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 water quality trading and offsets to achieve compliance with CWA regulatory requirements. Yet, neither the CWA nor the EPA's implementing regulations explicitly address water quality trading. In the absence of explicit statutory language or regulations, EPA has provided guidance for permitting authorities and stakeholders to consider when developing market-based programs, including water quality trading 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.