Stormwater Definitions

Below are some definitions of terms used in discussing stormwater pollution.

BMP - Best Management Practice: Activities or structural improvements that help reduce the quantity and improve the quality of stormwater runoff.

Clean Water Act (Water Quality Act): Legislation that provides statutory authority for the MPDES program (also known as the Federal Water Pollution Control Act).

Conveyance: The process of water moving from one place to another.

Discharge: The volume of water (and any sediment) that passes a given location within a given period of time.

EPA: Environmental Protection Agency.

Erosion: When land is diminished or worn away due to wind, water, or glacial ice. Often the eroded debris (silt or sediment) becomes a pollutant via stormwater runoff.

Illicit Connection: Any discharge to a Municipal Separate Storm Sewer System that is not composed entirely of stormwater and is not authorized by a separate NPDES permit or included in an approved Stormwater Pollution Prevention Plan (for instance, a business connecting illegally into the city's storm sewer system).

Joint Powers Agreement Water Management Organization: A joint powers agreement water management organization has the general authorities specified in Minnesota Statutes Sections 103B.211 through 255 and specific authorities agreed to through a joint powers agreement between the municipalities and townships within the watershed area (for instance, the Lower St. Croix Water Management Organization, of which Cottage Grove is a part).

MCM - Minimum Control Measure: Key areas to be addressed by units or agencies wishing to discharge stormwater in their stormwater management plans.

MPCA: Minnesota Pollution Control Agency.

MS4 Municipal Separate Storm Sewer System: A publicly-owned conveyance or system of conveyances that discharges to waters of the U.S. or waters of the State, and is designed or used for collecting or conveying stormwater.

NPDES - National Pollutant Discharge Elimination System: Name of the surface water quality program authorized by Congress as part of the 1987 Clean Water Act. NPDES is the EPA's program to control the discharge of pollutants to waters of the U.S.; in Minnesota, the MPCA is the permitting authority and also controls the discharge of pollutants to the waters of the State.

Outfall: The point where stormwater discharges from a sewer pipe, ditch, or other conveyance to a receiving body of water.

Runoff: Water that becomes polluted when it picks up things like grass clippings, leaves, pesticides, motor oil, and pet waste, and flushes them into storm drains and eventually into bodies of water, such as the Mississippi River.

SWPPP - Storm Water Pollution Prevention Plan: A plan or program to describe how an MS4 evaluates potential pollutant sources and selects and implements appropriate measures designed to prevent or control the discharge of pollutants in stormwater runoff.

Watershed: A watershed, or drainage basin, is the area of land from which rain and snowmelt flow and eventually enter a lake, river, or wetland. Even if your home is not next to a lake, river, or wetland, you still live in a watershed. For more information about watersheds and those in Minnesota, visit the Minnesota Association of Watershed Districts' website.

Watershed District: Watershed districts are special purpose local units of government (established under Minnesota Statutes Chapter 103D) that work to solve and prevent water-related problems. The boundaries of the districts follow those of a natural watershed, and the districts are usually named after that watershed. Because water does not follow political boundaries, it makes sense to manage natural resources on a watershed basis. This type of management allows for an overall, holistic approach to resource conservation. An example is the South Washington Watershed District, of which the City of Cottage Grove is a part.