The City of Washington, Indiana

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Storm Water Program

What is the MS4 Storm Water Program?

Polluted storm water run-off is often transported to municipal separate storm sewer systems (MS4s) and ultimately discharged into local rivers and streams without treatment. U.S. EPA’s Storm Water Phase II Rule establishes an MS4 storm water management program that is intended to improve the Nation’s waterways by reducing the quantity of pollutants that storm water 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 MS4 discharges, these pollutants can impair the waterways, thereby discouraging recreational use of the resource, contaminating drinking water supplies, and impacting the habitat for fish, other aquatic organisms, and wildlife

In 1990, U.S. EPA promulgated rules establishing Phase I of the National Pollutant Discharge Elimination System (NPDES) storm water program. The Phase I program for MS4s requires operators of “medium” and “large” MS4s, that is, those that generally serve populations of 100,000 or greater, to implement a storm water management program as a means to control polluted discharges from these MS4s. The Storm Water Phase II Rule extends coverage of the NPDES storm water program to certain “small” MS4s but takes a slightly different approach to how the storm water management program is developed and implemented.

The Storm Water Phase II Final Rule requires operators of small Municipal Separate Storm Sewer Systems (MS4s) to obtain National Pollutant Discharge Elimination System (NPDES) permit coverage because their storm water discharges are considered “point sources” of pollution. All point source discharges, unlike nonpoint sources such as agricultural run-off, are required under the Clean Water Act (CWA) to be covered by federally enforceable NPDES permits. Those systems already permitted under the NPDES Phase I storm water program, even systems serving less than 100,000 people, are not required to be permitted under the Phase II Storm Water Program. NPDES storm water permits are issued by an NPDES permitting authority, which in Indiana is the Indiana Department of Environmental Management (IDEM).

MS4 permit conditions must be satisfied (i.e., development and implementation of a Storm Water Quality Management Plan (SWQMP) and periodic reports must be submitted on the status and effectiveness of the program.

MS4 permits are typically General Permits. General Permits are referred to as a permit by Rule. The state promulgated Rule contains the requirements and provisions that must be met by the permittee, IDEM does not issue a permit that is unique to the MS4.

The permittee complies with the requirements by submitting a detailed Storm Water Quality Management Plan that describes the MS4s goals and objectives to improve water quality.

What are the primary elements that are contained in a Storm Water Quality Management Plan (SWQMP)?

The SWQMP includes minimum control measures that cover a broad spectrum of issues that are associated with storm water run-off, these measures include:

  • Public Education and Outreach
  • Public Participation and Involvement
  • Illicit Discharge Detection and Elimination
  • Construction Site Storm Water Runoff Control
  • Post-Construction Storm Water Management
  • Municipal Operations Pollution Prevention and Good Housekeeping
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