Agenda - Environmental Policy Board - 03/02/2015

Home

Updated Storm Water Management Plan (SWMP) City of Ramsey, Minnesota at such elevation at least fifteen (15) feet beyond the outside limits of the structure erected thereon. The area of a pond's HWL plus 1 foot of freeboard shall be contained entirely within an outlot that is owned and maintained by the City. The numerous natural depressions found throughout Ramsey have been incorporated into the SWMP as ponding areas. Wetlands may be, and are currently being used for stormwater storage for larger rainfall events. They may continue to be used for this purpose — even after upstream development, provided that: 1. There is acceptable Best Management Practice pretreatment of the runoff in accordance with the MPCA NPDES/SDS Construction Permit, Section III.DG., Permanent Stormwater Management System. 2. The bounce from the normal water level to the high water level does not exceed two feet. The effective use of ponding areas enables the installation of outflow sewers with reduced capacities since the design storm duration is effectively increased over the total time required to fill and empty the ponding reservoirs. Storm sewers represent a sizable investment for the community and this investment can be more efficiently utilized by ponding storm water in designated ponding areas and allowing smaller diameter pipes to be used as outfall lines. Equally as important as flood control and cost considerations, is the use of ponding areas to: 1. Improve water quality; 2. Return storm water to the groundwater table; 3. Increase water amenities in developments for aesthetic, recreational and wildlife purposes. For water quality ponds, the storage below the outlet is the most important consideration. The area and depth of the ponds may differ from the values presented here, storage below the outlet must be provided so that the prescribed pollutant loading of the system is not exceeded. Amenity aspects are maximized by careful planning in the initial development of any residential or industrial area and by integrating the ponding system into an overall comprehensive SWMP. The wildlife aspects of the ponding areas shall be maximized in design and the proper location of the trail system will allow good access to these areas for wildlife observation. B. Model Results Odd numbered Figures from Figure 11 through Figure 23 are maps of critical SSA pond data superimposed on the most recent aerial photo of Ramsey. They are color coded to highlight whether the 100 -year storm conditions as follows:) Green — The pond functions properly and the peak elevation is fully contained within the pond Yellow — The peak pond elevation is above the emergency overflow spillway Section X February 20, 2015March 6, 2015 Page 65 Formatted: Highlight Comm a nt ed [ LL4] : Still working on Figures