Agenda Packets - 2023/07/24 - Laserfiche WebLink

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Executive Summary Background The City of Mounds View retained Stantec to conduct a stormwater pond assessment to identify maintenance actions as part of its Stormwater Maintenance Program. This assessment provides the City with information to better understand the current condition of its ponds and provides a plan for recommended dredging to restore pond function. It also provides recommendations to the City for enhancements to improve the function and aesthetics of selected ponds as well as to restore vegetation surrounding the ponds to improve aesthetics and create recreational and educational opportunities. Methodology Stantec performed sediment surveys of 27 ponds in the City to determine basin bathymetry, including current sediment depth and "depth to refusal', or original sediment depth. This was used to estimate the original and current available pond volume and corresponding loss of storage volume. Ponds at or approaching 50% loss of storage volume were targeted for dredging to replace lost volume. For ponds nearing 50% loss, the age of the pond in conjunction with lost volume was used to extrapolate a time frame for dredging. RASl1ItR Seven ponds were determined to need dredging within the next five years. These are listed in Table 3.2. It will be necessary to sample the sediment in advance of dredging in order to determine the appropriate method of disposal. Relatively clean sediment can be placed on the land as fill, while sediment with a high level of pollutants will need to be placed in a regulated landfill. Recommendations Recommendations for maintaining and restoring the ponds and surrounding areas were developed. Maintenance includes both general inspection and cleanup of debris or garbage, unclogging outlets, and performing minor repairs. Major maintenance would be dredging of the ponds to restore pond storage. Pond restoration includes both upland vegetation restoration in the area surrounding ponds as well as water quality improvements to the pond itself. The upland vegetation restoration focused on the ponds to be dredged, with the restoration work to be performed concurrent with or immediately following dredging. The goal would be to improve vegetative quality, habitat, and aesthetics, and provide recreational and educational opportunities. Upland vegetation restoration would also be performed around Silver View Pond, even though this is not slated for near -term dredging, as this was identified by the City as a high priority for improvement. Water quality restoration would likewise focus on Silver View Pond, with a goal of improving aesthetics (visual, odors) for park users.