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Memorandum to: Kent Peterson Bituminous Roadways October 7, 2010 Page 5 Table 3: Predicted total future daytime noise levels under normal conditions. Plant Noise Level Under Total Predicted Existing Normal Operations at Future Daytime Location Daytime L50 each Location Noise Levels #1 59.7 46.1 59.9 #2 65.9 44.2 66.0 #3 62.5 41.3 62.5 #4 56.3 40.4 56.5 The temporary crushing operation would create additional noise beyond the normal operational conditions. The crushing operation would be louder than the equipment in use at the plant under normal operations and would therefore add noise to the proposed project site. The noise levels created by the crushing operation were calculated for each of the four noise monitoring locations. These noise values were then added to the predicted future noises levels of the combined existing noise plus the plant under normal operations. This returned a predicted future noise level at each location with the addition of the proposed plant plus while the crushing operation is one site. There are two potential locations on the project site for the mobile crushing operations. The crusher would be located at each location for a portion of two to three week period the crusher is on site and in operation: The noise levels heard at a location are dependant on the distance from the noise source. As a result, for the calculations in Table 4 that predict the future noise levels at the monitoring locations during crushing, the crusher location that was closest to each monitoring location was used for the calculation. This calculation would then provide the greatest possible increase in noise at a location due to the presence of the plant and the crusher for future noise levels. Table 4: Total predicted future daytime noise levels site including crushing Plant Noise Total Level Under Predicted Existing Normal Crusher Noise Future Daytime Operations at Level at each Daytime Location L50 each Location Location Noise Levels #1 59.7 46.1 56.7 61.6 #2 65.9 44.2 56.0 66.6 #3 62.5 4L3 51.6 62.9 #4 56.3 40.4 51.0 57.5 The noise generated by the proposed project during crushing operations will result in a 0.5 to 1.9 dBA increase to the existing noise levels at the four monitored locations near the project site. Based on MPCA noise guidance, a 1 dBA increase is not detectable by the human ear and a 3 dBA increase is considered the threshold of perception (A Guide to Noise Control in Minnesota; MPCA, 2008). As a result, the small increases in noise created by the proposed T ■0425.61nmumsu R \1 f 2909 Roseville CU Noiselm[mo-2O) 0-104)6 doe