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City of Santa Ana <br />Environmental Checklist <br />have the potential to overlap, thus emissions are summed. <br />a Localized thresholds derived froth SCAQMD Localized Significance Threshold Tables and are based on <br />the project location (Source Receptor Area [SRA] 17, the Central Orange County), project area <br />disturbed in any given day (5 acres for Phase I and 2 acres for Phase 11), and the distance to the nearest <br />sensitive receptor (25 meters). <br />Source: SCAQMD Localized Significance Threshold Methodologyfor CEQA Evaluations, and <br />Particulate Mottet•(PM) 2.5Significance Thresholds and Calculation Methodology. <br />Source: ICF 2012. <br />As indicated in Table 3 -9, implementation of Mitigation Measures AQ -1, AQ -2, and AQ -3 will result in <br />reductions of all criteria pollutant emissions, most notably of PM10 by 33% for the worst -case <br />scenario in Phase 1. Implementation of these mitigation measures would reduce emissions of PM10 <br />below the SCAQMD significance threshold. As such, air duality emission impacts related to <br />construction would be less than significant after implementation of mitigation. <br />Table 3 -9. Estimate of Localized Construction Emissions (pounds per day) After Implementation of <br />Mitigation <br />Localized Construction Emissions <br />ROG NOx <br />CO <br />SOx PM10a <br />PM2.5 <br />Phase I <br />Excavation & Soils import and Rough Grading <br />& Bldg Pad Prep 2012 <br />11 100 <br />43 <br /><1 8 <br />6 <br />SCAQMD Localized Significance Threshold (5 <br />acres) <br />- 183 <br />1253 <br />- 13 <br />7 <br />Exceed Threshold? <br />No No <br />No <br />No No <br />No <br />Notes: <br />Construction emission calculation worksheets are included in Appendix A. <br />a PM10 emissions estimates take into account compliance with SCAQMD Rule 403 requirements <br />for fugitive dust suppression, which require that no visible dust be present beyond the site <br />boundaries, as well as the use of EPA Tier 2 equipment. <br />b Implementation of Excavation & Soils Import and Rough Grading & Bldg Pad Prep 2012 and <br />Fine Grading, Bldg Construction, Asphalt Parking Lots & Architectural Finishing 2013 within <br />Phase I have the potential to overlap, thus emissions are summed. <br />Source: ICF 2012. <br />Local Operational Impacts <br />Within an urban setting, vehicle exhaust is the primary source of CO. Consequently, the highest CO <br />concentrations are generally found close to congested intersections. Under typical meteorological <br />conditions, CO concentrations tend to decrease as the distance from the emissions source (i.e., <br />congested intersection) increases. For purposes of providing a conservative, worst -case impact <br />analysis, CO concentrations are typically analyzed at congested intersection locations, because if <br />impacts are less than significant close to congested intersections, impacts will also he less than <br />significant at more distant sensitive receptor locations. <br />Project traffic during the operational phase of the project would have the potential to create local <br />area CO impacts. SCAQMD recommends a quantitative hot -spot evaluation of potential localized CO <br />impacts when volume -to- capacity ratios are increased by 2% at intersections with a level of service <br />(LOS) of C or worse. Given these criteria, no intersections met the aforementioned requirements for <br />The Academy Charter High School 3 27 tune 2012 <br />Initial Study/Mitigated Negative Declaration ICF 00914.11 <br />li :S11191, <br />