ARCHIVED REPORTS_DRAFT ENVIRONMENTAL IMPACT REPORT

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traffic analysis prepared for this project, and default and SJVAPCD-recommended model settings and parameters attributable to construction period and site location. Table 4.3-7 summarizes the modeled project-generated,operation-related(regional) emissions of criteria air pollutants and precursors from area and mobile sources. Refer to Appendix B for detailed modeling input parameters and results. Total Emissions Based on the modeling conducted,operation-related activities would not result in total project-generated emissions of ROG or NOx that exceed SJVAPCD's significance threshold of 10 tpy(refer to Table 4.3-7). Thus,project- generated,operation-related emissions of criteria air pollutants and precursors would not violate or contribute substantially to an existing or projected air quality violation,expose sensitive receptors to substantial pollutant concentrations,or conflict with air quality planning efforts.As a result,this impact would be less than significant. IMPACT Air Quality—Exposure of Sensitive Receptors to Toxic Air Contaminant Emissions. The project would 4.3-3 not expose sensitive receptors to substantial emissions of TACs because construction emissions would be temporary and would rapidly dissipate with distance from the source and proposed operations would not result in the exceedance of the SJVAPCD's screening criteria for project's resulting in significant TAC emissions. As a result, this impact would be less than significant. The exposure of sensitive receptors from on-site project-generated construction-related and operation-related sources is discussed separately below. On-Site Construction-Related Equipment Emissions Construction-related activities would result in short-term project-generated emissions of diesel PM from the exhaust of off-road heavy-duty diesel equipment for site preparation(e.g., excavation, grading, and clearing); paving; application of architectural coatings; and other miscellaneous activities. Diesel PM was identified as a TAC by ARB in 1998. The potential cancer risk from the inhalation of diesel PM, as discussed below, outweighs the potential noncancer health impacts (ARB 2003). At this time, SJVAPCD has not adopted a methodology for analyzing such impacts and does not recommended the completion of health risk assessments (HRAs) for construction-related emissions of TACs,with a few exceptions(e.g.,where construction phase is the only phase of project) (Reed,pers. comm.,2007). It is important to note that construction equipment emissions would be reduced over the period of project development. In January 2001, EPA promulgated a Final Rule to reduce emission standards for 2007 and subsequent model year heavy-duty diesel engines. These emission standards represent a 90%reduction in NOx, 72%reduction of nonmethane hydrocarbon(NMHC)emissions, and 90%reduction of PM emissions in comparison to the 2004 model year emission standards. In December 2004,ARB adopted a fourth phase of emission standards (Tier 4)in the Clean Air Non-road Diesel Rule that are nearly identical to those finalized by EPA on May 11,2004.As such, engine manufacturers are now required to meet after treatment-based exhaust standards NOx and PM starting in 2011 that are more than 90%lower than current levels,putting emissions from off-road engines virtually on par with those from on-road heavy-duty diesel engines. More specifically,the dose to which receptors are exposed is the primary factor used to determine health risk(i.e., potential exposure to TAC emission levels that exceed applicable standards). Dose is a function of the concentration of a substance or substances in the environment and the duration of exposure to the substance. Dose is positively correlated with time,meaning that a longer exposure period would result in a higher exposure level for the maximally exposed individual. Thus,the risks estimated for a maximally exposed individual are higher if a fixed exposure occurs over a longer period of time. According to the Office of Environmental Health Hazard Assessment,health risk assessments,which determine the exposure of sensitive receptors to TAC emissions, Manteca WQCF and Collection System Master Plans EIR EDAW City of Manteca 4.3-23 Air Quality