The Clean Water Act 101

The CWA is a bedrock environmental law that aims to end water pollution in the United States by regulating pollutants and setting standards for water quality. 

The main goal of the CWA is “to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” To do this, the law declared that “the discharge of any pollutant by any person shall be unlawful” without a permit that specifies how much pollution can be released. 

The ambition of the law marked a sharp turn from how waste was previously managed—which is to say, hardly managed at all. Two of its original goals included making all waters “fishable and swimmable” by 1983 and having zero water pollution discharge by 1985. While we failed to reach those goals, the CWA has helped many of our once-dying waterways to recuperate. And it keeps many aquatic ecosystems healthier by regulating industrial and municipal activities that can also damage our health.

The CWA, as we know it today, refers to the 1972 amendments made to the Federal Water Pollution Control Act (FWPCA). The FWPCA was originally passed in 1948 and was the first major law to address water pollution. While it provided state and local governments with funds to research water pollution, there was minimal federal oversight—no goals, guidelines, objectives, or limits to pollutants. It was essentially a figure-it-out-yourself fund for each state. 

The CWA was amended in 1977, 1981, 1987, and 2014, and lawmakers have passed several additional pieces of legislation to expand on some of the CWA’s provisions.

By the 1960s, bodies of water across the United States were considered to be on the brink of death: 240 million gallons of sewage waste were dumped into the Potomac River every day;  an oil well blowout near Santa Barbara, California, spewed 100,000 barrels of oil into the Pacific Ocean; an oil slick creeping across Ohio’s Cuyahoga River caught on fire—an incident that quickly became a symbol of the country’s deteriorating water quality. 

Across the country, people were galvanized by these awful conditions. Rivers, lakes, and other waterbodies were no longer seen as dumps but rather as precious resources. And Congress wrote a law that reflected that sentiment.

The CWA includes a mandate that the U.S. Environmental Protection Agency (EPA) work to eliminate pollution from surface waters, referred to as “waters of the United States.” 

The law requires the agency to set standards for water quality and issue pollution permits—allowing industries and municipalities to continue doing business while striving to lessen their negative impacts. As with other major laws, such as the Clean Air Act, the federal government typically sets the nationally applicable rules, and then states implement and enforce them on a day-to-day basis.

The CWA remains a powerful toolbox for citizens, the environment, and the economy. Among other things, its provisions empower those impacted by pollution to sue polluters and motivate private businesses to invest in new technologies. (The law does have limits, however: It does not address groundwater contamination or drinking water standards, at least not directly.) 

Here are some of its most important functions. 

The CWA sets and maintains water quality standards

To start, the CWA requires states, territories, and Tribes to implement plans to maintain measurable water quality standards (WQS), which are based on recommended pollution limits developed by the EPA and must be reviewed and approved by the agency. These aren’t blanket standards for all bodies of water; rather, they vary based on a given waterbody’s designated uses, including:

• protection and propagation of fish, shellfish, and wildlife
• recreation
• public drinking water supply
• agricultural, industrial, navigational, and other purposes

Another component of WQS is the antidegradation requirement, which protects the existing quality of healthy waters and might require the implementation of additional measures to prevent decline. 

The EPA maintains a WQS Handbook to help states develop their standards. 

The CWA regulates pollution

By regularly updating guidelines and permits, the CWA seeks to continuously limit the amount of water pollution allowed over time. To ensure these guidelines make scientific and economic sense, the law distinguishes factors like the source of the contaminants and whether that source existed before, or was built after, the latest pollution-fighting technology became available. Here’s what the regulations take into account.

Point source pollution

Point source pollution, put simply, is contamination that comes from a single identifiable source, like a pipe. To discharge most effluent (that is, water pollution) from a point source, the polluter needs to obtain a permit through the National Pollutant Discharge Elimination System (NPDES) program—sometimes called a Section 402 permit. The permits are issued for up to five years at a time, after which they must be renewed.

Each NPDES permit is tailor-made for the type of discharger, such as a factory or town wastewater treatment plant, and for the waterbody that is impacted. The EPA sets and periodically updates national minimum discharge standards, called “effluent limitations guidelines.” These guidelines consider available technologies and, since new facilities can more easily utilize new technologies than existing ones, they also consider whether the facility is already operating or not. Effluent limitations guidelines require the use of the best available tools to control pollution. 

