MS4 Permit

MS4 Permit

In response to the 1987 Water Quality Amendments to the Clean Water Act, the EPA published the rules for Phase I of the National Pollutant Discharge Elimination System (NPDES) stormwater program in 1990.  The Phase I program requires municipalities with populations of 100,000 or greater to implement a stormwater management program as a means to control discharges from the “Municipal Separate Storm Sewer System” (MS4).  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, etc.)
  • Not a combined sewer.
  • Not part of a Publicly Owned Treatment Works (sewage treatment plant).

The NPDES stormwater program is a permit-based program that established requirements that municipalities must meet to discharge storm water from MS4s to the nation’s surface waters.  Under the conditions of the permit, the City of Omaha is required to possess the legal authority to control storm drain system pollutants, continue mapping its storm sewer system, monitor stormwater discharges, and develop and implement comprehensive management programs. The permit also increases impervious area treatment goals, requires the implementation of trash reduction strategies, and environmental site design for new and redevelopment projects to the maximum extent practicable. The City of Omaha is operating under a Phase I permit issued October 1, 2008.  A new permit is issued every 5 years.

In March 2003, EPA initiated the Phase II program, which required smaller MS4s located in urbanized areas to implement a storm water management program.  Douglas County, Sarpy County, Washington County, La Vista, Ralston, Bellevue, Papillion, and Boys Town of Omaha are operating under a Phase II permit issued August 1, 2009. These permits are also reissued every 5 years.

Stormwater management programs for both the Phase I and Phase II require that communities reduce the discharge of pollutants to the “maximum extent practicable”. The regulations require that the management programs address a minimum of six elements, that when implemented are expected to result in significant water quality benefits.  The six elements are listed below:

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