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3.4 Noise r� 'alM As shown in Table 3.4-3, average noise exposure at measurement site 4, which is assumed to adequately represent the closest residences to the north of the project site,is approximately 59 dB �i Leq with an hourly noise exposure range of 51-63 dB Leq during the 9 p.m.to 5 a.m. hours of the measurement survey. Likewise, average measured ambient noise exposure at measurement site 1' A to the east was approximately 43 dB Leq with a range of 35-48 dB Lea• The anticipated project asphalt plant noise exposure at the closest residences to the north (43 dB Leq)would, on average, be more than 10 dB below the existing ambient noise exposure, and would not be expected to contribute significantly to the existing noise environment at this receiver or other receivers along I tJ_ East River Road to the north of the project. At site A,project asphalt plant noise exposure(40 dB Leq)would, on average, increase the noise environment by approximately 2 dB (from 43 dB Leq to 45 dB Leq). Given a significant increase threshold of+5 dB based on the relatively low existing ambient noise exposure,the anticipated increase in noise exposure from asphalt plant operations during the 9 p.m.to 5 a.m.hours would not be considered significant. Project-Related Noise Exposure from Haul Trucks A detailed assessment of expected project-related haul truck noise exposure at the closest residences t : along East River Road is provided within the Bollard Acoustical Consultants,Inc. report of August 18, 2010. The following utilizes reference noise level measurements and assumed truck operations from that report. Regulatory Standards and Ambient Noise Level Increases Standard Heavy Truck Operations(1Vo Optimization of Operating Parameters) # Noise exposure at the closest residential properties along East River Road from proposed project haul truck trips was calculated using the measured average truck passby noise exposure(average SEL)and operational data presented in the BAC report of August 18,2010.Haul truck noise exposure at the closest residences to East River Road were calculated from the following equation. FI Ldn = SEL,vg +I Uog(Neq)--T t In this case, SEL,,v,is the average measured SEL,or 86 dB at 40 feet(approximately 83 dB at 60 feet);Neq is the equivalent number of haul truck operations calculated by adding the number of Fit daytime trips(between 9 p.m. and 10 p.m.) and 10 times the number of nighttime trips(between 10 p.m.=5 a.m.), or approximately 1,886(248 total truck trips); and T is approximately 49.4 or I OLog(seconds in a 24-hour day). Using the reference noise level data, operations,and the equation above,project-related haul k trucks would be expected to produce noise exposure of approximately 66 dB La„at the closest 'r I residences to the project on East River Road(60 feet from centerline). This noise exposure IM.+ exceeds the applicable noise exposure limit of 65 dB Ldn established by the County. Optimized Heavy Truck Operations Parameters The project developer has proposed to operate all project trucks using noise-mitigating Operating g 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. Munn&Perkins Quarry Excavation Permit 3.4-13 ESA 7211086 Draft ER April 2011 A 11