In addition to technology-based limits, NPDES permits may also incorporate water quality–based limits. Take those issued for coal-fired power plants. Any plant operator anywhere in the country will have to limit the releases of mercury, arsenic, and other pollutants as required by the effluent guidelines. But if a particular facility is located on a river where there's a water quality standard to protect people who fish (and eat their catch), the operator might need to control those releases even more.

Nonpoint source pollution 

So what about pollution that comes from many different and diffuse sources? An example of this “nonpoint” source pollution occurs when rainfall picks up lawn care chemicals and carries them into a local stream.

As you can imagine, nonpoint source pollution is much harder to manage—but it’s no less important to control. The CWA’s Section 319, added in 1987, requires states to identify harmful nonpoint source pollution and to manage it, such as with green infrastructure.

Dredge and fill materials

In addition to the NPDES permit that governs pollution, the CWA’s Section 404 permit regulates the discharge of “dredged” or “fill” materials into water, including wetlands. This usually includes solid material, such as rock, sand, soil, or construction debris dumped into a waterbody. To issue these permits, the U.S. Army Corps of Engineers (Army Corps) looks at potential negative impacts of the materials on public water supplies, fishing and recreation areas, and/or wildlife. The permits commonly apply to things like commercial development, mining, and the construction of dams, levees, or highways. 

Oil spills and other hazardous accidents

While the point source pollution governed by CWA permits is meant to be very controlled and even predictable, the CWA also covers unplanned events, like spills of oil and other hazardous substances. In fact, Section 311 of the law requires the EPA to adequately prepare for and respond to these incidents. 

The Oil Pollution Act of 1990 amended the CWA to make it easier to recover the costs of cleanup from the companies responsible. This was in direct response to the 1989 Exxon Valdez oil spill, which dumped 11 million gallons of oil into Alaska’s Prince William Sound. More recently, the CWA has helped U.S. taxpayers recoup more than $18 billion from oil company BP following its Deepwater Horizon disaster in the Gulf of Mexico, and $50 million from petrochemical manufacturer Formosa Plastics for illegally dumping plastic and other pollutants into Texas waterways. 

The CWA invests in wastewater treatment

One of the reasons our waterways were so polluted before the CWA came into play was because of our aging, insufficient wastewater treatment processes. Imagine if the water we flushed down our toilets wasn’t treated before being released into the environment. (This still happens in places where stormwater overwhelms combined sewer systems. And yeah: It’s gross.)

The Clean Water State Revolving Fund (CWSRF), added in 1987, is a loan and grant program to help communities build out and improve their water infrastructure, including sewage treatment plants, pumping stations, and sewage overflow controls. The 2022 Bipartisan Infrastructure Law included a much-needed boost in funds to the CWSRF: $11.7 billion, with an additional $1 billion to address PFAS (per- and polyfluoroalkyl substances, aka “forever chemicals”) and other emerging contaminants.

The CWA empowers citizens

The CWA doesn’t just empower the government to protect our waters. It also allows for citizens to bring lawsuits against those responsible for harmful, illegal discharges. Section 505 grants that anyone who might be affected by the violation of the CWA—assuming a government agency hasn’t already taken sufficient action—can file a civil action. The law also enables citizens to sue the EPA for failing to carry out its responsibilities under the CWA. 

Yes! The CWA has substantially cleaned up our waters over the last few decades: 

• Technology-based standards prevent more than 700 billion pounds of toxic pollutants from entering our waters every year.
• The NPDES program regulates approximately 200,000 point source polluters, including sewage treatment facilities, oil refineries, and construction sites. 
• A total of $650 billion has gone toward improving wastewater treatment plants.
• Rates of wetland losses dropped, following the initial passage of the CWA.
• Wastewater from the majority of homes and businesses is now treated.
• People around the country are able to more safely swim and fish in their local waterways.

Even some of the waters that were catalysts for public advocacy, like the Cuyahoga River and Monterey Bay, California, have become popular tourist and recreation sites as marine life has rebounded.

Many clean water advocates say that the CWA has failed to go far enough, especially to meet its original goals, which include the complete elimination of water pollution discharges. 

And most of our waters do still face serious issues today. The EPA’s most recent National Lake Assessment from 2017 found that around 45 percent of lakes across the country were in poor biological condition. The main issue was nutrient pollution, which can lead to harmful algal blooms and dead zones. Meanwhile, the agency’s river- and stream-related assessment found that less than one-third of these channels were in good biological condition. 

