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Water: Total Maximum Daily Loads (303d)

Appendix B - Supporting Programs

Guidance for Water Quality-Based Decisions:
The TMDL Process

EPA Water Quality Criteria andStandards

The water quality standards program, as envisioned in Section 303(c) of the Clean Water Act, is a joint effort between the States and EPA. The States have primary responsibility for setting, reviewing, revising and enforcing water quality standards. EPA develops regulations, policies, and guidance to help States implement the program and oversees States activities to ensure that State adopted standards are consistent with the requirements of the Act and the implementing Water Quality Standards regulation (40 CFR Part 131). EPA has authority to review and approve or disapprove State standards and, where necessary, to promulgate Federal water quality standards.

A water quality standard defines the water quality goals of a waterbody, or portion thereof, by designating the use or uses to be made of the water, by setting criteria necessary to protect the uses, and by preventing degradation of water quality through antidegradation provisions. States adopt water quality standards to protect public health or welfare, enhance the quality of water, and serve the purposes of the Clean Water Act. "Serve the purposes of the Act" (as defined in Sections 101(a), 101(a)(2), and 303(c) of the Act) means that water quality standards should: 1) include provisions for restoring and maintaining chemical, physical, and biological integrity of State waters, 2) provide, wherever attainable, water quality for the protection and propagation of fish, shellfish, and wildlife and recreation in and on the water ("fishable/swimmable"), and 3) consider the use and value of State waters for public water supplies, propagation of fish and wildlife, recreation, agriculture and industrial purposes, and navigation.

In the current Water Quality Standards regulation, section 131.11 encourages States to adopt both numeric and narrative criteria. Criteria protect both short-term (acute ) and long-term (chronic) effects. Numeric criteria are important where the cause of toxicity is known or for protection against pollutants with potential human health impacts or bioaccumulation potential. Numeric water quality criteria may also be the best way to address nonpoint source pollution problems. Narrative criteria can be the basis for limiting toxicity in waste discharges where a specific pollutant can be identified as causing or contributing to the toxicity but there are no numeric criteria in the State standards, or where toxicity cannot be traced to a particular pollutant. Whole effluent toxicity (WET) testing is also appropriate for discharges containing multiple pollutants because WET testing provides a method for evaluating synergistic and antagonistic effects on aquatic life. Biological criteria provide a means to measure aquatic community structure and function. EPA considers a combination approach of narrative, numeric, and biological criteria necessary to protect beneficial uses fully from the broad range of point and nonpoint sources of pollution.

In addition, the Clean Water Act in Section 303(c)(2)(B) requires States to adopt numeric criteria for priority toxic pollutants for which EPA has published criteria guidance when the discharge or presence of these pollutants could reasonably be expected to interfere with the designated uses in affected waters. States may adopt criteria with Statewide application or site-specific criteria.

EPA's regulation requires each State to adopt, as part of its water quality standards, an antidegradation policy consistent with 30 CFR 131.12. The regulation also requires each State to have implementation methods for its antidegradation policies, i.e., decision criteria for assessing activities that may impact the integrity of a waterbody. Activities covered by the antidegradation policy and implementation methods include both point and nonpoint sources of pollution. Section 131.12 effectively sets out a three-tiered approach for the protection of water quality. "Tier 1" (40 CFR 131.12 (a)(1)) of antidegradation maintains and protects existing uses and the water quality necessary to protect these uses. "Tier II" (section 131.12(a)(2)) protects the water quality in waters whose quality is better than that necessary to protect "fishable/swimmable" uses of the waterbody. Outstanding national resource waters (ONRWs) are provided the highest level of protection under the antidegradation policy ("Tier III").

States may, at their discretion, adopt policies in their standards affecting the application and implementation of standards. EPA specifically recognizes mixing zones, variances, low flow exemptions, and schedules of compliance for water quality-based permit limits. Guidance on these subjects is available from EPA's Office of Water Regulations and Standards, Criteria and Standards Division.

