SITE INFORMATION AND CORRESPONDENCE

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No Further Action Required Request Report Tracy Byron Road-Tracy,California December 1,2011 SAIC estimated the total potential cancer risk to a hypothetical construction worker from oral, dermal and inhalation exposures to on-site soil in Area 3 to be 4E-07. This level of cancer risk is below the de minimis level of 1 E-06. SAIC estimated the total potential non-cancer hazard from oral, dermal, and inhalation exposures ' to on-site soil to be 0.0004 in Area 1 and 0.005 in Area 2. These levels of hazard are significantly less than a hazard index of 1,and therefore indicate an acceptable non-cancer health hazard for exposures to on-site soil for a hypothetical resident. SAIC also estimated the total potential non-cancer hazard from oral,dermal,and inhalation exposures to on-site soil for a potential construction worker in Area 3 to be 0.04,which is also less than a hazard index of 1, and indicates an acceptable non-cancer health hazard for a potential construction worker. ' SAIC queried the California Natural Diversity Database(CNDDB), maintained by the California Department of Fish and Game(DFG),to search for threatened, endangered, or sensitive species in the vicinity of the Site. The database report identified two threatened species near the Site within the Union Island Quad: seven occurrences of the Alameda whipsnake at or beyond the 1-mile radius from the Site, and three occurrences of Swainson's hawk just inside or beyond the 1-mile radius from the Site. The Swainson's hawk prefers open prairie habitat and agricultural 1 fields where it can feed on insects and small rodents. Although the northern portion of the Site currently meets these criteria,the property is within the sphere of influence of the City of Tracy's General Plan. The General Plan notes that this area will be developed for industrial,commercial, ' and office uses near Interstate 205,with some low-density residential uses located farther from the highway(City of Tracy, 2004). Therefore, future development is not likely to provide adequate habitat for the Swainson's hawk. This assessment indicates that a threat to sensitive ecological receptors does not appear to exist(DFG, 2011). Estimated on-site residential cancer risk exceeds the de minimis level in Area 1, but is at the lower end of the risk management range of 1E-06 to IE-04, and non-cancer health hazards are well below the de minimis level. Estimated on-site cancer risk is below the de minimis level in Areas 2 and 3. A construction worker scenario was utilized in the evaluation of Area 3. These are conservative estimates of risk. The results of this HHSE indicate that exposure to chemicals in soil at the Site should not result in unacceptable health risks for an adult or child on-site resident in Areas 1 and 2, or for a construction worker in Area 3. The ecological screening evaluation suggests there is no suitable habitat for any threatened species at the Site. Therefore, no remedial action is necessary at the Site to protect human or ecological health, and a risk management decision of no further action can be made for on-site affected soil (SAIC, 2011; Appendix B.4). The Central Valley RWQCB concurred with the findings of the HHSE and supporting documentation that the Site is a candidate for closure,and recommended separate soil and ' groundwater management plans be developed and implemented for each area, for use if future construction activities require management of affected soil and groundwater at the Site. The Central Valley RWQCB also requested preparation of this NFAR Request Report (Central Valley RWQCB, 2011; Appendix D). 3 SAIC