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2.7 Stormwater Pond Treatment Capacity Evaluation GPS and elevation data from the stormwater pond survey was imported into AutoCAD Civil3D software. The geographically -referenced survey data points including water surface, pond bottom transects, and inlet and outlet location points were used to create elevation contours which represent the current pond bottom conditions. These contours were (lien used to calculate current pond volumes for comparison to MPCA recommendations and to estimate the volume of sediment that has been deposited in the pond since it was constructed. The figure below shows a conceptual profile of a typical stormwater pond. The permanent pool, or dead storage Volume, is the volume below the pond's outlet elevation. The flood pool is the volume between the outlet elevation and the flood elevation or overflow point. Using the contours created of the pond in AutoCAD Civil 3D, AutoCAD Civil 3D volume calculation tools, and the outlet elevation data, the permanent pool volume and wetted surface area of the pond were determined. The degree of sediment deposition (as a percentage of original permanent pool volume) and the quantity of sediment needing removal to recreate the pond's originally constructed contours were evaluated by comparing existing permanent pool volume estimates to "original" permanent pool volumes. As such, the "original" permanent pool volumes were estimated based on information found in the 1989 Silver View Pond Management plan and current conditions. Current pond permanent volume and surface size were compared with MPCA Stormwater Manual pond design recommendations to determine whether opportunities exist to improve the functionality of the pond beyond its original construction or existing condition. MPCA recommends a permanent pool volume of 1,800 cubic feet of storage per acre of watershed area. MPCA recommends an additional water quality storage volume of 0.5 inches per acre of impervious area within the watershed of the pond. The MPCA Stormwater Manual method was selected for this analysis to aid P: h1pis 23 MN 612462102 SiNct view Pond Asset menl Worki dc, Ripon %llvvr view Pond Assessmcnl-rinpt.dnen