The Purple Line appears likely to displace a section of the Capital Crescent Trail that runs under Wisconsin Avenue in Bethesda. (Mark Gail/THE WASHINGTON POST)

A Montgomery County Council committee recommended Thursday rerouting a popular hiker-biker trail along streets in downtown Bethesda if a Purple Line transit link is built.

It would be too expensive and risky to rebuild the trail — along with the light-rail line — inside the trail’s existing tunnel beneath Wisconsin Avenue, officials said.

The council’s transportation committee also asked Maryland transit planners to continue studying the possibility of building a sidewalk through the tunnel, next to the rail line. A sidewalk would be narrower than a 12-foot-wide trail, supporters said, and it would provide pedestrians and cyclists direct access to the Purple Line station from the Bethesda Row shopping and restaurant district.

The state’s chief transit planner on the Purple Line project also told council members the state is no longer considering trying to save construction costs by running light-rail trains across Connecticut Avenue in North Chevy Chase rather than over a bridge.

Michael Madden, the Maryland Transit Administration’s manager on Purple Line planning, said after the meeting that planners stopped analyzing an at-grade crossing after hearing from the community. Opponents of the idea, which Madden disclosed March 1 under questioning from the council, had said that requiring traffic to stop for trains would further snarl the heavily congested road.

A rendering that depicts a Purple Line tunnel that would run beneath Bethesda. (Courtesy of Maryland Transit Administration)

Council members said their decision boiled down to money. With budgets tight, committee members said, the county can’t afford to spend an estimated $50.9 million to squeeze the trail into a “concrete box structure” that would run through the tunnel but above the trains’ overhead power lines. Rerouting the trail along streets would cost an estimated $3.5 million, according to state transit planners.

Rebuilding the trail inside the tunnel, along with the rail line, would be highly risky, state planners have said, because it would affect critical support columns for two office buildings.

Council President Roger Berliner (D-Potomac-Bethesda) said he was “extremely disappointed” that he had to support rerouting the trail along local streets, but he said rebuilding it in the 1,200-foot tunnel “is just too risky and too costly.”

The committee voted to allot $49.5 million total for trail construction costs between Bethesda and Silver Spring. The county’s costs could escalate depending on how much the state agrees to contribute, council staff said. Although the trail is the county’s responsibility, the county will argue that the state should cover such costs as building retaining walls because those expenses are attributable to construction of the transit line, the staff said.

The state’s plan for a 16-mile light-rail line between Bethesda and New Carrollton still has no construction funding. State officials are seeking federal aid for half of the estimated $1.93 billion in construction costs. Construction would begin in 2015 at the earliest, officials have said.

The tunnel issue has been debated by some residents and trail advocates who say state and county officials have long promised that the trail would remain in the tunnel to provide a safe crossing beneath busy Wisconsin Avenue.

The full council still must approve the trail money as part of the county’s six-year capital spending plan, which it is scheduled to hash out in May.

County Executive Isiah Leggett (D) has said it is “premature and troubling” for the council to designate money to local projects related to a Purple Line before federal and state money to build the transit link is secured.

Allotting money over the next six years to rebuild the trail and build high-speed elevators to connect a street-level Purple Line station with Bethesda’s Red Line Metrorail station would siphon off money from county projects needed to alleviate traffic and improve bicycle and pedestrian safety, Leggett wrote Wednesday in a letter to Berliner.