Municipal storm water permit overview

Storm water pond surrounded by grass and trees — Storm water pond
DNR Photo - Pete Wood

About 245 municipalities in Wisconsin are currently required to have a Municipal Separate Storm Sewer System (MS4) permit under NR 216, Wis. Adm. Code [exit DNR]. An MS4 permit is required for a municipality that meets one of the following criteria:

It is located within a federally-designated Urbanized Area [exit DNR]
Its population equals 10,000 or more based on the latest decennial census; or
When the Department of Natural Resources designates the municipality for permit coverage in accordance with s. NR 216.025. The MS4 permits are effective for a period of up to five years, at which point the permits are updated and re-issued.

Municipal permits require storm water management programs

The MS4 Permits require permitted municipalities to reduce polluted storm water runoff by implementing storm water management programs. Although MS4 Permits usually do not contain numerical effluent limits like in other WPDES Permits, the MS4 Permit's storm water management programs (also referred to as the six minimum control measures) requires the implementation of a variety of best management practices.

To learn more about the MS4 Permit, please visit the Wisconsin DNR's MS4 Best Management Practices (BMP) Menu which contains a variety of tools and resources to assist MS4 Permittees in complying with their MS4 Permit.

Review of municipal programs and reports

DNR may review the programs and activities that municipalities will use to comply with the MS4 permit. Municipalities are also required to submit an annual/biennial report to the DNR to document progress and compliance with the permit requirements.

» MS4 eReporting - Access online water permit system