Order Code 97-831
Updated November 20, 2008
Clean Water Act and Total Maximum Daily
Loads (TMDLs) of Pollutants
Specialist in Resources and Environmental Policy
Resources, Science, and Industry Division
Section 303(d) of the Clean Water Act requires states to identify waters that are
impaired by pollution, even after application of pollution controls. For those waters,
states must establish a total maximum daily load (TMDL) of pollutants to ensure that
water quality standards can be attained. Implementation was dormant until states and
EPA were prodded by lawsuits. The TMDL program has become controversial, in part
because of requirements and costs now facing states to implement this 35-year-old
provision of the law, as well as industries, cities, farmers, and others who may be
required to use new pollution controls to meet TMDL requirements. In July 2000, EPA
issued revisions to strengthen the program. The rule was widely criticized, and
congressional interest was high. The 2000 rule did not go into effect, and in March
2003, EPA withdrew the rule to consider whether to issue an entirely new rule or other
options; no timetable has been announced. Consequently, the program continues to
operate under regulations issued in 1992. Congress has several options to address
TMDL issues, which remain contentious, but whether it will do so in the 111th Congress
is unknown for now.
The Clean Water Act (CWA) contains a number of complex elements of overall
water quality management. Foremost is the requirement in Section 303 that states
establish ambient water quality standards for water bodies, consisting of the designated
use or uses of a water body (e.g., recreational, public water supply, or industrial water
supply) and the water quality criteria which are necessary to protect the use or uses.
Through permitting, states or the Environmental Protection Agency (EPA) impose
wastewater discharge limits on individual industrial and municipal facilities to ensure
that water quality standards are attained. However, Congress recognized in the act that,
in many cases, pollution controls implemented by industry and cities would be
insufficient, due to pollutant contributions from other unregulated sources.
Under Section 303(d) of the act, states must identify lakes, rivers, and streams for
which wastewater discharge limits are not stringent enough to achieve established water
quality standards, after implementation of technology-based controls by industrial and
municipal dischargers. For each water body, states are required to set a total maximum
daily load (TMDL) of pollutants at a level that ensures that applicable water quality
standards can be attained and maintained. A TMDL is essentially a pollution budget, a
quantitative estimate of what it takes to achieve state water quality goals, setting the
maximum amount of pollution a water body can receive without violating water quality
standards, including a margin of safety. If a state fails to do this, EPA is required to
develop a priority list for the state and make its own TMDL determination. A TMDL is
both a planning process for attaining water quality standards and a quantitative assessment
of problems, pollution sources, and pollutant reductions needed to restore and protect a
river, stream, or lake. TMDLs may address all pollution sources, including point sources
such as municipal sewage or industrial plant discharges; nonpoint sources, such as runoff
from roads, farm fields, and forests; and naturally occurring sources, such as runoff from
The TMDL itself does not establish new regulatory controls on sources of pollution.
However, when TMDLs are established, municipal and industrial wastewater treatment
plants may be required to install new pollution control technology. States and EPA
enforce the TMDLs through revisions to existing permits which include the pollutant
limits and a schedule for compliance. For waters impaired by nonpoint source runoff,
because there are no federal controls over these sources under the Clean Water Act, the
primary implementation measures are state-run nonpoint source management programs
coupled with state, local, and federal land management programs and authorities and
financial assistance programs. For example, farmers and ranchers may be asked to use
alternative methods in their operations to prevent fertilizers and pesticides from reaching
streams. States may require cities to manage or control runoff from streets.
EPA acknowledges that a vigorous TMDL program is needed because significant
water quality problems persist in the nation’s waters, more than 30 years after enactment
of the CWA. TMDLs are one element of state water quality management programs.
Other activities include standard setting, monitoring, permitting, and enforcement.
