District resident Will Hackman steadies his inflatable kayak before launching down the Potomac River in Paw Paw, W.Va., in July for a two-day paddle to raise awareness about a natural gas pipeline potentially planned for the area. (Reza A. Marvashti/For The Washington Post)

Clean-water activists who have spent much of 2017 attempting to block a proposed natural gas pipeline beneath the Potomac River and C&O Canal in western Maryland will have a chance to testify Tuesday evening at a state environmental hearing in Hancock, Md.

The Maryland Department of Environment is holding a hearing on whether to award a clean water permit for a 3.5-mile pipeline that would bring natural gas from Pennsylvania to West Virginia, bisecting the narrowest slice of Maryland's panhandle.

Environmentalists say that brief stretch could jeopardize the drinking water supply for about 6 million people, including much of the Washington metropolitan area. West Virginia business leaders say the natural gas is needed to bring economic development to an area that is short of jobs. Proponents say the pipeline would be safe.

The environmentalists, who have enlisted support from nine members of the D.C. Council, are asking Maryland Gov. Larry Hogan (R) to refuse the permit for what they are calling the Potomac Pipeline.

They have jammed local government meetings since February and staged several protests on the upper Potomac during the summer. In October, they demonstrated on the banks of the Potomac in Georgetown.

Another demonstration is schedule Tuesday night in Hancock.

Hogan, who earlier this year banned fracking in Maryland, has until March to grant or deny the permit, or the state loses the right to step in.

Federal regulators recently approved the much-larger Mountain Valley and Atlantic Coast pipelines in Virginia, while the State Water Control Board approved the first and delayed the permit for the second. Those pipelines drew large demonstrations and became a major issue in Virginia's recent election.

The Maryland pipeline, sought by TransCanada, has gotten much less attention, partly because about a dozen pipelines already cross the Potomac in Maryland alone, and partly because the proposed crossing is about 100 miles from the D.C. metropolitan area.