Stormwater Regulations

On May 8, 2013, the San Diego Regional Water Quality Control Board (Regional Board) adopted a new Municipal Separate Storm Sewer System (MS4/Stormwater) Permit (National Pollution Discharge Elimination System Permit, No. R9-2013-0001) that covered the San Diego County Copermittees.  Order No. R9-2015-0001 was adopted on February 11, 2015, amending the Regional MS4 Permit to extend coverage to the Orange County Copermittees.  Order No. R9-2015-0100 was adopted on November 18, 2015, amending the Regional MS4 Permit to extend coverage to the Riverside County Copermittees and make minor revisions.  This Permit mandates that the County of San Diego develop new and updated Runoff Management Plans and Programs, including Water Quality Improvement Plans and a Jurisdictional Runoff Management Program.  These documents were submitted to the Regional Board on June 26, 2015.  Permit requirements are generally implemented in the unincorporated County under authority of the Watershed Protection, Stormwater Management, and Discharge Control Ordinance (WPO).

The amended MS4 Permit, like all previous iterations, requires the County to establish and maintain adequate legal authority to implement all updated MS4 Permit provisions.  The WPO has been amended to ensure that it is current with the minimum requirements of the recently amended MS4 Permit.  The amendments include updating terminology and definitions related to land development priority development projects (PDPs), removal of outdated sections, minor updates to discharge prohibitions, and the incorporation of an optional program to allow development projects to satisfy some of its stormwater compliance obligations at off-site locations.

On January 27, 2016 the County Board of Supervisor’s adopted the Watershed Protection, Stormwater Management, and Discharge Control Ordinance (WPO). The WPO became effective February 26, 2016. 

Watershed Protection Ordinance


Stormwater (MS4) Permit, Reports and Plans

  • Water Quality Improvement Plans - Submitted to the Regional Water Quality Control Board on September 29, 2015.  These plans outline how the County will improve water quality in the region. 
  • Trash Amendments Track 1 Implementation Plan - Submitted to the Regional Water Quality Control Board on December 3, 2018.  The plan provides a map of identified Priority Land Uses, storm drain inlets and drainage, a time schedule to achieve full compliance with the trash discharge prohibition, a proposed approach to using Equivalent Alternative Land Uses to achieve compliance, and a summary of coordination with Caltrans.

Other State Water Resources Control Board Permits


Manuals & Resources

  • Best Management Practice Design Manual Webpage. For land development and public improvement projects, this manual focuses on project design requirements and related post-construction requirements. The manual includes Chapters, Appendices, and Submittal Templates.
  • County Development Resources WebpageThe categories include: Manuals, Green Infrastructure, Design Templates & Details, GIS, Cost Tools, Prior Lawful Approval, Stormwater Regulations, Submittal Templates, Hydromodification, Calculators & Modeling Software, Maintenance, Training, and Help.
  • Regional Development Resources Webpage. Project Clean Water is the page devoted to regional resources. Categories include: Model BMP Design Manual, Model BMP Design Manual Help Desk, Water Quality Equivalency Guide, Watershed Management Area Analysis (WMAA), and Training Materials.