Integrating them with the TMDL program is difficult because of factors such as different
program purposes and schedules. Most states have lacked the resources to do TMDL
analyses, which involve complex assessment in order to ascribe and quantify
environmental effects for particular discharge sources. Baseline water quality monitoring
data for the analyses (to identify impaired waters and pollution sources) is limited. EPA
has both been reluctant to intervene in the states and has also lacked resources to do so
itself. Thus, there was little implementation of the provision which was enacted in 1972.
Only in 1992 did EPA issue regulations requiring states every two years to list waters that
do not attain water quality standards and establish TMDLs to restore water quality.
Responding to the failure of both states and EPA to meet these requirements,
however, environmental groups filed lawsuits in 38 states in the last few years.
Environmentalists see implementation of Section 303(d) as important both to achieving
the overall goals and objectives of the act and pressuring EPA and states to address
nonpoint and other sources which are responsible for many water quality impairments
nationwide but have not been controlled up to this point. Of the suits tried or settled, 22
resulted in court orders requiring expeditious TMDL development by states or EPA.
The TMDL litigation falls into five general categories, according to EPA: (1)
situations in which a state has failed to perform any Section 303(d) activities; (2)
situations in which a state has engaged in some but insufficient activities to implement
Section 303(d); (3) challenges to EPA’s listing of impaired waters, TMDL approval
decisions, or EPA’s promulgation of TMDLs; (4) situations in which plaintiffs are using
TMDL requirements to achieve other CWA objectives, such as forcing improved water
quality monitoring programs; and (5) challenges to the substance or content of TMDLs.1
Because of the lawsuits and existing requirements of the law, in August 1997, EPA
issued interpretive guidance which for the first time called on states to develop long-term
schedules for implementing TMDLs. Under that guidance, EPA directed states to
establish TMDLs in order to meet water quality standards within 8 to 13 years.2
Development of TMDLs is increasing (since 1996, states and EPA have developed more
than 34,000), but many more remain to be completed. The most recent state 303(d) lists,
submitted in 2004 and 2006, identified over 41,000 waterbodies as not meeting water
quality standards, affecting more than 300,000 miles of rivers and shorelines and 5
million acres of lakes.
In August 1999, EPA proposed revisions to the TMDL regulations to clarify and
strengthen the program. The key proposed changes included a new requirement for a
more comprehensive list of impaired and threatened waterbodies; a new requirement that
states, territories and authorized Indian tribes establish and submit schedules for
establishing TMDLs; a new requirement that the listing methodologies be more specific,
subject to public review, and submitted to EPA; clarification that TMDLs include 10
specific elements; a new requirement for an implementation plan in TMDLs; and new
public participation requirements.
EPA’s proposal had few strong supporters, for varying reasons. States, which would
be directly affected by the proposal, criticized the burdens that new requirements would
place on them. They are concerned that they lack the resources to meet tight deadlines
for developing and implementing TMDLs. Further, states say that TMDLs should not
necessarily be prioritized over and should be integrated with other elements of existing
water quality management programs. Industry groups are greatly concerned about
impacts of new pollution control requirements. But, municipal and industrial point source
groups urge states and EPA to ensure that TMDL requirements do not fall
disproportionately on their discharges, while possibly failing to address nonpoint source
contributions to impaired waters. Farm groups and others with nonpoint discharges
question EPA’s authority to include nonpoint source pollution in the TMDL program. The
forestry industry vigorously criticized potential impacts of the proposal.
Environmentalists, who support the need for a stronger and more comprehensive TMDL
For a summary of TMDL litigation by state, see information on EPA’s website:
This is a longer time frame than has been mandated as a result of some of the TMDL litigation.
The schedules for TMDLs in lawsuits concluded by consent decrees and settlement agreements
range from 4 years to 20 years; most call for a 10-year development schedule.
program, objected to the lengthy time periods in the proposal before water quality
improvements are likely to occur. They have criticized the lack of aggressive
implementation of a program that has existed in the law since 1972.
