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4.6 Air Quality r points such as major highways and heavily traveled and congested roadways. This increase ., in traffic would not only add more vehicles on the road but the increased congestion would cause non-project traffic to travel at slower speeds,thus increasing CO emissions. This impact is less than significant. r Vehicular emissions were computed using CARB's emission factor model, EMFAC2002. EMFAC is CARB's computer model designed to estimate past, present, and future on-road r emissions of HC,CO, NO.,PM,and SO2. It is anticipated that the production rate at the plant will vary from 1.7 to 4.0 million tons per year. At these rates, quarry operations will generate approximately 437 to 613 truck loads per day(annual average) and approximately 699 to 981 truck loads per day (peak seasonal). The approximate distribution of the proposed truck traffic would be as follows: .� 1. North toward Stockton, 70% 2. East toward Modesto, 15% 3. West toward the Bay Area, 10% _ 4. South toward Los Banos, 5% The following intersections, which were evaluated in the analysis of traffic impacts, were also ` evaluated in this air quality analysis: 1. Blewett and Koster 2. Bird and Blewett 3. Bird and SR 132 4. Koster and SR 132 5. Welty and SR 132 6. McCracken and SR 132 7. Blewett and Welty 8. SR 132 and Interstate 5 9. SR 132 and Interchange 580 10. Interstate 5 and Interstate 580 11. SR 33 and Welty The screening method set forth in California Line Source Dispersion Model (CALINE) was used to estimate worst-case CO concentrations during the peak hour at the intersection of Blewett/ Koster Road and SR 132/Welty. As this is the intersection most affected by project-related traffic, it was assumed that if CO concentrations at this intersection would not exceed the ambient air quality standards, the project's contribution to impacts at other intersections affected to a lesser extent by project traffic would also not be substantial. Three proposed haul routes were examined(see the Transportation and Traffic section for more details)using the assumptions that: 1. All trucks entering and exiting the site would use Blewett and Bird Roads. .. 2. Traffic would be distributed as noted except that trucks would have the option of using Koster Road for access to and from SR 132. 3. Similar to distribution above except that trucks would leave the site traveling north on Koster Road to Blewett Road, then east on Blewett Road to Welty Road, north on r RMC Pacific Vernalis Quarry Mining and Reclamation Project 4.6-29 ESA/203015 Draft Environmental Impact Report May 2006 r