Amazon.com description: Product Description: In 2011, one acoustical monitoring system was deployed at Saint Croix National Scenic Riverway (SACN) for 34 days. The purpose of this monitoring effort was to characterize existing sound levels and estimate natural ambient sound levels as well as identify audible sound sources prior to the proposed re-opening of the Zavoral Gravel Mine in Scandia, Minnesota. At the time that this report was written, an EIS was being prepared for the reopening of the gravel mine, as required under the State of Minnesota Rules of decision-making.