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ENVIRONMENTAL IMPACT REPORTADDENDUM Bristol Street Widening Phase IIIA — Civic Center Drive to Washington Avenue x iCRITEjA i p_L1 UiSl! BIfA l A & R31 `PMN'THAbE NOx CO PM10 PMes Trenching 41 19 2 2 Paving 16 11 1 1 SCAQMD Threshold 183 1253 13 7 Exceeds Threshold? No No No No Source: Air Quality Assessment Report (URS 2013a), Notes: NOx =nitrogen oxides; CO =carbon monoxide; PMro =particulate matter less than less than or equal to 10 microns in diameter; PM2.5 = particulate matter less than less than or equal to 2.5 microns in diameter. Intersection Hot -Spots While the proposed Project would not result in any direct sources of localized emissions due to the roadway street lighting being powered by electricity, changes in LOS or traffic volumes due to the Project may cause indirect sources of localized emissions. While emissions of motor vehicles have improved due to more stringent vehicle emissions standards and the use of cleaner burning fuels, they continue to be the primary source of local emissions within the study area. Localized areas where ambient concentrations exceed national and/or state standards for CO are known as hotspots. The SCAQMD defines typical sensitive receptors as residences, schools, playgrounds, childcare centers, athletic facilities, long -term health care facilities, rehabilitation centers, convalescent centers, and retirement homes. Because CO is produced in greatest quantities from vehicle combustion and does not readily disperse into the atmosphere, adherence to AAQS is typically demonstrated through an analysis of localized CO concentrations. Areas of vehicle congestion have the potential to create pockets of CO called "hot spots." These pockets have the potential to exceed the state one -hour standard of 20 parts per million (ppm) or the eight -hour standard of 9 ppm. Note that the federal levels are based on one- and eight -hour standards of 35 and 9 ppm, respectively. Thus, an exceedance condition would occur based on the state standards before the federal standards. The following intersections were modeled for CO hotspots as detailed in the Air Quality Assessment Report (URS 2013a): Bristol Street and 17"' Street Bristol Street and Washington Avenue As shown in Table 6, both the 1- and 8 -hour CO concentrations at the intersections that were affected by the proposed Project would be substantially below the California and federal AAQS for CO. Potential CO impacts related to the Project alternatives are below AAQS and would not result in a significant air quality impact from CO hotspots. TABLE 6 CO HOTSPOT ANALYSIS (PPM) CONCENTRATION CAAQS CONCENTRATION CAAQS 1 -Hour 8 -Hour Bristol Street and Civic Center Drive Bristol Street and Washington Avenue ANA 305 -011 (PER 02) CITY OF SANTA ANA (01/19/2015) YU PAGE 34 City Council 16 – 77 9/17/2024