Section 305(b) -- Water Quality Assessment

Section 305(b)28 establishes a process for reporting information about the quality of the nation's water resources to EPA and Congress. Each State, Territory, and Interstate Commission develops a program to monitor the quality of its surface and ground waters and report the current status of water quality biennially to EPA. This information is compiled into a biennial report to Congress. The 305(b) report allows EPA to:

  • Determine the status of water quality.
  • Identify water quality problems and trends.
  • Evaluate the causes of poor water quality and the relative contributions of pollution sources.
  • Report on the activities underway to assess and restore water quality.
  • Determine the effectiveness of control programs.
  • Ensure that pollution control programs are focused on achieving environmental results in an efficient manner.
  • Determine the workload remaining in restoring waters with poor quality and protecting threatened waters.
  • Use information from the lists of waters developed under sections 304(l) and 319 and continue to maintain and update the statutorily-required lists of waters identified under sections 303(d) and 314.

For each assessed waterbody, information is provided on the water quality-limited status, use nonattainment causes and sources, cause magnitude, and source magnitude. Much of the information from the 305(b) assessments provide useful information for developing lists of water quality-limited segments asked for in section 303(d).

Section 304(l) -- Impaired Waters

Section 304(l)29 required lists of impaired waters and sources to be submitted to EPA as a "one time" effort. These lists of waters (known as the short, long, and mini lists) provide three types of designations for impaired waters and source impacts. The mini list (section 304(l)(1)(A)(i)) is a list of waters that the State does not expect to achieve numeric water quality standards for priority pollutants (section 307(a)) after technology-based requirements have been met, due to point or nonpoint source pollution. The long list (section 304(l)(1)(A)(ii)) is a comprehensive list of waters that are not meeting the fishable and swimmable goals of the Act whether due to toxicity or other impairments; point or nonpoint sources; or toxic, conventional, or nonconventional pollutants. A waterbody which meets its designated use criteria and does not meet fishable/swimmable criteria would be listed on the section 304(l) long list but not necessarily on the section 303(d) list of waters needing TMDLs. It would be appropriate for a State to use the information on all waters from its long lists and apply these data in developing the section 303(d) list of waters that still do not meet applicable water quality standards. The short list (section 304(l)(1)(B)) is a list of State waters that are not expected to meet applicable standards after technology-based controls have been met, due entirely or substantially to discharge of toxic pollutants from point sources. A fourth list is the list of point source dischargers of priority toxic pollutants to waters listed under section 304(l).

Section 319 -- Nonpoint Source Program

One key initiative of the 1987 Water Quality Act Amendments to the Clean Water Act was the addition of section 319 which established a national program to control nonpoint source pollution. Under this program, States are asked to assess their NPS pollution problems and submit that assessment to EPA. These assessments include a list of "navigable waters within the State which, without additional action to control nonpoint sources of pollution, cannot reasonably be expected to attain or maintain applicable water quality standards or the goals and requirements of this Act." Other paragraphs of section 319 require the identification of categories and subcategories of NPS pollution which contribute to the identification of impaired waters; descriptions of the procedures for identifying and implementing BMPs; control measures for reducing NPS pollution; and descriptions of State and local programs used to abate NPS pollution. Based upon the assessments, State nonpoint source management programs are prepared and presented to EPA for approval. Once these programs are approved, grant funds are made available for the implementation of the program.

Section 319 assessments identify waters with impairments due primarily to NPSs for which TMDLs (including LAs) may need to be developed to establish protection of water quality. States are encouraged to use these tools where appropriate to achieve or protect beneficial uses of the water.

Section 314 -- Clean Lakes Program

Historically, the Clean Lakes Program has been active in awarding grants for the study and restoration of publicly-owned lakes. Under this program, states are encouraged to develop integrated water quality strategies that include lake and reservoir management, restoration, and protection activities. EPA provides financial assistance as available; however, greater emphasis is now on developing technical support material (e.g., a Lake and Reservoir Restoration Guidance Manual).

Section 320 -- National Estuary Program

Authorized by Congress in 1985, and formally established in 1987 by amendments to the Clean Water Act, the National Estuary Program (NEP) builds upon the lessons of the Chesapeake Bay, Great Lakes, and other earlier programs in a geographic, basin-wide approach to environmental management. The EPA Administrator selects estuaries for NEP participation through State governors' nominations. To be selected estuaries must demonstrate a likelihood of success and evidence of institutional, financial, and political commitment to solve their problems.

