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No Further Action Required Request Report US Can—Welty Road September 24, 2013 SAIC estimated total potential cancer risk to a hypothetical resident from oral, dermal, and inhalation exposures to on-site soils to be 2E-06. This level of risk is within the lower end of the risk management range of 1E-06 to 1E-04 established by Cal/EPA and DTSC. This is a conservative estimate of risk, and actual risks are believed to be significantly lower. SAIC estimated the total potential non-cancer hazard index from oral, dermal, and inhalation exposures to on-site soils to be 0.02. This level of hazard is far less than a hazard index of 1, and therefore indicates an acceptable non-cancer health hazard for exposures to on-site soils for a hypothetical resident. SAIC queried the California Natural Diversity Database(CNDDB; California Department of Fish and Game, 2011)to search for threatened, endangered,or sensitive species in the vicinity of the Site. The database report identified six threatened or endangered species in the surrounding vicinity of the Site: the San Joaquin kit fox, Swainson's hawk,western yellow-billed cuckoo, delta button-celery, riparian(San Joaquin Valley) woodrat, and the riparian brush rabbit. Of the identified species,there were no occurrences within 1 mile of the Site. The closest occurrence was a Swainson's hawk identified in 2003, approximately 1.6 miles northwest of the Site. This assessment indicates that a threat to sensitive ecological receptors does not appear to exist. The estimated excess lifetime cancer risk of 2E-06 for potential on-site residents is within the lower end of the risk management range of 1 E-06 to 1 E-04 established by Cal/EPA and the EPA. Potential non-cancer health hazards are below the de minimis levels. The results of the HHSE indicated that exposure to chemicals present in on-site soils and groundwater at the Site should not result in unacceptable health risks for a potential adult or child resident. The ecological screening evaluation indicated that threatened or endangered species have not been historically observed within 1 mile of the Site. Therefore, SAIC concluded no remedial action is necessary at the Site to protect human or ecological health, and a risk management decision of NFAR can be made for on-site affected soils and groundwater. The Central Valley RWQCB concurred with the findings of the HHSE and supporting documentation that the Site is a candidate for closure, and recommended that a soil and groundwater management plan(SGMP)be developed. The Central Valley RWQCB also requested preparation of this NFAR Request Report(Appendix D; Central Valley RWQCB, 2012). 3. TRI-REGIONAL RECOMMENDATIONS FOR A NO FURTHER ACTION REQUIRED REQUEST REPORT Section 3.1 provides information outlined in section 6.5 of the Tri-Regional Recommendations to support the request for closure at this low-risk site with TPH in groundwater at levels above WQOs, including discussions of plume-size stability, the timeframe projected to meet WQOs, and verification that there are no current or anticipated uses of the affected groundwater. Section 3.2 supports a decision by the Central Valley RWQCB to issue an NFAR letter with the documentation requirements outlined in section 6.6 of the Tri-Regional Recommendations. A completed Checklist of Required Data for No Further Action Requests is provided in Table 1. 3 SAIE