Orono_Route_Permit_Application - Docket # W002/TL-11-223

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clearances. Displacement can occur when an existing structure is located within the right-of-way for a new transmission facility. The proposed transmission line will be designed so that all existing residences are located outside of the right-of-way. Furthermore, the Proposed Route includes realignment of existing transmission Line 0831 and associated structures off of two residential properties as part of the Project. See Appendix B.2. The proposed Project will not require displacement of occupied residences. Mitigative Measures It is not anticipated that any buildings or residences will be displaced by the Project. Therefore, no mitigative measures are proposed. Xcel Energy will work with landowners where buildings or residences are near the proposed transmission structures to ensure appropriate placement of such structures. 6.2.4 Noise Transmission Line Noise Transmission conductors produce noise under certain conditions. The level of noise depends on conductor conditions, voltage level and weather conditions. Noise emissions from a transmission line occur during certain weather conditions. In foggy, damp, or rainy weather, power lines can create a crackling sound when a small amount of electricity ionizes the moist air near the wires. During heavy rain, the background noise level of the rain is usually greater than the noise from the transmission line. As a result, people do not normally hear noise from a transmission line during heavy rain. During light rain, dense fog, snow, and other times when there is moisture in the air, transmission lines can produce noise. Noise levels produced by a 115 kV transmission line are generally less than outdoor background levels and are therefore not usually audible. Since human hearing is not equally sensitive to all frequencies of sound, the most noticeable frequencies of sound are given more "weight" in most measurement schemes. The A -weighted scale corresponds to the sensitivity range for human hearing. Noise levels capable of being heard by humans are measured in decibels ("dBA"). A noise level change of 3 dBA is barely perceptible to human hearing. A 5 dBA change in noise level, however, is clearly noticeable. A 10 dBA change in noise level is perceived as a doubling of noise loudness, while a 20 dBA change is considered a dramatic change in loudness. Table 9 shows noise levels associated with common, everyday activities. Table 9 Common Noise Sources and Levels Noise Source ' et Engine (at 25 meters) Sound Pressure Level .: 140 et Aircraft (at 100 meters) 130 Rock Concert 120 Pneumatic Chipper 110 jackhammer (at 1 meter) 100 Chainsaw. Lawn Mower at 1 meter 90 Heavy Truck Traffic 80 Business Office, Vacuum Cleaner 70 Orono Project June 7, 2011 MPUC Docket No. E002/TL-11-223 42