Congress enacts the Clean Water Act to “restore and maintain the chemical, physical, and biological integrity of the Nation’s waters.” The Act provides a comprehensive framework for addressing both point source and non-point source pollution. States are directed, subject to Environmental Protection Agency (EPA) approval, to develop and enforce comprehensive water quality standards establishing water quality goals for all intrastate waters. The Act also requires permits for the discharge of pollutants into navigable waters from point sources (the NPDES program) and establishes a Total Maximum Daily Load (TMDL) program aimed at restoring “impaired” waters that fail to meet water quality standards.