Clean Water Act – An Overview


In 1948, Congress adopted the Federal Water Pollution Control Act, 33 U.S.C §§ 1251-1387. In 1972, that law was significantly amended. The 1972 law and its subsequent amendments are commonly known as the Clean Water Act (“CWA”). The objective of the CWA is “to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” The CWA operates by requiring National Pollution Discharge Elimination System (NPDES) permits for “point source” discharges of pollutants into navigable waters, authorizing water quality standards for surface waters, assisting with funding for the construction of municipal sewage treatment plants, and planning for control of nonpoint source pollution.

The Environmental Protection Agency (“EPA”) is the primary agency tasked with implementing and enforcing the CWA. However, it also works with state environmental agencies and the U.S. Army Corps of Engineers (“Corps”). While EPA is responsible for implementing the majority of the CWA, the Corps is in charge of issuing permits for discharges of dredged and fill material into waters of the United States. EPA grants permits for all other pollutant discharges.

National Pollutant Discharge Elimination System

The NPDES system requires a permit before any pollutant can be discharged from a point source into a water of the United States. Discharging a pollutant from a point source into a water of the United States without a valid NPDES permit is a violation of the CWA. It can result in fines and a responsibility to mitigate any damage. Therefore, it is important to know when an NPDES permit is required and when it is not. To do so, it is necessary to define the terms “discharge of a pollutant,” “point source,” and “waters of the United States,” and to examine some recent decisions from the United States Supreme Court.

Discharge of a Pollutant

Under the CWA, the phrase “discharge of a pollutant” is defined as “any addition of any pollutant to navigable waters from any point source” and “any addition of any pollutant to the waters of the contiguous zone or the ocean from any point source.” In other words, a pollutant discharge occurs when a pollutant is introduced into either a navigable water, or the ocean, including the contiguous zone, which is the 24 nautical mile stretch of ocean between the coastline and territorial seas over which states maintain control. The term “pollutant” is then broadly defined to include “dredged spoil, solid waste, incinerator residue, sewage, garbage, sewage sludge, munitions, chemical wastes, biological materials, radioactive materials, heat, wrecked, or discarded equipment, rock, sand, cellar dirt and industrial, municipal, and agricultural waste.” Adding any of these substances into a navigable water or the ocean via a point source requires an NPDES permit.

Point vs. Nonpoint Source

It is important to understand the difference between a point source and a nonpoint source because a NPDES permit is only required for pollutants that are discharged from a point source.

Under the CWA, a point source is defined as “any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, or vessel or other floating craft.” The term does not include agricultural discharges and return flows from irrigated agriculture. Although the CWA definition provides examples of things that fall under the category of point source, it is not an exhaustive list. So long as something is a “discernible, confined, and discrete conveyance,” it could be considered a point source.

A nonpoint source refers to any other source of water pollution that does not meet the legal definition of point source. A common nonpoint source of pollution is runoff carried into water through rainfall or snowmelt. Additions of pollutants into waters covered by the CWA from nonpoint sources do not require NPDES permits. Nonpoint sources are typically left to the individual states to regulate through mandatory or voluntary mandates.

Waters of the United States

The term “waters of the United States” is key to the CWA because it determines which waters are protected by the Act and which are not. Only discharges of pollutants into  waters of the United States (“WOTUS”) are covered by the CWA and can therefore be federally regulated, potentially requiring an NPDES permit.

The CWA prohibits the discharge of any pollutant from a point source into navigable waters. The term “navigable waters” is defined by the text of the CWA as “the waters of the United States, including the territorial seas.” However, the CWA does not define the term “waters of the United States.” Instead, the term is defined by EPA through regulations, which are often influenced or informed by Supreme Court decisions.

