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SECTIONTHREE Technical Approach All four elements must be present for an exposure pathway to be complete and for exposure to occur Incomplete exposure pathways do not result in actual human exposure and are not included in the exposure or risk assessments as discussed in U S EPA (1989a) Thus, an analysis of exposure pathways allows the assessment to focus only on those pathways which have the potential to impact human health Each potential pathway considers the possibility of chemicals being transported to human receptors via various environmental media, considering the physical characteristics of the site vicinity Both average exposure scenarios and reasonable maximum exposure (RUE) scenarios will be developed for each exposure pathway The RASE is meant to represent the most exposed mchvidual in a population, while the average exposure represents the 50th percentile for the potentially exposed population C e,the "average individual') Both RARE and average exposure scenarios are evaluated in this assessment The exposure pathway analysis will evaluate the following transport media soil, groundwater, and air 3.1.4 Identify Exposure Points and Concentrations Identified exposure points are those locations where humans may be exposed The exposure points are defined site-specific locations where humans are present and potentially exposed Exposure points may be diff'erent.for various human populations for example, site workers and the nearest resident The risk evaluation evaluates potential exposures for populations that may be on or near the site Such populations may include workers, near-site residents, and trespassers A large number of assumptions concerning site use, behavior patterns of exposed populations, and chenucal behavior are incorporated into the exposure assessment Such assumptions include, for example o The frequency of exposure of individuals to contaminated media from the site o The duration of exposure of individuals to contaminated media from the site o Selection of receptors In evaluating potential exposures, guidance provided in the Exposure Factors Handbook (EFH) (U S EPA, 1989b), Standard Default Exposure Assumptions (SDEF) (U S EPA, 1991), and Superfund Exposure Assessment Manual (SEAM) (U S EPA, 1988) will be used The generic guidance values will be modified, as appropriate, based upon site-specific conditions or current literature The rationale !• for deviations from agency guidance or standard default exposure assumptions will be clearly ® T 11 097AWTOCKTOMREPoaroac?-nom%" 34