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<br />Mike Falk <br />7 May 1996 <br />Page 2 <br /> <br />The predicted sound levels are shown in the table below. <br /> <br />PREDICTED SOUND LEVELS <br />(dBA) <br /> <br /> Car Wash Vacuum Compressors <br />Source (at 20') 61 71 72' <br />Business NE 41 52 35 <br />Business NW 36 49 31 <br />Business SW 44 55 34 <br />Home East 44 46 38 <br />Home South 43 51 42 <br />Home West 35 50 31 <br /> <br />1 Predicted levels assume a barrier wall surrounding the compressors. The level shown is the predicted <br />level of the source only and does not include background noise which is likely to range on the order of35 <br />to 40 dBA in the nighttime hours. <br /> <br />The table suggests that noise levels from the car wash and compressors will be well below the <br />Minnesota Pollution Control Agency (MPCA) commercial and residential noise standards for the <br />nighttime period (10 pm to 7 am). Thus, no restrictions on car wash operation appears <br />warranted because of noise level. <br /> <br />The table indicates that the Vacuum will probably meet the MPCA nighttime L50 standard of 50 <br />dBA (which permit the vacuum to be operated up to 30 minutes of nighttime hours). However <br />at the home south and west ofthe site, the level is around 50 dBA. With a typical background <br />level during nighttime hours of 40 dBA or lower in the early morning hours, the vacuum (with <br />its unique sound) would be clearly audible. A level of 10 dBA over ambient could be considered <br />intrusive. A level of 15 dBA over ambient could be considered a highly adverse impact. Thus, it <br />is recommended that a vacuum with this sound level not be operated during the hours of 10 pm <br />to 7 am unless it is appropriately enclosed in a sound enclosure that will yield no more than 35 <br />dBA at the nearest residential structure. <br /> <br />The above analysis related to the vacuum can be revised once specific information on sound <br />levels is available. However, even the type of equipment observed at the Superamerica station, <br />noise control measures could be implemented to bring noise levels below the MPCA nighttime <br />standards. <br /> <br />Please let me know if you have any questions on the information presented in this Memorandum. <br /> <br />kathnois.mem 96015 <br />