The Federal Clean Water Act Section 303(d) requires that States identify waters that do not or are not expected to meet water quality standards (beneficial uses, water quality objectives and the antidegradation policy) with the implementation of technology-based controls. Once a waterbody has been placed on the 303(d) list of impaired waters, states are required to develop a Total Maximum Daily Load (TMDL) to address each pollutant causing impairment. A TMDL defines how much of a pollutant a waterbody can tolerate and still meet water quality standards. Each TMDL must account for all sources of the pollutant, including: discharges from wastewater treatment facilities; runoff from homes, forested lands, agriculture, and streets or highways; contaminated soils/sediments, legacy contaminants such as DDT and PCBs on-site disposal systems (septic systems) and deposits from the air. Federal regulations require that the TMDL, at a minimum, account for contributions from point sources (permitted discharges) and contributions from nonpoint sources, including natural background. In addition to accounting for past and current activities, TMDLs may consider projected growth that could increase pollutant levels. TMDLs allocate allowable pollutant loads for each source, and identify management measures that, when implemented, will assure that water quality standards are attained.
California state law (Porter-Cologne Water Quality Control Act, California Water Code Section
13000 et. seq.) requires the Regional Board to formulate and adopt water quality control plans,
or Basin Plans, for all areas within its region. The Basin Plans must include an implementation
plan that describes how the water quality standards established in the Basin Plan will be met.
TMDLs, with their associated implementation plans, are adopted into the Basin Plans through the
Basin Planning process.
In general, when developing TMDLs, the Regional Board undertakes the following five steps:
A complete TMDL must contain all of the following elements:
The process might take two to six years from the beginning of a TMDL project to a Basin Plan amendment. The time required depends on the complexities of scientific and policy issues, the availability of scientific information, and whether additional research studies and data are needed.
Developing TMDLs is only the first step toward solving water quality problems. TMDLs must be implemented to ensure the restoration of water quality standards. TMDLs specify a set of actions to improve water quality that can include the following:
Public participation is a vital part of the TMDL process. Those interested in TMDLs are often referred to as stakeholders. Each TMDL has its own stakeholder process, which can include attending meetings, submitting written comments on draft reports, and reviewing posted items on the Regional Board website. Sometimes, the Regional Board will seek public assistance with tasks, such as data gathering, data analysis, or public education efforts.
To receive notifications by e-mail, subscribe on-line to our TMDL Projects, electronic mailing list.
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Bacterial Indicator TMDLs for the Middle Santa Ana River
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