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Total Maximum Daily Loads (TMDLs) and 303(d) list of water quality limited segments Announcements Select a Topic
What are TMDLs?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. How are TMDLs developed?
In general, when d eveloping TMDLs, the Regional Board undertakes the following five steps:
- Involve Stakeholders
: Stakeholders can be the general public, business interests, local, state or federal government entities, environmental groups, or anyone concerned with a particular water body. The
Regional Board involves stakeholders at the beginning of the process in order to provide ongoing input to the Regional Board on the development of TMDLs.
Assess water body:
In this step, sources and amounts, or "loads" of the pollutant to the impaired water body, are identified. In addition to calculation of daily pollutant loads, this analysis may also consider seasonal pollutant loads as well as annual pollutant loads. Then the overall effect of these loads on the water body is determined.
Define the Total Load and Develop Allocations
: The loading capacity is the maximum allowable pollutant load that may be discharged to a water body and still achieve water quality standards. The total allowable load is then allocated among all sources that
have been previously identified. TMDLs can address single pollutants or combinations of pollutants. Federal regulations provide that TMDLs can be expressed as mass, thermal energy, toxicity or other appropriate
measures.
Develop Implementation Plan: This step is a description of the approach and
activities to be undertaken to ensure that the allocations are met. The parties responsible for carrying out the actions are identified. The implementation plan also specifies any additional studies
or data that are needed to refine the TMDL, and the monitoring that is to be conducted to determine whether the implementation of the TMDL results in achieving water quality standards.
Amend the Basin Plan:
State law requires that TMDLs be incorporated into the Basin Plan through the Basin Planning process. The Basin Plan amendment legally establishes
a TMDL and provides the basis for regulatory requirements. Basin Plan amendments are adopted through a public process that requires approval by the Regional Board, the State Water Resources Control Board, the
California Office of Administrative Law, and USEPA.
TMDL Elements
A complete TMDL must contain all of the following elements:
- Problem Statement:
Describes the water body, impaired beneficial uses, and pollutant(s) causing
the impairment.
- Numeric Targets:
Expresses the desired condition of the water body to protect beneficial
uses. Defines indicators and associated target(s) necessary to meet numeric or narrative water quality objectives.
- Source Analysis:
Assesses the relative contributions of different pollutant sources or causes
and the extent of necessary reductions/controls.
- Linkage Analysis:
Describes the relationship between numeric target(s) and sources and
estimates the ability of the water body to assimilate the pollutant.
- Allocations:
Allocates responsibility for pollutant reduction. Allocations may be specific to agencies or persons (businesses), or general by source category or sector. The sum of individual allocations must equal the total allowable pollutant level.
- Margin of Safety:
Accounts for uncertainty associated with calculating pollutant loads and their impact on water quality. The margin of safety may be implicit (i.e., through use of conservative assumptions) or explicit (i.e., by assigning a specific allocation to the margin of safety).
- Implementation Plan:
Details pollution prevention, control, and restoration actions, responsible parties and schedules necessary to attain water quality standards. Identifies enforceable measures (e.g. prohibition) and triggers for Regional Board action (e.g., performance standards).
- Monitoring/Re-evaluation:
Describes the monitoring strategy that will be used to evaluate the effectiveness of the TMDL and a schedule for reviewing and, if necessary, revising the TMDL and associated implementation elements.
How long does it take to develop a TMDL? 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. How are TMDLs implemented? 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:
- Enhancing pollution prevention programs for wastewater and urban runoff.
- Cleaning up contaminated soils/sediments, legacy contaminants.
- Reducing pollution from agriculture, animal feedlots, septic systems, and marinas.
- Restoring habitat for fish, birds, and other wildlife.
- Working with local governments to create or revise ordinances and other policies.
- Ongoing monitoring to track water quality improvements.
How can I get involved? 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. Additional TMDL Information
The 303(d) list of water quality limited segmentsThe Federal Clean Water Act Section 303(d) requires that States assess the quality of their waters every two years and publish a list of those waters not meeting the water
quality standards established for them. Water quality standards include beneficial uses, water quality objectives necessary to protect these uses and the antidegradation policy, and are found in the Basin Plan.
For water bodies placed on the 303(d) List of Water Quality Limited Segments,
states are required to develop Total Maximum Daily Loads (TMDLs) for the pollutant(s) that are causing standards impairment.
Water bodies are included on the 303(d) List of Water Quality Limited Segments after evaluation
of existing water quality data using the methodology for determining impairment identified in the
Water Quality Control Policy for Developing California's Clean Water Act Section 303(d) List and the Functional Equivalent Document
, both adopted by the Sate Water Resources Control Board in September 2004.Once a water body is placed on the 303(d) List of Water Quality Limited Segments, it remains on the list until a TMDL is adopted
and the water quality standards are attained or there are sufficient data to demonstrate that water quality standards have been met and delisting should take place.
Santa Ana Region's Approved 303(d) Lists of Water Quality Limited Segments:
2006 303(d) List - Link to State Baord 303(d) site 
2002 303(d) List
1998 303(d) List
1996 303(d) List
1994 303(d) List
1991 303(d) List
1990 303(d) List
1986 and 1987 303(d) List
Additional Information on the 2006 303(d) List of Water Quality Limited Segments:
Approved 2006 Revision of the Clean Water Act Section 303(d) List of Water Quality Limited Segments
- Includes links to documents pertaining to Section 303(d) listings for the Santa Ana Region and all other regional boards.
Notice of public solicitation for water quality data and information for the 2008 Integrated Report - List of Impaired Waters and Surface Water Quality Assessment - Federal Clean
Water Act Sections 303(d) and 305(b)
Contact persons regarding the 303(d) List of Water Quality Limited Segments:If you have any questions or comments regarding the 303(d) List please contact Pavlova Vitale at (951) 782-4920 or Hope Smythe at (951) 782-4493.
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