Congressional interest was high: by the time the final rule was signed in July 2000,
13 congressional hearings had been held, and a number of legislative proposals to modify
the Clean Water Act or delay the rule had been introduced.3 EPA attempted to respond
to the criticism with flexibility on some of the most contentious points. While the revised
rule was undergoing final review, Congress adopted a provision in the FY2001 Military
Constructions/FY2000 Urgent Supplemental Appropriations Bill, stating that no funds
may be used in FY2000 or FY2001 to “make a final determination on or implement any
new rule relative to” the August 1999 proposal. Because President Clinton intended to
sign the bill into law but opposed the TMDL provision, the Administration accelerated
its review, allowing the EPA Administrator to sign it before President Clinton signed the
appropriations bill on July 13 (P.L. 106-246). In the final rule, EPA acknowledged
Congress’s action in the legislation and delayed the effective date of the rule’s changes
until October 31, 2001. The text of the final rule was published on July 13, 2000.4
The final rule built on the existing regulatory program and added details, specific
requirements, and deadlines requiring states to implement plans to clean up polluted
waters. It retained key elements of the 1999 proposal for more comprehensive
identification of impaired waters, schedules and minimum elements for TMDLs, and new
public participation requirements. For some interested parties, what was most of interest
was what was not included in the final rule. EPA dropped several provisions that were
most controversial, including some potentially affecting agriculture and forestry. (See
CRS Report RL30611, EPA’s TMDL Program: Highlights of the Final Revised Rule.)
The Bush Administration announced in October 2001 that it would delay the effective
date of the rule until May 2003, to allow for further review.
In March 2003, EPA withdrew the 2000 rule in order to consider initiating an
entirely new rule or other options. Officials said that additional time was needed to
decide whether and how to revise the program and that allowing the rule to take effect in
May 2003 would disrupt the ongoing review. No further timetable was announced. As
a result, current program requirements under the 1992 regulations and court-sanctioned
TMDL schedules remain in place. One EPA view, widely reported, was that a new rule
is not essential, because states are improving and will continue to improve the pace at
which TMDLs are established, even under existing rules. Many environmentalists say
that, short of retaining the 2000 rule, the best action would be to leave the 1992 rules in
place, because, although flawed, those rules are preferable to a new rule that might
weaken the program. Other stakeholders have urged EPA to adopt different strategies.
States and many industries favor a new rule with greater implementation and enforcement
During the 106th Congress, hearings were held by the House Agriculture Committee; House
Transportation and Infrastructure Committee; Senate Agriculture, Nutrition and Forestry
Committee; and Senate Environment and Public Works Committee.
U.S. Environmental Protection Agency, “Revisions to the Water Quality Planning and
Management Regulation and Revisions to the National Pollutant Discharge Elimination System
Program in Support of Revisions to the Water Quality Planning and Management Regulation;
Final Rules,” 65 Federal Register No. 135, July 13, 2000, pp. 43586-43670.
flexibility than either the 2000 rule or existing regulations. In mid-2002, EPA developed
a draft revised rule which it informally circulated among interest groups and federal
agencies for many months, but EPA has not proposed a new rule or indicated what future
actions might be taken.
Issues for Congress
A number of issues and options for Congress are apparent.
Do nothing at this time. EPA had hoped that its regulatory proposals
would achieve improvements to the TMDL program and not require
legislative changes to the Clean Water Act, since the outcome of the
legislative process is uncertain. Since withdrawal of the 2000 rule in
2003, stakeholders have been awaiting future EPA decisions.
Strengthen the current program. Environmentalists have long sought
to strengthen the program, and some favor amending the act to: impose
clear deadlines on states and EPA to carry out Section 303(d), as there
are no deadlines in current law; make clear that EPA has a nondiscretionary duty to act if a state fails to do so and define what EPA
actions would follow; and ensure that states periodically update lists of
impaired waters, so that implementation evolves as water quality
Provide flexibility or limit the program. The need for flexibility to
develop and implement TMDLs is a key issue for states and industry.
