Legal Definitions - Clean Water Act (CWA)

The Clean Water Act (CWA) is a foundational United States law designed to protect and restore the quality of the nation's waters. Its primary goal is to prevent pollution in rivers, lakes, and coastal areas, making them safe for people and wildlife.

The CWA achieves its goals through two main strategies, primarily enforced by the Environmental Protection Agency (EPA) in partnership with state governments:

• Setting Water Quality Standards: The CWA requires states to classify their bodies of water (like rivers, lakes, and streams) based on their intended uses – for example, whether they are used for swimming, fishing, drinking water, or supporting aquatic life. For each designated use, states must establish specific water quality standards and develop plans to ensure these standards are met. These plans often involve setting limits on the total amount of pollutants that can enter a water body daily (known as Total Maximum Daily Loads or TMDLs) and requiring industries to use the best available pollution control technologies. The EPA reviews and approves these state plans, and if a state fails to create adequate standards, the EPA can step in to develop them.
• Regulating Pollution Discharges: The CWA makes it illegal for any "point source" – a specific, identifiable location like a factory pipe or a municipal sewage treatment plant – to discharge pollutants into U.S. waters without a special permit. This permit, called a National Pollution Discharge Elimination System (NPDES) Permit, is issued by the EPA or by states authorized by the EPA. These permits specify what types and amounts of pollutants can be discharged, and they include requirements for monitoring and reporting. The term "pollutant" is defined very broadly under the CWA, covering substances like chemicals, industrial waste, and even heated water. However, certain types of runoff, such as agricultural stormwater, are generally not covered by these permits.

The CWA's protections apply to "navigable waters" of the United States, a term that has been interpreted broadly to include not only major rivers and lakes but also many wetlands and smaller streams that connect to them. Before an NPDES permit is issued, the public is given an opportunity to review the proposed permit and submit comments or raise concerns.

Here are some examples of how the Clean Water Act applies:

• Example 1 (Water Quality Standards): Imagine a river, the "Clearwater River," that flows through several towns. Local residents use parts of it for kayaking and fishing, and a nearby city draws its drinking water from another section. Under the CWA, the state environmental agency would designate these uses for different parts of the Clearwater River. They would then set specific water quality standards for bacteria levels (for swimming), chemical contaminants (for drinking water), and oxygen levels (for fish). To meet these standards, the state might establish Total Maximum Daily Loads (TMDLs) for certain pollutants, limiting how much treated wastewater a municipal plant can discharge upstream, ensuring the river remains safe for all its designated uses.
  • How this illustrates the CWA: This example demonstrates how the CWA mandates states to classify water bodies by their intended use and then set specific water quality standards and pollution limits (like TMDLs) to protect those uses, with EPA oversight.
• Example 2 (NPDES Permit): A new textile manufacturing plant, "Greenweave Mills," is built near a small creek that eventually flows into a larger river. The plant's industrial process generates wastewater that, even after initial treatment, contains some dyes and chemicals. Before Greenweave Mills can begin operations and discharge this treated wastewater into the creek, it must apply for and obtain an NPDES Permit from the state's environmental protection department (which is authorized by the EPA). This permit will specify the maximum allowable concentrations of dyes, chemicals, and other substances in the discharged water, and it will require the plant to regularly monitor its discharge and report the results to the state.
  • How this illustrates the CWA: This scenario highlights the CWA's requirement for "point sources" (the textile plant's discharge pipe) to obtain an NPDES Permit before releasing any pollutants into U.S. waters, detailing the limits and monitoring obligations.
• Example 3 (Scope - Wetlands): A real estate developer plans to construct a large housing subdivision and wants to fill in a low-lying, marshy area on the property to create more buildable land. This marshy area, though sometimes dry, is regularly saturated with water and is directly adjacent to a tributary that flows into a navigable river. Because this wetland is considered part of the "waters of the United States" under the CWA's broad interpretation, the developer would need to obtain a permit from the U.S. Army Corps of Engineers (which enforces CWA Section 404 related to dredge and fill activities in wetlands) before filling it. Without such a permit, altering the wetland could be a violation of the CWA.
  • How this illustrates the CWA: This example demonstrates the broad scope of the CWA, extending its protection beyond just major rivers and lakes to include interconnected wetlands, and requiring permits for activities that could impact these areas.