The EPA supports market-based mechanisms, including water quality trading under the Clean Water Act (CWA). The Agency has long interpreted the CWA to allow pollutant reductions from market-based approaches such as water quality trading to achieve compliance with CWA regulatory requirements. Yet, the National Pollutant Discharge Elimination System (NPDES) regulations do not explicitly address market-based approaches. In the absence of explicit statutory language or regulations, the EPA has provided guidance for permitting authorities and stakeholders to consider when developing market-based programs. The Agency is proposing to clarify how water quality trading and other market-based approaches may be used by NPDES permitting authorities in permits to meet applicable water quality standards.