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Noise Source' Sound Pressure <br />Conversational Speech, Typical TV Volume <br />Level .: <br />60 <br />Library <br />50 <br />Bedroom <br />40 <br />Secluded Woods <br />30 <br />Whisper <br />10 <br />a A Guide to Noire Control in Minnesota Acoustical Properties, Measurement, Analysis and Regulation, Minnesota Pollution Control Agency <br />("MPCA'�, 2008. <br />In Minnesota, statistical sound levels ("L" or Level Descriptors) are used to evaluate noise levels and <br />identify noise impacts. The standards are expressed as a range of permissible dBA within a one hour <br />period; L50 is the dBA that may be exceeded 50 percent of the time within an hour, while L10 may be <br />exceeded 10 percent of the time within an hour. <br />Land areas, such as picnic areas, churches, or commercial spaces, are assigned to an activity category <br />based on the type of activities or use occurring in the area. Activity categories are then categorized <br />based on their sensitivity to traffic noise. The Noise Area Classification ("NAC" list in the MPCA <br />noise regulations to distinguish the categories. Residential areas, churches, and similar type land use <br />activities are included in NAC 1; commercial -type land use activities are included in NAC 2; and <br />industrial -type land use activities are included in NAC 3. Table 10 identifies the established <br />daytime and nighttime noise standards by NAC. <br />Table 10 <br />Noise Standards by Noise Area Classification <br />The noise levels from the proposed double circuit 115 kV transmission line are expected to be only <br />slightly higher than the existing GRE 69 kV transmission line that is connected to the Orono <br />substation. The GRE transmission line will be disconnected from the Orono Substation as a part of <br />this Project. Therefore, noise levels from the new 115 kV transmission line should not be noticeably <br />greater than existing levels. <br />The proposed transmission lines were modeled using the Bonneville Power Administration CFI8X <br />model to evaluate audible noise from transmission lines. Where possible, the model was executed as <br />a worst-case scenario benchmark, to ensure that noise was not under -predicted. Table 11 presents the <br />LS and L50 noise levels predicted for proposed transmission line structures and voltages for the Project. <br />Orono Project June 7, 2011 <br />MPUC Docket No. E002/TL-11-223 43 <br />Daytime <br />Noise <br />Standard <br />Nighttime <br />Noise <br />Standard <br />Area <br />Noise <br />Classification <br />L50 (dBA) <br />L10 (dBA) <br />L50 (dBA) <br />L,0 <br />(dBA) <br />1 <br />1 <br />1 <br />1 <br />:1 <br />:1 <br />The noise levels from the proposed double circuit 115 kV transmission line are expected to be only <br />slightly higher than the existing GRE 69 kV transmission line that is connected to the Orono <br />substation. The GRE transmission line will be disconnected from the Orono Substation as a part of <br />this Project. Therefore, noise levels from the new 115 kV transmission line should not be noticeably <br />greater than existing levels. <br />The proposed transmission lines were modeled using the Bonneville Power Administration CFI8X <br />model to evaluate audible noise from transmission lines. Where possible, the model was executed as <br />a worst-case scenario benchmark, to ensure that noise was not under -predicted. Table 11 presents the <br />LS and L50 noise levels predicted for proposed transmission line structures and voltages for the Project. <br />Orono Project June 7, 2011 <br />MPUC Docket No. E002/TL-11-223 43 <br />