Total Maximum Daily Load (TMDL) and the 303(d)

What are TMDLs?

Section 303(d)(A)(1) of the Federal Clean Water Act (CWA) requires states to identify waterbodies that do not meet water quality objectives and are not supporting their beneficial uses. Each state must submit an updated list, called the 303(d) List, to the U.S. Environmental Protection Agency (USEPA) every two years for approval. In addition, the law requires states to establish priority ranking for water bodies on the lists and develop control plans, called Total Maximum Daily Loads (TMDLs), to address the impairment. A TMDL serves as the means to attain and maintain water quality standards (WQSs) for the impaired water body. CWA Section 303(d) and 40 Code of Federal Regulation (CFR) Section 130.2 et seq., specify the components and requirements of a TMDL.

If a State fails to develop a TMDL, or if USEPA rejects the State's TMDL, USEPA must develop one (CWA 303(d)(D)(2), 40 CFR 130.6(c)). Upon approval of the TMDL by USEPA, the State is required to incorporate the TMDL, along with appropriate implementation measures, into the State Water Quality Management Plan (40 CFR 130.6(c)(1), 130.7).

Integrated Report

The Integrated Report is the biennial reporting method used by the State in compliance with federal requirements to report on the status of its surface waters. The Integrated Report consists of the 305(b) Water Quality Inventory Report and the 303(d) List of Impaired Waterbodies, which together make up an assessment of all surface water bodies with categorizations determining what actions are required to protect or improve individual waters of the state. TMDLs are then developed as needed based on the categorizations in the Integrated Report. Each Integrated Report biennial cycle consists primarily of assessments from the three Regional Water Quality Control Boards that are identified "on-cycle" by a notice of solicitation.  Past and current Region 7 Integrated Reports when the Regional Water Board was on-cycle are provided one the Region 7 Integrated Report program page.  

Additional information about Integrated Reports is also available on the State Water Board’s Integrated Report program page.

TMDL Projects

TMDLs Under Development

This TMDL will address ammonia and toxicity impairments in the New River. A California Environmental Quality Act (CEQA) Scoping meeting for this project was held on January 13, 2022.

Available Documents:

This TMDL will address bifenthrin, cypermethrin, and lambda-cyhalothrin impairments in the New and Alamo Rivers. A California Environmental Quality Act (CEQA) Scoping meeting for this project was held on February 25, 2022. This TMDL was adopted by the Regional Water Board on July 9, 2024.

The following documents are available:

Regional Water Board Review

This TMDL will address ammonia, dissolved oxygen, and toxicity impairments in the Coachella Valley Stormwater Channel. A California Environmental Quality Act (CEQA) Scoping meeting for this project was held on July 28, 2022.

Available Documents:

This TMDL will address chloride, indicator bacteria, and toxicity impairments in the Alamo River. A California Environmental Quality Act (CEQA) Scoping meeting for this project was held on August 10, 2021.

Available Documents:

This TMDL will address dissolved oxygen and nutrient impairments in the Salton Sea. An in-person California Environmental Quality Act (CEQA) Scoping meeting for this project was held on January 31, 2023 and a second virtual meeting on February 2, 2023.

Available Documents:

Approved TMDLs

This TMDL is part of the Imperial Valley Agricultural General Order and will address PCBs, chlordane, chlorpyrifos, DDT, diazinon, dieldrin, and toxaphene impairments in Alamo River, Imperial Valley Drains, and New River. The TMDL was adopted by the Regional Board on May 10, 2022. The TMDL was adopted by the State Water Resources Control Board at a public hearing on November 15, 2022. The TMDL was approved by the Office of Administrative Law on May 24, 2023. This TMDL was approved by U.S. Environmental Protection Agency on March 19, 2024 and is in effect.

The following documents are now available:

Regional Water Board Review

State Water Board Review

Office of Administrative Law

This project was developed as a TMDL alternative as part of the Palo Verde Agricultural General Order and addresses DDT and toxaphene impairments in the Palo Verde Outfall Drain and Lagoon. The Palo Verde Agricultural Order was approved by the Regional Water Board on May 15, 2019 and the associated TMDL alternative was approved by USEPA on May 11, 2022 as part of the 2020/2022 Integrated Report.

This TMDL is part of the Coachella Valley Agricultural General Order and will address PCBs, DDT, dieldrin, and toxaphene impairments in the Coachella Valley Stormwater Channel. This TMDL alternative was approved by USEPA on May 11, 2022 as part of the 2020/2022 Integrated Report.

The TMDL was adopted by the Regional Board June 27, 2001, approved by the State Board on February 19, 2002, approved by the Office of Administrative Law on May 3, 2002, and approved by U.S. EPA on June 28, 2002.

This TMDL addresses sedimentation and siltation in the Alamo River. Information about this TMDL can be found in Chapter 4, section V.B of the Basin Plan. Documents, such as the Staff Report and Appendices are available upon request.

