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� Wenck <br />• <br />May 14, 2009 <br />Mike Murlowski <br />BelAir Excavating <br />2200 Old Highway 8 NW <br />New Brighton, MN 55112 <br />ATTACHMENT ONE <br />Wenck Assoclatas, Int - <br />1 800 <br />nc.1800 Pioneer Creak Cif. <br />P.O. Box 240 <br />Maple Plain, MN 55358-0249 <br />(703)479-4200 <br />Fax (783) 4794242 <br />E-mail: wenckmplMwenck,com <br />Re: Addendum No. 2 to Sound Mitigation Plan of December 22, 2008 <br />Recycle Crushing Operation <br />New Brighton, MN <br />Wenck Project No. 2284-01 <br />Mr. Murlowski: <br />This letter presents addendum no. 2 to the December 2008 sound mitigation plan for the <br />recycle crushing operation at the BelAir Excavating facility in New Brighton. The <br />purpose of this addendum is to present the evaluation of the proposed berm effectiveness <br />on the tailgate "bang" sound from the facility. <br />Sound level measurements of a typical end dump truck tailgate `bang" were made at a <br />distance of 50 feet perpendicular to the truck's direction of travel. The measurements <br />were made using a Quest 2400 Type 1I sound level meter (SIN TN6070059). The meter <br />was calibrated according to the manufacturer's instructions using a Quest QC -1.0 <br />calibrator (SIN QE6090114). The meter was set to `A' scale, fast response in the peak <br />hold mode. <br />Ten "bang" events were measured and the arithmetic average was 100.8 dBA, The sound <br />was extrapolated to the residential area of Rockstone Court to the west of the property. <br />The extrapolation calculations were performed using spherical divergence and the path <br />length difference method for a simple barrier. The configuration sketch of the sound <br />source, barrier and receiver are shown in the attached SK -2. <br />The calculations are summarized below: <br />Description <br />Sound Level, dBA <br />Tail ate Sound at 50 feet <br />100.8 <br />Extrapolated Tailgate Sound — Present <br />Berm <br />63.5 <br />Extrapolated Tailgate Sound — Proposed <br />Berm <br />56.5 <br />Bachround — Rockstone Court <br />45.2 <br />TA2284\WAddendum #2 to Sound Mitigation Letter.doc <br />