Natural resource planning tools


Minimum Impact Design Standards (MIDS) for Storm Water Management

Minimum Impact Design Standards (MIDS) were developed by the Minnesota Pollution Control Agency to minimize storm water runoff and pollution and thereby help maintain natural resources health. They are a prerequisite for and guide the selection of best management practices required for each individual site. They must be applied in a way to mimic each site's natural hydrology and protect features such as riparian buffers, wetlands, steep slopes, mature/healthy trees, floodplains, woodlands, and highly permeable soils.

Guiding principles

  • Maximize water quality improvement
  • Maximize infiltration
  • Minimize impervious surfaces
  • Protect natural features
  • Showcase "keeping the raindrop where it falls"

Performance goal

The performance goal for storm water volume and pollution reduction is to capture and infiltrate 1.1 inches of runoff volume from impervious surfaces on sites without restrictions. Compliance with the performance goals must be verified with modeling or calculating, using the MIDS calculator,This link leads to an external site.P8, WinSLAMM, or other methods.

Development of new public water access sites

The performance goal applies to all constructed impervious surfaces.

Redevelopment of existing sites

The performance goal applies to any new or fully reconstructed impervious surfaces. Mill overlay and other resurfacing activities are not considered full reconstructions.

Sites with restrictions

All projects should first attempt to fully meet the volume reduction performance goal of 1.1 inches retention. If the engineer/designer is unable to achieve the full performance goal due to site restrictions as documented, the Flexible Treatment Option Approach shall apply in the order of the sequence outlined below. Examples of site restrictions:

  • Karst geology
  • Shallow bedrock
  • High groundwater
  • Poor soils (infiltration rates are too low or too high, problematic urban soils)
  • Hotspots or contaminated soils

Alternative 1

  • Achieve at least the 0.55 volume goal, and
  • Remove 75% of the annual total phosphorus load, and
  • Consider and present as options the merits of relocating project elements to address varying soil conditions and other constraints across the site.

Alternative 2

Note: For this alternative, higher priority will be given to best management practices that include volume reduction. Secondary preference is to employ filtration techniques, followed by rate control best management practices.

  • Achieve volume reduction to the maximum extent practicable, and
  • Remove 75% of the annual total phosphorus load, and
  • Consider and present as options the merits of relocating project elements to address varying soil conditions and other conditions across the site.