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National Pollutant Discharge Elimination System (NPDES)

Stormwater Discharges from Municipal Sources-Developing an MS4 Program

Remember to throw your gloves in the trash

Owners/operators of regulated municipal separate storm sewer systems (MS4s) are required to develop, implement, and enforce a stormwater management program (SWMP). The focus of the SWMP is to describe how the MS4 will reduce the discharge of pollutants from its sewer system and addresses these program areas:

Use the guidance and references on this page to help you develop your SWMP.

Construction Site Runoff Control

Include a program in your SWMP to reduce pollutants in stormwater runoff to your MS4 from construction activities that disturb ≥ 1 acre of land.

Illicit Discharge Detection and Elimination (IDDE)

Stormwater and certain authorized types of uncontaminated non-stormwater are the only discharges that should enter your MS4. Illegal dumping and connections can result in illicit discharges of non-stormwater wastes like car oil and sanitary waste into it. Include a program in your SWMP to detect and eliminate illicit discharges to your system.

Pollution Prevention/Good Housekeeping

Minimizing the potential pathways for contaminants carried in runoff is a key way to control pollutant discharges from MS4s. Include a program to prevent or reduce pollutant runoff from municipal operations into the storm sewer system.

Post-Construction Runoff Control

Managing stormwater after construction activities end is a key part of the SWMP. Include a program to reduce pollutants from new development and redevelopment projects that disturb ≥ 1 acre of land.

Public Education and Outreach

An informed and knowledgeable community is crucial to the success of your SWMP. Implement a public education program on the impacts of stormwater that includes steps to reduce pollutants in stormwater runoff.

Public Involvement/Participation

The public can provide you with valuable input and assistance in developing, implementing, updating, and reviewing your SWMP. Include efforts to reach out and engage all economic and ethnic groups in your public participation program.

Program Effectiveness

Provide measurable goals in your SWMP so you can evaluate the program’s effectiveness and make adjustments as necessary. As part of the program, compile a report on program progress that includes things like the status of compliance with permit conditions, results of any information collected and analyzed, summaries of planned stormwater activities, and any changes that have been made.

Total Maximum Daily Loads

Know whether your storm drain system discharges to an impaired water body or a water body with an approved Total Maximum Daily Load (TMDL). Include a process in your SWMP for addressing the TMDL if necessary.

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