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Peter MacNicholl <br /> Page 3 <br /> May 17, 2006 <br /> - All hotspots have been delineated and appropriate remedial actions have <br /> been/will be implemented. <br /> - Soil confirmational data will be included in the updated HHRA. <br /> - The updated HHRA will be used to provide general information on potential <br /> human health risk from exposure to COPCs in soil onsite. <br /> 3. Sampling Locations and Chemicals of Potential Concern: The Draft SAP states <br /> that soil boring locations are designed based on previous site investigation results and <br /> potential human activities onsite, e.g. open ground near buildings and traffic areas. Soil <br /> samples will be analyzed for COPCs and chemicals of concern (CDCs) previously <br /> identified. <br /> 3.1. Exposure Area 1: According to Figure 5, among the 12 soil borings located on EA1, <br /> soil samples collected from 4 locations will be subjected to polycyclic aromatic <br /> hydrocarbon (PAH) analysis (in addition to volatile organic chemical-VOC and metal <br /> analyses). The four proposed soil borings are located in the southern boundary of EA1 <br /> (southern boundary of the Central Area). The Draft SAP provides no spatial information <br /> of previously identified COPCs onsite. HERD recommends including a figure in the <br /> SAP detailing previous site investigation results, especially locations of COPCs <br /> detected and the rationale for the four selected locations. <br /> 3.2. Exposure Area 2: All soil samples collected from EA2 will be subjected to VOC, <br /> metal and pesticide analyses. Considering the pesticide mix area (S-1) and Site 26 <br /> (lead and hexavalent chromium as COCs) located nearby, HERD concurs with the <br /> proposed sampling plan for the area. <br /> 3.3. Naphthalene: We understand that the site has been fully characterized and the <br /> Draft SAP is designed to fill soil data gaps for an updated HHRA. Therefore, only <br /> previously identified COPCs and CDCs will be included in the chemical analysis plan. <br /> However, due to recent changes in toxicity criteria, some chemicals which were not <br /> previously identified as COCs due to their low concentrations may become COCl. For <br /> example, Cal/EPA recently adopted an inhalation cancer slope factor (CSF;) for <br /> naphthalene and recommend using the CSF; for evaluation of ingestion exposure based <br /> on route-to-route extrapolation. Considering the relatively high cancer slope factor of <br /> naphthalene, the relative high volatility of the chemical (the chemical is considered as a <br /> VOC), and the presence of PAHs and petroleum products onsite, we recommend <br /> including naphthalene as a COPC in the chemical analysis of soil and soil gas samples. <br /> 4. Physical Parameters of Soil: In order to provide a site-specific vapor intrusion risk <br /> evaluation, the Draft SAP proposes collecting site-specific soil parameters like moisture <br /> content and relative carbon content in soil. HERD recommends also collecting other <br /> physical parameters of the soil onsite (e.g. soil type, soil porosity, and bulk soil density <br /> etc.) to provide site-specific inputs for the vapor intrusion modeling. <br />