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4.Minor Revisions to the Draft Environmental Impact Report 4 w total risks from exposure to all toxic air contaminants in the ambient air. The actual risk level at any particular location would require a site-specific study of all DPM emission sources in the area as well as the spatial relationships between the sources, stationary and mobile,and the location being analyzed. The analysis in this EIR estimates the increase in risk from the project only on nearby receptors. Since the estimated project-related increase in risk is greater than 10 in a - - million,potentially feasible mitigations are considered. i ` TAC emission points within the asphalt plant includes a natural-gas fired burner on the drying drum,the mixing drum,natural gas-fired hot oil heater in the asphalt oil storage tanks,other 'L asphalt plant handling such as truck loadout and silo filling,and storage piles. The drying and mixing drum are ducted to a fabric filter stack to the atmosphere. The hot oil heater is vented directly to the air. f` The California OEHHA has determined the chronic exposure to TACs can cause carcinogenic and non-carcinogenic health effects as documented in their Risk Assessment Guidelines. The OEHHA has specified AEL for specific TACs. An AEL is the probability of aoquirin some ome health effects. OEHHA has also established a unit risk value for specific TACs.A unit risk value is the probability of contracting cancer if exposed to an average concentration of 1 uWm3 for 70 t. years The carcinogenic and non-carcinogenic health risks due to the asphalt batching operations were estimated by conducting dispersion modeling of TAC emissions from asphalt operations: both the hot mix plant and fugitive emissions from loadout, silo filling, and storage. In 2005,the California Office of Environmental Health Hazard Assessment(OEHHA) added a chronic Reference Exposure Limit(REL) for crystalline silica. Silica is a hazardous substance when it is inhaled,and the airborne dust particles that are formed when the material containing the silica is broken, crushed,or sawn pose potential risks. Based on analysis of the geology within the area and engineering documentation,the crystalline silica content within the aggregate ` processing was assumed to be 25 percent of the PM10 emissions. The crystalline silica content within the unpaved circulation areasother fugitive dust sources and concrete processing was r assumed to be 30 percent of the PMte emissions. Mitigation Measures Measure 4.6.4a: The applicant shall either utilize new model year on-site machinery equipped with the best available DPM control technology,or retrofit its fleet of excavators, on-site haul trucks, and front end loaders with catalyzed DPM filters to minimize DPM L emissions,or, in those limited instances where the retrofit would impede the function or life of the equipment,or presents safety concerns, the applicant shall comply with alternative measures developed by the Air Board. 6. Measure 4,6.4b: Implement Mitigation Measures 4.6.1. L Impact Significance After Mitigation: If all the equipment identified(i.e., on-site diesel excavators, loaders, and haul trucks)had catalyzed particulate filters,with a DPM control efficiency of 85 percent, the maximum incremental lifetime cancer risks would be 7 and 9 Lcancers per million(assuming a 70-year exposure)and between 4 and 8 cancers per million L Cemex Vernats Quarry Mining and Reclamation PmieG 4-53 ESA/203015 Final Environmental Impact Report June 2008 L