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• • Draft Supplemental Environmental Impact Report Page IV.0-9 • Forward Inc. Landfill 2018 Expansion Project • As discussed in the 2013 EIR, the existing elevated traffic noise levels related to landfill and other existing truck traffic in the area already exceed the County's maximum allowable exposure level of 65 dBA Ldn along several road segments in the project areas. Like the 2013 EIR, this SEIR applies an adjustable threshold based on absolute noise level. When existing exterior noise levels are more than • 65 dBA Ldn at a residential receptor, the threshold would be an increase of 3 dBA. This adjustable • threshold is a methodology based on a federal noise study of neighborhood annoyance related to airports that has been used extensively in California in City and County Noise Elements for assessing the effects of highway transportation noise levels (FICON, 1992). Impact C.1. Construction Noise Impacts (Revises 2013 EIR Impact C.1.) Temporary construction noise would result during site preparation activities for the project, such as the proposed creek relocation and preparation of the proposed expansion areas. Noise levels associated • with such activities would be short-term and would be similar to the equipment noise levels that are • already occurring at the landfill. Such activities would not substantially affect existing noise levels in the vicinity of the project and would have no effect on the long-term noise exposure in the project vicinity. • The revised project includes the development of expansion areas within the permitted landfill boundary,but does not include the previously proposed horizontal expansion onto the adjoining 184- acre Brocchini property. Eliminating the 184-acre expansion area would reduce construction noise impacts by eliminating noisy construction activities on this property compared with the 2013 project. • Construction noise impacts of the revised project would remain less than significant. • Impact C.2. Truck Traffic Noise Impacts (Revises 2013 EIR Impact C.2.) The 2013 EIR determined that noise level increases attributed to the project would exceed the • significance criteria at residential properties along each of the five roadway segments throughout the • project area where residences would be most affected by the project. The revised project would result in slightly decreased levels of traffic noise impacts compared to those described in the 2013 EIR(due to refinements in modeling and truck-size assumptions). In addition, traffic noise impacts would occur • for a shorter duration because the revised landfill closure date is 2036 instead of 2039. • The 2018 modeled noise levels along the five roadway segments are presented in Table IV.0-4. The ambient conditions along all these road segments currently exceed 67 dBA, and the increases of 2.6 to 3.9 dBA that would be attributable to the project(at maximum permitted daily trips)would be • considered significant along all segments except French Camp Road west of Austin Road. Therefore, impacts associated with project-generated traffic noise increases would be significant. The following measure was proposed as part of the project: • • As recommended mitigation in the 2000 EIR and implemented by the applicant, the landowner • or tenant at 9690 Austin Road shall be provided with the option of requesting a sound wall or • noise barrier to reduce noise exposure both in the front yard and within the home. Additional noise monitoring and measures will be undertaken to demonstrate compliance with