As Wiscasset, Waterville & Farmington Railway Museum continues building a bridge in its parking lot, the Alna nonprofit is a step closer to the project that would put the bridge over Trout Brook and grow the narrow gauge route.

Monday night, the planning board unanimously approved the museum’s application for a shoreland zoning permit, on the conditions the museum run any design changes by the board and provide a post-construction report.

Member Lynne Flaccus wondered if the board should also require the museum to get all the other governmental permits it needs for the project. Some towns do, but it was not needed because the project will not happen without the other permits, fellow member Peter Tischbein said.

The planned “mountain extension” takes its name from that part of the original rail route, bridge project manager Jason Lamontagne said. The project still needs Maine Department of Environmental Protection permitting and the U.S. Army Corps of Engineers’ review, Lamontagne said.

In an interview outside the meeting, Lamontagne said the museum has worked to minimize the project’s environmental impact. He told the board, plans call for raising the rail bed with retaining walls that will lessen the fill needed. “It prevents encroachment into natural resources,” Tischbein explained about the walls. And in response to a question from Flaccus, Lamontagne said passages will be left for wildlife every 120 feet.

Hannah Chamberlain, land steward for neighbor Midcoast Conservancy, told the board: “I’m pretty comfortable with everything that’s in the document.”

Most of the questions and comments came from Flaccus. She asked museum representatives to keep in mind, the water there rises and drops quickly. “Just be ready for it.” Also, watch for beaver dams and check fish and game laws on what measures are allowed and when, she said.

The bridge arrived in pieces at the museum on Cross Road in October. It was free, a gift from the National Park Service and the National Society for the Preservation of Covered Bridges, museum officials have said. Lamontagne said assembly is going well. Plans call for a moving company to take the bridge to the site for an August installation. The work may continue through early September, Lamontagne told the board.

He added in an email to the Wiscasset Newspaper afterward, “(The) ‘Mountain Extension’ ... will do a fabulous job of demonstrating the engineering advantage of the two-foot narrow gauge, as it was able to follow the landscape very closely ... Also, we were very pleased to work with our neighbors at the site, Midcoast Conservancy ...”