The MS4 general permit is reissued about every five years, and MS4s covered under the permit must re-apply for coverage under the new permit.
Public entities that own or operate an MS4 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.
- Public education and outreach, which includes teaching citizens about better stormwater management
- Public participation: Include citizens in solving stormwater pollution problems
- A plan to detect and eliminate illicit discharges to the storm sewer system (like chemical dumping and wastewater connections)
- Construction-site runoff controls
- Post-construction runoff controls
- Pollution prevention and municipal “good housekeeping” measures, like inspecting and maintaining infrastructure, covering salt piles, and street sweeping
The regulated entity must identify best management practices (BMPs) they will implement to reduce pollution from reaching impaired wasters covered by a total maximum daily load (TMDL) study. They must also identify BMPs and measurable goals for each minimum control measure, and submit an annual report on the implementation of the SWPPP.
MS4 mapping tool
Use the MS4 mapping tool to view MS4 boundaries, defined urban areas, impaired waters, outstanding resource value waters, trout waters, and approved TMDL study areas. Note: This is best viewed with pop-up blockers disabled and screen resolution set to 1024x768 or higher.