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Human Health Screening Evaluation Mountain House Development Site#6 January 18,2011 conservative and health-protective assumptions used to develop this HHSE, it is likely that the actual on-site potential risks and hazards will be lower than those presented here. SAIC utilized a residential scenario in this assessment; however, the crude-oil affected soil and groundwater found at the Site are located primarily within and beneath the utility/highway corridor easements and beneath a portion of an adjacent agricultural field(Figure 2). In addition, three borings (SB-21, SB-22, and GP-152) contain the highest PAH concentrations, and thus account for a majority of the risk. These three borings are located in the utility/highway corridor, not on private property. 8. ECOLOGICAL SCREENING EVALUATION 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 five threatened or endangered species in the Clifton Court Forebay area: the California tiger salamander, vernal pool fairy shrimp, vernal pool tadpole shrimp, California red-legged frog, Swainson's hawk, and San Joaquin kit fox. Five occurrences of Swainson's hawk have been recorded at the edge of the 1-mile radius around the Site. The remaining species have not been observed near the 1-mile radius around the Site. This assessment indicates that a threat to sensitive ecological receptors does not appear to exist (CDFG, 2010). The database records from this CNDDB query are included as Appendix E. 9. RECOMMENDATIONS Potential on-site residential cancer risk exceeds the de minimis level, but is at the lower end of the risk management range of 1 E-06 to 1 E-04, and non-cancer health hazards are well below the de minimis level. This is a conservative estimate of risk. Additionally, a residential scenario was evaluated in this assessment; however, the crude-oil affected soil and groundwater found at the Site, and the soil boring data that contributed the greatest risk, lie primarily within and beneath the utility/highway corridor easements and beneath a portion of an adjacent agricultural field. 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. The ecological screening evaluation suggests there do not appear to be 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 soils. 10. REFERENCES Cal/EPA, 1999. Preliminary Endangerment Assessment Guidance Manual, Department of Toxic Substances Control. June. 2010a. Chronic Reference Level Exposure Database(internet database), Office of Environmental Health Hazard Assessment(OEHHA). July. 2010b. Toxicity Criteria Database(internet database), Office of Environmental Health Hazard Assessment(OEHHA). July. CDFG, 2010. California Natural Diversity Database. July. CDPH, 2004. Maximum Contaminant Levels (MCLS), (internet database). August. 12 FMM sclence to solvtioos