OC Watersheds TMDLs
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 layman’s terms, a TMDL sets a limit for the total amount of a particular pollutant
that can be discharged to a waterbody, such that the 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) List 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:
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