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i~ i~ Environmental Checklist For CEQA Compliance with the forecasts for the subregion as adopted by SCAG, and as such are consistent with the AQMP. B. Less Than Significant Impact with Mitigation Incorporated. As discussed above, the project site is located within the Basin. State and federal air quality standards are often exceeded in many parts of the Basin. The proposed project would contribute to air pollutant emissions during construction (short-term) and operations (long-term). A discussion of the project's potential construction-period and operations-period air quality impacts are provided below. Regional Construction Impacts The SCAQMD has established methodologies to quantify air emissions associated with construction activities such as air pollutant emissions generated by operation of onsite construction equipment; fugitive dust emissions related to site preparation activities; mobile (tailpipe) emissions from construction worker vehicles and haul/delivery truck trips; and off gassing emissions of reactive organic compounds (ROC), which occur during the application of architectural coatings and asphalt paving. Emissions would vary from day to day, depending on the level of activity, the specific type of construction activity occurring, and, for fugitive dust, prevailing weather conditions. With respect to the proposed project, construction activities are anticipated to start around November 2007 and require approximately 16.5 months to complete. Construction would occur in four phases. Phase 1 would require 6 weeks and would consist of the demolition of existing onsite structures. Phase 2 would require 1 month and would consist of grading and site work (24,917 cubic yards of cut and 31,555 cubic yards of fill). Phase 3 would require 3 months and would consist of roadway improvements and paving along West Alton Avenue. Phase 4 would require 14 months and would consist of the construction and finishing of the 38 detached single-family housing units. A copy of the anticipated construction schedule is provided in the air quality appendix to this IS/MND document (Appendix A). A construction-period mass emissions inventory was compiled based on an estimate of construction equipment, scheduling, and phasing assumptions provided by Manning Homes. More specifically, the mass emissions analysis takes into account the following: 1. Combustion emissions from operating onsite construction equipment, 2. Mobile-source combustion emissions from worker commute and haul-truck travel, and 3. Mobile-source and fugitive PM2.5 and PM,o emissions resulting from the 24,917 cubic yards of cut, 31,555 cubic yards of fill, and 6,638 cubic yards of soil import on site. Emissions for on-road mobile sources, off-road construction equipment, and off gassing were calculated using the URBEMIS 2002 emissions inventory model; fugitive PM~o emissions were compiled using the calculation formulas provided in the CEQA Air Quality Handbook (appendix to Chapter 9); and PM2.5 emissions were calculated using the SCAQMD guidance document. titled Methodology to Calculate Particulate Matter (PM) 2.5 and PM 2.5 Significance Thresholds (October 2006). A conservative estimate of the project's regional mass emissions during construction is presented in Table 3-1. As shown therein, ROC, CO, SOX, PM,o, and PM2_5 emissions would be less than significant, but NOX emissions would exceed the SCAQMD regional significance threshold of 100 pounds per day. As such, Alton Court Initial Study/Mitigated Negative Declaration 3-17 August 2007 J$S 00635.07 75A-83