Public entities that own or operate an MS4 are required to develop and implement a stormwater pollution prevention program (SWPPP) to reduce the discharge of pollutants from their storm sewer system, to the maximum extent practicable. An effective SWPPP has six components, called minimum control measures (MCM).
- Public education and outreach, which includes teaching the public about better stormwater management
- Public participation: Include residents in solving stormwater pollution problems
- A plan to detect and eliminate illicit discharges to the storm sewer system (like chemical dumping and wastewater connections)
- Construction-site runoff controls
- Post-construction runoff controls
- Pollution prevention and municipal “good housekeeping” measures, like inspecting and maintaining infrastructure, covering salt piles, and street sweeping
The regulated entity must identify best management practices (BMPs) they will implement to reduce pollution from reaching impaired waters covered by a total maximum daily load (TMDL) study. They must also identify BMPs for each minimum control measure, and submit an annual report on the implementation of the SWPPP.
MCM 1: Public education and outreach
An educated and informed community can not only prevent pollution in stormwater, but also identify and report illicit discharges or construction activities that may negatively affect stormwater. Permittees must create an education and outreach program to inform residents about the impacts of stormwater and foster proper stormwater management behaviors.
- Minnesota public education and outreach resources
- Municipal Separate Stormwater System toolkit — Resources to help meet permit requirements related to education
- Public education and outreach guidance (EPA)
MCM 2: Public participation/involvement
Permittees must motivate people in their communities to act to prevent stormwater pollution. Common activities in Minnesota include storm drain stenciling, storm drain adoption programs, and volunteer monitoring programs.
MCM 3: Illicit discharge detection and elimination
Storm sewers in Minnesota generally discharge directly to lakes, rivers, and wetlands. Ideally, only stormwater should enter a storm sewer system. Permittees must implement a program to detect and eliminate illicit discharges to their systems.
- Minnesota illicit discharge detection and elimination resources
- Illicit discharge detection and elimination minimum control measure (U.S. EPA)
- Illicit discharge detection and elimination guidance (EPA)
MCM 4: Construction site stormwater control
Stormwater running off construction sites can carry sediment and other pollutants into nearby wetlands, rivers, and lakes. Permittees must enforce construction site stormwater runoff controls to reduce the impacts of land disturbing activities on stormwater.
- Minnesota construction site stormwater control resources
- Construction site stormwater control guidance (EPA)
MCM 5: Post-construction stormwater management
Managing stormwater onsite post-construction can mitigate the impacts of paved surfaces. Permittees must enforce a post-construction stormwater management program that prevents or reduces stormwater pollution in new and redevelopment projects.
- 2013 Technical Support Document for post-construction stormwater management (wq-strm4-59e) - This document is for historical reference purposes only, as it is for the expired 2013 MS4 General Permit.
- Minnesota post-construction stormwater management resources
- Post-construction stormwater management guidance (EPA)
- Minimal impact design standards: Community assistance package (p-gen3-16)
- Minimal Impact Design Standards fact sheet (p-gen3-07)
MCM 6: Pollution prevention/good housekeeping
It's generally easier and less expensive to prevent pollution than to restore surface waters once they're polluted. Permittees must take steps to prevent stormwater pollution, as the first line of defense for many pollutants entering storm sewer systems.
- Minnesota pollution prevention/good housekeeping resources
- Pollution prevention/good housekeeping guidance (EPA)
- Pollution prevention and the MS4 program (wq-strm4-26) — A guide to utilizing pollution prevention activities to meet MS4 general permit requirements
- Managing stormwater sediment: Best management practice guidance (wq-strm4-16)
- Stormwater and wetlands: Planning and evaluation guidelines (wq-strm1-07)
- Untreated stormwater runoff to lakes, streams, and wetlands (wq-strm4-28)
- Swimming pool and hot tub water discharges best management practices (wq-wwprm2-03)
Unlike other National Pollutant Discharge Elimination System (NPDES) permits, MS4 permits don't specify end-of-pipe discharge effluent limits. MS4 permits use program requirements to reduce pollutants discharged. Permittees have the flexibility to select which practices they'll use to meet permit requirements. The MPCA evaluates permittees for program compliance, the appropriateness of their management practices, and progress towards their identified and measurable goals. Learn more in the Minnesota Stormwater Manual.
Parties subject to the MS4 general permit must submit their annual reports to the MPCA by June 30. The report details permit activities from the previous calendar year. Get more details from the Minnesota Stormwater Manual.