On top of that, the CWA is under frequent and intense attacks from polluting industries and their political allies. 

Continued pollution and lack of enforcement resources

Without regular data collection, it’s easier for polluters to illegally dump their waste and face few repercussions. The CWA requires states and territories to monitor the status of protected bodies of water but the EPA’s water quality report showed only half of the waters had been assessed. 

New types of pollution

Untold numbers of new pollutants and sources of pollution have emerged since the CWA was passed—some naturally occurring but many man-made. These “emerging contaminants” are substances and microorganisms that may pose risks to human health or the ecosystem. 

Microplastics and PFAS are of growing concern, especially because of their risk to human health. These and other contaminants, including the pharmaceuticals we ingest that make their way through our sewage, are not broken down in the standard wastewater treatment process that the CWA requires.

Legal challenges 

For decades, polluting industries have sought to undermine the CWA by limiting which pollutants and sources can be regulated, as well as which waterbodies qualify for protection. (This, despite how important clean water supplies are to many lucrative industries.) 

Here are some of the most recent attacks on the CWA.

The Trump administration’s Dirty Water Rule: Anti-science and illegal

In 2015, then president Barack Obama’s EPA and Army Corps published the Clean Water Rule to clarify the scope of protections in the CWA—and specifically included wetlands and streams. 

But developers have long argued that wetlands should not be protected because they are not navigable waters. And in 2019, the Trump administration repealed the 2015 rule and replaced it with what environmental advocates called the “Dirty Water Rule” because of how it drastically eliminated protections for millions of miles of waterways. The administration couldn’t even estimate this rule’s potential impacts, and the EPA’s own advisors warned that parts of the rule were not based on science at all. 

The Dirty Water Rule was rejected by a federal judge in 2021. But these attacks continued…

Sackett v. U.S. Environmental Protection Agency: Reducing which waters are protected

In May 2023, a controversial U.S. Supreme Court decision gutted the Clean Water Act’s protections for wetlands and many streams. Before the Sackett v. EPA case, Congress, agencies, and the courts all understood the CWA to protect most surface waters: oceans, lakes, streams, and wetlands. But the Sackett decision ruled out protections for an estimated tens of millions of acres of wetlands across the country, including swamps, marshes, and bogs—all havens for biodiversity.

The case centered around an Idaho couple who ran an excavation company and dumped 1,700 cubic yards of gravel and sand into wetlands without a permit. The Supreme Court’s decision to side with the polluters ultimately narrowed the CWA’s wetlands protections to just those with a “continuous surface connection” to a larger body of water. This redefinition also eliminated protections for rain-dependent streams. 

Loper Bright Enterprises v. Raimondo: Weakening agency authority

In another Supreme Court decision, this one in June 2024, the Court’s conservative majority decided in Loper Bright Enterprises v. Raimondo to upend 40 years of precedent known as the Chevron deference, a long-standing principle that when a law is vague, a federal court should defer to a federal agency’s expertise and reasonable interpretation of the law.

This new decision will allow judges to substitute their own views about the meaning of a statute when reviewing actions by not only the EPA but all government agencies. It’s too early to know how exactly it will specifically impact environmental and health protections, but it will likely make it harder for agencies to solve complex problems like water pollution—therefore putting public health at risk.

With the understanding that rulings like Sackett will have far-reaching impacts, many legislators are taking action to codify water protections into the law. For example, in 2023, more than 100 members of the House introduced the Clean Water Act of 2023 to reinstate wetland, river, and stream protections.

But major pieces of federal legislation like this can take years to pass, especially with powerful opponents fighting against it. In the meantime, it will be up to the states, Tribes, and localities to protect the wetlands and streams in their jurisdictions. 

What is NRDC doing to defend the CWA?

As part of a coalition that includes states, Tribes, cities, businesses, and conservation groups, NRDC has joined the America the Beautiful Freshwater Challenge, announced by the Biden White House in April 2024, to protect and restore 8 million acres of wetlands and 100,000 miles of rivers and streams by 2030.

NRDC also collaborates with partners across the country, like the Clean Water for All coalition and Brewers for Clean Water, to bring greater awareness to the need for water protections. 

Alongside these initiatives, we’ll continue our work in the courts and on Capitol Hill to advocate for the full restoration of the CWA to its original purpose—to clean up our waterways and keep them free of pollutants for future generations.