Terry Baker, the president of the Washington County Commissioners, voiced concerns during a telephone news conference on Thursday about a proposed natural gas pipeline.

“The dangers are high, in my opinion,” Baker said.

The call was organized by environmental groups, including the Potomac Riverkeeper Network. Officials from Montgomery County and Washington, D.C., also were scheduled to speak, but they were not on the line. Upper Potomac Riverkeeper Brent Walls said he did not know why they were not available.

Columbia Gas Transmission, part of TransCanada, is seeking a federal permit to build the pipeline from southern Pennsylvania through Maryland and under the Potomac River near Hancock. It would connect with a pipeline planned by Mountaineer Gas in West Virginia.

Residents from Washington County and several other parts of Maryland have opposed the plan. They have cited the potential for environmental damage from the horizontal directional drilling process, pollution from potential leaks and contamination of water supplies.