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dIIvId_~b _.1__ 1313 5t#h st;reet; S.B. . suite 322 · minneapolis. mn 55414 telephone: 612-331-4571 · fax: 612-:3:31-4572 ~b -Z ~ ('~ ii&h 2 January 1998 MEMORANDUM TO: Kim Lee City of Roseville 2660 Civic Center Drive Roseville, MN 55113 FROM: David Braslau nitoring at Wilcoxon Residence RE: Results of Supplemen ~ This memorandum reports on supplemental noise measurements taken at the Wilcoxon residence on 22 and 23 October 1997. Continuous readings were made between 6 pm Q "continuous" noise levels as governed by !be Minnesota noise standards) are shown m EXIllBIT 1. These are hourly averages, so that the first hourly reading begins at 1900 hours or 7 pm. It can be seen that the level generally varies between 53 and 54 dBA during the period. Between 10 pm and 7 am, this noise level is 3 to 4 dBA over the L50 noise standard (50 dBA). In Ap' 1996, readings were taken between 10 pm and 8 am. A comparison between the L50 v es measured during these two time periods is shown in EXIllBIT 2. It can be at the 1997 readings are approximately 4 dBA lower than the 1996 readings. The average sound levels during this time period were 57.8 dBA (1996) and 53.6 dBA (1997) for an average difference in sound level of 4.2 dBA. The sound fence recommended in my Memorandum to Mike Falk of 10 May 1996 suggested that the top of the fence be 5 feet above the ACI roof level to achieve an 8 dBA reduction in noise level, bringing it close to the MPCA standard. My observation during the 1997 sound level measurements was that the top of the fence was not 5 feet above the ACI room since much of the equipment was still visible from the Wilcoxon deck. However, a 4 dBA reduction may not be unreasonable for the fence as currently constructed. The additional fence height needed to reduce the noise level to 50 dBA could be calculated if exact elevations of the ACI roof, currently constructed fence and Wilcoxon deck could be established.