WOTUS has had various regulatory definitions in the decades since the CWA was passed. For a complete look at the past definitions of WOTUS, click here to view NALC’s “Waters of the United States: Timeline of Definitions.” The most recent regulatory definition of WOTUS was issued by EPA in late 2022 and went into effect in March 2023. Often referred to as the “2023 rule” or “2023 definition,” EPA’s latest definition of WOTUS aimed to officially return the regulatory definition to where it had been in the 1980s, and to also incorporate the Supreme Court’s 2006 landmark WOTUS decision, Rapanos v. U.S. The 2023 identified six general categories of water body that would be considered a WOTUS. Those categories included: (1) traditionally navigable waters; (2) impoundments of waters already identified as a WOTUS; (3) tributaries of traditionally navigable waters or WOTUS impoundments that are either relatively permanent, or that alone or in combination with similarly situated waters in the region significantly affect the chemical, physical, or biological integrity of navigable waters; (4) wetlands adjacent to traditionally navigable waters or a permanent or continuously flowing impoundment or tributary,  or any wetlands that either alone or in combination with similarly situated waters in the region significantly affect the chemical, physical, or biological integrity of a traditionally navigable water; and (5) any interstate lakes, ponds, streams, or wetlands that do not fall into any of the other categories, provided that the water is either relatively permanent, or on its own or in combination with similarly situated waters in the region significantly affects the chemical, physical, or biological integrity of a traditionally navigable water. For a more in-depth look at the 2023 rule, click here.

EPA’s 2023 WOTUS definition has garnered numerous legal challenges. Less than a month after the 2023 rule went into effect, it was enjoined in 27 different states. Then, on May 25, 2023, the Supreme Court issued its long-awaited decision in Sackett v. U.S., effectively overruling various aspects of the 2023 WOTUS definition. While EPA has yet to issue a revised definition of WOTUS as of June 2023, the agency has announced that it will be interpreting the phrase “waters of the United States” consistent with the Supreme Court’s Sackett decision.

Sackett v. U.S.

In Sackett v. U.S., No. 21-454 (2023), the United States Supreme Court was asked to consider the scope of wetlands jurisdiction under the CWA. Specifically, the plaintiffs asked the Court to consider when a wetland could be considered a WOTUS, an issue that judges and regulators have struggled with since the CWA was enacted. In Sackett, the plaintiffs urged the Court to formally adopt the plurality’s test in Rapanos v. U.S. and hold that the word “waters” in “waters of the United States” refers only to permanent, continuous flowing streams, oceans, rivers, and lakes, and that only those wetlands that share a continuous surface connection with such waters can be included in the definition of WOTUS.

Before agreeing to hear Sackett, the Supreme Court had not issued a ruling on WOTUS since 2006 when the Court delivered its decision in Rapanos v. U.S., 547 U.S. 715 (2006). In that case, the Supreme Court was asked to consider when a wetland could be included in the definition of WOTUS. Instead of issuing a majority opinion, the Court delivered one plurality opinion authored by Justice Scalia and joined by three other Justices, one concurring opinion authored by Justice Kennedy writing for himself, and one dissenting opinion. The plurality opinion concluded that the definition of WOTUS should be limited to water bodies that are “relatively permanent, standing, or continuously flowing[.]” Only those wetlands that shared a continuous surface connection with such waters would then be included in the definition of WOTUS. In contrast, Justice Kennedy concluded that wetland jurisdiction should be determined on a case-by-case basis, based on whether the wetland possessed a ”significant nexus” with a recognized WOTUS. According to Justice Kennedy, a significant nexus exists when a wetland “either alone or in combination with similarly situated lands in the region, significant affect[s] the chemical, physical, and biological integrity of other covered waters[.]” Following the Rapanos decision, courts and EPA tended to apply Justice Kennedy’s significant nexus test either on its own or in conjunction with the plurality’s opinion. In the 2023 WOTUS rule, EPA included language incorporating both Rapanos tests into the WOTUS definition.

In Sackett, the Supreme Court revisited its ruling in Rapanos. Ultimately, the Court agreed with the plaintiffs, issuing a 9-0 decision that formally adopted the plurality’s “continuous surface connection” test and overturned Justice Kennedy’s “significant nexus” test. Following the Court’s ruling in Sackett, the word “waters” in “waters of the United States” will be understood to refer to open, flowing bodies of waters such as rivers, lakes, oceans, and streams. Only those wetlands that share a “continuous surface connection” so that it is “difficult to determine where the ‘water’ ends and the ‘wetland’ begins” will then be included in the definition of WOTUS. If a waterbody falls into the definition given by the Court in Sackett, it is likely that any discharges of pollutants made into that water body from a point source will require a NPDES permit.

