Appendix A Noise Study Report - Laserfiche WebLink

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5. Study Methods and Procedures The existing and future 2040 traffic (design year) noise levels at all 92 receptor locations were modeled using either the worst -case traffic operations (prior to speed degradation) or peak -hour traffic volumes, whichever were lower. The worst -case traffic condition is assumed to be level of service C and is generally loudest when vehicles on a given roadway travel at free -flowing traffic conditions. Accordingly, the worst -case traffic volume assumptions are based on the maximum number of vehicles that can typically travel in a given lane while still resulting in free -flowing traffic conditions. The worst -case traffic condition is assumed to be 750 vehicles per lane per hour (vplph) on Fairview Street and other local roadways. The a.m. peak -hour traffic volume was selected over the p.m. peak -hour traffic volume because the worst - hour noise levels based on the long-term (24-hour) noise level measurements occur during the a.m. hour. The a.m. and p.m. peak -hour traffic volumes were obtained from the Traffic Impact Analysis (LSA 2018). A summary of traffic data inputs for existing and future conditions is provided in Appendix A. TNM 2.5 is sensitive to the volume of trucks on the roadway because trucks contribute disproportionally to traffic noise. Vehicle distributions on Fairview Street were obtained from traffic counts collected during ambient noise level measurement. Vehicle distribution on other local roadways in the project area was assumed to be similar to Fairview Street. Table 5.1 shows the vehicle distribution and vehicle speeds for each vehicle category in the project area used to calculate existing and future traffic noise levels. Table 5.1. Vehicle Distribution Roadway Vehicle Distribution % Vehicle Speed (mph) Medium Heavy Medium Heavy Autos Trucks Trucks Autos Trucks Trucks Fairview Street and all other local 95 4 1 45 45 45 roadways Source: Compiled by LSA (May 2018). mph = miles per hour 5.4. Methods for Identifying Traffic Noise Impacts and Consideration of Abatement Traffic noise impacts are considered to occur at receptor locations where predicted design -year noise levels are at least 12 dBA greater than existing noise levels, or where predicted design -year noise levels approach or exceed the NAC for the applicable activity category. Where traffic noise impacts are identified, noise 28 Fairview Street Improvements from 9th Street to 16th Street and Bridge Replacement Project Noise Study Report