EPA has proposed a new draft guidance on the scope of the Clean Water Act (CWA): fhttp://www.epa.gov/indian/pdf/wous_guidance_4-2011.pdf
Although they do not have the force of law, guidances help the field offices apply the law. This draft guidance interprets several recent court decisions, especially as to how to decide if bodies of water are covered by the CWA. It discusses "navigable and interstate waters," but also discusses whether and how other wet areas (e.g., wetlands, tributaries, etc.) might be considered to be covered by the CWA, and therefore subject to regulation by EPA. See page 5 of the document for a summary of key points.
EPA has stated its intent to finalize the documents based on comments received, and then to begin a rule making to incorporate it into EPA regulations. Comments can be submitted directly to the EPA and/or to US Senators and Representatives.