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Human Health Screening Evaluation <br /> Mountain House Development Site#6 January 18,2011 <br /> low concentrations, below the Water Quality Objectives (WQOs; Central Valley RWQCB, 2007; <br /> Appendix C), in groundwater samples. The low concentrations of VOCs in groundwater <br /> samples indicate that the potential risks associated with this pathway are low; therefore, SAIC <br /> did not quantitatively evaluate the potential for vapor intrusion of volatile chemicals to indoor air <br /> from groundwater. <br /> SAIC quantitatively evaluated risk from exposure to COPCs through the exposure routes of <br /> incidental ingestion of soil and dermal contact with soil, inhalation of wind-blown dust for non- <br /> volatile constituents, and inhalation of chemical vapors from soils for volatile constituents <br /> (Figure 3). <br /> 3. CONSTITUENTS OF POTENTIAL CONCERN AND <br /> EXPOSURE CONCENTRATIONS <br /> The COPCs for the Site were identified during previous site investigations. All soil analytical <br /> data collected between 0 and 10 feet bgs during the previous investigations were utilized to <br /> evaluate exposure in this assessment. All of the Site soil analytical data are included in <br /> Appendix C. <br /> Condor and SAIC collected samples of on-site soil potentially affected by former OVP and <br /> TAOC operations, and submitted the samples for analysis of critical hydrocarbon constituents of <br /> crude oil identified in the PEA Guidance Manual. It should be noted that metals are not typically <br /> considered critical constituents of crude oil at former OVP and TAOC sites (SAIC, 2007; <br /> Appendix D); therefore, the soil samples were not analyzed for metals. <br /> The previous site investigations indicated that the on-site soil is affected by TPH and relatively <br /> low levels of BTEX and polynuclear aromatic hydrocarbons (PAHs). Two distinct areas of <br /> TPH-affected soil, Area 1 and Area 2, are shown on Figure 2. <br /> All analytes detected in at least one sample between 0 and 10 feet bgs are considered COPCs. <br /> Toluene and methylnaphthalenes were not detected in any soil samples; therefore, these analytes <br /> are not considered COPCs in soil. Benzene, ethylbenzene, xylenes, and PAHs are considered <br /> COPCs for the Site, and were evaluated quantitatively in this HHSE (Tables 1 and 2). <br /> 3.1 ON-SITE SOIL IMPACTS AND EXPOSURE CONCENTRATIONS <br /> Condor(2001) and SAIC (2008 and 2010) characterized impacts to on-site soils with regulatory <br /> oversight provided by the Central Valley RWQCB. The investigations specifically included the <br /> collection of on-site soil samples to support the development of this HHSE. Data of adequate <br /> analytical quality (e.g., low detection limits) were collected to support this HHSE. A total of <br /> 49 soil samples were collected from 0 to 10 feet bgs from 38 soil borings, and were used to <br /> evaluate risks and hazards. SAIC performed this HHSE after the Central Valley RWQCB was <br /> satisfied that the Site had been adequately characterized(Central Valley RWQCB, 2010). <br /> A summary of the analytical results for BTEX and PAHs for soil samples collected from 0 to <br /> 10 feet bgs are provided in Tables 1 and 2, respectively. <br /> SAIC calculated exposure point concentrations (EPCs) as the upper confidence limit (UCL) of <br /> the mean soil concentration for each of the COPCs. SAIC used an EPA statistical software <br /> program, ProUCL Version 4.00.05, to analyze the datasets provided in Tables 1 and 2. All <br /> COPCs had a high number of non-detect results. Therefore, as recommended in the ProUCL <br /> User's Guide (EPA, 2010a), nonparametric statistical methods were used to develop the EPCs <br /> 4 SAIL® <br /> from sukin?to Solvtloas <br />