Municipal Separate Storm Sewer Systems

Delaware Department of Natural Resources and Environmental Control

Municipal Separate Storm Sewer Systems (MS4)

MS4 is a national program that was introduced into the National Pollutant Discharge Elimination System (NPDES) as a two-part permitting system in 1990 and then grew in 1999. It is to ensure that pollutants from stormwater runoff are not washed or dumped into surface water. To make sure this doesn't happen, municipalities that have separate storm sewer systems need to create a management program and must acquire the MS4 permit from their respective state. Permitting Phase I covers larger municipal and community areas, while Phase II covers smaller municipal, community, and urbanized areas, as well as some non-government stormwater systems.

Permitting Phases in Delaware

Phase I: Individual Permit - covers New Castle County, (NCC), NCC DelDOT, Delaware City, City of New Castle, City of Wilmington, Elsmere, and Newport.

Phase II: General Permit, tiers I and II

National Pollutant Discharge Elimination System

The NPDES is a permit program, established in 1972 by the Clean Water Act. Since the NPDES's inception, the Environment Protection Agency, has been able to place limits on pollutant discharge and protect the country's waterways. This has protected and ensured that each state's bodies of water are safe for uses such as swimming, provide drinking water, and most importantly supporting the aquatic environment.

There are two types of permits:

  • General 
    • General permits are for state-wide activities, mostly in association with industry
  • Individual
    • Individual permits are more for case-by-case activities and are not covered by general permits

Pollutants types include, but are not limited to, "nutrients, heavy metals, pesticides, herbicides, and synthetic organic compounds like fuels, waste oils, solvents, lubricants, and grease."

MS4 & Our Yard Waste Program

The use of rigid containers is not only beneficial to the health and well-being of our Public Works crew, but to our stormwater runoff as well. Rigid containers will be able to keep yard waste better contained and keep unwanted animals from breaking open bags. This is especially important on rainy days. We want to do our part in making sure that pollutants, including yard waste ones like those mentioned above, stay out of our stormwater runoff and surface water areas.