U.S. EPA has redefined the term "navigable waters" for purposes of the Spill Prevention, Countermeasure and Control rule (SPCC rule) (40 C.F.R Part 112). Restored to the regulatory definition promulgated by EPA in 1973, the term now includes:
On its face, and for the time being, this is a significant reduction in the definition's reach.
[Update: A Federal Register copy of the rule can be found here.]