ARCHIVED REPORTS_HUMAN HEALTH SCREENING EVALUATION 2012

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Human Health Screening Evaluation US Can—Welty Road March 19,2012 SAIC estimated cancer risks and non-cancer hazards from exposure to on-site soils and groundwater using algorithms and the screening-level model developed by Cal/EPA DTSC, which were based on EPA, Cal/EPA, and DTSC guidance and methodology. The equations evaluated exposures to soils by dermal, oral, and inhalation exposure routes using health- protective, conservative reasonable maximum exposure parameters. SAIC used the screening- level model to evaluate exposures to groundwater by inhalation of VOCs, also using health- protective, conservative reasonable maximum exposure parameters. Additionally, cancer and non-cancer toxicity values promulgated by Cal/EPA OEHHA and EPA (IRIS)were used to quantitatively estimate potential risk and hazards. Therefore, it is unlikely that the risks and hazards estimated during the development of this HHSE are significantly underestimated. Considering the conservative and health-protective assumptions used to develop this HHSE, it is likely that the actual cancer risks and non-cancer hazards for a potential resident will be much lower than those presented here. 6. HUMAN HEALTH SCREENING EVALUATION CONCLUSIONS On-site residential cancer risk of 2E-06 is at the lower end of the risk management range of 1 E-06 to 1 E-04 established by Cal/EPA and EPA. Non-cancer health hazards of 0.02 are well below the de minimis level. SAIC evaluated the uncertainties in this HHSE and determined that they have been reduced to an acceptable level. The results of this HHSE indicate that exposure to chemicals in soil at the Site should not result in unacceptable health risks for a potential adult or child on-site resident. 7. ECOLOGICAL SCREENING EVALUATION 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 database record from this CNDDB query is included as Appendix F. 8. RECOMMENDATIONS 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 EPA. Potential non-cancer health hazards are below the de minimis levels. The results of this HHSE indicate 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, no remedial action is necessary at the Site to protect human or ecological health, and a risk management decision of no further action required can be made for on-site affected soils and groundwater. 14 SAIE