PITTSBURGH — The shale gas drilling industry wants to use barges to move its potentially toxic wastewater across rivers and lakes to disposal sites across the country, but the U.S. Coast Guard must first decide whether it’s safe.

“It may be hazardous,” said Commander Michael Roldan, chief of the Coast Guard’s Hazardous Material Division, stressing the word “may.”

He told Public Source, an independent, nonprofit news organization based in Pittsburgh, the waste can’t currently be shipped by barge.

The Coast Guard regulates the nation’s waterways, and Roldan couldn’t say when the agency would decide whether drilling wastewater can be shipped by barge. That’s partly because experts from the Environmental Protection Agency and the Transportation and Energy departments have weighed in, and a committee established by the White House will likely review the draft proposal.

The oil and gas industry uses water and chemicals to stimulate production of natural gas locked in shale, and some of that water comes back to the surface.

The industry currently recycles some of it, and uses trucks to take it to industrial treatment plants or deep injection wells for treatment or disposal.

The waste is mostly water, but can also contain ultra-salty brines, heavy metals, natural radioactivity, and some of the chemicals used to free gas.

Roldan said the Coast Guard has a process in place for requests to transport chemicals or other substances by barge, but the shale wastewater issue is undergoing “a higher level of review” since there are some unusual aspects to the issue.