Polluted stormwater runoff can have significant adverse impacts on the environment and human health. One way to stop polluted runoff from invading our waterways is to prevent it from entering our stormwater systems. Certain stormwater system operators are responsible for verifying that they take steps to protect their systems against polluted runoff in a process called MS4 permitting.
What is an MS4?
MS4 stands for Municipal Separate Storm Sewer System. An MS4 is system of structures that convey stormwater runoff into local water bodies. An MS4 may consist of roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, manmade channels, storm drains, or any combination of these, so long as it designed or used for collecting or conveying stormwater.
Why do some MS4s require permits?
In communities with MS4s, stormwater discharges directly into water bodies. To prevent pollutants that can be picked up by runoff from reaching water bodies, the Federal government requires some MS4 operators to obtain permits verifying that their systems are designed not to cause an adverse impact on water quality in water bodies.
What are the requirements to receive an MS4 permit?
The application for an MS4 permit has several requirements, including developing a Stormwater Master Plan (SWMP). The SWMP must address six Minimum Control Measures, which include the following:
- Public Education & Outreach
- Public Participation & Involvement
- Illicit Discharge Detection & Elimination (IDDE)
- Construction Site Runoff Controls
- Post-Construction Runoff Controls (PC)
- Pollution Prevention/Good Housekeeping (PP/GH)
Do you have to renew an MS4 permit?
The National Pollutant Discharge Elimination System (NPDES) Phase II MS4 permits must be renewed every five years, and permit compliance audits are a regular part of the permit renewal process.
How often is an MS4 audited?
Each MS4 is audited at least once per permit term, typically around the time the permit expiration approaches.
How can WithersRavenel help with an MS4 permit?
WithersRavenel’s Stormwater Team can answer your questions about the MS4 permitting process, prepare a stormwater management plan, and support the development of a successful MS4 permit application.
Contact us to get started on your MS4 permitting process today!
This post was originally published on August 26, 2020, and was updated on September 20, 2022, and April 23, 2024.