A new rule will clarify the waters to be regulated under the US Clean Water Act (CWA).
Here is the USEPA webpage with information and giving access to applicable documents, including the results of action in the US courts, and the current definition being referred to (40 CFR 230.3(s)).
Already in operation is draft guidance – see here for the USEPA summary of the 2011 draft guidance.
Here is the 2011 draft guidance itself.
Here is 40 CFR 230.3 (CWA definitions) on its own. The definition of “waters of the United States” – waters subject to the US federal Clean Water Act – is found at 40 CFR 230.3(s) on the next page at (s)).
The definition is also found at 40 CFR 122.2 here. Scroll down to waters of the United States or waters of the US.