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DRAFT <br /> 1.2.1 Exposure to Chemicals in Soil <br /> Inhalation exposure can occur from fugitive dust emissions and volatile emissions to <br /> outdoor air. For evaluating the inhalation route of exposure to fugitive dusts in outdoor <br /> air, the ambient air particulate levels were assumed to be equal to the National Ambient <br /> Air Quality Standard for the annual average respirable portion (PM,,,) of suspended <br /> particulate matter of 50 µg/m3, representing conservative conditions (Cal/EPA, 1994; <br /> updated 1996). <br /> Volatile emissions from chemicals present in soil were modeled using vapor diffusion <br /> equations presented by the American Society for Testing and Materials (ASTM, 1996) as <br /> described in Section 1.2.3. For VOCs, the evaluation of inhalation exposures was limited <br /> to volatile emissions (exclusion of airborne particulate exposures). <br /> Indoor and outdoor exposures to VOCs in soil were evaluated for the construction, <br /> landscape maintenance, and residential receptors. For the commercial worker, only <br /> indoor air exposure to VOCs in soil was evaluated since the risk estimates for landscape <br /> maintenance worker would be conservatively protective of outdoor exposures to the <br /> commercial worker. <br /> Other routes of exposure evaluated included soil ingestion and dermal contact for all <br /> receptors except the commercial worker. It was assumed that the commercial worker <br /> would be protected by the outdoor risk estimates for the landscape maintenance worker. <br /> 1.2.2 Exposure to Chemicals in Groundwater <br /> j <br /> Although area-specific water use information was not available for this evaluation, it is <br /> g P <br /> assumed that the shallow groundwater is likely not suitable for potable use based on the <br /> expected total dissolved solids of the shallow groundwater and the expected sustainable <br /> yield from shallow groundwater wells in the investigation areas. It is anticipated that <br /> potable water supply for future Site use will be provided by a public water purveyor. <br /> SOMA 99-2218 4 12/10/99 <br />