Keeping bodies of water clean is a priority for everyone, which is why the Illinois Environmental Protection Agency (EPA) mandates MS4 permits. 

What are MS4 permits?

Short for Municipal Separate Storm Sewer Systems, MS4 permits are required for municipalities that have water discharging into state or federal waters. Because that encompasses nearly all cities and villages, it's important to know what is expected of permit-holders and why these efforts are so important. 

Contaminants need protection

There are plenty of ways water can become contaminated before it reaches a river or stream. Whether it's roadway grease carried by rainwater, drainage from fire hydrants or street residue from sweeping and construction debris, the potential for pollutants is present. MS4 permits and subsequent monitoring processes ensure none of those contaminants find their way into state or federal waters. 

Securing an MS4

To begin the process of securing an MS4 permit, a municipality must submit a notice of intent to the Illinois EPA. The permit outlines all the requirements needed for submission, which can be complex and varied. Municipalities are also required to specify which bodies of water they drain into and pinpoint specific discharge points. 

Continued responsibility

Once a municipality successfully secures an MS4 permit, the responsibility doesn't end there. Municipalities must develop, implement and enforce a stormwater management program. This program must include six minimum control measures, including public education and outreach, public involvement, illicit discharge detection and elimination, construction site stormwater runoff control, post construction stormwater management and pollution prevention for municipal operations.

Municipalities must also develop and implement a monitoring and assessment program to evaluate the effectiveness of the Best Management Practices, or BMPs, implemented to reduce pollutants and water quality impacts. This program includes conducting quarterly monitoring at specific locations along the receiving waterway. During these assessments, water samples are tested for nutrients and chemical makeup to identify and rectify any unwanted contaminants entering the water. If contamination is detected, further testing and corrective actions are essential to locate and mitigate the source of the problem.

Leonard Dane is a Senior Environmental Health and Safety Scientist who has designed, supervised and executed fisheries sampling for three decades. He leads a team that performs water quality monitoring using innovative technology and conducts metric scoring, statistical analysis and reports. Contact him at This email address is being protected from spambots. You need JavaScript enabled to view it..