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CCP 01-21-2003
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CCP 01-21-2003
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<br />I <br />.. <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />.. <br />I <br />I <br />I <br />I <br />I <br />I <br />-. <br />I <br />I <br /> <br />Noise Analysis <br /> <br />Noise is defined as any unwanted sound. Sound travels in a wave motion and produces a <br />sound pressure level. This sound pressure level is commonly measured in decibels. <br />Decibels (dB) represent the logarithmie increase in sound energy relative to a reference <br />energy level. A sound increase of 3 dB is barely perceptible to the human ear, a 5 dB <br />inerease is clearly notieeable, and a 10 dB increase is heard as twice as loud. For example, <br />if the sound energy is doubled (e.g., the amount of traffic doubles), there is a 3 dB increase <br />in noise, which is just barely noticeable to most people. On the other hand, if traffie <br />increases to where there is 10 times the sound energy level over a referenee level, then <br />there is a lO dB inerease and it is heard as twice as loud. <br /> <br />To approximate the way that an average person hears sound, an adjustment, or weighting, <br />of the high- and low- pitched sounds is made. The adjusted sound levels are stated in units <br />of "A-weighted decibels" (dBA). In Minnesota, traffic noise impacts are evaluated by <br />measuring and/or modeling the traffic noise levels that are exceeded 10 pereent and <br />50 percent of the time during the hours of the day and/or night that has the heaviest traffic. <br />These numbers are identified as the LIO and L50 levels. For example, an LIO value <br />of 65 decibels means that the noise level was at or greater than 65 decibels <br />during 10 percent of the measurement period (i.e., more than 6 minutes per hour). <br /> <br />Regulatory Framework <br /> <br />The MPCA is the governmental regulatory agency responsible for implementing <br />regulations controlling traffic noise in Minnesota. Minnesota State noise standards have <br />been established specifically for daytime and nighttime periods. For residential land uses <br />(identified as Noise Area Classifieation 1 or NAC- I), the Minnesota State standards for LIO <br />are 65 decibels for daytime and 55 decibels for nighttime; the standards for L50 are <br />60 decibels for daytime and 50 decibels for nighttime. For parkland with no overnight uses <br />(such as Cummings Park), NAC-l daytime standards apply to both daytime and nighttime <br />noisc levels. <br /> <br />Minnesota Statute 116.07, Subd. 2a. states that municipal and county roads, except in the <br />cities of Minneapolis and St. Paul, are exempt from state noise standards. All the roads <br />near the proposed project site are county or city roads (with the exception ofI-694) and are <br />therefore exempt from standards. State standards are included in this study for reference <br />only and are depicted in Table 22. <br /> <br />TABLE 22 <br />MINNESOTA STATE NOISE STANDARDS <br /> <br /> MPCA State Noise Standards <br />Land Use Code Day (7 a.m. - 10 p.m.) dBA Night (10 p.m. - 7 a.m.) dBA <br />Residential NAC-1 Llo of 65 Lso of 60 LIO of 55 LsD of 50 <br /> . ~ <br />Commercial NAC-2 LIO of 70 Lso of 65 Llo of70 LsD of 65 <br /> -"-. <br />Industrial NAC-3 LIO of 80 Lso of 75 LID of 80 L500f75 <br /> <br />Guidant Campus Master Plan <br />Final AUAR and Mitigation Plan <br /> <br />- 49- <br /> <br />January 2003 <br />
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