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4. ENVIRONMENTAL ANALYSIS i 4.6 AIR QUALITY Significance after Mitigation: With implementation of the above appropriate mitigation measures and compliance with Regulation VII,the construction impacts would be less-than- significant. Impact 4.6.2: Project Operational-Phase Emissions Impact. The proposed surface mining of topsoil,sand and gravel would take place on approximately 659 acres within the Project Site. The proposed mining operation would consist of the extraction of 1.7 to 4.0 million tons per year of aggregate materials(sand and gravel)over a 26 to 60 year period. The operation would be open pit,sand and gravel harvesting and processing. The impacts of operational air quality emissions of criteria pollutants are potentially significant. The processing facility would consist of conveyors, screens,crushers, and scrubbers. There would be a Ready Mix Plant and an Asphalt Plant. A portable,concrete recycling plant, owned and operated by an outside contractor,would intermittently be placed in the middle of the plant .a. site to produce base material. The processing facility would include an aggregate processing plant, ready mix concrete plant, asphalt batch plant,and stockpiles. The ready mix plant, with an estimated production of 350,000 cubic yards per year, would include a cement silo,aggregate bins,conveyors, baghouse,bermed admixture tank farm,reclaimer and concrete lined washout basins. The asphalt plant,with an estimated production of 400,000 tons per year,would be ., owned and operated by others. It would include a batch tower, aggregate bins,baghouse, and hot oil tanks. ti Approximately 75 percent of the processing plant would involve a wet screening process. The wet plant would consist of scrubbers,crushers,coarse material washers,fine material washers, conveyors,and wet screens for washing and sizing of materials. The other approximately 25 percent of the material would be processed through a dry circuit. This circuit would consist of conveyors,crushers, and dry screens for the sizing of the crushed aggregates. Scrapers would be used to strip and remove topsoil, overburden, and clays. Excavators would be used for the harvesting of the sand and gravel lenses. Haul trucks would be loaded with sand and gravel material for a short haul from the excavator to a field conveyor line. Loaders would be used within the plant area for truck loading of some of the sand and gravel products. The graders and compactors would be used for haul road maintenance and the building of reclamation structures. Topsoil would be stripped and removed by using scrapers, and stockpiled in the berms for use in landscape areas and future reclamation. The highest volume of stockpiled topsoil would reach approximately 50,000 cubic yards. The stockpiles would be watered and track rolled to prevent erosion,and would be seeded for further protection if necessary. The on-site equipment and material haul roads would be unpaved. The types of equipment to be used in the mining and hauling of the material include the following: RMC Pacific Vernalis Quarry Mining and Rmlamation Project 4.6-21 ESA 1203015 Administrative Draft Eat Mawb 2004