Many favor policies that would not commit them to specific timeframes
for establishing and implementing TMDLs, but instead call for schedules
to reflect the availability of sound science and resources. Water quality
data are so limited, particularly concerning nonpoint sources, that many
fear that TMDL decisions will be based on unsound information and will
impose unneeded or inappropriate control mandates. The Government
Accountability Office reported in 2000 that inconsistent monitoring, data
collection, and listing procedures used by states to identify impaired
waters have hindered efforts to develop effective TMDL programs
(Water Quality: Key EPA and State Decisions Limited by Inconsistent
and Incomplete Data, GAO-00-54).
Clarify the program’s impact on nonpoint sources. Nonpoint sources
(both urban and rural) cause or contribute to water quality impairments
throughout the United States. Section 303(d) currently does not specify
whether TMDLs should cover nonpoint sources, but EPA’s long-standing
interpretation is that nonpoint sources of polluted runoff should be
included, along with point sources. EPA’s interpretation was upheld in
a key court case (Pronsolino v. Marcus, 91 F.Supp.2d 1337 (N.D.Cal
2000) aff’d, Pronsolino v. Nastri, 291 F.3d 1123 (CA9 2002)). To limit
TMDL implementation only to point sources would likely impose
disproportionate requirements on cities and industries, which have been
the traditional focus of the CWA’s regulatory requirements. The 2000
rule explicitly included nonpoint source-impaired waters in the program.
Farming and forestry groups contend that other non-regulatory CWA
programs are directed at nonpoint source pollution, and they were
concerned that EPA intended to regulate their activities through permits.
They favor excluding nonpoint sources from TMDLs, so that they do not
bear the costs of implementation and pollution controls. EPA
acknowledges that it lacks regulatory authority over nonpoint sources and
only can influence their activities through use of grants and funding.
Consider the resource question. Both EPA and states face significant
financial and technical challenges, and costs of the TMDL program have
been particularly controversial. The agency projected that the incremental
cost of the 2000 rule to states would be about $23 million per year, but
states argued that costs would be higher. States use a portion of CWA
grant funds (Section 106) for TMDL development, along with numerous
other water quality management activities, including standard setting,
permitting, and enforcement. Since FY2001, appropriations for these
grants have averaged $196 million per year.
Further study and analysis. EPA’s FY2001 appropriation bill, P.L.
106-377, required studies by the National Academy of Sciences (NAS)
and EPA on the scientific basis of the program and on the costs to states
and businesses of implementing the TMDL rules. The NAS report,
issued in June 2001, concluded that scientific knowledge exists to move
forward with the program but recommended certain types of changes,
such as utilizing iterative, adaptive implementation and revision, as
scientific data and information improve. EPA’s review of the 2000 rule
since 2001 was at least partly to consider how to respond to those
recommendations. EPA issued a draft report on program costs (including
the 2000 rule) in August 2001, estimating that average annual costs to
states and EPA of developing TMDLs could be $63-$69 million, while
implementation costs for pollutant sources could be between $900
million and $4.3 billion per year, depending on states’ actions.
Finally, the attention to the TMDL program raises challenging questions about the
quality of the nation’s waters. After 35-plus years of implementing the CWA, EPA and
states acknowledge that a substantial portion of the nation’s waters still are impaired or
threatened by pollution. The most recent national inventory of water quality reported that
nearly 40% of surveyed water bodies remain too polluted for fishing, swimming, and
other designated uses.5 Yet those numbers only represent rivers, streams, and lakes
actually surveyed by state monitoring programs — typically about one-third of all waters.
The TMDL assessments developed by states yield more precise water quality information
and identify large numbers of waters requiring additional measures before water quality
standards are attained. How the Obama Administration will address these issues is
unknown for now. Additional congressional oversight of these issues is likely.
U.S. Environmental Protection Agency, Office of Water, The National Water Quality Inventory:
Report to Congress, 2002 Reporting Cycle, Washington, October 2007, EPA-841-R-07-001.
Report is available at [http://www.epa.gov/305b/2002report/].