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Munn&Perkins Quarry Excavation Permit truck noise exposure would be expected to exceed the applicable County noise exposure limit of 65 dB L&.With the proposed optimization of haul truck operations using specified parameters, project haul truck noise exposure would not be expected to exceed the County exterior noise exposure limit.Project haul truck noise exposure within the closest residences to the project would not be expected to exceed the applicable County interior noise exposure limit of 45 dB Ldp. Assuming typical,not optimized operations of the project haul trucks,noise exposure from this source would be expected to add no less than 2 dB to the noise environments of residences on East River Road(60 feet from roadway centerline)closest to the project site. This noise exposure increase would be considered significant based on the applicable 1.5 dB increase criterion.Assuming the proposed operation of project haul trucks using the optimized parameters discussed above,noise exposure from this source would be expected to add less than 1 dB to the noise environments of receivers on East River Road near the project site.This noise exposure increase would be considered less than significant. The probability of awakenings due to project haul truck operations on East River Road was calculated to be approximately 89 -93 percent for residences 60 feet from the centerline of the roadway. The lower probability(89 percent)is related to the application of proposed optimized truck operating parameters, with the upper probability(93 percent)assuming typical operations. The probability of awakenings was calculated to be 99- 100 percent when the cumulative effects of existing vehicle traffic and project haul trucks on East River Road were combined. The increase in probability of awakenings due to the project haul trucks was calculated to be 7-8 percent.This level of increase is considered significant. Mitigation Measure 3.4.1: All project trucks shall be operated using noise-mitigating operating parameters when entering or leaving the plant on East River Road. Based on testing conducted by Bollard Acoustical Consultant, Inc.,the quietest haul truck operating parameters were as follows. • Empty Trucks: Travel speed at 38-43 mph with engines in 8t1i gear at 700-800 rpm. • Loaded Trucks: Travels speed of 33-35 mph with engines in 6th or 7 ear at 1 400-1,600 r p p gg � m.p Furthermore,truck parking anywhere along River Road and the use of jakc breaks at the McHenry Ave/River road intersection is prohibited. Significance After Mitigation: Application of the proposed optimized haul truck operating parameters in Mitigation Measure 3.4.1 would be expected to effectively mitigate project-related noise exposure from the perspective of the applicable County noise exposure level criteria and noise exposure level increase criteria. However, application of the optimized haul truck operating parameters would not appreciably mitigate the significant increase in probability of residential awakenings due to project haul truck operations. Due to the significant increase in probability of residential awakenings in the project area due to project haul truck passbys,this impact is considered significant and unavoidable. Munn&Perkins Quarry Excavation Permit 3.4-16 PSA 1211086 Draft EIR April 2011