Stormwater & MS4 Permit

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Municipal Separate Storm Sewer System (MS4)

As stormwater flows over streets and other impervious surfaces, it sweeps up pollutants such as oils, chemicals, bacteria and sediments. This polluted stormwater runoff can have a negative impact on water quality and recreational uses of our lakes and streams. Managing stormwater runoff is very important for restoring or protecting surface waters (lakes, rivers and wetlands).

In order to reduce pollutants and polluted stormwater runoff from reaching surface water, counties, cities, campuses or areas of land may be required to have a  Municipal Separate Storm Sewer System (MS4). An MS4 is any conveyance or system of conveyances (for example streets, ditches, catch basins, curbs, gutters, and storm drains) designed or used for collecting or conveying stormwater. Carver County, in partnership with the cities of Carver, Chaska, Chanhassen, and Victoria, operates and maintains an MS4 to manage stormwater runoff from county roads and other County facilities.


Municipal Separate Storm Sewer System (MS4) Permit

MS4 operators (ex. Cities, counties) are required to obtain a permit to reduce the amount of sediment and pollution that enters surface and ground water from storm sewer systems. All permits and MS4 systems are overseen by the Minnesota Pollution Control Agency (MPCA).

Carver County obtained its first MS4 permit in 2006 and renewed the permit in 2014. The permit requires the County to develop a Stormwater Pollution Prevention Plan (SWPPP). The SWPPP lays out the steps the County will take to reduce pollution through actions in each of the following areas.

  1. Public Education and Outreach
  2. Public Participation / Involvement
  3. Illicit Discharge Detection and Elimination
  4. Construction Site Runoff Control
  5. Post-Construction Runoff Control
  6. Good Housekeeping for Municipal Facilities


MS4 Documents and Reports

Carver County SWPPP

2017 Annual Report - coming soon

2016 Annual Report