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Draft Environmental P Impact Report Page IV.E-5 Forward Inc. Landfill Expansion Project medium evaluated for the site was ambient air. Exposure point concentrations for off-site receptors were estimated using agency-approved emission and dispersion modeling techniques. The primary route of exposure was assumed to be inhalation due to exposure to volatile compounds and particulate emissions. Chemicals and associated sources evaluated in the risk assessment include: • Volatile compounds organic (VOCs)emitted in landfill gas (LFG); ' • VOCs emitted as products of incomplete LFG combustion; • Particulates emitted from landfilling, stockpiling, and wind erosion of Class II waste; • Vehicle exhaust emissions from the heavy equipment, including diesel exhaust �. particulates; • Volatile organics emissions from the groundwater treatment facility(GTF);and • Volatile organics emissions from the leachate ponds. Emissions from the following sources were evaluated but determined to be negligible: • Volatile emissions from landfilling from piles; • Emissions during landfilling of asbestos containing materials (ACM); • Volatile organics emissions from the sedimentation ponds; and • Emissions from the material recycling facility(MRF). The risk driver for the risk assessment was the diesel exhaust particulates from the daily use of the heavy equipment used in the landfill operations. These particulates comprised about 80% of the health risk contaminants generated at the facility. For purposes of the EIR,the baseline conditions for the risk assessment was assumed by SCS to be the existing permitted conditions. For the purposes of this HRA, a list of "regulated toxic compounds" was developed from the current list of HAPS regulated by the EPA under the federal CAA and chemicals regulated by the CARE under the AB 2588 air toxic "hot spots" program. These lists were cross-referenced against the list of toxic substances expected to be present in LFG, as identified in the EPA's AP- 42 section on landfills. Diesel particulate emissions from vehicles were also included in this HRA. Conservative health risk methodologies were used in the risk assessment (SCS,2005)in order to estimate maximum potential health risks. These methodologies are anticipated to overestimate both non-carcinogenic and carcinogenic health risk, possibly by an order of magnitude or more. For carcinogenic risks, the actual probabilities of cancer formation in the populations of concern due to exposure to carcinogenic COPCs are likely to be lower than the risks derived using the risk assessment methodology. Further explanation of the conservative nature of the methodologies is provided throughout the body of the SCS (2008) document. Project VOC emissions are estimated to exceed the SJVAPCD's threshold of significance under both Baseline scenarios and both Future Potential options considered for the AQIA. The total carcinogenic risk for the current conditions (and the Project scenario)was calculated as greater than 10-5;however, the receptor is an unoccupied (northern)fenceline receptor. The highest cancer risk at a currently occupied receptor was 2.4 in a million(2.4 x 10-6).