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Project Conditions Again, using ANSI/ASA S12.9-2008 Part 6 and the vehicle/haul truck operations assumption presented above, the probability of awakenings from combined operations of existing traffic and Proposed Project haul trucks on East River Road in the project area was calculated to be approximately 100 percent. This probability is reduced to approximately 99 percent given the application of the haul truck noise exposure reduction parameters. Impact : Project asphalt plant operations would add to the noise environment in the project vicinity.This impact is less than significant. As described above, asphalt plant operations (on-site noise sources) during the hours of 9 p.m. to 5 a.m. would not be expected to produce noise exposure in excess of 43 dB 1-41-na„at the closest existing residential receivers to the north and east. This noise exposure level would not exceed the County's nighttime noise limits for outdoor activity areas of 45 dB hourly L,,and 65 dB Lm,. Existing ambient noise exposure at the closest residences to the north of project site (represented by measurement site 4)was measured to be in the range of 51-63 dB hourly Laq. Project asphalt plant operations would generally be more than 10 dB below the existing ambient noise exposure and would not be expected to add significantly to the noise environment at these receivers. Existing ambient noise exposure at the closest residences to the east of the project site (represented by measurement site A) was measured to be in the range of 35-48 dB hourly Leq, with an average hourly Laq of 43 dB during 9 p.m. to 5 a.m. hours. On average, project-related asphalt plant noise would be expected to add 2 dB to the noise environment at the closest residence to the east (site A). Given the relatively low ambient noise exposure at this location, a +5 dB threshold of significance is appropriate. Therefore, project-related noise exposure from on-site sources is not expected to add significantly to the noise environment at the closest receiver locations to the east of the project site. Mitigation Measures: None required. Impact : Off-site project haul truck traffic would add to the noise environment in the project vicinity.This impact is potentially significant. Off-site project haul trucks would increase noise exposure as described by the 24-hour day-night A-weighted average (Len) and the single event noise level (SEL). The increase in noise exposure is potentially significant based on the increase in ambient noise and the potential for sleep disturbance associated with periodic noise. As presented above, project haul truck noise would be expected to produce noise exposure of approximately 66 dB Ldn or 62 dB Lan at the closest residences to the project site on East River Road (60 feet from the roadway centerline) when operated under typical parameters or proposed optimized parameters, respectively. Assuming the typical truck operating parameters, project haul truck noise exposure would be expected to exceed the applicable County noise exposure limit of 65 dB Ldn. 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 L&- 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. San Joaquin County QX-89-0002/Aggregates Inc. Community Development Page 7