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City of Santa Ana -Park View at Town and Country Manor <br />Draft EIR <br />Carbon Monoxide Hot Spots <br />Impact 4.2 -3 Operation of the project would not cause or contribute to a localized carbon <br />monoxide violation at project- impacted traffic intersections. <br />Thresholds of Significance <br />Within an urban setting, motor vehicle exhaust is the primary source of carbon monoxide (CO) <br />emissions. Consequently, the highest ambient CO concentrations are generally found within close <br />proximity to congested intersection locations. The CO hotspot thresholds are represented by the most <br />restricted State or federal CO ambient air quality standards: <br />• 1 -hour CO standard: 20 ppm <br />• 8 -hour CO standard: 9 ppm <br />If the CO contributed by the project in combination with CO produced by non - project traffic exceeds <br />the above standards, then the project would have a significant impact. <br />Impact Analysis <br />A carbon monoxide (CO) hot spot is a localized concentration of CO that is above the State or <br />national 1 -hour or 8 -hour CO ambient air standards. Localized high levels of CO are associated with <br />traffic congestion and idling or slow- moving vehicles. To provide a worst -case scenario, CO <br />concentrations are estimated at project - impacted intersections, where the concentrations would be the <br />greatest. Intersections with the highest potential for CO hotspots were selected based on their average <br />delay, traffic volumes, and proximity to sensitive receptors. <br />This analysis follows guidelines recommended by the CO Protocol and the SCAQMD. According to <br />the CO Protocol, intersections with Level of Service (LOS) E or F require detailed analysis. In <br />addition, intersections that operate under LOS D conditions in areas that experience meteorological <br />conditions favorable to CO accumulation require a detailed analysis. The SCAQMD recommends <br />that a local CO hotspot analysis be conducted if the intersection meets one of the following criteria: <br />1) the intersection is at LOS D or worse and where the project increases the volume to capacity ratio <br />by 2 percent, or 2) the project decreases LOS at an intersection from C to D. <br />Using the CALINE4 model, potential CO hotspots were analyzed at intersections that operate at LOS <br />D or worse. As shown in Table 4.2 -10 and Table 4.2 -11, the estimated 1 -hour and 8 -hour average <br />CO concentrations at the opening year and General Plan buildout, respectively, in combination with <br />background concentrations are below the State and national ambient air quality standards. No CO <br />hotspots are anticipated because of traffic- generated emissions by the project in combination with <br />other anticipated development in the area. Therefore, the mobile emissions of CO from the project <br />are not anticipated to contribute substantially to an existing or projected air quality violation of CO. <br />Michael Brandman Associates 4.2 -21 <br />H\Cl t(PN- JMb327b32]003MMVB2]0030 Se 4GAvQ ity.DOc <br />