ARCHIVED REPORTS_HUMAN HEALTH SCREENING EVALUATION 2012

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Human Health Screening Evaluation US Can—Welty Road March 19,2012 the Ahern Road—Vernalis site. The Central Valley RWQCB concurred and determined that the extent of crude-oil affected groundwater at the Site has been adequately delineated(Central Valley RWQCB, 2011). A brief history of previous environmental investigations conducted at the Site is included as Appendix B. Analytical data from the previous investigations are included ' as Appendix C. 2. EXPOSURE PATHWAYS AND MEDIA OF CONCERN 1 SAIC constructed a conceptual site model (CSM)that identifies contaminant sources,release mechanisms,transport media, exposure pathways, exposure routes, and potential human receptors associated with the Site. SAIC evaluated an on-site residential land-use scenario for the Site as required in the PEA Guidance Manual. The CSM for the Site is shown on Figure 3. 2.1 SOIL SAIC evaluated direct soil exposure routes (incidental ingestion of soil and dermal contact with soil), and indirect exposure routes (inhalation of wind-blown dust for non-volatile constituents ' and inhalation of chemical vapors from soils for volatile constituents). The evaluation of risk associated with the soil exposure pathways in this HHSE is limited to the upper 10 feet of soil (approximately 3 meters), consistent with the residential land-use scenario as described in the PEA Guidance Manual. Only analytical results from soil samples collected between 0 and 10 feet below ground surface(bgs)have been included in this HHSE(Tables 1 and 2). 1 2.2 GROUNDWATER ' Four groundwater samples were analyzed for total dissolved solids (TDS) during the course of site investigations (Table 3). TDS concentrations in groundwater samples ranged from 779 milligrams per liter(mg/L; SB-25)to 1,280 mg/L(SB-44). The TDS concentrations in samples collected at the Site exceed five of the following current California Department of Public Health (CDPH)maximum contaminant levels (MCLs; CDPH, 2004) and RWQCB Water Quality Goals (WQG; RWQCB, 2008) for drinking water: • CDPH MCL: 500 mg/L, recommended. • CDPH MCL: 1,000 mg/L,upper. • CDPH MCL: 1,500 mg/L, short term. • RWQCB WQG, Criterion for Beneficial Use Designation of Municipal and Domestic ' Water Supply: 3,000 mg/L. • RWQCB WQG, CDPH, and EPA drinking water standards: 500 mg/L. ' • RWQCB WQG, Agricultural Water Quality Goal: 450 mg/L. • RWQCB WQG, EPA Ambient Water Quality Criteria for Taste and Odor or Welfare: 250 mg/L. The TDS results for groundwater at the Site do not exceed the criterion for beneficial use designation of municipal and domestic water supply(the screening level used during the 3 SAIC 1