55C - RESO - BRISTOL ST IMPROVEMENTS

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ENVIRONMENTAL IMPACT REPORT ADDENDUM Bristol Street Widening Phase IIIB — Washington Avenue to 17h Street 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 2013): • Bristol Street and 170' 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 r,XAAQS p- GAAQ a3n 1 -Hour 8-Hour w'x d °° .CONCENTRATION Bristol Street and 17th Street Northeast Receptor 6.9 20 4.7 9.0 No No Southeast Receptor 6.9 20 4.7 9.0 No No Southwest Receptor 7.0 20 4.7 9.0 No No Northwest Receptor 6.9 20 4.7 9.0 No No Bristol Street and Washington Avenue Northeast Receptor 6.6 20 4.5 9.0 No No Southeast Receptor 6.6 20 4.5 9.0 No No Southwest Receptor 6.7 20 4.5 9.0 No No Northwest Receptor 6.7 20 4.5 9.0 No No Source: Air Quality Assessment Report (URS 2013a). Note: CAAQS = California Ambient Air Quality Standards. As discussed previously, the proposed Project would not result in air pollutant concentrations that exceed the SCAQMD's LSTs for construction activities. In addition, the operations phase of the Project would not result in CO hotspots. As such, the construction and operations phases of the Project would not result ANA 111 -334 (PER -02 -0Q CITY OF SANTA ANA (11/25/2013 RE, V2) 132897 CM PAGE27 55C -42