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<br /> <br /> <br />Memorandum <br />February 26, 2025 <br />Page 10 <br />21202-23 North County Landfill_Noise DRAFT <br />and only nominal additions of refuse to this area are expected prior to final closure of the <br />landfill. The combined noise from all off-road equipment under the Maximum Noise Level <br />Scenario was compared to the Lmax thresholds in the County Noise Ordinance for stationary <br />sources referenced in Table 4. <br />Under the Typical Noise Level Scenario, it was assumed that the two loudest pieces of <br />equipment would operate simultaneously near the perimeter of Lined Area 1 throughout the <br />workday (i.e., more than 30 minutes). As discussed above, this is a conservative analysis <br />because Lined Area 1 is currently inactive and only nominal additions of refuse to this area are <br />expected prior to final closure of the landfill. The combined noise from off-road equipment <br />under the Typical Noise Level Scenario was compared to the Leq thresholds in the County Noise <br />Ordinance for stationary sources referenced in Table 4. <br />Modeling the potential noise impact at the closest noise-sensitive receptor is also conservative <br />because it represents a worst-case scenario for all nearby sensitive receptors exposed to noise <br />during project operation. An “acoustical usage factor” was used to account for the fact that <br />equipment would not operate at maximum capacity 100 percent of the time and was based on <br />assumptions that have been developed by the Federal Highway Administration.8 The types of <br />heavy off-road equipment that would be used on the project site (e.g., backhoe, dozer, and <br />grader) were provided by the project applicant (Attachment A). <br />As shown in Table 5, the estimated noise levels at the nearest noise-sensitive receptor for both <br />the Maximum Noise Level Scenario and Typical Noise Level Scenario are below the applicable <br />County Noise Ordinance daytime and nighttime noise standards for stationary sources. The <br />project would also result in a less than 1 dBA increase in ambient noise levels at the nearest <br />noise-sensitive receptor under the Maximum Noise Level Scenario, which would make no <br />perceptible difference. Therefore, the project’s use of off-road equipment would not generate <br />substantial noise levels at nearby noise-sensitive receptors during project operations. <br />Table 5. Potential Noise Impact at Nearest Sensitive Receptor from Off-Road Equipment <br />Operation Scenario <br />Maximum Noise Level Scenario <br />(dBA Lmax) <br />Typical Noise Level Scenario <br />(dBA Leq) <br />Existing Condition 57.1 44.0 <br />Project 58.0 44.0 <br />Daytime Thresholds 75 55 <br />Nighttime Thresholds 65 45 <br />Exceed Thresholds? No No <br />Source: Noise calculations included in Attachment A. <br /> <br />8 U.S. Department of Transportation, 2006. FHWA Highway Construction Noise Handbook. August.