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Regional Stormwater Program

Regulatory Background

The California State Water Resource Control Board and the nine Regional Water Quality Control Board (RWQCB), through the Clean Water Act, help address water pollution by regulating point sources that discharge pollutants, such as stormwater and non-stormwater discharges, to waters of the United States under the National Pollutant Discharge Elimination System (NPDES) Permitting Program. Orange County is located within two RWQCB regions: 

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The County of Orange, Orange County Flood Control District (OCFCD), and the 26 cities of North Orange County stormwater and non-stormwater discharges are regulated by a picture_as_pdf Phase I MS4 Permit issued by the Santa Ana RWQCB. Similarly, the County of Orange, OCFCD, and the 10 cities of South Orange County (south of El Toro Road) stormwater and non-stormwater discharges are regulated by a picture_as_pdf Phase I Regional MS4 Permit issued by the San Diego RWQCB.

These MS4 Permits require the development of the stormwater program(s) that aim to (1) effectively prohibit non-stormwater discharges into the storm drain system and (2) reduce the discharge of pollutants to the maximum extent practicable through the implementation of best management practices (BMPs) and other control strategies. These two permits also incorporate Total Maximum Daily Loads (TMDL). A TMDL sets a limit for the total amount of a particular pollutant that can be discharged into a water body, which ensures that pollutant loads from various sources will not impair the designated beneficial uses of the water body.  TMDLs applicable to North Orange County can be found on the Santa Ana RWQCB’s websiteexplore , and TMDLs applicable to South Orange County can be found on the San Diego RWQCB’s websiteexplore . The San Diego RWQCB’s San Diego Basin Plan Map web appexplore also provides useful information, such as watersheds with applicable TMDLs, impaired waters per the 2014 and 2016 California Integrated Report (Clean Water Act 303(d) list and 305(b) Report), and more.


H2OC Stormwater Program

While each Permittee has a plan outlining the strategies and activities they will implement to comply with MS4 Permit requirements, “H2OC” serves as the cooperative stormwater program, which includes all Orange County MS4 Permittees. As the “Principal Permittee” on both Santa Ana Region and San Diego Region MS4 Permits, the County guides development and implementation of the H2OC Stormwater Program, collaborating with Permittees to ensure compliance and prevent pollution in our waterways.