SOUTH DAKOTA Department of
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Surface Water

Stormwater Permit for Municipal Storm Sewer Systems

Polluted stormwater runoff is often transported to MS4s and ultimately discharged into local rivers and streams without treatment. The federal Clean Water Act, through the development of national Stormwater regulations, establishes an MS4 stormwater management program. This program is intended to improve surface water quality by reducing the quantity of pollutants that stormwater picks up and carries into storm sewer systems during storm events. Common pollutants include oil and grease from roadways and parking lots, pesticides from lawns, sediment from construction sites, and carelessly discarded trash, such as cigarette butts, paper wrappers, and plastic bottles. When deposited into nearby waterways through MS4 discharges, these pollutants can impair the waterways, thereby discouraging recreational use of the resource, contaminating drinking water supplies, and interfering with habitat for fish, other aquatic organisms, and wildlife.

 As a result of new federal regulations, referred to as the Phase II Stormwater Rule, for stormwater discharges from small Municipal Separate Storm Sewer Systems (MS4s), certain small municipalities are required to obtain a stormwater permit for their system.

What is an MS4?

A small MS4 is defined as a separate storm sewer system that is: owned or operated by a federal, state, city, town, county, association, district, sanitary district, or other public body with jurisdiction over the disposal of sewage, industrial wastes, or other wastes; and is located in an incorporated place that serves a population of less than 100,000 or that is located in one or more counties with unincorporated urbanized populations serving less than 100,000. This term includes systems similar to separate storm sewer systems in municipalities, such as systems at military bases, large hospital or prison complexes, and highways and other thoroughfares. The term does not include separate storm sewers in very discrete areas, such as individual buildings.

Who Must Apply for a Municipal Stormwater Permit?

Small MS4s meeting the following criteria must obtain a stormwater discharge permit for their system: 

* The Bureau of the Census determines urbanized areas by applying a detailed set of published criteria to the latest census data. Although the full definition of an urbanized area is complex, the Bureau of Census’ general definition is “a land area comprising of one or more places and the adjacent densely settled surrounding area that together have a residential population of at least 50,000 and an overall population density of at least 1,000 people per square mile.” Systems located in an urbanized area but serving a population less than 1,000 people may be waived from the permit requirements.

Stormwater Management Program

As part of the stormwater permit, you must develop and implement a Stormwater Management Program. In your program, you must address, at a minimum, the following control measures:

  1. Public education and outreach;

  2. Public participation/involvement;

  3. Illicit discharge detection and elimination;

  4. Construction site stormwater runoff control;

  5. Post-construction stormwater management; and,

  6. Pollution prevention/good housekeeping for municipal operations.

How do I get coverage under the Small MS4 Permit?

In South Dakota, DENR has issued the General Permit for Stormwater Discharges from Small Municipal Separate Storm Sewer Systems (MS4s). A general permit is a permit for a specific activity issued throughout the state. The permit covers anyone meeting the conditions of the general permit. There is no fee for this permit. An application package must be submitted to DENR and must include a complete Notice of Intent form, a map of the area served by the MS4, and a summary of the Stormwater Management Program that will be developed and implemented.  

You should make sure to read and understand the conditions of the permit. You may download an electronic version below or obtain a hard copy by contacting DENR.

DENR has additional information to help you:

You may obtain more information about requirements for stormwater discharges from small Municipal Separate Storm Sewer Systems by contacting Doug Baldwin at (605) 394-2229 or requirements for stormwater discharges associated with construction activities by contacting Laura Newman at 1-800-SD-STORM (1-800-737-8676) or industrial activities by contacting Jill Riedel at (605) 773-3351.

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