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MacArthur Project Modification - Santa Ana - Air Quality Assessment <br />KPC Environmental, Inc. <br />4.3 Determining Emission Significance <br />4.3.1 Emission Significance Thresholds <br />To identify projects that will adversely affect the regional air quality through direct and <br />indirect sources the SCAQMD has established significance thresholds to determine air <br />quality impacts of a project. The SCAQMD established these significance thresholds, in <br />part, based on Section 182 (e) of the Federal Clean Air Act, which identified levels of <br />volatile organic gases from stationary sources operating in extreme non-attainment <br />regions for ozone at 10 tons per year. The value set by the CAA was converted into <br />threshold levels in pounds per day for the construction and operational phases of a <br />project. <br />The SCAQMD states that any project located in the South Coast Air Basin (SCAB) <br />having daily emissions from both direct and indirect sources that exceed the emissions <br />thresholds should be considered significant. <br />To determine whether or not air quality impacts from the proposed project are significant, <br />impacts will be evaluated and compared to the significance criteria in the following table. <br />If impacts equal or exceed any of the following criteria, they will be considered <br />significant. <br />TnhlP d_d <br />Mass Dail Thresholds <br />Pollutant Construction Operation <br />N% 100 lbs/day 55 Ibs/day <br />ROGNOC 75 lbs/day 551bs/day <br />PM 10 150 lbs/day 150 lbs/day <br />sox 150 lbs/day 1501bs/day <br />CO 550 lbs/day 550 Ibs/day <br />PM2.5 55 lbs/day 551bs/day <br />In addition to the significance threshold for NOx, ROGNOC, PM10, SOx and CO, the <br />California State 1-hour and 8-hour CO standard is used for determining the existence of <br />CO Hotspots created directly or indirectly by a project. The criteria for CO Hotspots are <br />covered in the CO Hotspot Analysis of this report. <br />02/02/11 <br />9 <br />75B-117