• The CWA is designed to ensure that the nation’s waters are safe to the public and support fish and other aquatic life.
• The CWA has authority for responding to discharges of oil into the waters of the U.S.

The Clean Water Act (CWA) was enacted to regulate and cleanup polluted waters in the United States. It is designed to ensure that the nation’s waters are safe to the public and support fish and other aquatic life. Specifically, the CWA is designed to restore and maintain the chemical, physical, and biological integrity of the nation’s waters.

The CWA was one of the major environmental laws passed by Congress in the 1970s. It provides the Environmental Protection Agency (EPA) with two types of authority:

• Regulatory — To prevent and control discharges of pollutants into waters of the U.S.
• Response — To respond to releases of pollutants into waters of the U.S. Prior to the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), EPA and United States Coast Guard (USCG) worked under the CWA to clean up releases of oil and hazardous substances into the navigable waters of the U.S.

The CWA requires that all direct discharges to surface water comply with technology-based discharge standards. These standards require the use of best practicable control technology (BPCT) for conventional pollutants (e.g., suspended solids or fecal coliform) and best available technology (BAT) economically achievable for toxic (e.g., benzene or chloroform) and non-conventional (e.g., ammonia, nitrogen, or total solids) pollutants. EPA has published effluent guidelines for specific categories of industries. These guidelines are translated into specific effluent requirements in discharge permits.

The CWA requires a permit for any discharge into the nation’s waterways. For wastewater, only two discharge options are allowed:

• Direct discharge into surface water pursuant to a National Pollutant Discharge Elimination System (NPDES) permit; and
• Indirect discharge, which means that the wastewater is first sent to a publicly owned treatment works (POTW), and then after treatment by the POTW, discharged into surface water pursuant to an NPDES permit.

The NPDES permit is granted on a case-by-case basis and the terms of the permit depend on a number of variables. Essentially, the NPDES permit limits the permissible concentration of toxic constituents or conventional pollutants in effluents discharged to a waterway.

If the indirect discharge option is chosen, the generator of the wastewater cannot simply transfer the pollutants to a POTW. Rather, the wastewater must satisfy applicable pretreatment standards, where they exist.

Section 304 of the CWA directs EPA to publish water quality criteria for specific pollutants. EPA develops two types of criteria: one for the protection of human health and another for protection of aquatic life. These water quality criteria are non-enforceable guidelines used by states to set water quality standards for surface water. Section 303 requires states to develop water quality standards, based on federal water quality criteria, to protect existing or attainable uses (e.g., recreation, water supply) of surface waters.

How the CWA and CERCLA interact

The CWA-designated hazardous substances are incorporated into the CERCLA definition of hazardous substances. The CWA has authority for responding to discharges of oil into the waters of the U.S. The CWA 311 and CERCLA have similar response authorities for responding to discharges of CWA hazardous substances released into U.S. waters. In addition, CERCLA provides response authority for responding to discharges of other hazardous substances, pollutants, and contaminants into the environment. The NCP, the blueprint for managing responses to releases, governs both CWA and CERCLA responses.

Onsite CERCLA responses must comply with or waive substantive requirements of federal and state environmental laws that are determined to be applicable or relevant and appropriate requirements (ARARs). CWA and state discharge and water quality standards may be ARARs for onsite remedial actions at Superfund sites. The application of CWA and state ARARs is determined on a case-by-case basis. CERCLA responses conducted entirely onsite do not require CWA permits.