Southwest Harriet Stormwater Management Master Plan
HR Green was selected by the City of Minneapolis to prepare a flood reduction feasibility study in the neighborhoods southwest of Lake Harriet. The 365-acre area to the southwest of Lake Harriet and north of Minnehaha Creek has a long history of flooding due to inadequacies of the storm drain system. This area is heavily urbanized and is surrounded by a mix of residents, businesses, and public institutions including two community parks. Multiple flooding issues impacting private property has been identified in the project area over the past 40 years due to undersized infrastructure. Projects to reduce flooding have been proposed in the past; however, poor stakeholder support, cost constraints and constructability issues have prevented them from implementation. Since then, the City has entered into a Memorandum of Understanding (MOU) with the Minnehaha Creek Watershed District (MCWD) and the Minneapolis Parks and Recreation Board (MPRB) to encourage project collaboration. The MOU outlines how the three agencies will work together to identify multi-jurisdictional initiatives to achieve complex goals such as:
- Reducing flooding
- Achieving regional pollutant load reductions identified in TMDLs
- Reducing runoff volumes and peak flows to Minnehaha Creek
- Eliminating combined sewer overflows
HR Green led the collaborative efforts on this study that included workshop meetings with representatives of the MOU partners to accomplish project goals outlined by each of the partners. Using XPSWMM and Optimatics software, HR Green came up with infrastructure upgrades that would not only reduce flooding and private property impacts, but also stay within the set design parameters. With the fully developed, densely urbanized area, finding volume reducing solutions that were actually feasible was challenging. A holistic approach including both green and grey infrastructure techniques were used including storage within the street ROW and adjacent park properties. With all proposed upgrades, roughly 60 homes and businesses are expected to be removed from 100-year event flooding impacts.