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 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.

Quick Resources on C.3 Updates in MRP 3.0:

For Developers, Engineers, Planners, Project Applicants

For Contra Costa Permittee Municipal Staff