Agenda Packets - 2023/07/24 - Laserfiche WebLink

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Mounds View Stormwater Pond Assessment 4 RECOMMENDATIONS July 2023 4.2 UPLAND VEGETATION ASSESSMENT AND RESTORATION The dredging projects will provide the City an opportunity to replace impacted vegetation with more desirable species. Prior to any dredging work, it is recommended that a field assessment of current vegetation conditions be performed at each of the proposed dredging sites along with Silver View Park to inform park user and vegetation management needs and to help the City prioritize management efforts. The vegetation assessment should include a field assessment of current vegetation conditions and the site access required for dredging of the stormwater pond. Dredging projects require large equipment, areas of storage, and will result in significant disturbance of soils, trees, and vegetation of the site. The assessment will help the City determine the best point of access to minimize impacts to desirable vegetation. As part of the assessment, field observations for each site should be summarized in a findings letter that provides a map of each site with the areas evaluated, along with descriptions of cover types and acreage, dominant plant species, invasive or problematic weeds, significant/unique or sensitive features, restoration potential, and high-level management recommendations and cost estimates. Also noted should be areas of erosion, park user safety, educational and recreational opportunities, and constraints that should be considered in managing vegetation associated with the stormwater ponds. Following the field assessment, it is recommended that a public meeting be held to review findings and recommendations and obtain input on park user needs and desires. This will assist with management prioritization, with the goal of developing a list of priority sites, specific activities, and associated costs that should then be incorporated into an upland vegetation management plan. The upland vegetation management plan could be tailored for management tasks being performed by City staff or by contracted services, depending on City preference. 4.3 WATER QUALITY ASSESSMENT AND RESTORATION Based on preliminary feedback from the City, a water quality assessment of Silver View Pond is recommended. The goal would be to improve the aesthetics of the pond for park users, including weed/algae growth and odors, and reduce nutrient loading to downstream water resources. Improvements to the pond would be done in conjunction with upland vegetation management and restoration in the area surrounding the pond. The initial step would be data collection, including a site reconnaissance, collection of stormwater infrastructure plans in the pond's drainage area, and in -pond sampling of sediment, water quality, and vegetation. Results of the data collection, particularly the sampling, will drive the potential water quality improvements. As needed, selected water quality modeling would be performed. Potential improvements could include retrofitting of stormwater BMPs; implementing new BMPs within the park; selective dredging, particularly of forebay areas or silt plumes; aeration; chemical addition (e.g., alum); and removal of ecologically undesirable vegetation (chemical or harvesting). Retrofitting of BMPs in the storm sewer system would need to be coordinated with the City's street reconstruction schedule to minimize cost and disruption. 25