MS4 Permit – Municipal Separate Storm Sewer System
The City of Lake Elmo is a mandatory small MS4 city. This means that Lake Elmo is required by federal and state law to obtain and implement a NPDES Stormwater permit administered by the Minnesota Pollution Control Agency.
A municipal separate storm sewer system (MS4) is a system of designed conveyances for the purpose of collecting or conveying stormwater and owned or operated by the city. A stormwater conveyance system may consist of roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, and storm drains.
MS4 Permit Requirements
MS4s are required to develop and implement a stormwater pollution prevention program (SWPPP) to reduce the discharge of pollutants from their storm sewer system to the maximum extent practicable. The SWPPP must cover six minimum control measures. The MS4 must identify best management practices (BMPs) and measurable goals associated with each minimum control measure. An annual report on the implementation of the SWPPP must be submitted to the Minnesota Pollution Control Agency each year.
Special Waters and Impaired Waters
In addition, the MS4 cities that have stormwater watersheds that contribute to “specially protected” or “impaired waters” must implement additional best management practices and enhanced runoff controls for added protection to these water bodies. Lake Elmo must address additional controls for the following water bodies:
- Lake Jane
- Lake Elmo
- Sunfish Lake
- Brown’s Creek
- Unnamed Creek to Wilmes
- St. Croix River
- Lake St. Croix
- Mississippi River
- Lake Pepin