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Off-Site Project Heavy Truck Traffic Noise Impacts Relative to the County's 65 dB Ldn Exterior Noise Standard In the computation of Ldn, each nighttime truck passby is multiplied by 10 to account for the greater sensitivity of noise during nighttime hours. Based on 1 daytime and 7 nighttime hours of heavy truck traffic generation at maximum plant capacity, the Ldn at the nearest existing residence located 60 feet from the roadway centerline due to the project traffic alone would be approximately 63 dB Ldn. This level is below the County's 65 dB Ldn exterior noise level criteria applied to residential uses. Provided the nighttime truck operations can effectively utilize the optimized noise reduction operating parameters, project noise levels will be below 65 dB Ldn at the nearest residences. If, however, those parameters cannot be followed, the predicted noise level at the nearest residences would be 4 dB higher, or approximately 67 dB Ldn, which would exceed the County's 65 dB Ldn exterior noise standard. Because the applicant is proposing to utilize the optimized operating procedures, project traffic noise impacts at the outdoor activity areas of the residences located along East River Road are considered less than significant relative to the County's 65 dB Ldn exterior noise level standard. Off-Site Project Heavy Truck Traffic Noise Impacts Relative to the County's 45 dB Ldn Interior Noise Standard As noted previously, standard construction typically results in a traffic noise reduction of approximately 25 dB with windows closed. When windows are open, a building fagade noise reduction of approximately 10 dB can be expected, but the County's 45 dB Ldn interior noise level standard is applied with windows closed. The project is predicted to generate a noise level of approximately 63 dB Ldn at the nearest residential building facades. After subtracting the typical noise reduction provided by the residential building facades with windows closed (25 dB), the project by itself would generate interior noise levels during nighttime project operations of 38 dB Ldn within the nearest residences to East River Road. If the optimized operating procedures are not followed, interior noise levels would be 4 dB higher on average, or approximately 42 dB Ldn, which wqould still satisfy the County's 45 dB Ldn interior noise level standard. Because these levels are below the County's 45 dB Ldn standard, noise impacts of the project are predicted to be less than significant relative to the County's interior Ldn-based noise standard. Summary of impacts Relative to San Joaquin County Noise Standards This analysis concludes that, provided the optimized heavy truck operating procedures can be utilized during nighttime operations, project-generated noise levels are not expected to exceed adopted San Joaquin County noise standards applicable to residential uses at either interior or exterior locations. Therefore, relative to the adopted County noise standards, impacts of this project are considered to be fess than significant. Environmental Noise Analysis Munn&Perkins Expanded Hours of Operations—San Joaquin county Page 30