In 2009, the Minnesota Legislature allocated funds for minimal impact design standards (MIDS), which included developing stormwater-management performance and design standards as well as tools to facilitate low-impact design (LID) and other stormwater-management techniques. Barr’s first phase involved modeling and gathering information to help the MPCA and diverse stakeholder groups decide on performance goals that would best mimic natural hydrology for a variety of site types. Volume and pollutant reductions that could be achieved through BMPs were also considered. Barr evaluated the pros and cons of more than two dozen BMPs, including green roofs, bioretention basins, infiltration basins, infiltration trenches, underground infiltration, permeable pavement, tree trenches, swales, stormwater re-use, disconnection, sand filters, constructed wetlands, and stormwater ponds. We then defined BMP volume- and pollutant-reduction credits. We also developed a MIDS calculator that quantifies the required runoff-treatment volume for a given site. Users can also select BMPs that result in the desired runoff volumes, total phosphorus (TP), and total suspended solids (TSS). Barr provided designers and municipal and watershed regulators with hands-on training on how to use the calculator. In addition, we prepared a MIDS project addendum to the MPCA’s Minnesota Stormwater Manual.
Vice President Senior Water Resources Engineer
Vice President Senior Civil Engineer