Agenda - Environmental Policy Board - 03/02/2015

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Updated Storm Water Management Plan (SWMP) City of Ramsey, Minnesota We recommend that the undeveloped part of the WMISS watershed, lying immediately west of the RTC, treated in a similar fashion as the RTC. If a separate outfall can be created for this area, it could work in an almost identical fashion. If a separate outfall cannot be obtained, a large regional pond network is recommended. If the ponding alternative is taken, the regional pond network would need to store 100 percent of the runoff at a safe level prior to outletting into the RTC system. This would ensure that the RTC is not threatened by continued development upstream. Finally, the Highway 10 corridor is appears to have some pond overflow problems that are only associated with using the ditches as storage. We believe that the best fmancial and hydrological solution to alleviate these problem areas is to coordinate with MnDOT on any future TH 10 improvements. Any improvements to TH 10 are likely to involve new corridor stormwater management and funding. General Figures 30 through 34 are typical SSA output files for a single pipe/pond corridor. These are intended to illustrate the output potential of the model and software. If similar output files were created for every aspect of the entire system, this report would be too cumbersome. This is an example of what has been prepared for GIS access. Your staff can manipulate the data to get similar output for virtually any pipe, pond or ditch within Ramsey. It is extremely important that each area be re-evaluated at the time of fmal design to confirm the criteria used in this study and to make any changes that a proposed development may dictate. Special consideration must be given to areas that develop differently than shown in the Comprehensive SWMP, especially when a higher runoff coefficient is likely to result from development. All storm sewer facilities, especially those conveying large quantities of water at high velocities, should be designed with efficient hydraulic characteristics. Special attention should be given during final design to those lines that have extreme slopes and create high hydraulic heads. The Best Management Practices (BMPs) recommended by the MPCA should be followed wherever necessary. C. Recommendations The following recommendations are presented for the City Council's consideration based upon the data compiled in this report: 1. The SWMP as presented herein should be adopted by the City of Ramsey. 2. The recommended corrections for flood prone areas should be made as described herein and made a part of the storm water management system, where feasible. 3. Standard review procedures should be established, where feasible, to ensure all development within the City is in compliance with proper erosion control practices. 4. Detailed hydrologic analysis should be required, where feasible, during final design of all new developments and ponding areas. Section X February 20, 2015March 6, 2015 Page 69