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4.5 Noise V Mitigation Measures Measure 4.5.2: Implementation of Mitigation Measures 4.5.1a,4.5.1b,and 4.5.1c would reduce impacts of processing plant noise on local residents to a less-than-significant level. Impact Significance After Mitigation: Less than significant. r, Impact 4.5.3: Traffic associated with operation of the project would result in an increase in ambient noise levels on nearby roadways used to access the mine.This would be a significant impact. V Based on the traffic analysis prepared for this project, the project would generate approximately 1,962 additional one-way vehicle trips per day during periods of maximum output(summer ` months). Haul trips by heavy trucks to and from the project site would account for almost all of this increase. Truck trips would typically begin as early as 6:00 AM but on some occasions could occur continuously on a 24-hour basis. These trips would be distributed over the local road network and would affect roadside noise levels at sensitive receptor locations. To assess the impact of project traffic on roadside noise levels, noise level projections were made using the Federal Highway Administration's(FHWA)Noise Prediction Model for those road segments that would experience the greatest increase in traffic volume(as determined in the traffic section of this report) and that pass by sensitive receptors. The results of the modeling L effort are shown in Table 4.5-5. The traffic volumes used for the modeling effort are average morning weekday peak-hour volumes during periods when the mine is generating maximum output(summer)because that is when the project would generate the highest number of truck trips.Estimated noise levels shown in Table 4.5-5 correspond to a distance of approximately 50 feet from the centerline of applicable roadway segments, which is also the assumed distance to the closest sensitive receptors. Some of the residences located along project roadways are setback ` up to several hundred feet from the roadway centerline. In such cases,the noise levels in Table 4.5-5 can be attenuated(lessened)by at least 3 dBA per doubling of distance from the r roadway centerline. For example, where residences are located 100 feet from the roadway centerline noise levels in Table 4.5-5 can be reduced by 3 dBA, where residences are located 200 feet from the roadway centerline noise levels can be reduced by 6 dBA, where residences are setback 400 feet from the roadway centerline noise levels can be reduced by 9 dBA, and so on. The net increases in roadside noise levels shown in Table 4.5-5 would be the same regardless of distance from the roadway centerline. r RMC Pacific Vernalis Quarry Mining and Reclamation Project 4.5-19 ESA/203015 Draft Environmental Impact Report May 2006 r