The TMDL was adopted by the Regional Board on October 10, 2001, approved by the State Board on March 21, 2002. It was also approved by the Office of Administrative Law on March 23, 2002, and approved by U.S. EPA on August 14, 2002.

This TMDL addresses pathogens in the New River. Information about this TMDL can be found in Chapter 4, section V.A of the Basin Plan. Documents, such as the Staff Report and Appendices are available upon request.

The TMDL was adopted by the Regional Board on June 26, 2002, approved by the State Board on November 19, 2002, approved by the Office of Administrative Law on January 13, 2003, and approved by U.S. EPA on March 31, 2003.

This TMDL addresses sedimentation and siltation in the New River. Information about this TMDL can be found in Chapter 4, section V.C of the Basin Plan. Documents, such as the Staff Report and Appendices are available upon request.

The TMDL was adopted by the Regional Board on June 21, 2006, approved by the State Board on April 18, 2007, approved by the Office of Administrative Law on August 2, 2007, and approved by U.S. EPA on September 24, 2007.

This TMDL addresses trash in the New River at the International Boundary. Information about this TMDL can be found in Chapter 4, section V.F of the Basin Plan. Documents, such as the Staff Report and Appendices are available upon request.

The TMDL was adopted by the Regional Board on January 19, 2005, approved by the State Board on July 21, 2005, approved by the Office of Administrative Law on September 8, 2005, and approved by U.S. EPA on September 30, 2005.

This TMDL addresses sedimentation and siltation in Imperial Valley Drains. Information about this TMDL can be found in Chapter 4, section V.D of the Basin Plan. Documents, such as the Staff Report and Appendices are available upon request.

The TMDL was adopted by the Regional Board on May 16, 2007, with revision later adopted by the Regional Board on June 17, 2010. The TMDL was subsequently approved by the State Board on July 19, 2011, approved by the Office of Administrative Law on February 2, 2012, and approved by U.S. EPA on April 27, 2012.

This TMDL addresses bacterial indicators in the Coachella Valley Stormwater Channel. Information about this TMDL can be found in Chapter 4, section V.H of the Basin Plan. Documents, such as the Staff Report and Appendices are available upon request.

The TMDL was adopted by the Regional Board on May 20, 2010. The TMDL was subsequently approved by the State Board on December 6, 2011, approved by the Office of Administrative Law on March 21, 2012, and approved by U.S. EPA on November 16, 2012.

This TMDL addresses dissolved oxygen in the New River at the International Boundary. Information about this TMDL can be found in Chapter 4, section V.G of the Basin Plan. Documents, such as the Staff Report and Appendices are available upon request.

Public Participation

The Colorado River Region tries to foster public participation during all phases of TMDL development to address as many technical and social issues as possible early in the process. Each TMDL project will have a unique approach to public participation dependent on the size of the watershed, the nature of the problem, who and how many interested parties or stakeholders emerge, etc. Public participation will at times take on one or more of these forms: occasional public workshops, regularly scheduled steering committee meetings, Technical Advisory committee meetings, Regional Board staff presentations at other organization's meetings, or written solicitations or request for comments sent by mail.

The public has the opportunity and legal right to review and comment on TMDLs before they are made a part of the Basin Plan. Essentially this means that the public has the opportunity to comment on Draft TMDLs in writing prior to Regional Board Hearings or verbally at Regional Board Meetings before a TMDL is adopted and implemented.

Bodies of water are listed as impaired after several steps. One of the steps is the review of information and/or data by Regional Board staff pertaining to a body of water. Regional Board staff will notify the public when the review process will occur, and publicly solicit information or data that would lead to a listing of a body of water.

This section provides other opportunities for the public to be involved in the TMDL process. If the section below is empty, this implies that no specific event is on the agenda in the near future. However, remember that the waters of the state belong to its citizens, and you are encouraged to participate in the process designed to protect this resource. Simply call the Regional Water Quality Control Board office and make inquiries to the staff person working on the body of water near you.

Data

The Regional Board utilizes a variety of data sources when considering changes to the 303(d) List or when developing TMDLs. Data sources include Toxic Substances Monitoring, monitoring data for regulated/unregulated discharges, and data from other local, state and federal agencies. The Regional Board prefers data that utilizes quality assurance/quality control procedures (QA/QC) that develop reliable water quality sampling results.

One major data source is the Surface Water Ambient Monitoring Program (SWAMP). SWAMP watershed characterization calls for dividing the Region into watershed rotation areas and conducting synoptic, tributary-based sampling each year in one of the areas. Over a five-year period, all the hydrologic units in the Region are monitored and evaluated. Permanent watershed sites are monitored monthly for conventional water quality parameters, and once during the year for sediment chemistry, bioaccumulation, and benthic invertebrate assemblages. In addition to the synoptic site selection approach, additional monitoring sites are established in each rotation area to provide focused attention on watershed and water bodies known to have water quality impairments. SWAMP utilizes QA/QC procedures to develop reliable water quality sampling results. Visit the SWAMP program page for more information. For information about data used for a specificTMDL, contact the staff person working on the TMDL

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