Marin cyclists revive push for Alto Tunnel restoration

The Marin County Bicycle Coalition wants to rebuild the Alto Tunnel between Mill Valley and Corte Madera as a path for bicyclists and pedestrians.

Advocates urged the Mill Valley City Council on Tuesday to place the tunnel on its agenda, hoping it would ask Marin County to continue studies of the project initiated in 2001 at the city’s request.

“We’re asking you to just agendize a conversation,” said Tarrell Kullaway, executive director of the Marin County Bicycle Coalition. “We’re not asking you to write a check, just to say that the questions that you asked 25 years ago are still worth considering today.”

“After a fuller picture of the costs and benefits of the project is known … decision makers in the county and in adjoining cities can decide whether to seek funding,” said Warren Wells, the organization’s policy and planning director.

The council took no action on the request from a dozen proponents who spoke at the meeting in green “Open Alto Tunnel” T-shirts.

“If it really can be opened, my grandchildren and I would love to walk through it, bike through it,” said Lee Larson, a Mill Valley resident. “Reopening this tunnel could reduce up to 2,000 vehicle miles traveled per day.”

“When I do have time, I go over Horse Hill, but it’s a long way out of the way,” said Eric Miller, a Larkspur resident and cyclist. “It’s a steep climb and it’s just not a convenient way to go.”

The 2,172-foot tunnel between Mill Valley and Corte Madera was built in the early 1880s by Chinese laborers for the Northern Pacific Railroad, according to local histories. Upon completion it was 16 feet wide and 20 feet tall and framed by redwood beams.

The tunnel was used for passenger rail service until 1940 and freight trains until 1971, when it was closed and sealed, according to a 2017 county report. Transit agencies and the county have studied the tunnel six times since its closure, initially for modern rail service and then for bike and pedestrian use.

In 1981, a portion near the southern entrance collapsed, damaging a home and underground utilities and leaving deep sinkholes. Shortly afterward, the former rail bed was converted into a multiuse path.

The county’s 2017 engineering assessment involved drilling into the hillside and taking photographs. It found rotting timber beams, numerous cave-ins and several feet of standing water, and noted a third of the tunnel’s length was filled with concrete. It estimated repair costs at $46.8 million.

The tunnel’s condition and restoration costs have not deterred cyclists from calling for its revival.

In 2000, the Marin County Bicycle Coalition prompted Mill Valley to request that the county study 11 issues related to the tunnel’s reuse. The tunnel was included in the county’s draft 2002 bike plan.

The cycling organization wants Mill Valley to ask the county to finish evaluating those issues. It submitted letters of support from the Sierra Club and Canal Alliance.

Only two opponents spoke during the meeting. One was John Palmer, a 56-year Mill Valley resident who wrote a series of articles from 2001 to 2003 on the tunnel’s history, collapse, engineering studies and arguments for and against rebuilding it.

“Tunnel advocates have consistently downplayed the scope of the proposal by using the term reopen, which we heard all night tonight,” said Palmer, president of the Scott Valley Homeowners Association. “The proper term is reconstruct.”

“The tunnel is filled at both ends with concrete and is completely collapsed in the middle, as the county’s studies have shown,” Palmer said. “It’s impossible to stage the kind of equipment necessary to do this proposal without massive disruption to the neighborhoods.”

Palmer estimated the reconstruction and redevelopment costs, which include obtaining rights of way, could exceed $100 million.

Later in the meeting, Councilmember Urban Carmel announced the county has allocated $630,000 to repave bike and pedestrian paths on Horse Hill.