The Environmental Protection Agency's (EPA) water rule passed a crucial test Thursday, gaining the approval of the agency's internal review board.
The EPA's Science Advisory Board noted in a peer review of the rule that there is "strong scientific support" for the agency's proposed Waters of the U.S. regulation.
The panel reviewed the EPA's draft report on the connectivity of waterways around the country.
"Relatively low levels of connectivity can be meaningful in terms of impacts on the chemical, physical, and biological integrity of downstream waters," the advisory board wrote.
The EPA is proposing to expand its jurisdiction to include small rivers and streams that flow into larger sources of water.
Environmental groups say the rule is needed to protect the nation's water sources from contamination, but business groups say it would be unduly expensive to comply with, particularly for farmers.
The EPA proposed the rule in April. The advisory board said it is "grounded in current science," but offered several recommendations to clarify the rule and improve transparency.
"The report should also clearly indicate that the definitions used for rivers, streams, and wetlands are scientific, rather than legal or regulatory definitions," the board wrote.
The public has until Nov. 14 to comment on the proposed rule.