Coastal Waccamaw Stormwater Education Consortium
Helping local governments meet requirements for stormwater education and public involvement

Stormwater Requirements

Stormwater and The Clean Water Act

Water pollution degrades surface waters threatening to make them unsafe for drinking, fishing, swimming, and other activities. As authorized by the Clean Water Act of 1972, the National Pollutant Discharge Elimination System (NPDES) permit program controls water pollution by regulating the discharge of pollutants into waters of the United States. Industrial, municipal, commercial, and other major developments must obtain permit coverage for discharges that lead directly to surface waters. In South Carolina, the SC Department of Health and Environmental Control (DHEC) administers the NPDES program. Since its introduction, the NPDES permit program is responsible for significant improvements to both the state and nation’s water quality.

Polluted storm water runoff is often discharged into local rivers and streams through pipes, ditches and ponds without treatment. EPA’s NPDES Stormwater Phase II Rule establishes a stormwater management program that is intended to improve the Nation’s waterways 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, 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 stormwater discharges, these pollutants can impair the waterways, thereby discouraging recreational use of the resource, contaminating drinking water supplies, and interfering with the habitat for fish, other aquatic organisms, and wildlife.

What is an MS4?

In 1990, EPA promulgated rules establishing Phase I of the NPDES stormwater program. The Phase I program for municipal separate storm sewer systems (MS4s) requires operators of “medium” and “large” MS4s, that is, those that generally serve populations of 100,000 or greater, to implement a stormwater management program as a means to control polluted discharges from these MS4s. The Stormwater Phase II Rule extends coverage of the NPDES stormwater program to certain “small” MS4s but takes a slightly different approach to how the stormwater management program is developed and implemented.

An MS4 is a conveyance or system of conveyances that is:

  • Owned by a state, city, town, village, or other public entity that discharges to waters of the U.S.;
  • Designed or used to collect or convey stormwater (including storm drains, pipes, ditches, ponds, etc.);
  • Not a combined sewer; and
  • Not part of a Publicly Owned Treatment Works (sewage treatment plant).

In South Carolina, SC DHEC requires all construction sites of one acre or more, many industrial sites, and all regulated small, medium and large MS4s to obtain NPDES stormwater permit coverage in order to discharge pollutants into Waters of the State.

What is a Stormwater Management Program?

The Phase II Rule defines a stormwater management program for a small MS4 as a program composed of six elements that, when implemented together, are expected to reduce pollutants discharged into receiving water bodies to the “maximum extent practicable” (MEP). These six program elements, or minimum control measures (MCMs), are

Public Education and Outreach on Stormwater Impacts;

Public Participation/Involvement;

Illicit Discharge Detection and Elimination;

Construction Site Runoff Control;

Post-Construction Stormwater Management in New Development and Redevelopment;

Pollution Prevention/Good Housekeeping for Municipal Operations;

The Coastal Waccamaw Stormwater Education Consortium (CWSEC) was developed specifically to address MCMs 1 and 2.

The Stormwater Management Plan for each CWSEC member MS4 is available on our members page. For more information on EPA stormwater regulations, please visit this link. You can also find DHEC laws and regulations at their Laws and Regulations page.


NPDES Stormwater Program at US EPA

NPDES Stormwater Program at SC DHEC

MS4s in South Carolina