Among the environmental problems addressed in the NEP estuaries are the loss of aquatic habitats, toxic contamination of estuarine sediments, increases in nutrient levels, bacterial contamination, and hypoxia. As methods for assessing and successfully managing these estuaries are developed, this national demonstration program aims to communicate its lessons to the more than 150 estuaries located along our coasts.

For approved estuaries, the Administrator convenes management conferences, a grouping of interested Federal, Regional, State, and local governments, affected industries, scientific and academic institutions, and citizen organizations. Management conferences strive for an open, consensus-building approach to defining program goals and objectives, identifying problems to address, and designing pollution prevention/control and resource management strategies to meet each objective. Management conferences are required to create and begin implementation of a Comprehensive Conservation and Management Plan (CCMP) designed to protect and restore the estuary.

Monitoring Program

Ambient water quality monitoring is a data gathering tool used for almost all water quality assessment. Monitoring programs serve to identify waters needing TMDLs, quantify loads, verify models, and evaluate effectiveness of water quality controls (including BMP effectiveness). Once TMDLs have been established for a given waterbody, follow-up monitoring is recommended to document improvement or lack of improvement. Since the TMDL process is iterative, monitoring data can provide the information for updating and revising current TMDLs. Ambient monitoring is used for setting permit conditions, compliance, and enforcement, and detecting new problems and trends.

Effluent Limitation Guidelines and Standards

EPA develops effluent limitation guidelines and new source performance standards for industrial dischargers. These are uniform technology-based limitations for industrial facilities discharging directly into the nation's waters. EPA also develops pretreatment standards for those facilities which discharge into Publicly Owned Treatment Works (POTWs).

During the effluent guidelines promulgation process, EPA develops a profile of the industry to determine pollutant loadings of untreated wastewater for which effluent limitation guidelines are being developed. Pollutants of concern and technologies for treating them are then identified. EPA then prepares estimates of total investment, operation and maintenance costs of complying with each technology option, and evaluates the regulatory options, both technically and economically, to select a technology as the basis for the guidelines.

Effluent limitations, guidelines, and standards are established for three types of industrial pollutants: conventional, toxic, and nonconventional. Effluent guidelines generally limit the amount of pollutant that can be discharged at an individual facility. The numerical limits in the guidelines are determined using industry-specific production data and the treatability data for the selected technology.

NPDES Permits and Individual Control Strategies

All discrete sources of wastewater must obtain a National Pollutant Discharge Elimination System (NPDES) permit that regulates the facility's discharge of pollutants. The approach to controling and eliminating water pollution is focused on the pollutants determined to be harmful to receiving waters and on the sources of such pollutants. Authority for issuing NPDES permits is established under section 402 of the CWA.30 Point sources are generally divided into two types: "industrial" and "municipal." Nationwide, there are approximately 50,000 industrial sources which include commercial and manufacturing facilities. Municipal sources, also known as POTWs, number about 15,700 nationwide. Wastewater from municipal sources results from domestic wastewater discharged to POTWs as well as the "indirect" discharge of industrial wastes to sewers.

Section 304(l)(1)(D) required, at a minimum, the development of individual control strategies (ICSs) for point source discharges of priority toxic pollutants to waters identified on the short list. (The short list is composed of State waters for which applicable section 307(a) priority pollutant standards are not expected to be achieved after technology-based controls have been met, due entirely or substantially to point sources.) An ICS consists of NPDES permit limitations and schedules for achieving established limitations, along with other documentation to demonstrate that the controls selected are appropriate and adequate.31

Marine and Estuarine Waters

In January 1990, EPA published its National Coastal and Marine Policy, which establishes EPA's goals for coastal and marine protection. They include:

  • Recover full use of the nation's shores, beaches, and water.
  • Restore the nation's shell fisheries and salt-water fisheries.
  • Minimize the use of coastal and marine water for waste disposal.
  • Improve and expand coastal science.
  • Support international efforts to protect coastal and marine resources.

EPA's programs to protect ocean and coastal waters and the Great Lakes from nutrient and toxic pollutants emanating from point and nonpoint sources are implemented under the Clean Water Act and the Marine Protection, Research, and Sanctuaries Act (Ocean Dumping Act).

