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Air Quality Guidelines to determine the potential impacts of the project on the existing <br /> environment. <br /> Construction Impacts <br /> Existing residences are located immediately adjacent to the project, so a health risk assessment <br /> of the activity was conducted that evaluated construction emissions of DPM. A dispersion <br /> model was used to predict the off-site concentrations resulting from project construction, so that <br /> lifetime cancer risks could be predicted. <br /> Construction period emissions were computed using the OFFROAD2007 model along with <br /> projected construction activity. The project information and preliminary construction schedule <br /> were obtained for the project along with an estimate of material to be imported or exported from <br /> the site. This analysis assumed the following construction schedule: <br /> l. Beginning in 2013, demolition of existing buildings would occur for 20 days (portion <br /> requiring use of diesel heavy-duty equipment may be substantially shorter); <br /> 2. Site grading and excavation would occur over a total period of 18 working days and <br /> involve the removal of 1,000 cubic yards of material; <br /> 3. Trenching would last about 15 workdays; <br /> 4. Exterior building construction would occur for 50 workdays; <br /> 5. Interior building construction that requires only a propane lift would occur over a period <br /> of 80 workdays; <br /> 6. Fine or finishing grading would require 20 workdays in 2014; and <br /> 7. Paving would occur over a period of 4 workdays in 2014. <br /> Construction period diesel exhaust emissions were computed using emission factors from the <br /> CARB OFFROAD model for off-road construction equipment and from the EMFAC2011 model <br /> for emissions from trucks (e.g., haul trucks). The number and types of construction equipment <br /> and diesel vehicles, along with the anticipated length of their use, for different phases of <br /> construction were based on a site-specific construction activity schedule. All of the construction <br /> equipment was assumed to be from model year 2005, which is representative of EPA Tier 2 <br /> equipment. This is similar to the same default assumptions used in the URBEMIS2007 model. <br /> Heavy duty truck trips were based on the amount of material to be hauled away during <br /> demolition of the existing structures, the amount of soil to be excavated and exported off-site, <br /> and the estimated number of cement trucks needed for the project. Onsite truck emissions were <br /> based on 86 truckloads for demolition and 50 truckloads for soil export during mass <br /> grading/excavation. Haul trucks were assumed to travel 400 feet onsite at a speed of 5 mph and <br /> 3 <br />