Introduction to the Clean Water Act

Dec. 26, 2016

A brief review of this law regulation that manages the quality of U.S. navigable waters

The Clean Water Act (CWA) is the comprehensive regulatory driver that controls ambient water quality and virtually all wastewater discharges to the water environment. The comprehensive nature of its regulatory scope and its many requirements have caused major investments just to understand all the elements of the responsibilities. In addition, major compliance challenges for the thousands of pollutant dischargers require intensive waste management activities and treatment and monitoring expenditures. It has also resulted in profound improvements in the condition of the nation’s waters since its inception.

The original ambient water protection legislation was enacted in 1948 and was called the Federal Water Pollution Control Act. The 1948 law provided a limited role for the federal government and did not significantly alter pollution control practices. It was completely rewritten and expanded in 1972, again in 1977, 1987 and again in 2002.

It is technically still the Federal Water Pollution Control Act but is now referred to as the CWA The CWA established the basic structure for regulating the discharge of pollutants into the "waters of the U.S." and regulating quality standards for surface waters. Section 101(a) states that the objective of this act is to restore and maintain the chemical, physical and biological integrity of the nation’s waters. Further it states that:

  • "It is the national goal that the discharge of pollutants into the navigable waters be eliminated."
  • "It is the national goal that wherever attainable, an interim goal of water quality which provides for the protection and propagation of fish, shellfish, and wildlife and provides for recreation in and on the water be achieved."
  • "It is the national policy that the discharge of toxic pollutants in toxic amounts is to be prohibited."
  • "It is the national policy that Federal financial assistance be provided to construct publicly owned waste treatment works."
  • "It is the national policy that area-wide waste treatment management planning processes be developed and implemented to assure adequate control of sources of pollutants in each State."
  • "It is the national policy that a major research and demonstration effort be made to develop technology necessary to eliminate the discharge of pollutants into the navigable waters, waters of the contiguous zone, and the oceans."
  • It is the national policy that programs "both point and nonpoint pollution sources should be controlled."1

Water Quality Standards (WQS) must be established. All affected waters must have use designations and numeric and/or narrative criteria that support those uses. Ant degradation policies are required to ensure that that waters meet their minimum water quality criteria and that high quality is not unnecessarily degraded. Water bodies must be monitored to determine whether the WQS are being met.

If WQS are being met, antidegradation policies and implementation methods are employed to keep the water quality at acceptable levels. Ambient monitoring is also needed to ensure compliance with WQS.

If the WQS are not being met, a strategy for meeting these standards is required. This can include establishing total maximum daily loads (TMDLs) and implementation plans. TMDLs allocate acceptable loads among sources of the relevant pollutants.

States have substantial rights and responsibilities in partnership with the U.S. Environmental Protection Agency (EPA). Section 101(b) states that the intent is to recognize, preserve, and protect the primary responsibilities and rights of States to prevent, reduce, and eliminate pollution, to plan the development and use of land and water resources.

The law is lengthy and complex, but there are several key features that are of particular interest to industrial and commercial facilities that discharge wastes to the aquatic environment. They are primarily point source dischargers to publically owned treatment works (POTWs), or direct dischargers. Nonpoint source dischargers are typically farms and forestry operations.

  • Ambient Water Quality Criteria (WQC) and WQS establish specifications forwater sources that receive wastes.
  • The National Pollutant Elimination Discharge System (NPDES) and its permit programs have requirements for point source dischargers and dischargers to POTWs.
  • Pretreatment requirements are intended to prevent disruption of POTW performance.
  • Industry Specific Effluent Guidelines establish performance expectations for treatment technologies for categories of industrial dischargers geared to the content of the wastes that they produce.
  • Industrial Storm Water requirements apply for discharges to surface waters or municipal separate storm sewers.
  • TMDLs establish quality requirements for water bodies where the technology based controls on point sources would not result in achieving water quality criteria for that water body.


WQC are EPA’s recommended levels of pollutants or water quality characteristics that will protect the designated uses (DU) of the receiving water body if they are achieved. They can be chemical, physical or biological, and are aimed at protection of aquatic animal and biota organisms. Human health based criteria will include exposures from drinking water, aquatic foods (e.g., fish and shellfish) and body contact, and wildlife criteria deal with pollutants with high bioaccumulation factors. The states and other entities are not required to adopt the numbers that EPA provides, but they must either adopt them or develop a scientifically based criterion that will provide the same level of protection.