To read the Supreme Court’s opinion in Sackett v. U.S., click here. To read Rapanos v. U.S., click here.

County of Maui

The United States Supreme Court has recently broadened what types of actions may require NPDES permits. In Cty. of Maui, Hawaii v. Hawaii Wildlife Fund, 140 S. Ct. 1462 (2020), the Court concluded that an NPDES permit was required “where there is a direct discharge from a point source into navigable waters or when there is the functional equivalent of a direct discharge.” The case concerned discharges of pollutants made from a wastewater reclamation facility into groundwater, which carried the pollutants about half a mile into the Pacific Ocean. Although the wastewater facility was making discharges of pollutants from a point source, groundwater is not typically considered a water of the United States under the CWA, so the wastewater facility operators did not apply for an NPDES permit before making the discharges. Ultimately, the Court determined that the discharges from the facility had served as the functional equivalent of direct discharges into the Pacific Ocean due to the small amount of time it took for the pollution to reach the Ocean through the groundwater, and the short distance the pollutants had to travel. Additional factors the Court considered to determine whether the discharges were the functional equivalent of a direct discharge included the nature of the material through which the pollutant traveled, the extent to which the pollutant was diluted while traveling, the amount of pollutant that entered the Pacific Ocean compared to the amount of pollutant that left the facility, the manner by which the pollutant entered the Pacific Ocean, and the degree to which the pollutant maintained its identity.

It is currently not clear how much this ruling from the Supreme Court will affect how the CWA is administered going forward. However, it is clear that in some instances, an action that results in a pollutant entering a water of the United States may require an NPDES permit even if the action is not a direct discharge from a point source into a navigable water.

To read the Supreme Court’s decision in Cty. of Maui, click here.

NPDES Permits & Nonpoint Source Pollution Control

EPA typically issues NPDES permits. However, states may receive authorization from EPA to issue NPDES permits to industries and municipalities and enforce permits. Most states have been authorized to administer the NPDES permit program. EPA administers programs for the remaining states and keeps an up-to-date list of the states with NPDES permitting authority here.

There are two types of NPDES permits, individual and general. An individual permit is issued to a single discharger to cover site-specific conditions and is issued directly to the individual discharger. General permits are written and issued to cover multiple dischargers with similar operations and types of discharges. Those permits are issued to no one person in particular, but instead, allow multiple dischargers to obtain coverage under the permit after it is issued. Obtaining coverage under a general permit tends to be quicker than an individual permit because coverage under a general permit typically occurs immediately, while coverage under an individual permit may take six months or longer.

NPDES permits set measurable limits on the amounts of pollutants allowed to be discharged. The limits may be based either on technology (“technology limits”) or water quality standards. They are written so that they cannot be attained simply by dilution of the wastewater. Permits may also contain best management practices (“BMP”) requirements. These are the best known and most practical methods for reducing pollution levels in a particular industry.

Dredged and Fill Material Permits

Section 404 of the CWA regulates the deposit of dredged and fill material into any WOTUS, including wetlands. “Dredge” is material excavated from a WOTUS, and “fill material” refers to any material used to replace an aquatic area with dry land, or to change the bottom elevation of a water body. Section 404 permits are issued by the U.S. Army Corps of Engineers (“Corps”), although the EPA has the authority to veto a 404 permit.

Generally, a 404 permit will only be issued if: (1) no practicable alternative exists that is less damaging to the aquatic environment, or (2) the nation’s waters would not be significantly degraded. In other words, when someone applies for a 404 permit, they have to show that steps have been taken to avoid direct impacts to wetlands, streams, and other aquatic resources; that all potential impacts have been minimized; and that compensation will be provided for any unavoidable impacts.

Like NPDES permits, 404 permits can be issued either individually or generally. Additionally, certain activities are exempt from the 404 program. Exempt activities include certain farming, ranching, and forestry practices that do not alter the use or character of the land; some construction and maintenance activities; and activities already regulated by states under other provisions of the CWA.

