55C - RESO - BRISTOL ST IMPROVEMENTS

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ENVIRONMENTAL IMPACT REPORTADDENDUM Bristol Street Widening Phase 1118 — Washington Avenue to I7 h Street Localized Constriction Impacts Localized air pollutant emissions are evaluated relative to the exposure of local sensitive uses to air pollutant concentrations generated by the proposed Project. These are pollutant concentrations which can be directly correlated to the health -based ambient air quality standards. This differs from regional emissions which were discussed previously in that regional emissions are used to assess how much air pollution is generated within an air basin and does not have a direct correlation with health effects. Localized Significance Thresholds (LSTs) have been developed by the SCAQMD for nitrogen oxides (NOx), carbon monoxide (CO), PM10, and PM2.5• The LSTs determine whether project - related emissions would substantially contribute to or exceed the ambient air quality standards and expose sensitive receptors to excessive concentrations of air pollutants. The LSTs differ based on distance such that a greater allowance in air pollutant emissions is allowed for construction activities occurring further from a sensitive use and a lesser allowance in emissions is given for construction activities occurring closer to sensitive uses. Only short -term emissions occurring at the Project site for the Project's construction phase were included to determine if sensitive receptors local to the Project site would be adversely affected. Emissions generated by construction activities disperse rapidly with distance from the construction site. Individual construction phases were compared against the SCAQMD's LST significance criteria. As shown in Table 5, Project emissions would not exceed the LST screening level criteria for CO, nitrogen dioxide (NO2), PM10, or PM2.5. Because emissions associated with this alternative would be less than the LST, onsite construction emissions would not be expected to exceed the federal or California AAQS at the nearest sensitive receptors. As such, no significant air quality impacts related to localized air pollutants would occur from the construction phase. TABLE 5 LOCALIZED SIGNIFICANCE THRESHOLDS ANALYSIS FOR CONSTRUCTION ACTIVITIES Notes: NOx = nitrogen oxides; CO = carbon monoxide; PMro = particulate matter less than less than or equal to 10 microns in diameter; PM2,5 = pariculale 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 ANA 111 -334 (PER- 02 -01) CITY OF SANTA ANA (11/25/2013 REV2) 132897 CM PAGE 26 55C -41 M CID PM10 i Demolition 66 41 4 3 Grading 60 34 6 4 Trenching 41 19 2 2 Paving 16 11 1 1 SCAQMD Threshold 183 1253 13 7 Exceeds Threshold? No No No No Notes: NOx = nitrogen oxides; CO = carbon monoxide; PMro = particulate matter less than less than or equal to 10 microns in diameter; PM2,5 = pariculale 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 ANA 111 -334 (PER- 02 -01) CITY OF SANTA ANA (11/25/2013 REV2) 132897 CM PAGE 26 55C -41