The TMDL Implementation and MS4 Section administers the Phase I and Phase II municipal separate storm sewer system (MS4) permits and the Caltrans MS4 Permit programs for the entire Region. This regulates stormwater pollution from municipal sources. We issue permits to cities and counties that require them to take certain actions to reduce stormwater pollution. Then, we conduct audits and inspections to see if the permittees are in compliance. We also implement the TMDLs (total daily maximum loads). For more information on TMDL development, see the TMDL Program page.
We work in parts of Orange, Riverside, and San Bernardino Counties within the Santa Ana Watershed as seen on the map below. Please click on the link for the area you are interested in:
Questions, comments, concerns? Email: RB8-stormwater@waterboards.ca.gov
We’ll keep you up to date with the latest news about our projects. Don’t worry, you’ll only hear about the topics you’re interested in.
Documents are in Adobe Acrobat format - viewer is available below.
(Page last updated 1/8/26)
Ex Parte Communications Do I Need a Permit? Fees Make a Payment Help / Business Help Grievance Procedure
Board Priorities Decisions Pending & Opportunities for Public Participation Employment Frequently Asked Questions Grants & Loans Laws / Regulations Plans / Policies Public Records Center
