MS4 Storm Water Permit/Plan


Under the authority of the Federal Clean Water Act and Water Pollution Control Act, the Missouri Department of Natural Resources (MDNR) has regulatory authority to require local government entities, like St. Charles County, to improve or maintain storm water quality within their boundaries. To accomplish this, the MDNR issues a permit to the county known as the Municipal Separate Storm Sewer System (MS4) Permit (PDF)

The permit establishes a 5-year plan setting out how the county will help improve the quality of impaired waters of the nation and assure that unimpaired waters remain unimpaired. The county is also required to complete a biennial report that updates the status of the county’s progress in implementing its 5-year storm water plan.


The permit requires the county to address 6 Minimum Control Measures (MCM). The county's 5-year plan to address these 6 MCMs is included in the permit. Information regarding the different county staff positions that have responsibility for each measure and a prioritized schedule to address each measure are also included in the permit.


Missouri Department of Natural Resources (MDNR) Storm Water Regulations