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Water quality protection along county roads

Municipal Storm Sewer System (MS4) permitting

Hennepin County manages 2,200 lane miles of roadway and right-of-way throughout the county. An important part of this work is the proper treatment and discharge of stormwater. This is governed by the Municipal Storm Sewer System (MS4) permitting by the Minnesota Pollution Control Agency.

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Any substance that is not stormwater or from a fire hydrant may be considered stormwater contamination. It is illegal to place anything in the stormwater system including:

  • Sediment
  • Oil/petroleum products
  • Soaps/detergents
  • Household or industrial chemicals
  • Agricultural waste
  • Sewage

To report any suspected contamination, go to

To learn more about proper disposal of the items listed above, visit Hennepin County's green disposal guide.

The county inspects drainage infrastructures annually to ensure both proper drainage and that structures are properly filtering for water quality protection purposes. Road upgrades and maintenance include studying water quality for the best management practice and upgrading infrastructure when necessary.

MS4 Storm Water Pollution Prevention Program (SWPPP)

The Storm Water Pollution Prevention Program covers six minimum control measures to help reduce the discharge of pollutants from our storm sewer system, to the maximum extent practicable. The minimum control measures (MCMs) include:

  • MCM 1 - Public education and outreach
  • MCM 2 - Public participation/involvement
  • MCM 3 - Illicit discharge detection and elimination
  • MCM 4 - Construction site runoff control
  • MCM 5 - Post-construction site runoff control
  • MCM 6 - Pollution prevention/good housekeeping

Hennepin County follows best management practices for each of these six minimum control measures.

Learn more about the Municipal Separate Storm Sewer System (MS4) permit

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