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<br /> <br /> <br />Memorandum <br />March 25, 2025 <br />Page 8 <br />21202-23 North County Landfill_AQ_0307 <br />Table 1. Air Quality Thresholds of Significance <br />Impact Analysis Pollutant Threshold of Significance <br />Criteria Air Pollutants <br />(Construction and <br />Operation1) <br />CO 100 tons per year <br />NOx 10 tons per year <br />ROG 10 tons per year <br />SOx 27 tons per year <br />PM10 15 tons per year <br />PM2.5 15 tons per year <br />Health Risks and Hazards <br />(Combined) <br />Tox air <br />Contaminant <br />For the Maximally Exposed Individual: <br />Cancer risk increase > 20.0 in one million <br />Chronic hazard index > 1.0 <br />Acute hazard index > 1.0 <br />1 Construction emissions, operational emission from permitted equipment and activities, and operational <br />emissions from non-permitted equipment and activities are evaluated separately. <br />Source: Valley Air District, 2015 <br /> <br />The Valley Air District has established that preliminary screening can be used to determine with <br />a fair level of certainty that the effect a project has on any given intersection would not result in <br />a CO hotspot. According to the Valley Air District, a project would result in a less-than- <br />significant impact related to localized CO concentrations if neither of the following screening <br />criteria are met at all intersections affected by the development project: <br />• A traffic study for the project indicates that the Level of Service (LOS) on one or more <br />streets or at one or more intersections in the project vicinity will be reduced to LOS E or <br />F; nor <br />• A traffic study indicates that the project will substantially worsen an already existing LOS <br />F on one or more streets or at one or more intersections in the project vicinity. <br />The Valley Air District identified some common types of facilities that have been known to <br />produce odors, including sanitary landfills, and established screening levels for potential odor <br />sources, in the form of screening distances, to semi-quantitatively assess a project’s potential to <br />adversely affect area receptors. For projects that would result in sensitive receptors being <br />located closer than the screening level distances, the Valley Air District has established the <br />following significance threshold for odor problems: <br />• More than one confirmed complaint per year averaged over a three-year period, or <br />• Three or more unconfirmed complaints per year averaged over a three-year period.