What is a TMDL?

What is the TMDL Process?

The Total Maximum Daily Load (TMDL) process provides a flexible assessment and planning framework for identifying load reductions or other actions needed to attain water quality standards (i.e. water quality goals to protect aquatic life, drinking water, and other water uses). Clean Water Act 303(d) established the TMDL process to guide application of state standards to individual waterbodies/watersheds. The process has six steps:

1. Identify Quality Limited Waters- The Regional Board identifies and prepares a list [303(d) list] of waters that do not or are not expected to meet water quality standards after applying existing required controls (e.g. minimum sewage treatment technology).

2. Establish Priority Waters/Watersheds- The Regional Board prioritizes waters/watersheds and target high priority waters/watersheds for TMDL development.

3. Develop Technical TMDLs- For listed waters, the Regional Board develops technical TMDLs that will achieve water quality standards, allowing for seasonal variations and an appropriate margin of safety. A technical TMDL is a quantitative assessment of water quality problems, contributing sources, and load reductions or control actions needed to restore and protect individual waterbodies.

4. EPA Promulgates Technical TMDL- EPA promulgates the technical TMDL developed by the State and publishes the TMDL in the Federal Register. EPA will use the federal public comment process and the Regional Board will respond to comments for EPA.

5. Develop Implementation Plan and Monitoring Plan- The Regional Board is responsible for developing an implementation plan and monitoring plan.

6. Incorporate the TMDL into the Basin Plan- The Regional Board is required to incorporate the entire TMDL including the technical TMDL, implementation plan, and monitoring plan into the Basin Plan.

EPA reviews and approves lists of quality-limited waters requiring TMDLs and specific TMDLs. If EPA disapproves a list or TMDL, EPA is required to establish the list and/or TMDL. EPA and tribal governments are currently clarifying how TMDL process requirements will be addressed in Indian country. Landowners, other agencies, and other stakeholders are encouraged to assist the Regional Board in developing TMDLs for specific watersheds.

Background Info

The Calleguas Creek Watershed (CCW), though relatively small in area and minor in both the number and size of its surface water bodies, suffers from more water quality impairments than most California watersheds, as defined by the USEPA's 303 (d) list. The watershed has experienced dramatic growth over the past 40 years, made possible by the importation of water. The introduction of large volumes of imported water together with rapid growth of both agricultural and urban land uses has altered the watershed's hydrological system in ways that are just beginning to be understood.

Local stakeholders, along with the Los Angeles Regional Water Quality Control Board (LARWQCB), began a watershed planning process in 1996 intended to develop a better understanding of the watershed and to develop a strategy to address the water quality impairments to both surface and groundwater resources. However, early planning efforts were derailed by a legal action of parties not involved in the WMP. This legal action resulted in a Consent Decree among Los Angeles area environmental interests groups, the USEPA and the LARWQCB. This Consent Degree has imposed a time schedule for development of TMDLs for the Watershed and imposed a new urgency to act.

Despite the disruption in the watershed planning process, the stakeholders have gained a much greater understanding of the watershed. The stakeholders firmly believe that the most effective means of addressing the water quality impairments on the watershed is through a comprehensive watershed based plan, rather than through the traditional incremental approach to each impairment. Both the USEPA and the LARWQCB have been supportive of the comprehensive approach, but lack the resources to pursue such a large task in addition to their on-going responsibilities in the region. Also, the LARWQCB and EPA have been skeptical of the ability of the stakeholders within the Watershed to carry out such an effort, while still meeting the Consent Decree schedule.

In response to the concerns of the LARWQCB and the EPA a comprehensive series of work plans, designed to address the surface water quality impairments in the watershed, were developed by the stakeholders and submitted for concurrence of approach. Each work plan focuses on groups of similar constituents related to water quality impairments. The Salts Work Plan will address chloride, total dissolved solids (TDS), sulfate and boron. The Toxicity Work Plan will address toxicity, sediment toxicity, organophosphate pesticides, and chlorpyrifos in fish tissue. The Metals Work Plan will address copper, nickel, mercury, zinc and selenium. In addition, a work plan to address Historic Pesticides and PCBs has also been developed. The Bacteria Work Plan is also included even though it is not specifically listed within the Consent Decree because there is significant stakeholder interest.

Although the outlines and flow charts for each work plan are similar, the anticipated approach of each work plan to ultimately address water quality impairments is unique. The agencies responsible for these work plans believe that some impairments can and will be removed by the implementation of current and proposed actions and projects in the CCW. Other impairments will be examined on a reach-by-reach basis to determine, if in fact, impairment exists and what the appropriate water quality objective (WQO) may be for that reach. In other work plans early effort may be placed on development of a TMDL. In each case a TMDL will be developed on schedule, but only if necessary.

This plan is the first of its kind on a very complex watershed. Its success will depend upon the cooperative efforts of the local stakeholders, in particular the responsible agencies; and the regulatory agencies, in particular the LARWQCB. The plan's success will be measured by the plan's ultimate ability to improve the overall water resources of the Watershed. To help ensure the stakeholder led effort meets regulatory requirements various TMDL development guidance documents are being used as reference: EPA Region 9 Guidance for Developing TMDLs in California; the SWRCB SB 469 TMDL Guidance: A Process for Addressing Impaired Waters in California; and the LA-RWQCB: Draft Strategy for Developing TMDLs and Attaining Water Quality Standards in the Los Angeles Region