The Clean Water Act was passed in 1972 and provides a framework for regulating pollutant discharges into U.S. water bodies. Since establishment of the CWA, case studies across the nation have shown significant water quality improvements.

The overarching goal of the CWA is to restore and maintain the chemical, physical and biological integrity of U.S. waters. To do this, the Act focuses on eliminating discharges of pollutants and toxic substances and achieving a level of water quality necessary for wildlife survival and human recreation. To meet these goals, the CWA requires entities to obtain permits before releasing pollutants into surface waters.

The system for granting and regulating permits is called the National Pollutant Discharge Elimination System (NPDES). The NPDES Program addresses point sources of pollution or discharges from treatment plants, discharges from industrial facilities and urban runoff. Implementation of the NPDES Program in California is handled by the State.

The CWA includes four elements in addition to the NPDES Program: 1) a system of minimum national effluent standards for each industry, 2) water quality standards, 3) provisions for special problems such as toxic chemicals and oil spills and 4) a construction loan program for publicly owned treatment works.

Water quality standards are set by the States. In California, standards are set by the California State Water Resources Control Board and nine Regional Water Quality Control Boards. Section 303(d) of the CWA requires that each State then identify a list of impaired water bodies that fail to meet the appropriate standards. The CWA also mandates that States establish Total Maximum Daily Loads (TMDLs) for the pollutants present in impaired water bodies. A TMDL specifies the amount of a particular pollutant that a body of water can receive and still meet water quality standards. The TMDL Program requires that States develop plans for reducing pollutant loading in order to acheive TMDLs.