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DRAFT <br /> Consequently, the ingestion route of exposure was not evaluated for shallow groundwater <br /> for any of the receptors. <br /> However, VOC emissions from groundwater volatilized through the soil and into outdoor <br /> and indoor air can result in exposure to chemicals through inhalation. Volatile emissions <br /> for chemicalsP resent in groundwater were modeled using vapor diffusion equations <br /> presented by the ASTM (1996) as described in Section 1.2.3. <br /> Dermal exposure to groundwater was not evaluated for the construction worker, <br /> landscape maintenance worker, commercial/industrial, and residential exposure scenarios <br /> since it is unlikely that these receptors would be in contact with shallow groundwater at <br /> 1 the Site. <br /> For the commercial worker,only indoor air exposure to VOCs in groundwater was <br /> evaluated since the risk estimates for landscape maintenance worker would <br /> conservatively also protect the commercial outdoor worker. <br /> 1.2.3 Volatilization Factor Development <br /> This section describes the methods used to estimate air exposure point concentrations of <br /> i <br /> volatile organic compounds(VOCs) detected in groundwater and soil. Vapors of VOCs <br /> 1 can diffuse from the groundwater into soil gas, through the pore spaces in subsurface soil, <br /> and into indoor or outdoor air. Concentrations of such vapors were estimated using <br /> volatilization factors (VFs) developed using vapor diffusion equations presented by <br /> ASTM (1996). The VFs represent a ratio describing the relative concentrations of VOCs <br /> tin air that might result from a-concentration of the VOC in groundwater or soil. The <br /> equations address VOC concentrations in the groundwater as a vapor source, vapor loss <br /> ( from the groundwater to air in porous soil, and vapor migration upward by diffusion <br /> through three layers with different resistances to that diffusion. The layers are(1) the <br /> capillary zone, which is the capillary zone-soil above the groundwater that contains water <br /> drawn upward from the groundwater by capillary action; (2) the soil layer, which is soil <br /> SOMA 99-2218 5 12/10/99 <br />