The Environmental Protection Agency and Army Corps of Engineers have moved forward on a proposed rule that the agencies say aims to spell out more clearly which bodies of water fall under federal regulatory jurisdiction and which do not.

EPA and the Corps said they had sent the draft proposal on Sept. 17 to the White House Office of Management and Budget, which now will coordinate a review of the proposal by various other federal agencies. EPA and the Corps did not release the text of their joint proposal.

Inter-agency reviews of proposed regulations typically take months to complete. After that, a proposed rule is published and a public comment period follows. After agencies study those comments,  a final regulation—sometimes changed from the proposed version—could be issued.

The Clean Water Act states that “waters of the United States” are subject to federal regulation. For construction companies, that means that work in areas that meet the definition—notably certain wetlands—requires a Corps of Engineers permit.

But for years, determining what wetlands and types of streams are waters of the U.S. has been anything but clear, even after major U.S. Supreme Court wetlands cases in 2001 and 2006 took a stab at providing an answer.

In a Sept. 17 blog post, EPA Acting Assistant Administrator for Water Nancy Stoner and Acting Assistant Administrator for research and development Lek Kadeli said the draft proposal “will provide will provide greater consistency, certainty and predictability nationwide by providing clarity for determining where the Clean Water Act applies and where it does not.”

In a statement on the EPA web page, the agencies say they are focusing on making clear how the definition applies to wetlands and to smaller waters that feed larger ones.

The agency also released a draft report from its Science Advisory Board that, according to Stoner and Kadeli, concludes that streams, including small or intermittent ones, and wetlands have important effects on downstream waters. EPA is seeking public comments on that study.