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1 I I Noise Source a Sound Pressure Level (dBA) Conversational Speech,Typical TV Volume 60 Library 50 I Bedroom 40 Secluded Woods 30 Whisper 10 I a A Guide to Noise Control in Minnesota Acoustical Properties,Measurement,Analysis and Regulation,Minnesota Pollution Control Agency ("MPCA"),2008. I In Minnesota, statistical sound levels ("L" or Level Descriptors) are used to evaluate noise levels and identify noise impacts. The standards are expressed as a range of permissible dBA within a one hour period;L50 is the dBA that may be exceeded 50 percent of the time within an hour,while L10 may be Iexceeded 10 percent of the time within an hour. Land areas, such as picnic areas, churches,or commercial spaces, are assigned to an activity category based on the type of activities or use occurring in the area. Activity categories are then categorized I based on their sensitivity to traffic noise. The Noise Area Classification ("NAC" list in the MPCA noise regulations to distinguish the categories. Residential areas, churches, and similar type land use activities are included in NAC 1; commercial-type land use activities are included in NAC 2; and I industrial-type land use activities are included in NAC 3. Table 10 identifies the established daytime and nighttime noise standards by NAC. I Table 10 Noise Standards by Noise Area Classification I Daytime Noise Standard Nighttime Noise Standard Noise Area Classification L;0 (dBA) L10 (dBA) L;0 (dBA) L10 (dBA) 1 60 65 50 55 I 2 3 65 70 65 70 75 80 75 80 The noise levels from the proposed double circuit 115 kV transmission line are expected to be only Islightly higher than the existing GRE 69 kV transmission line that is connected to the Orono substation. The GRE transmission line will be disconnected from the Orono Substation as a part of this Project. Therefore, noise levels from the new 115 kV transmission line should not be noticeably Igreater than existing levels. The proposed transmission lines were modeled using the Bonneville Power Administration CFI8X I model to evaluate audible noise from transmission lines. Where possible,the model was executed as a worst-case scenario benchmark,to ensure that noise was not under-predicted. Table 11 presents the L5 and L50 noise levels predicted for proposed transmission line structures and voltages for the Project. I I I Orono Project June 7,2011 MPUC Docket No. E002/TL-11-223 43