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4.6 Air Quality V • Conflict with,or obstruct implementation of the applicable air quality plan(s); L • Violate'any air quality standard or contribute substantially to an existing or projected air quality violation; i` • Result in a cumulatively considerable net increase of any criteria pollutant for which the project region is non-attainment under an applicable federal or state ambient air quality standard(including releasing emissions which exceed quantitative thresholds IVA for ozone precursors—that is, 10 tons per year of ROG or NOx); • Expose sensitive receptors to substantial pollutant concentrations;or • Create objectionable odors affecting a substantial number of people. ` Additionally, the Valley Air District has established thresholds of significance for construction impacts, project operations,and cumulative impacts. For construction impacts,the pollutant of greatest concern to the Valley Air District is PMIQ.2 The Valley Air District recommends that significance be based on the control measures to be implemented during project construction (SJVAPCD, 2002). Compliance with Regulation VIII and implementation of appropriate mitigation measures to control respirable particulate matter(PMIo)emissions are considered to be L sufficient to render a project's construction-related impacts less than significant. The Valley Air District's Guide for Assessing and Mitigating Air Quality Impacts(GAMAQ1)contains a list of feasible control measures for construction-related PMio emissions. v The Valley Air District's GAMAQI also includes significance criteria for evaluating operational- phase emissions from direct and indirect sources associated with a project. Indirect sources Ift include motor vehicle traffic associated with the project and do not include stationary sources covered under permit with the Valley Air District. For this analysis,the project would be considered to have a significant effect on the environment if it would exceed the following thresholds: • Cause a net increase in pollutant emissions of ROG or NO.exceeding 10 tons per W. year. • Cause a violation of state CO concentration standards. The level of significance of ` CO emissions from mobiles sources is determined by modeling the ambient concentration under project conditions and comparing the resultant 1- and 8-hour concentrations to the respective state CO standards of 20.0 and 9.0 parts per million. Cause visible dust emissions due to onsite operations and thereby violate Valley Air District Regulation VIII.' 6. 2 Construction equipment emits CO and ozone precursors.The SJVUAPCD has determined that these emissions would cause a significant air quality impact only in the case of a very large or very intense construction project (SJVUAPCD,2002).The GAMAQI mentions that construction projects lasting for many months may exceed the District's annual threshold for NOx emissions. 3 Visible dust is defined by the SJVUAPCD as"visible dust of such opacity as to obscure an observer's view to a V degree equal to or greater than opacity of 20 percent,for a period or periods aggregating more than three minutes in any one hour." r RMC Pacific Vernalis Quarry Mining and Reclamation Project 4.6-17 ESA/203015 Draft Environmental Impact Report May 2006 r