WS 07-14-2009 - Laserfiche WebLink

Home Browse Search

ATTACHMENT TWO Barr Engineering Company __.-. _..-.. 4700 West 77th Street e Minneapolis, MN 55435-4803 R Phone: 952-832-2600 - Fax: 952-832-2601 - www.barr.com An EEO Employer is BAR" " Minneapolis, MN - Hibbing, MN • Duluth, MN • Ann Arbor, MI • Jefferson City, MO • Bismarck, ND Memorandum To: Janice Gundlach, City of New Brighton From: Andrew Skoglund, Barr Engineering Company Subject: Review of Noise Mitigation Documents for Belaire Excavating's Facility Date: 2/13/09 Project: 23/62-1007 c: Dan Fetter Barr has reviewed the January 22, 2009 letter report by Wenck Associates, Inc regarding noise evaluation and mitigation planning for the Belaire Excavating's facility in New Brighton, Minnesota. Wenck's report summarized sound measurements that were conducted at a nearby residence to assess noise related to Belaire's crushing and material handling operations. Wenck's analysis did not directly address the New Brighton zoning code, but did demonstrate existing compliance with Minnesota standards during the period of testing. The effect of impulsive sounds like truck tailgate impacts during unloading, which has been a particular source of neighborhood noise complaints, isn't captured well by the metrics used in these standards. The monitoring performed of the facility demonstrated compliance with the Minnesota Noise standards, and the report also asserted compliance with the New Brighton noise ordinance. While the language of the city noise ordinance is dated and some of the technical language has evolved. there are better means to address the ordinance than the testing methods that were used. The report simplified the octave band standards into an overall sound level, which is not consistent with the apparent intent of the ordinance. Overall sound levels likely would have been included in the noise ordinance if that had been the intent of the City. Compliance with the overall level is not a guarantee of meetine the octave band limits. Octave bands uses in current practice correlate reasonably well with the ranges identitiea in the oramance and could be used as a comparison to the levels defined in the code. The report also included a conceptual sketch for a proposed sound mitigation berm. The berm would reduce the overall noise levels of Belaire's operation if it is operated in the manner proposed. However, tailgate noise may still be discernable despite a reduction in overall sound levels. The proposed barrier mitigation is a legitimate means of noise control. However, the elevations of the operation depicted in the proposed drawings do not appear to match past operations, which include a very tall stockpile operation where trucks unload and create the impulsive tailgate noise. Creating a berm 25 feet above the those existing activities would seem to require a rather substantial increase in berm height or decrease in stockpiling elevation. It should also be noted that construction of this size of berm would likely involve much of the noise -generating activity it is intended to address. The tailgate noise of the trucks may still be of concern with a barrier. While the overall level of the noise would be decreased by the intervening barrier, the nature of the noise is still abrupt and jarring and may be C7