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ANALYSIS OF POTENTIAL PROJECT NOISE IMPACTS As noted previously, the project would continue the historic practice of allowing nighttime processing and transporting of aggregate products (primarily asphalt) as needed when contracts specifically require nighttime deliveries of such materials. Relative to those historic operations, the ongoing practice of providing paving materials at night would not represent a change in noise levels and, therefore, no new noise impact would be identified. However, noise generated during previous nighttime asphalt plant operations was not included in the assessment of baseline conditions for this study. That information is provided strictly for historical context. Relative to nights when no paving activities are taking place, nighttime operations of the Munn & Perkins facility will generate noise by operation of the asphalt plant and by increased traffic on Fast River Road. As a result, an assessment of the potential noise impacts of both on-site equipment operations and off-site truck traffic passbys relative to those quieter ambient conditions is provided in this analysis. Impact Evaluation Relative to County Noise Standards Impacts of Nighttime Asphalt Plant Operation Relative to County Exterior Noise Standards for Stationary Sources Even under atmospheric conditions which are favorable to propagation of sound over large distances, asphalt plant noise levels are predicted to be at or below the County's 45 dB Leq noise criteria outside of the nearest existing residences, and well below the County's 65 dB _.. Lmax nighttime standard. The Appendix B data indicate that background nighttime ambient.noise levels (levels measured ... during which the plant was not operating), varied considerably. For example, the measured ambient noise level at Site A during the 2 am hour of Monday, September 291' was 36 dB Leq (Appendix B-3); whereas at 11 pm on that same night it was measured to be 44 dB Leq. �. Because the asphalt plant was not operating during either of these hours, and because it is reasonable to assume that agricultural harvesting operations were not taking place during these late nightlearly morning hours, it is clear that other local sources of ambient noise contributed to the affected the measurement results. Because of this variability in ambient noise conditions, it is difficult to predict which ambient noise environment would be present on nights during which nighttime paving projects would require operation of the Munn & Perkins asphalt plant. Regardless, the analysis of isolated Munn & Perkins asphalt plant noise generation provided earlier in this report indicates that, because the asphalt plant noise levels are below the County noise standards at the nearest residences to the east, and because the County noise standards are currently exceeded by sources of noise other than the asphalt plant, future exceedances of the County noise level standards during nighttime operations of the Munn & Perkins asphalt plant would not be driven by the noise generation of that plant equipment. As a result, noise impacts associated with expanded hours of asphalt plant equipment operation are predicted to be foo.-x, tww sicmi�lrw7f relative to County standards. 1_nvironrnenta!Noise Analysis Munn &Perkins Expanded Hours of Operations—San Joaquin County Page 29