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<br />require that every reasonable effort be made to obtain a substantial noise reduction. Mn/DOT <br />defines a substantial noise reduction as 5dBA or more from a noise impact. <br /> <br />The Minnesota Pollution Control Agency has also established guidelines for both residential <br />and industrial zones and acceptable SPL maximums for both. <br /> <br />These guidelines, measured in dBA, are stipulated in the form of LID and Lso. Simply stated, <br />LID means that the measured SPL (in dB A) must not exceed a certain threshold more than <br />10% of the time (for a one hour survey), and Lso, being a level, which must not be, exceeded <br />more than 50% of the time (again, for a one hour survey). <br /> <br />These thresholds are listed as SPL (dBA) maximums by the MPCA for residential areas, as <br />follows: <br /> <br />7030.0050 Noise Area Classification (NAC)l (Household Units including Farm Houses)1 <br /> <br />Daytime <br /> <br />L5D <br /> <br />LID <br /> <br />60dBA <br /> <br />65dBA <br /> <br />Nighttime <br /> <br />LSD <br /> <br />LID <br /> <br />(1 0:00PM-7:00AM) 50dBA <br /> <br />55dBA <br /> <br />1,,/\ Guide to Noise Control in Minnesota", Brian Timcrson, MPeA <br /> <br />2.0 MINNOISE Model Results <br /> <br />As stated in Section 3.0 "Evaluation and Process", the augmented FHW A noise prediction <br />software MINNOISE was used to predict noise levels at 20 virtual receptor sites along the <br />study corridor. <br /> <br />MINNOISE calculates the amount of potential noise directly related to traffic speeds, traffic <br />mix (% cars, trucks, heavy trucks) and peak hour percentages of predicted future traffic <br />(2030). Traffic volumes were taken from a traffic analysis perfoffi1ed in 2007 as part of the <br />original EA. <br /> <br />Speed assumptions were based on posted speeds and adjusted for traffic approach speeds <br />during higher volumes (rush hours). <br /> <br />FHW A and MnlDOT procedures allow for only one descriptor to be used in modeling and <br />projecting future noise results. In this instance predicted results will be deteffi1ined using the <br />Llo descriptor only. <br /> <br />The existing and 2030 projected LID noise levels at the 20-receptors are presented in figure 3. <br />Please refer to Appendix A for baITier and receptor locations. <br /> <br />NOise Barrier Analysis <br />Highway 10 <br /> <br />Page 3 <br />