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1 Draft Supplemental Environmental Impact Report Page IV.0-2 ' Forward Inc.Landfill 2018 Expansion Project Several time—averaged scales represent noise environments and consequences of human activities. The most commonly used noise descriptors are the equivalent A—weighted sound level over a given time ' period (Leq)2;average day—night 24—hour average sound level (Ldn) 'with a nighttime increase of ten dBA to account for sensitivity to noise during the nighttime;and community noise equivalent level (CNEL)4, also a 24—hour average that includes both an evening and a nighttime weighting. ' Noise Standards All jurisdictions have noise exposure standards designed to assure that noise does not excessively ' impact the quality of life of its citizens. For noise sources amenable to local control,noise exposure to noise-sensitive land uses is usually regulated by ordinances. These ordinances limit the allowable noise levels at the property line of the receiving land use. For the most common noise sources, such as cars,trucks,trains or airplanes, local jurisdictions are preempted from regulating the noise emissions from the source. Control of exposure due to preempted sources is managed by discretionary land use ' decisions relative to the receiver. Noise ordinance standards are typically stated in terms of the Leq metric, or in terms of allowable exposures over stated short time periods. Lmax,the maximum noise level for a specified duration and time period, also is used. In San Joaquin County,noise ordinances are part of the Ordinance Code. The land use decision standards typically use the weighted 24-hour Ldn or CNEL. Ldn and Leq-based ' land use standards are also articulated in the San Joaquin County General Plan. Below are summaries of the applicable ordinance codes and policies of the General Plan. San Joaquin County Ordinance Code ' Transportation Noise Source Standards. Section 9-1025.9(Chapter 9-1025,Division 10,Title 9) of the San ' Joaquin County Ordinance Code, at Subsection(a), "Transportation Noise Sources,"requires that all new noise-sensitive developments mitigate noise levels due to transportation sources at any noise sensitive areas to the levels shown in Table IV.0-2. ' The Ordinance also states that if new or expanded transportation facilities cause the levels in Table IV.0-2 to be exceeded, the source is required to mitigate the noise impact. The noise impact from any new landfill traffic would thus be potentially significant if it would cause noise levels at any of the noise sensitive land uses shown in Table IV.0-2 to be exceeded. An acoustical analysis should identify mitigation measures to reduce the noise effects to be within the standards of Table IV.0-2 or provide a ' detailed explanation stating why mitigation is infeasible (Section 9-0125.9 (d)(4)). Stationary Noise Source Standards. Sub-section(b), "Stationary Noise Sources," of Section 9-1025.9 ' establishes requirements that noise-sensitive uses be protected from stationary noise sources, and that new or expanded stationary noise sources mitigate their impact at any noise-sensitive use. The noise ' The Equivalent Sound Level(Lea)is a single value of a constant sound level for the same measurement period duration,which has sound ' q energy equal to the time—varying sound energy in the measurement period. ' Ldn is the day—night average sound level that is equal to the 24—hour A—weighted equivalent sound level with a ten—decibel penalty ' applied to night between 10:00 p.m.and 7:00 a.m. CNEL is the average A—weighted noise level during a 24—hour day,obtained by addition of five decibels in the evening from 7:00 to 10:00 p.m.,and an addition of a ten—decibel penalty in the night between 10:00 p.m.and 7:00 a.m. 1