Marine and estuarine waters are, in many cases, the ultimate sink for pollutants which emanate from upland sources. Estuarine and marine waters are particularly complex and it is often difficult to predict pollutant fate and transport. To address the increased complexity and effect on aquatic life, water quality management efforts must increase accordingly. TMDLs can be a useful tool for management of marine and estuarine waters. Technical guidance is currently being revised to support estuarine modeling.32


Contaminated ground water discharge to surface water may be a source of contaminants in water quality-limited surface waters. While ground water and surface water are often treated as separate systems, they are in reality highly interdependent components of the hydrologic cycle. Subsurface interactions with surface waters occur in a variety of ways. In several studies, ground water discharge accounted for as much as 90% or more of stream flow in humid regions. Therefore, the potential pollutant contributions from ground water to surface waters should be investigated when developing TMDLs. Additional information is available from the EPA Office of Ground Water Protection.


The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) or "Superfund" provides broad federal authority to respond directly to releases or threatened releases of hazardous substances. This law also provides for the cleanup of inactive or abandoned hazardous waste sites. Under CERCLA, EPA assesses the nature and extent of contamination at a site, determines the public health and environmental threats posed by a site, analyzes the potential cleanup alternatives, and takes action to clean up the site. In instances where a CERCLA site has impact on a nearby waterbody, the level of cleanup needed to maintain water quality standards of surface waters should have a direct relationship to the TMDL for the affected surface waters. As part of the CERCLA process, all "applicable or relevant and appropriate requirements" of statutes such as the CWA must be followed. Load allocations developed pursuant to section 303(d) may, in appropriate circumstances, be "applicable or relevant and appropriate."

POTWs that discharge CERCLA hazardous substances in effluent at levels that equal or exceed NPDES permit limitations, or for which no specific limitations exist, or in spills or other releases, may be subject to the notification requirements and liability provisions under CERCLA. In addition, POTWs that disposed of sludge in impoundments or landfills that are Superfund sites may be required to pay for cleanup of those sites. At times, POTWs may be requested to accept wastewaters from Superfund cleanup activities. If discharge of CERCLA wastewaters to a POTW is deemed appropriate, the discharger must ensure compliance with substantive and procedural requirements of the national pretreatment program and all local pretreatment regulations before discharging wastewater to the POTW.

The provisions of CERCLA extend well beyond the regulation of POTW discharges. The most common types of Superfund sites governed by CERCLA include abandoned hazardous waste sites and inactive mines, many of which do not discharge to POTWs.


The Superfund Amendments and Reauthorization Act (SARA, Hotline 800-535-0202), which amended CERCLA, also established in Title III a new program to increase the public's knowledge of and access to information on the presence of hazardous chemicals in their communities and releases of these chemicals into the environment. Title III (Community Right to Know Program) requires facilities to notify State and local officials if they have extremely hazardous substances present at their facilities in amounts exceeding certain "threshold planning quantities." If appropriate, the facility must also provide material safety data sheets on hazardous chemicals stored at their facilities, or lists of chemicals for which these data sheets are maintained, and report annually on the inventory of these chemicals used at their facility. The law may also require facilities to submit information each year on the amount of toxic chemicals released by the facilities to all media (air, water, and land), if they fall within Standards Industrial Classification Codes 20 to 39 and meet certain threshold limits.

28 -- USEPA. 1989. Guidelines for the Preparation of the 1990 State Water Quality Assessment (section 305(b) Report). OW/OWRS. Washington, D.C. Back.

29 -- USEPA. March, 1988. Final Guidance for Implementation of Requirements under section 304(l) of the Clean Water Act as Amended. OWRS and OWEP. Washington, D.C. Back

30 -- USEPA. 1989. Overview of selected EPA Regulations and Guidance Affecting POTW Management. OW/OMPC, EPA 440/69-89/008. Washington, D.C. (Hotline: 800-424-9346) Back

31 -- USEPA. 1987. Permit Writer's Guide to Water Quality-based Permitting for Toxic Pollutants. OW/OWEP, EPA 440/4-87-005. Washington, D.C. Back

32 -- USEPA. Technical Guidance Manual for Performing Wasteload Allocations, Book III - Estuaries. Back

Table of Contents Chapter 1 Chapter 2 Chapter 3
Chapter 4 Appendix A Appendix B Appendix C
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