C.3 Requirements: Development

New C.3 Requirements

The San Francisco Bay Regional Water Quality Control Board has adopted the third reissuance of the Municipal Regional Stormwater Permit, or MRP 3.0.  This reissuance includes significant changes and additional requirements in Provision C.3.  Summary of key changes below. 

Effective July 1, 2023:

  • Impervious surface threshold for most projects will drop from 10,000 to 5,000 sq ft, including for new roads and the addition of a travel lane to an existing road.​
  • New categories of regulated projects include:
    • Road and sidewalk repair projects ≥ 5,000 contiguous sq ft
    • Road reconstruction and pavement widening ≥ 1 contiguous acre
    • Detached single family home that creates or replaces ≥ 10,000 sq ft

Please note that the C.3 Guidebook and related resources referenced in this site are in the process of being updated to reflect new permit requirements.  Stay tuned!


*To obtain Word document versions of templates (like the Stormwater Control Plan Template) or other documents marked with an asterisk, please contact the CCCWP at 925-313-2360

Provision C.3 requires site designs for new developments and redevelopments to minimize the area of new roofs and paving. Runoff should be dispersed to landscaping where possible. Where feasible, pervious pavements can be used so that runoff can infiltrate to the underlying soil. Remaining runoff from roofs and pavement must be treated using bioretention. In some developments, the rates and durations of site runoff must also be controlled.

In addition, project applicants must execute agreements to maintain stormwater treatment and flow-control facilities in perpetuity.

The C.3 requirements are separate from, and in addition to, Provision C.6 requirements for erosion and sediment control and for pollution prevention measures during construction.

Contra Costa municipalities have adopted the Contra Costa Clean Water Program's Stormwater C.3 Guidebook (PDF) to establish criteria and to assist applicants through the process of submittals and reviews.

Most publications accessible from the C.3 pages are formatted for both on-line navigation and 2-sided printing. Many require Adobe Acrobat Reader 7.0 or later. Acrobat Reader is available free at



What's New

  • Coming Soon!  Updates to the C.3 Guidebook are underway to reflect the new requirements in MRP 3.0 and will supersede the 7th edition.  

  • (NEW) 2-page C.3 Factsheet/Handout for Developers, Engineers, Planners, and Project Applicants on the New in MRP 3.0 page.

  • MRP 3.0, adopted May 11, 2020 by the San Francisco Bay Regional Water Quality Control Board.  

  • Stormwater Control Plan template (PDF)* to assist applicants in preparing the required project submittal (based on the 7th Edition).

  • Example Stormwater Control Plans for a Commercial Project and for a Residential Subdivision on the C.3 Guidebook page.

  • Example Stormwater Facilities Operation and Maintenance Plans for a Commercial Project and for a Residential Subdivision on the C.3 Guidebook page.

  • Stormwater Facilities Operation and Maintenance Plan template (PDF)*.

  • Stormwater C.3 Guidebook 7th Edition (PDF), approved June 21, 2017. Supersedes the 6th Edition in effect since 2012.

  • Suppliers of bioretention soil mix are listed here.

  • IMP Sizing Calculator available at the C.3 Guidebook page. It includes a help document.