Agenda - Council - 06/11/2024 - Laserfiche WebLink

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Executive Summary Hydrodynamic devices. If all of these practices were installed, significant volume and pollutant reductions could be accomplished. However, funding limitations and landowner interest make this unlikely. Instead, it is recommended that projects be installed in order of cost-effectiveness (pounds of pollution reduced per dollar spent). Other factors, including a project's educational value/visibility, construction timing, total cost, or non -target pollutant reduction also affect project installation decisions and will need to be weighed by resource managers when selecting projects to pursue. For each type of recommended retrofit, conceptual siting is provided in the project profiles section. The intent of these figures is to provide an understanding of the approach. If a project is selected, site - specific designs must be prepared. In addition, many of the proposed retrofits (e.g. iron -enhanced sand filter pond benches and pond modifications) will require engineered plan sets if selected. This typically occurs after committed partnerships are formed to install the project. Committed partnerships must include willing landowners, both public and private. The 448 acre target study area was divided into 16 catchments and two drainage networks (groups of catchments draining to a common point) based on drainage patterns influenced by topography and stormwater infrastructure. The Mississippi River network consists of seven catchments (320 acres), and the Rum River network consists of nine catchments (128) acres. Based on WinSLAMM model results, the Mississippi River network contributes an estimated 101 acre-feet of runoff, 28,083 pounds of TSS, and 85 pounds of TP annually to the Mississippi River. The Rum River network contributes an estimated 61 acre-feet of runoff, 19,764 pounds of TSS, and 63 pounds of TP annually to the Rum River. The tables in the Project Ranking and Selection section (pages 14 - 17) summarize potential projects ranked by cost-effectiveness with respect to either TP or TSS. Potential projects are organized from most cost-effective to least based on pollutants removed. Installation of projects in series will result in lower total treatment than the simple sum of treatment achieved by the individual projects due to treatment train effects. Reported treatment levels are dependent upon optimal site selection and sizing. More detail about each project can be found in the catchment profile pages of this report. Projects that were deemed unfeasible due to prohibitive size, number, or expense were not included in this report. City of Ramsey Stormwater Retrofit Analysis