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SECTIONFOUR Aposure Rssessmeu$ <br /> 4.2.1 Exposure Pathways <br /> This section discusses the potential release and transport of chemicals from subsurface soil at the site <br /> and identifies exposure pathways by which the receptor populations identified in Section 4 1 may be <br /> Potentially exposed to chemicals <br /> An exposure pathway describes a specific environmental pathway by which an individual can be <br /> exposed to chemical constituents present at or originating from a source An exposure pathway <br /> includes five necessary elements <br /> o A source of chemical <br /> o A mechanism of chemical release to the environment <br /> io An environmental transport medium <br /> o A point of potential human contact <br /> 0 A human intake route <br /> Each of these five elements must be present for an exposure pathway to be complete and for chemical <br /> intake to occur Incomplete exposure pathways do not result in human exposures Without exposure, <br /> there can be no risk, therefore, incomplete exposure pathways have not been included in the risk <br /> characterization process This section focuses on the complete exposure pathways that have been <br /> identified at the Shop 10 site(Figure 4-1) <br /> 4.2.2 Chemical Release Mechanisms and Transport Media <br /> Residuals COCs present in the soul have been identified as a potential source for chemical release <br /> Environmental media potentially involved in the transport of chemical constituents from this source <br /> include soil, groundwater, and air The mgestion of groundwater, inhalation of chemicals from soul and <br /> groundwater volatihization, dermal exposure to soil, and soul ingestion were quantitatively evaluated for <br /> potential health risk and hazards as part of this risk assessment <br /> In estimating risks from soil ingestion and dermal exposure, soil concentrations measured on site were <br /> used (Table 3-1) In estimating risks to onsite workers from inhalation of volatiles from soil and <br /> groundwater, fate and transport modeling were used In estimating risks from groundwater ingestion, <br /> two hypothetical wells were established 500 feet and 1,000 feet downgradient and groundwater <br /> concentrations were estimated using fate and transport modeling discussed below These distances <br /> were selected based on the nearest well located at 1,000 feet cross gradient and the hypothetical well <br /> located at 500 feet was selected to be extra conservative in the risk analysis Details of the models and <br /> Parameters used are described in Section 4 4 3 1 <br /> T11B67973(=NAWOCKTOMREPORT%SkpREP#1 DW&FEB4DB1 WOGNA%SNA 4-3 <br />