Agenda - Council - 04/09/2018 - Laserfiche WebLink

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1. EXECUTIVE SUMMARY City Improvement Project 18-09 proposes to construct a regional infiltration basin in the southeast corner of the COR between the Midwest Medical Examiner's office and Ramsey Boulevard, north of the regional stormwater pond. The City of Ramsey is a member of the Lower Rum River Watershed Management Organization (LRRWMO) whose purpose is to manage the surface water resources within the boundaries of the organization in a consistent, cost effective and environmentally appropriate manner. The LRRWMO Third Generation Plan, adopted in 2012, requires infiltration of the first one inch of runoff (volume reduction) from all impervious surfaces on the site. The Drinking Water Supply Management Area (DWSMA) for the municipal water supply wells overlies the COR. State Law discourages or prohibits infiltration in a DWSMA. Final determination of the infiltration exclusion area in the DWSMA is a local decision. The City of Ramsey discussed the options with other jurisdictions and set the 10 year capture zone as the infiltration exclusion zone The Third Generation Plan has a mitigation sequence defined that must be followed when infiltration is not permitted on a new development site. The prioritized process includes on site infiltration, off site infiltration, other non -volume control treatment on site, or contribution to a stormwater impact fund, which can be used to construct volume reduction practices where infiltration is permitted. The Parkview East Apartment building was one of the first projects to be proposed in the COR after the Third Generation Plan was adopted. The developer opted to contribute to the volume mitigation fund. The City was required to submit a letter to the LRRWMO stating that the City would have an infiltration basin in place by July 1, 2018. This letter was required before the LRRWMO would issue the permit for Parkview East Apartments. All subsequent projects in the COR received LRRWMO approval conditioned on the regional infiltration basin being in place by July 1, 2018. City staff has evaluated multiple sites, trying to find a location that would provide the needed infiltration volume for the undeveloped sites in the COR, while preserving development opportunities. The area selected is in the southeast corner of the COR between Rhinestone Street and Ramsey Boulevard, north of the existing pond and south of the Midwest Medical Examiners building. The maps of the project area and project are located in Appendix A. A summary of the engineer's opinion of probable costs is included in Appendix B. This project would best be constructed as a stand-alone project and is necessary, feasible, and cost-effective from an engineering standpoint, and can be constructed as proposed herein. Feasibility Report COR Infiltration Basin City of Ramsey Project No. 18-09 Page 1