What is C.3?

C.3 refers to Provision C.3 of the County’s NPDES Permit, which was added to the Permit in 2003.  This provision requires stormwater runoff from projects creating and/or redeveloping at least 10,000 square feet of impervious surface to treat stormwater runoff with permanent stormwater management facilities, and requires projects creating and/or redeveloping to design such facilities to control runoff rates and volumes (in addition to treatment).  Projects that are not required to comply with C.3 still implement permanent stormwater controls to the maximum extent practicable.

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1. How do I calculate the Flood Control flow data point? Do I need to know the post development design flows for my project?
2. How do I determine the 25-year 24-hour storm depth
3. What are Pollutants of Concern (POCs)?
4. What are Stormwater Best Management Practices (BMPs)?
5. What is a Watershed?
6. What is an illicit discharge and who do I call to report it?
7. What is an NOI and what permits does it cover?
8. What is C.3?
9. What is NPDES and who oversees it?
10. What is the design storm for my project?
11. What is the difference between a Stormwater Pollution Prevention Plan (SWPPP) and a Stormwater Control Plan (SWCP)?
12. What is the difference between point source and non-point source?
13. What is the difference between the County Watershed Program and the Contra Costa Clean Water Program?
14. What is the difference between the storm drain system and the sanitary sewer?
15. What is the drainage easement across my property? Can I build on it? What can I do on it?
16. Who do I contact if I have flooding on my street?