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Mounds View Stormwater Pond Assessment 4 RECOMMENDATIONS July 2023 existing pond related to a golf course. Because they receive no direct stormwater runoff, we recommend the City further investigate these basins and potentially reclassify them. Based on the survey analysis, many of the ponds surveyed show significantly lower sedimentation levels and rates than expected (see Table 3.2). We recommend the City would be best served to conduct further diagnostic investigations into factors that might be contributing to low sedimentation levels; including whether they be pollutant loading based or pond sedimentation performance based. Additional analysis options include: • Stormwater monitoring of pond influent and effluent monitoring would help to determine the sediment loads coming into the pond from the watershed and if that load is being captured in the pond or not. This would help to determine if the low pond sedimentation is from low inputs or low capture. • Creating a model and comparing the measured sediment volumes presented in Table 3.1 to the predicted sediment volumes from the modeled sediment loads. • A short-circuiting evaluation to monitor the movement of water through the pond to determine if stormwater is passing through the pond too quickly and not allowing for the suspended sediments to settle out. Pond level monitoring and/or water budgeting to determine pond response to storm events and permanent pool water levels and fluctuations. • For those ponds identified as part of a treatment train, upstream BMPs could be inspected and evaluated to determine their performance. 4.6 10-YEAR MAINTENANCE PLAN Using the survey data, field inspections, estimated cleanout dates from Table 3.2, additional basin analysis recommendations from Section 4.5, and the general recommendation of performing sedimentation surveys every 5 years, a 10-year Maintenance Plan by Pond was created (see Table 4.4). The plan includes survey of sediment depths every five years (or five years from the most recent dredging) to determine the need for future dredging. It also includes sediment sampling the year prior to dredging to determine the appropriate disposal method. It should be noted that ponds in proximity to one another were grouped together in order to minimize cost, disturbance, and restoration. 28