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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. Pervious surfaces should be used instead of paving so that runoff can infiltrate to the underlying soil when feasible. 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.

Links:

  • Stormwater Control Plan template, in MS Word format, to assist applicants in preparing the required project submittal (based on the 6th Edition; update pending).
  • Suppliers of bioretention soil mix are listed here.
  • IMP Sizing Calculator available at the C.3 Guidebook page.