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• EPA Guidance (EPA 1989b)and the EPA Exposure Factors Handbook ., (EPA 1989a) • Professional judgment t In this risk assessment, average and reasonable.maximum exposures were calculated to provide some measure of the range and uncertainty in potential exposures. The average case represents a set of exposure assumptions considered to be central values or best estimates. The average case is, nevertheless, conservative in its„exposure, estimates because it assumes that exposure routinely occurs. The reasonable maximum case is developed to provide an upper bound on exposure. Because reasonable maximum exposure estimates are based .on a combination of conservative assumptions, the estimates are highly unlikely to reflect exposures that-are generally encountered at the site. Specific conservative assumptions that tend t overestimate p p o o e estimate actual site risks are fisted { below: • It was assumed"that occupational employees would ingest 100 percent of the average daily water amount from the site and not from other sources, like home and restaurants. • It was assumed that occupational employees would shower onsite every day that they work at the site. { For inhalation exposures for occupational employees it was assumed that they would work outside 8 hours per day with an inhalation rate that indicates strenuous activity. • As a conservative approach, potential risks from the YFS site were evaluated for hypothetical future residents. These scenarios are of low probability because the future land use at the site has been designated ` as a motor freight terminal, which means the facility will be maintained and not made'available for other uses in the near future. !Li_ v c. • For adult and child residential exposures it wasassumed that 100 j percent of all ingested water would come from the groundwater and not .�� other sources. _ S:\LDC\YHLLO.Rn May 4,1995 7-4