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, which was amended in October 2023. 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 has dropped 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 have been updated to reflect new permit requirements.

MRP 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 to establish criteria and to assist applicants through the process of submittals and reviews.

Explore C.3 Requirements Subpages

New in MRP 3.0
- Outlines key changes in C.3 requirements between MRP 2.0 and MRP 3.0
- Includes archive of quick resources, including a factsheet and table with acreage thresholds for C.3.b. Regulated Projects
C.3 Guidebook
- Includes the latest C.3 Stormwater Guidebook and guidance materials.
  - Development Review Checklist and Frequently Asked Questions
  - Templates: Stormwater Control Plans, Operation and Maintenance (O&M) of Stormwater Facilities
- Includes Interactive Tools: Bay Area Hydrology Model (BAHM) links, Hydromodification Management (HM) resources, Integrated Management Practices (IMPs) Calculator
- Includes Resources for Design Professionals: low-irrigation plant selection list, Green Infrastructure (GI) Details and Specifications, and links to relevant external resources.
Guidance to Municipalities
- Includes guidance specific to municipal staff, including the Capital Improvement Project (CIP) Project Review Checklist for Roadways and Parking Lots
Submittals to the Regional Water Boards
- Includes archive of past items that CCCWP member agencies have submitted to the San Francisco Bay Regional Water Quality Control Boards as part of MRP requirements.
C.3 Workshops & Conferences
- Includes recent and past C.3 Training Workshop materials and other presentation materials.
Additional Resources
- Includes additional resources not part of the other pages but that may still be useful for developers and municipal staff involved in site design and C.3 compliance.