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_ 4 ENVIRONMENTAL ANALYSIS 4.6 AIR QUALITY non-carcinogenic health effects. The OEHHA has specified an acceptable exposure level(AEL) of DPM as a non-carcinogen of 5 micrograms per cubic meter(annual average). OEHHA has also established a unit risk value for DPM, which is the probability of contracting cancer if .. exposed to an average concentration of one microgram per cubic meter(µg/m3)for 70 years. The unit risk value established for DPM is 300 in a million per microgram per cubic meter. The carcinogenic and non-carcinogenic health risks from the Proposed Project were estimated by conducting dispersion modeling of TAC emissions from sources associated with the Proposed Project. For the on-site equipment that are part of the Project, it was assumed,as a worst case, that all equipment would use diesel fuel,even though future equipment may be required to reduce DPM emissions by using alternative fuels or alternative engine technologies. It should be noted that on-site equipment would move within the property as selected phases of the quarrying ` become operational. Thus,DPM exposure would increase or decrease as on-site equipment moves closer or further from sensitive receptors. The dispersion modeling analysis and health risk results were based on the worst-case results. The estimated DPM emissions from the Proposed Project are 3.30 tons per year(1.92 tons from on-site equipment and 1.39 tons from haul trucks). It was assumed half of the equipment would operate near the plant site and the remaining half would operate at the mining extraction area. Modeling accounted for the duration (in years)and location of each phase of operations(see Project Description). The operation would occur in nine phases over the course of 26 to 60 years. Operation was assumed to not r occur on Sundays; to be 24 hours a day(during periods of peak demand)throughout the year. DPM emissions were modeled using U.S.EPA-approved dispersion models to estimate ambient air concentrations at nearby residences. Detailed modeling methodology and background data is contained in Appendix D. The maximum annual average DPM concentration over a 70-year period at these receptors was determined to be 0.153 µg/m3. Using the DPM unit risk factor, as established by OEHHA,the maximum incremental carcinogenic risk is estimated to be 46 in a million. Under the 2.85 million and 1.7 million production levels,the risk is estimated to also be 46 in a million(given differences in mining duration and annual emission rates). This increment is greater than the significance threshold of 10 in a million. The maximum annual average concentration of 0.153 gg/m3 is less than the non-carcinogenic AEL of 5 µg/m3, thus leading to a hazard index of 0.031 compared to a significance threshold of 1. Therefore,the maximum ` carcinogenic health risks from DPM associated with the Proposed Project are considered to be significant. Additional information regarding the dispersion modeling and the health risk assessment are found in Appendix D. Controls,such as retrofitting non-road equipment engines with CARB-certified DPM filters and catalysts while using ultra low sulfur fuel(ULSD), when available, would reduce DPM emissions from equipment by 85 percent. The traps catch the particulate matter and allow the catalysts to "burn"the DPM when using ULSD. With the use of CARB-certified catalysts only in conjunction with ULSD,the control efficiency is about 50 percent. The best and most appropriate candidates for retrofitting would be the excavators,on-site haul trucks, and front end loaders. This equipment is used most often and most frequently,which r allows the engine to reach critical internal temperature for proper operation of the DPM filters. RMC Pacific Vernalis Quarry Mining and Reclamation Project 4.6-2.5 FSA 1203015 Administrative Draft EOL March 2004