Laserfiche WebLink
Human Health Screening Evaluation <br /> Mountain House Development Site#6 January 18,2011 <br /> aggregate non-cancer hazard for oral, dermal, and inhalation routes is provided in Table 13. <br /> SAIC estimated the total potential non-cancer hazard from oral, dermal, and inhalation exposures <br /> to on-site soils to be 0.002. This level of hazard is far less than a hazard index of 1, and therefore <br /> indicates an acceptable non-cancer health hazard for exposures to on-site soils for a hypothetical <br /> resident. <br /> 6.3 ON-SITE GROUNDWATER <br /> The affected on-site groundwater exceeds numerous California and federal TDS standards for <br /> drinking water as well as agricultural-use criteria. Therefore, shallow groundwater at the Site is <br /> not likely to be used as a drinking-water source. For these reasons, the groundwater direct <br /> exposure route was considered incomplete and was not evaluated quantitatively(Figure 3). The <br /> low concentrations of VOCs in groundwater samples indicate that the potential risks associated <br /> with this pathway are low. The potential for vapor intrusion of volatile chemicals to indoor air <br /> from groundwater was not quantitatively evaluated. <br /> 7. UNCERTAINTIES <br /> Uncertainties were inherent to the human health cancer risk and non-cancer health hazard <br /> evaluation performed during this HHSE. Site-specific conditions that contribute most <br /> significantly to the uncertainty of the risk and hazard estimates are identified and discussed <br /> below. <br /> Three site investigations were conducted with the oversight of the Central Valley RWQCB <br /> between 2001 and 2010. Condor and SAIC collected 49 soil samples from 38 borings at depths <br /> between 0 and 10 feet bgs. Detection limits for the COPCs in the boring samples ranged from <br /> 0.00033 to 0.1 mg/kg. Data of adequate analytical quality(e.g., low detection limits) were <br /> collected to support this HHSE. <br /> SAIC performed this HHSE at the request of the Central Valley RWQCB, and after the Central <br /> Valley RWQCB was satisfied that the Site had been adequately characterized. Consequently, <br /> uncertainties in this HHSE were reduced to an acceptable level. The on-site soil impacts are <br /> believed to be well-characterized; therefore, EPCs were evaluated as the UCL of the mean soil <br /> concentration for each COPC evaluated in this HHSE. The UCL is a conservative estimate of <br /> the mean concentration, and is unlikely to lead to underestimation of exposure concentrations. <br /> SAIC did not quantitatively evaluate the potential for vapor intrusion of volatile chemicals to <br /> indoor air from groundwater. However, the detections of volatile constituents in groundwater <br /> were few and low, indicating that this is not a complete exposure pathway and thus poses <br /> minimal risk. <br /> SAIC estimated potential on-site exposures and resulting risks and hazards in this HHSE using <br /> algorithms developed by Cal/EPA DTSC, which were based on EPA and Cal/EPA DTSC <br /> guidance and methodology. The equations evaluated exposures to soils by dermal, oral, and <br /> inhalation exposure routes using health-protective, conservative reasonable maximum exposure <br /> parameters. Additionally, cancer and non-cancer toxicity values promulgated by Cal/EPA Office <br /> of Environmental Health and Hazard Assessment (Cal/EPA, 2010a and 2010b) and EPA <br /> Integrated Risk Information System(EPA, 2010b)were used to quantitatively estimate potential <br /> risk and hazards. Therefore, it is unlikely that the risks and hazards estimated during the <br /> development of this HHSE are significantly underestimated. In fact, considering the <br /> from sclence to Solvtloas <br />