Minimal Impact Design Standards (MIDS) represent the next generation of stormwater management in Minnesota. The emphasis today is on keeping the raindrop where it falls in order to minimize stormwater runoff and pollution and preserve natural resources. Low Impact Development (LID) is an approach to stormwater management that mimics a site’s natural hydrology as the landscape is developed and preserves and protects environmentally-sensitive site features such as riparian buffers, wetlands, steep slopes, valuable (mature) trees, floodplains, woodlands and highly permeable soils.
Recognizing the value of LID to Minnesota’s high valued water and natural resources, the 2008 Legislature directed the MPCA to develop MIDS.
Minn. Stat. § 115.03, subd. 5c reads: "The agency shall develop performance standards, design standards, or other tools to enable and promote the implementation of low impact development and other storm water management techniques. For the purposes of this section, "low impact development" means an approach to storm water management that mimics a site's natural hydrology as the landscape is developed. Using the low impact development approach, storm water is managed on site and the rate and volume of predevelopment storm water reaching receiving waters is unchanged. The calculation of predevelopment hydrology is based on native soil and vegetation". Upon passage of the legislation, a stakeholder group was created to guide the MPCA in the development of MIDS. This group met monthly for three years and was instrumental in creating the MIDS work products.
Adapting and using LID approaches offers multiple benefits including minimizing and reducing the amount of pollution reaching our lakes, rivers and streams and helps to recharge groundwater resources. MIDS establishes unified LID standards, approaches and credits so we can consistently apply these principals across Minnesota communities. MIDS helps communities measure progress toward water and natural resource protection and restoration goals. MIDS will also be used as the highest standard for meeting the stormwater practice for Minnesota Green Step Cities.
The concepts behind MIDS can essentially be used by all Minnesotans – we can all do our part in minimizing stormwater runoff and pollution. MIDS was specifically developed for designers, engineers, planners, contractors, stormwater managers, landscape architects, public works staff, landscape industry, land use regulators and others involved in new development and redevelopment projects. MIDS methodologies will provide tools for these individuals to quantify reductions in post-development runoff and pollutant loading from a wide variety of LID practices.
Specific examples of how the MIDS package can be used, including the MIDS calculator, include the following.
A Community Assistance Package (CAP) is being developed to provide ordinances and tools that help integrate LID principles, including the MIDS performance goals and calculator, into a package that can be used by local units of government. These tools can be used by communities to help them achieve MIDS performance goals for stormwater volume. The CAP will include instructions about how to use the checklists, and various training materials and approaches used during implementation in several test or pilot communities.
The credit calculator is a tool designed to quantify reductions in post-development runoff and pollutant loading using a variety of LID practices. This graphic user interactive tool allows individuals to enter a project’s site conditions and determine the amount of stormwater volume retention needed and the pollution loading (sediment and phosphorus). The calculator then provides a method to enter their stormwater practices of choice and determine (calculate) the amount of stormwater volume and pollution reduction (credit) they can achieve. Currently, the credit calculator includes LID practices for green roofs, bioretention basins, infiltration basins, permeable pavement, infiltration trench/tree box, swales, filter strips and sand filters. Other practices will be added in the future. The calculator includes convenient links to specific design specifications for LID practices that are found within the Minnesota Stormwater Manual.
MIDS Fact Sheet: File:MIDS fact sheet.pdf