Site. 5.o MASS CALCULATION 5.1 Estimation of Hydrocarbons Removed During the 2005 excavation conducted by CSL Environmental, 10,403 tons of soils were removed from the Site. Based on a review of available soil analytical data from confirmation samples collected after the excavation, the 2005 excavation removed the vast majority soil contaminants. 7 i