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SAN LEANDRO SHORELINE DEVELOPMENT DRAFT EIR CITY OF SAN LEANDRO AIR QUALITY Local CO Hotspots Congested intersections have the potential to create elevated concentrations of CO, referred to as CO hotspots. The significance criteria for CO hotspots are based on the California AAQS for CO, which is 9.0 ppm (8 -hour average) and 20.0 ppm (1 -hour average). However, with the turnover of older vehicles, introduction of cleaner fuels, and implementation of control technology, the SFBAAB is in attainment of the California and National AAQS, and CO concentrations in the SFBAAB have steadily declined. Because CO concentrations have improved, the BAAQMD does not require a CO hotspot analysis if the following criteria are met: ■ The Project is consistent with an applicable congestion management program established by the County Congestion Management Agency for designated roads or highways, the regional transportation plan, and local congestion management agency plans. ■ The Project would not increase traffic volumes at affected intersections to more than 44,000 vehicles per hour. ■ The Project traffic would not increase traffic volumes at affected intersection to more than 24,000 vehicles per hour where vertical and/or horizontal mixing is substantially limited (e.g., tunnel, parking garage, bridge underpass, natural or urban street canyon, below -grade roadway)." Community Risk and Hazards The BAAQMD's significance thresholds for local community risk and hazard impacts apply to both the siting of a new source and to the siting of a new receptor. Local community risk and hazard impacts are associated with TACs and PM2.5 because emissions of these pollutants can have significant health impacts at the local level. For assessing community risk and hazards, sources within a 1,000 -foot radius are considered. Sources are defined as freeways, high volume roadways (with volume of 10,000 vehicles or more per day or 1,000 trucks per day), and permitted sources." ■ The Project would generate TACs and PM2.5 during construction activities that could elevate concentrations of air pollutants at the surrounding residential receptors.32 The thresholds for construction -related local community risk and hazard impacts are the same as for Project operations. The BAAQMD has adopted screening tables for air toxics evaluation during construction." Construction -related TAC and PM2.5 impacts should be addressed on a case-by-case basis, taking into consideration the specific construction -related characteristics of each project and proximity to off-site receptors, as applicable.34 30 Bay Area Air Quality Management District, 2011 (revised), California Environmental Quality Act Air Quality Guidelines. 31 Bay Area Air Quality Management District, 2011 (revised), California Environmental Quality Act Air Quality Guidelines. 32 Students and staff of Garfield Elementary School are located further from the Project site than the abutting residential homes to the north and east. Additionally, the exposure period for school-based receptors (e.g., 8 hours per day, 5 days per week, and 180-240 days per year) are much lower than for residential receptors (e.g., 24 hours per day, 7 days per week, and 350 days per year). Ultimately, the overall exposures to TACs for the sensitive receptors at Garfield Elementary School would be much lower compared to TAC exposures for the nearby residences. Therefore, only the on-site and off-site residents were considered sensitive receptors for this evaluation. ss Bay Area Air Quality Management District, 2010, Screening Tables for Air Toxics Evaluations during Construction. 34 Bay Area Air Quality Management District, 2011 (revised), California Environmental Quality Act Air Quality Guidelines. 4.2-20 DECEMBER 2014