The Santa Ana Water Board has released an updated Tentative MS4 Permit and initiated a 75-day public comment period that ends on July 20, 2026. Written comments must be received by the deadline identified in the public notice. The Santa Ana Water Board will hold a public hearing on July 24, 2026 to hear a presentation from board staff and receive public comment on the Tentative Order. The Santa Ana Water Board will not take action on the Tentative Order but may give direction to staff. The Santa Ana Water Board will close the hearing on July 24 and continue its consideration of the Tentative Order to a meeting on August 21, 2026. The agenda for that meeting will be provided at a future date.
For the redline version of the Tentative Order that describes changes made to the March 1st, 2024 tentative order, see: Tentative Order R8-2026-0034 (Redline Version)
For more information and instructions on how to provide comments, see the Revised Public Notice.
Ruling on Requests Concerning the Order of Proceedings (Posted July 22 2026)
Board Member Disclosures of Ex Parte Communications Regarding the Proposed Sana Ana Regional MS4 Permit (Posted July 14, 2026)
Ruling on Requests Concerning Hearing Procedures and Party Status (Posted July 14, 2026)
Order of Proceedings for the Public Hearing on Tentative Order R8-2026-0034, National Pollutant Discharge Elimination System Permit and Waste Discharge Requirements on July 24, 2026 (Posted July 14, 2026)
The Santa Ana Water Board has regulated pollution from urban areas through three separate permits issued to each of the three counties and their cities within the watershed. These permits were first issued in the 1990s and have been renewed four times since then. The permits are known as Municipal Separate Storm Sewer System (MS4) permits. An MS4 is a conveyance or system of conveyances (including roads with drainage systems, city streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains) usually owned by a city or county. The Santa Ana Water Board is renewing the MS4 permits for a fifth time. Instead of issuing three separate permits, the Santa Ana Water Board is proposing to adopt a single MS4 permit for all the counties and cities in the Santa Ana River watershed.
This webpage will be updated when new actions are taken. The proposed MS4 permit will go through public review before the Santa Ana Water Board adopts it.
Tentative NPDES Permit and Waste Discharge Requirements for Discharges of Pollutants in Urban Runoff from the Municipal Separate Storm Sewer Systems in the Counties of Orange, Riverside, and San Bernardino (NPDES No. CAS618000) – On March 1, 2024, staff of the Santa Ana Water Board released a tentative permit for regulating discharges of pollutants in stormwater and urban runoff from Municipal Separate Storm Sewer Systems (MS4s) in Orange, Riverside, and San Bernardino Counties on a regionwide basis. On March 5, 2024, staff of the Santa Ana Water Board announced the release of the tentative permit and a Board workshop in a message sent via GovDelivery. This message initiated a 60-day public comment period that would have ended May 4, 2024. A Board workshop occurred on March 15, 2024. In response to comments during the March 15th Board workshop, Santa Ana Water Board staff extended the public comment period deadline from May 4 to July 3, 2024. The Santa Ana Water Board held a board workshop on September 13, 2024, to discuss and solicit feedback on the Tentative Permit.
A staff report is also available that provides a non-technical summary of the draft permit:
More information on other MS4 Permits, including the permits that are in effect until the effective date of the Regional MS4 Permit after adoption, can be found on the Municipal Permits page.
Keep up to date on this project by joining our mailing list. Please go to https://public.govdelivery.com/accounts/CAWRCB/subscriber/new?qsp=santa_ana and sign up to receive notifications on "Region 8-Stormwater-Regionwide MS4 Permit".
To review the reports of waste discharge, please contact the file review desk at FileReview8@waterboards.ca.gov
For additional information regarding the Regional MS4 Permit program, contact Hero Alexander (951) 782-4419.
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(Page last updated 7/22/26)
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