EQB & MN Rules - Laserfiche WebLink

Home Browse Search

Orono Substation Replacement Project Noise Assessment 2.0 NOISE CONCEPTS AND TERMINOLOGY The State limits for a residential location are L10=65 dBA and L50=60 dBA during the daytime(7:00 a.m.–10:00 p.m.)and L10=55 dBA and L50=50 dBA during the nighttime (10:00 p.m.–7:00 a.m.)(Minn.Rules 7030.0040). This means that during a one-hour period of monitoring,daytime noise levels cannot exceed 65 dBA for more than 10 percent of the time,and cannot exceed 60 dBA more than 50 percent of the time. The L50 level is used to address continuous sources,i.e.sources that are operated for more than 30 minutes of an hour. Potential sound levels from the proposed replacement substation are compared with this standard to ensure that the substation will be in compliance with State noise standards. A basic introduction to noise levels and common terminology can be found in the publication by the Minnesota Pollution Control Agency(MPCA),A Guide to Noise Control in Minnesota, which was updated in October 2008 and can be found at the following website: http://www.pca.state.mn.us/publications/p-gen6-01.pdf(MPCA Noise Guide). Page two of the MPCA Noise Guide is a listing of decibel levels of common noise sources which is listed below with some distances added for clarity. The L50 NNS is 50 dBA which,from the table below,is similar to sound level in a library. Decibel levels of common noise sources 140 Jet Engine(at 25 meters) 130 Jet Aircraft(at 100 meters) 120– Rock Concert(at 10 meters from loudspeakers) 110 Pneumatic Chipper(at one meter) 100- Jackhammer(at one meter) 90 Chainsaw,Lawn Mower(at one meter) 80- Heavy Truck Traffic(at 15 meters) 70-- Business Office,Vacuum Cleaner(at three meters) 60 Conversational Speech,Typical TV Volume(at 2-3 meters) 50 — Library 40- Bedroom 30--- Rural woods 20 Concert Hall/Recording Studio David Braslau Associates,Inc. Page 4