New Development / C.3

Provision C.3 in the Municipal Regional Permit (MRP) requires site designs for new developments and redevelopments to minimize the area of new roofs and paving. Where feasible, pervious surfaces should be used instead of paving so that runoff can infiltrate to the underlying soil. Runoff should be dispersed to landscaping where possible. Remaining runoff from impervious areas 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 allow municipalities to verify that stormwater treatment and flow-control facilities are maintained in perpetuity.

The California Regional Water Quality Control Board for the San Francisco Bay Region reissued the MRP in November 2015 (MRP 2.0). MRP 2.0 governs discharges from municipal storm drains operated by 79 local government entities, including those in Contra Costa County. 

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

Through the Contra Costa Clean Water Program, Contra Costa municipalities have prepared a Stormwater C.3 Guidebook 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, available free at www.adobe.com.

What’s New

  • Stormwater Control Plan template, in MS Word format, 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.
  • Stormwater Facilities Operation and Maintenance Plan template.
  • Example Stormwater Facilities Operation and Maintenance Plans for a Commercial Project and for a Residential Subdivision on the C.3 Guidebook page.
  • Stormwater C.3 Guidebook 7th Edition, 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.

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