COMPLIANCE INFO_FINAL INITIAL STUDY/MITIGATED NEGATIVE DECLARATION 5/25

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Memorandum March 25, 2025 Page 14 21202-23 North County Landfill_AQ_0307 The on-road DPM emissions from trucks travelling by sensitive receptors along the haul route were estimated based on the net increase in average daily truck trips in the project vicinity. Emission factors for exhaust and fugitive emissions were derived from CARB’s EMFAC2021 database. The model input parameters, assumptions, and results are summarized in Attachment C. The annual average concentrations of DPM during project operation at sensitive receptors along the haul route were estimated using the American Meteorological Society/U.S. EPA regulatory air dispersion model (AERMOD). For the analysis, emissions of exhaust PM10 were used as a surrogate for DPM, which is a conservative assumption because more than 90 percent of DPM is less than 1 micron in diameter. The input parameters and assumptions used for estimating emission rates of DPM from trucks are included in Attachment C. PM10 emissions from off-site trucks were modeled as a line source along a representative section of the haul route (East Harney Lane between SR-88 and North County Landfill entrance road). The North County Landfill operates from 7:00 am to 5:00 pm, seven days per week. The AERMOD model input parameters included five years of Valley Air District meteorological data from the Stockton Met Site (Site ID 23237) located approximately 16 miles to the southwest of the North County Landfill. For sensitive receptors along the haul route, a uniform grid of receptors spaced approximately 50 meters apart with receptor heights of 1.8 meters was placed along the haul route as a means of developing isopleths (i.e., concentration contours) that illustrate the air dispersion pattern. In addition, lines of discrete receptors spaced approximately 20 meters apart and approximately 20 meters (65 feet) away from the haul route centerline were created for ground level receptors at heights of 1.8 meters to calculate concentrations at the closest sensitive receptors to the haul route. Comparing to other sensitive receptors identified above, the residential receptors identified along the haul route are among the receptors that are closest to the road and have a longer exposure duration and frequency than other sensitive receptors along the haul rout, such as school children. Therefore, the discrete residential receptors modeled at 20 meters (65 feet) from the centerline of the haul route represent a reasonable worst-case scenario. Based on the annual average concentrations of DPM estimated using AERMOD, potential health risks were evaluated for the maximally exposed individual resident (MEIR) along the haul route. The incremental increase in cancer risk at the MEIR was assessed for an individual initially exposed to DPM as a fetus during the third trimester of pregnancy until the age of 18, assuming 18 years of exposure to project operation emissions (between 2025 to 2043). This exposure scenario represents the most sensitive individual who could be exposed to adverse air quality conditions in the vicinity of the haul route. The input parameters and results of the health risk assessment are included in Attachment C.