Water Quality Standards & TMDLs

One of the main objectives of the CWA is to “maintain the chemical, physical, and biological integrity of the Nation’s waters.” To help achieve that goal, the CWA implements a water quality standards-based approach for regulating water quality. Under the CWA, the EPA is tasked with developing national water quality criteria, which are then used as a basis for state water quality standards. Those standards are then the legally enforceable limits that are used to evaluate water quality impairment. The CWA requires states to keep a list of all waters which have become impaired and submit that list to EPA every two years. For each water on the list, the state identifies which pollutant is causing the impairment, and then establishes a total maximum daily load (“TMDL”) of the pollutant in violation. Once a TMDL for a particular pollutant is in place on a waterbody, it sets the limit for the amount of that pollutant that can be discharged into the waterbody per day.

Water Quality Standards

Water quality standards are scientifically measurable standards that quantify the goals of the CWA and include designated uses, water quality criteria, and antidegradation policies. Designated uses are the uses of a waterbody that society would like to achieve in a location such as fishing, industrial water supply, or agricultural irrigation. Water quality criteria are the conditions necessary to achieve a waterbody’s designated uses. Finally, antidegradation policies are rules implemented by states to prevent waterbodies with higher than normal water quality from becoming impaired in the future. When assigning designated uses to waterbodies, several policies must be followed. Any use that the waterbody has achieved since November 28, 1975, even if it is not possible at present, must be included in the designated uses for that waterbody. Because the broad goals of the CWA include fishing and swimming, every waterbody must include those designated uses unless the downgrading process has been followed to allow the reduction of quality in a waterbody. Waste transport may never be a designated use. If multiple designated uses are defined for a waterbody, the designated uses requiring the highest water quality sets the standard. Designated uses may only be reduced by following a downgrade process that demonstrates that the water quality goals are unattainable because of natural background conditions, irreversible human-caused conditions, resulting in substantial environmental harm, or excessive social and economic cost. Under EPA regulations, an existing use may never be removed from the designated uses for a waterbody.

The water quality criteria are the technical conditions required to reach the designated uses in a particular water body, including concentrations of pollutants, temperature, pH, and “no toxic chemicals in toxic amounts.” However, acceptable water quality criteria can also include narrative descriptions that are difficult to quantify scientifically. These include no objectionable bottom deposits, no unsightly floating debris, or no nuisance odor or color. The CWA requires that water quality criteria be established based on the latest scientific knowledge.

The antidegradation policy is a required component of CWA water quality standards that states are required to adopt and enforce. These policies are designed to protect waterbodies with water quality that is higher than standards require and prevent degradation or loss of existing uses. EPA regulations direct states to include three levels of protection in their antidegradation policies. The first level protects existing uses and requires that the level of water quality necessary to sustain those uses be maintained. The second level requires that states maintain water quality that exceeds levels necessary to support recreation and wildlife uses, unless a lower water quality is necessary to allow important economic or social development. Finally, the third level of antidegradation policy requires that states maintain water quality in high qualities waters that are considered “outstanding National resource[s],” including waters within national and state parks, wildlife refuges, and waters with “exceptional recreational or ecological significance.”

Total Maximum Daily Load

If a waterbody does not attain the proper water quality standards, then a strategy is implemented to reach the required standard. The most common approach is the use of a Total Maximum Daily Load (“TMDL”), which is the maximum amount of a pollutant in a particular area of an impaired waterbody that would allow the water quality standards to be met. Ideally, TMDLs are adopted on a watershed basis so that a comprehensive system of restoration and antidegradation of water quality is reached. The EPA must approve TMDLs, and if the EPA and the state cannot agree, the EPA may establish a TMDL through federal rulemaking. TMDLs may be established for individual waterbodies or may cover entire watersheds that span across multiple states. Currently, the largest TMDL in the country is the Chesapeake Bay TMDL which includes waterbodies in six states and the District of Columbia.

Once a TMDL is established for a waterbody, the allowable amount of pollutant discharge is divided among various sources as determined by the states. These allocations are called Wasteload Allocation for point sources, and Load Allocation for nonpoint sources. The Wasteload Allocation for a point source is generally included as part of a discharger’s NPDES permit.  Many methods are used under the CWA to try to meet TMDL requirements, including NPDES and section 404 permits, grants for nonpoint source pollution reduction, and a revolving loan fund for construction or improvement of water treatment plants.