The Coast Guard is reviewing the comments from both sides, and it has the authority to approve or modify the rule. But there is no timeline for a decision, spokesman Carlos Diaz said.

A leading industry group supports using barges for the waste but isn't happy with the details of the Coast Guard proposal. In a Dec. 6 letter, the Marcellus Shale Coalition hailed the potential to reduce the waste being transported by highway but complained the proposal set the threshold too low for naturally occurring radiation, which would effectively prevent wastewater from being shipped by barge.

A spokeswoman for the U.S. Environmental Protection Agency couldn't immediately say Friday whether they have a position on the barge wastewater issue.

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