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PROJECT NOISE GENERATION Methodology for isolation of Asphalt Plant Noise During the expanded hours of operations, mining and aggregate crushing/screening activities would not occur. Therefore, the most significant source of on-site noise generation at the - residences to the east during the expanded hours of facility operations would be the operation of the asphalt plant. The Table 4 data, in conjunction with the Appendix B graphs, provide a comprehensive evaluation of the overall ambient noise environment present at Sites A and B during the week of monitoring. However, to assess the potential impacts associated with use of the asphalt plant by itself (without the concurrent noise generation of the aggregate mining, crushing, and screening activities, as well as local activities and natural sounds), it is important to isolate the noise generated by the asphalt plant from the rest of the noise environment. BAC used logs of asphalt and rock plant usage during the week-long noise monitoring program • with a detailed statistical analysis of the noise measurement results shown in Appendix B to determine the noise generation of the asphalt plant in isolation. Specific analysis of median (L50), and background (L90), noise levels was conducted for both the hours in which the asphalt plant was in operation, as well as the hours adjacent to those hours during which time the plant was known not to be in operation. From this assessment, it was concluded that, during the hours the asphalt plant was reportedly operating, background (L90) noise levels were computed to be approximately 42-43 dB at the residences represented by noise measurement sites A & B, with measured variations of . between +/- 5 dB believed to be likely due to changes in atmospheric conditions and operation of the main rock processing equipment during those same hours. From this analysis, it was concluded that asphalt plant noise generation at the nearest residences to the east averages between 35 and 45 dB, with a mean of approximately 40 dB. Because the noise generation of the asphalt plant is dominated by the operation of the burner at large distances from the plant equipment, and because the burner is a steady-state noise source, maximum (Lmax), and average (Leq), noise levels associated with the operation of the asphalt plant equipment are not appreciably different at the nearest residences located over 2,000 feet away. Environmental Noise Analysis Munn& Perkins Expanded Hours of Operations— San Joaquin County Page 19