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C A M B R I A Ms.Lori Duncan September 9,2005 Potentially Exposed Receptors and Exposure Pathways: The site is an active Shell-branded service station. Properties surrounding the site are commercial, with residential properties nearby. The potentially exposed receptors addressed by this risk analysis are on-site commercial occupants and construction workers and off-site residential and commercial receptors. Applicable exposure pathways are included in Attachment C. Ingestion of impacted groundwater is considered a potentially complete exposure pathway. Although it is considered unlikely that shallow on-site groundwater would be consumed, this pathway is evaluated. Off-site groundwater ingestion by residential receptors is also evaluated as it may be used in the future. A well survey identified four wells (three domestic wells and one © destroyed municipal well) within 2,000 feet of the site. The closest well is a domestic well approximately 450 feet from the site. Cambria conducted a door-to-door survey and confirmed that this well is not used. Ingestion of and dermal exposure to impacted soil is a potential complete exposure pathway. The site and areas immediately surrounding the site are currently covered with concrete sidewalks and pavement. However, it is considered a complete potential exposure pathway since a future change of land use in the area could provide exposure to construction workers or occupants. Because the current and expected future land use is commercial, commercial exposure was assumed and evaluated. COCl were detected in soil samples collected from the suspected source areas on the site. Therefore, ingestion of, dermal exposure to, and inhalation of particulates from impacted soil are considered complete exposure pathways for on-site receptors. Because volatile COCl have been detected in soil and groundwater samples, inhalation of volatile COCs outdoors and indoors resulting from volatilization from surface and subsurface soil and groundwater is considered a complete exposure pathway. Protective Target Risk Levels: Consistent with the Cal-EPA policy on evaluating chemical carcinogenic effects under the Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65), a commercial target carcinogenic risk level of 100-5 is proposed for class A and B carcinogenic COCs. The target risk level for COCs that exhibit noncarcinogenic effects (any other systemic effects but cancer), such as ethylbenzene,toluene and xylenes,is a hazard quotient (HQ) of 1.0 per USEPA and ASTM default values. 7