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Stormwater Definitions

Background
Stormwater may seem like a non-issue to many people. Some may wonder why we should be concerned about stormwater at all. After all, it seems like it is just something that takes care of itself: As long as there are gravity and air, storm water will continue to run downhill and eventually evaporate. However, stormwater can be a major source of pollution. Consider for a moment:

What happens to the rain after it hits the roof of your house?

It goes into the gutters.
Okay, but then where does it go?

It flows through your downspout, runs across your driveway and through your yard.
Okay, but then where does it go?

Well, some of it seeps into your yard and some of it runs into your street, along the curb and gutter and into the storm sewer. True. Stormwater is created by precipitation and runoff from land, pavements, building rooftops and other surfaces. Some of the water does seep into the ground and some of it enters the storm sewer system. The storm sewer system is a way for the water to get to ponds, other storm sewer pipes, and also into our local bodies of water, including the Mississippi River.

However, on the way to the water bodies, storm water runoff accumulates pollutants such as oil and grease, pesticides, sediment, litter, chemicals, nutrients, metals, and bacteria as it travels across land. Heavy precipitation or snow melt also can cause sewer overflows which may lead to contamination of other water sources. Pollution prevention is a major reason why we want to manage our storm water.

The U.S. Environmental Protection Agency controls storm water and sewer overflow discharges through its National Pollutant Discharge Elimination System (NPDES). NPDES created guidelines for municipalities and other agencies for minimizing or reducing stormwater pollution; the permit is administered by individual states. The Minnesota Pollution Control Agency (MPCA) issued permits to the City of Cottage Grove and other units of government which allows them to discharge storm water to waters of the state, after meeting certain requirements.

Non Degradation
Pursuant with the City of Cottage Grove Municipal Separate Storm Sewer System (MS4) General Permit, the City of Cottage Grove has completed its Nondegradation Review. The City’s Nondegradation Review includes a nondegradation analysis (Loading Assessment) and documents how the City intends to address nondegradation rules (Nondegradation Report and Proposed SWPPP Modifications), as outlined in the MS4 General Permit. A copy of the document will be available at the front desk of the City of Cottage Grove Public Works Facility.

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 which 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 storm water runoff.

Illicit Connection
Any discharge to a Municipal Separate Storm Sewer System that is not composed entirely of storm water and is not authorized by a separate NPDES permit or included in an approved Storm Water 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 storm water in their storm water 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 Stat, and is designed or used for collecting or conveying storm water.

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 storm water 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 storm water 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.