A TMDL (Total Maximum Daily Load) is defined in federal regulations as “the sum of the individual waste load allocations for point sources and load allocations for nonpoint sources and natural background such that the capacity of the waterbody to assimilate pollutants (the Loading Capacity) is not exceeded.”

In other words, a TMDL sets a limit for the total amount of a particular pollutant that can be discharged to a waterbody.  This limit ensures that pollutant loads from all sources will not impair the designated beneficial uses of the waterbody. The timeframe for compliance with TMDL targets varies, but may take many years. TMDLs will often include a compliance schedule, identifying interim and final targets.

A TMDL is developed when a waterbody has been identified as impaired. Section 303(d) of the federal Clean Water Act requires states to establish a listing of all impaired waterbodies and to rank those waterbodies according to priority for TMDL development. This list, called the 303(d) List is updated every two years and is developed by the Regional and State Water Quality Control Boards and approved by EPA.

The following TMDLs have been established or are being developed for Orange County waterbodies. To find out more about each TMDL, please click on the links below:

Contact Info

Jian PengSection Chief  | phone icon (714) 955-0650 |  envelope | all TMDLs

Stuart Goong | phone icon (714) 955-0656 | envelope | 
Newport Bay Nutrient; Toxics (Organochlorines; Selenium; Metals; Diazinon and Chlorpyrifos); Fecal Coliform TMDLs; Coyote Creek Metals and Bacterial TMDLs

Stella Shao  | phone icon (714) 955-0651  | envelope |
Aliso Creek, San Juan Creek; South County Coastal Area Indicator Bacterial (including Baby Beach), Newport Bay Sediment, Selenium TMDLs

Jamie Habben | phone icon (714) 955-0653  |  envelope |
Newport Bay Sediment TMDL

Rita Abellar  | phone icon (714) 955-0662  |  envelope |
Baby Beach Bacterial TMDL, Coyote Creek Metals and Bacterial TMDLs, Newport Bay Metals, Sediment TMDLs

Suzie Given  | phone icon (714) 955-0654  |  envelope | 
Newport Bay Nutrient, Fecal Coliform TMDLs