Many potential DU categories and subcategories are designated, including:

  • Public water supply
  • Recreation in and on the water
  • Protection and propagation of fish and shellfish
  • Agricultural
  • Industrial
  • Navigation
  • Others such as ceremonial uses, shellfish grazing, wildlife protection, endangered species protection, drinking water source protection and hydroelectric power

The WQC and WQS provide numeric and narrative descriptions of the DUs They are usually quantitative measures, such as pollutant concentrations, temperature, pH, turbidity or toxicity. They can also include narrative statements such as "no toxic chemicals in toxic amounts."


Discharging from a point source (for example, a pipe, ditch, tank or vehicle) to "waters of the U.S." is illegal without a permit under Section 402 of the CWA. Conveyances also include ships and offshore oil rigs. All these and some others are considered direct dischargers. The National Pollutant Discharge Elimination System (NPDES) and its permit programs, which can be implemented by states, tribes, territories or sometimes the EPA, establish requirements for point source dischargers to water. Although the long-range goal of the CWA is zero discharge, the permits set limits on the permissible discharges in a given time period.


The National Pretreatment Program, which is part of the NPDES, requires "indirect" industrial and commercial dischargers, or those that discharge wastewater to a publicly owned treatment works (POTWs), such as municipal wastewater treatment plants, to obtain permits that specify the effluent quality to be achieved by pretreatment or other controls before discharge to a sewer. The pretreatment controls are intended to prevent interference with or disruption of the POTW so that its discharges will not harm receiving waters or the environment. POTWs are designed to treat domestic sewage. Many other pollutants are not well-managed by conventional POTWs. Therefore, pretreatment requirements help to protect the environment by protecting the waste amelioration functions of the POTW.

Effluent guidelines

Industrial Effluent Guidelines under 40 CFR 405-499, provide industry specific treatment technology and performance expectations for at least 58 categories of direct industrial dischargers. Those Effluent Guidelines also apply to ‘indirect dischargers’ who will be sending wastes to municipal sewers. Existing industrial direct dischargers are subject to defined Best Available Technology (BAT) if the pollutant is either a toxic or gray area pollutant. Best Conventional (BCT) applies to suspended solids, pH, oil, grease and biochemical oxygen demand. POTW’s must provide Best Practicable Technology (BPT). New sources are required to meet technology based limits called New Source Performance Standards that are often more stringent than existing source requirements. The standards are not risk based, but rather on the capabilities of control technologies. Discharge permits would contain numerical values aimed at protecting receiving waters.

Industrial stormwater

NPDES permits also cover discharges from storm sewers, stormwater associated with industrial activities, runoff from larger construction sites, mining operations, animal feed lots and aquaculture activities above designated thresholds. Industrial facilities are included in 11 categories — including manufacturing; mineral, metal, oil and gas; hazardous wastes; steam electric plants; recycling facilities; transportation; treatment works; landfills; light industry; and construction greater than 1 acre.


Total maximum daily loads (TMDLs) must be developed for waters affected by pollutants in which the many existing point-source, technology-based controls would not result in achieving the WQC. Numerous point-source control programs are described in this column. However, because of the multiplicity of dischargers into a receiving water, its characteristics and often nonpoint sources that contribute substantial pollutant loads to water bodies, WQS might not be attained. TMDLs are "pollutant budgets" for a water body that result in attaining WQS. CWA regulators are encouraged to produce TMDLs on a watershed basis to involve more holistic analyses and comprehensive watershed strategies.

The TMDL is the acceptable amount, or the pollutant cap, that reflects the carrying capacity of the of the water body. Once the cap has been established, including margins of safety, the pollutant loads are allocated among the different sources. This is obviously a complex endeavor that requires substantial amounts of data, analyses, controversies and judgments before it can be accomplished for a watershed.

Recent significant EPA actions

The CWA applies to "navigable waters," which are broadly defined in the CWA as "waters of the U.S. (WOTUS)." Recently, EPA issued regulations that significantly expanded the definition of WOTUS that result in greatly expanding the scope and costs of CWA implementation and are creating major controversies. Opposing parties are concerned that this expansion is beyond the scope of coverage of the CWA and creates an unwarranted federal intrusion on state prerogatives.

Those regulations have been appealed and the court has blocked their implementation pending judicial review, which is now underway. Briefs have been filed by appellants and amici curiae and additional respondent briefs will be filed during the next few months. A decision might be expected in 2017, but appeals to the U.S. Supreme Court should also be expected. On the other hand, the new administration might initiate the legal process to withdraw the expansive regulation for reconsideration.

CWA conclusions

This brief overview of the CWA was extracted substantially from the EPA’s Watershed Academy website. It provides a detailed description of the CWA and its many facets and is highly recommended as a starting point for anyone interested in becoming knowledgeable about the CWA before reading the CWA and its supporting texts.


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