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HUMAN HEALTH SCREENING EVALUATION <br /> FORMER VERNALIS PUMP STATION <br /> 1. INTRODUCTION <br /> The Benham Companies, LLC, an SAIC Company(SAIC-Benham)performed this Human <br /> Health Screening Evaluation (HHSE) for the former Vernalis Pump Station(the site) located in <br /> Vernalis, San Joaquin and Stanislaus counties, California (Figure 1). SAIC-Benham performed <br /> this HHSE on behalf of Chevron Environmental Management Company(CEMC). <br /> The Central Valley Regional Water Quality Control Board(RWQCB) is the lead regulatory <br /> agency for environmental issues related to former crude-oil operations at the site. Investigations <br /> have been conducted at the site since 1995, and groundwater monitoring and sampling were <br /> conducted at the site between 1998 and 2008. In a November 2008 letter, the Central Valley <br /> RWQCB agreed that adequate groundwater monitoring data had been collected from the site, and <br /> requested that a human health risk assessment be conducted (Central Valley RWQCB, 2008; <br /> Appendix A). SAIC-Benham prepared this HHSE in response. <br /> SAIC-Benham performed this HHSE determine the potential human health cancer risks and non- <br /> cancer health hazards associated with exposure to soil and groundwater residuals from historical <br /> crude-oil pump station operations for hypothetical future residential land use of the site. The <br /> results of this HHSE will be used to develop a remedial strategy for the site, if necessary. SAIC- <br /> Benham developed this HHSE using approaches and methodology consistent with those <br /> presented in the Preliminary Endangerment Assessment(PEA) Guidance Manual (California <br /> Environmental Protection Agency [Cal/EPA] Department of Toxic Substances Control [DTSC], <br /> 1999). <br /> The PEA screening evaluation methodology conforms to standard regulatory human health risk <br /> assessment guidelines promulgated by Cal/EPA and the United States Environmental Protection <br /> Agency(EPA) for the performance of health risk assessments. Evaluating potential risks to <br /> human health using the PEA Manual's HHSE procedure is consistent with CEMC's Consistent <br /> Technical Approach(CTA)prepared by Geomatrix Consultants, Inc. (Geomatrix, 2005). It <br /> should be noted that the screening evaluation likely overestimates the risks associated with the <br /> conditions of the site as the evaluation was based on conservative default assumptions. SAIC- <br /> Benham used default assumptions (i.e., residential land-use scenario) to ensure that the <br /> evaluation was performed in a health-protective, conservative manner. If necessary and <br /> appropriate, a site-specific human health risk assessment may be performed at a later date to <br /> further refine the estimate of potential health risks. <br /> 1.1 SYNOPSIS <br /> SAIC-Benham evaluated health risks to hypothetical future residents and the potential threat to <br /> sensitive ecological receptors from exposure to soil in a residential land-use scenario at the site. <br /> Shallow groundwater is unlikely to be used as a drinking-water source at the site; therefore, it <br /> was not evaluated quantitatively in this HHSE. The results of this HHSE indicate that the site <br /> does not pose a health risk to future residents and that there are no sensitive ecological receptors <br /> within I mile of the site; therefore, no further action is required with respect to on-site soils. <br /> ffm#� <br /> I ��ZZ The Benham Companies,LL[ <br /> ...frtj`® A Wholly Owned Subsidiary <br /> From&mxe to Solanoss <br />