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

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Background Background Many factors are considered when choosing which subwatersheds to analyze for stormwater retrofits. Water quality monitoring data, non -degradation report modeling, and TMDL studies are just a few of the resources available to help determine which water bodies are a priority. Stormwater retrofit analyses supported by a Local Government Unit with sufficient capacity (staff, funding, available GIS data, etc.) to greater facilitate the process also rank highly. For some communities a stormwater retrofit analysis complements their MS4 stormwater permit. The focus is always on a high priority waterbody. The drainage areas studied for this analysis are located in the City of Ramsey and discharge to either the Mississippi or Rum Rivers. Those discharging to the Mississippi River are located along the southern boundary of Ramsey primarily between Ramsey Blvd. NW on the west and Tungsten St. NW on the east. The railroad tracks just north of US-10 serve as much of the northern boundary. The total area of the seven catchments that comprise the Mississippi River network is 320 acres. The nine catchments discharging to the Rum River are located on the eastern boundary of the City primarily between Alpine Dr. NW on the north and Bunker Lake Blvd. NW on the south. All catchments are primarily east of St. Francis Blvd. NW. The total area of the nine catchments that comprise the Rum River network is 128 acres. These catchments were selected for analysis because they drain to high priority waterbodies, and existing treatment in many of the catchments was lacking. Therefore, stormwater retrofits may provide cost-effective options for additional treatment of runoff, thereby improving water quality in the Mississippi and Rum Rivers. The catchments analyzed are urbanized. Development throughout the City of Ramsey has resulted in the installation of subsurface drainage systems (i.e. stormwater infrastructure) to convey stormwater runoff, which increased due to the coverage of impervious surfaces throughout the catchments. The runoff generated within the areas targeted for this analysis is still conveyed to the Mississippi and Rum Rivers, as it was historically. However, the runoff is now captured by catch basins and directed underground before being discharged to the Mississippi and Rum Rivers via stormwater pipe. Stormwater runoff from impervious surfaces can carry a variety of pollutants. While stormwater treatment to remove these pollutants is adequate in some areas, other areas were built prior to modern-day stormwater treatment technologies and requirements. The City of Ramsey and LRRWMO contracted the ACD to complete this SRA for the purpose of identifying and analyzing projects to improve the quality of stormwater runoff to the Mississippi and Rum Rivers. Overall subwatershed loading of TP, TSS, and stormwater volume were estimated for selected drainage areas. Proposed retrofits were modeled to estimate each practice's capability for removing pollutants and reducing volume. Finally, each project was ranked based on the estimated cost-effectiveness of the project to reduce pollutants. City of Ramsey Stormwater Retrofit Analysis