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Mr. Jeff Hejl February 5, 2021 <br />Boston Scientific Corporation Page 2 <br /> <br /> <br />The City of Arden Hills ordinances reference the State of Minnesota noise requirements. <br />Minnesota Rule 7030: Noise Pollution, prepared by the MPCA, has requirements for maximum <br />allowable sound levels by receiving land use evaluated at the point of the nearest receiver. <br />Table 1 shows the Rule 7030 L101 and L502 noise limits per noise area classification (NAC). <br />NAC 1 is residential and recreational land use, NAC 2 is commercial, and NAC 3 is industrial. <br />Table 1 – MPCA Code Requirements <br /> <br />Boston Scientific is zoned as Industrial, but the nearest receiving property lines are <br />Residential. Therefore, the requirements for noise are an L50 of 60 dBA and an L10 of 65 dBA <br />during the daytime and an L50 of 50 dBA and an L10 of 55 dBA during the nighttime. All the <br />requirements are to be evaluated over 1-hour periods and apply to the location of the nearest <br />receiver, which is at the residences, not on the BSC property. <br />Since the chiller equipment will operate continuously during the day and night, the lower <br />nighttime requirement of 50 dBA at the residential property line will be used as the design <br />goal for chiller noise mitigation. <br />To determine the existing noise in the area around Building 14, 24-hour long noise <br />measurements were made at locations A and B shown in Figure 1. The measurements results <br />are in Attachment A. Table 2 summarizes the measurement results. There was a lot of traffic <br />noise from Hwy 694 at the site and it was difficult to separate the existing BSC noise from the <br />traffic sources. From the data, we estimate the BSC noise contribution is below 49 dBA, <br />therefore we will combine that level with the new noise from the chillers to evaluate mitigation <br />design in comparison with the 50 dBA design goal. <br />Table 2 – Summary of Noise Measurement Results <br /> <br /> <br /> <br />1 L10 is the sound level that is exceeded 10% of the time during a measurement period. <br />2 L50 is the sound level that is exceeded 50% of the time during a measurement period. <br />L10 L50 L10 L50 <br />1 Residential 65 dBA 60 dBA 55 dBA 50 dBA <br />2 Commercial 70 dBA 65 dBA 70 dBA 65 dBA <br />3 Industrial 80 dBA 75 dBA 80 dBA 75 dBA <br />Noise Area <br />Classification <br />Receiver <br />Type <br />Daytime (7AM - 10PM)Nighttime (10PM - 7AM) <br />Metric A B Notes <br />L90 49 dBA 45 dBA for 24 hour period <br />L50 49 dBA 45 dBA lowest hourly level <br />L10 51 dBA 47 dBA lowest hourly level <br />Location