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CHAPTERFOUR Environmental Consequences and Mitigation <br />Table 3.1-6, Category 2 shows the project noise impact exposure used to identify the level of <br />impacts based on an existing noise exposure level of 54 dBA. <br />Other residences located within a mile radius of the grade crossing will hear the train horn, but <br />impacts will be below moderate or severe. The noise levels will be well below the 65 dBA <br />threshold and will not require mitigation. <br />Residences located within ahalf--mile radius of the tracks will hear train noise, but impacts will <br />be below moderate or severe. The noise levels generated by the locomotive and coal rail cars <br />will be well below the 65 dBA threshold and will not require mitigation. Normal background <br />noise levels will resume after the train has passed the proximity of the residences. <br />Water Pipeline <br />No noise impacts will result from this project feature. <br />Transmission Line <br />No noise impacts will result from this project feature. <br />Temporary Impacts <br />Construction equipment would be the primary source for noise that creates a temporary noise <br />impact. This noise would be most noticeable from construction of the railroad alignment and <br />pipeline corridor, at the grade crossings, and from trucks traveling on the roads to the daily work <br />area. There will also be temporary noise impacts from construction of the transmission line. <br />Construction noise at the mine facilities would dissipate before any sensitive receptors would be <br />affected. <br />Noise from rock blasting would be generated during the first six months of the mine and <br />associated linear facility startup operations. Rock blasting would be required to build the mine <br />benches and some access roads. Rock blasting would be conducted in accordance with current <br />mining standards to reduce injuries that may result from a premature blast, fly rock, misfires, and <br />fumes. The air blast and vibration may be heard and felt within a 1,250 foot radius of the blast <br />area. Vehicles traveling on SH 139 may see the dust cloud from the rock blast, but will likely <br />not hear the sound or feel the vibrations. <br />Permanent Impacts <br />Residents in the Mack vicinity would hear train horns up to eight times per day as trains pass <br />through the two at-grade crossings. Receptor R10, near the CR 10 grade crossing, will be <br />severely impacted by train horn noise. The noise levels will increase approximately 12 dBA, and <br />exceed the 65 dBA HUD standard at this receptor, with each pass of the train. There would be <br />no permanent noise impacts resulting from operations at any other location. Mine operations <br />will generate noise, but there are no sensitive receptors in the area that would be affected. Noise <br />may cause some wildlife to avoid the operations areas. <br />Mitigation Measures <br />The criteria to mitigate severe railroad horn noise impacts can be found in the FTA Transit Noise <br />and Impact Assessment Manual, which has been adopted by the FRA. The criteria states that <br />mitigation should be considered when there is a 5 dBA increase in Ld„ or Leq, and the total noise <br />level exceeds 65 dBA. Mitigation measures include tall earth berms or noise walls to reduce <br />noise to acceptable FTA levels. Other noise mitigation measures can include insulating the <br />4-45 <br />DBMS 600 <br />