Workshop Tomorrow on Marin’s Alto Tunnel

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Cycling enthusiasts have long dreamed of reopening the rotting, 125-year-old Alto Tunnel as a key link in a greenway stretching from the Golden Gate Bridge to Cloverdale. Now they may get their chance, as the county's Non-motorized Transportation Pilot Program begins a $225,000 study of three routes between the two southern Marin towns.

The tunnel between Mill Valley and Corte Madera is the focus of a transportation workshop tomorrow night in Marin County. 

The other two routes are well known to any cyclists who've ridden north of Mill Valley: an existing bike path over Horse Hill by Highway 101 and the twisty Camino Alto, which climbs to about 450 feet on the hill above the tunnel. Neither route is pedestrian-friendly, and many cyclists shy away from Camino Alto because of its narrow lanes, fast cars and afternoon traffic jams.

The 16-foot-wide tunnel would link existing bike paths on both sides of the hill. Southern Pacific sealed the 2,172-foot passageway in 1971, dooming its 12-by-14 redwood supports to rot in the stagnant, moist darkness. The southern entrance collapsed during a rainstorm in 1981 and several other portions have been filled to protect the homes on the hilltop.

“People are very, very excited about the tunnel," said Andy Peri, a spokesman for the Marin County Bike Coalition who predicted dozens of cyclists will show up. "One woman just called me and told me she’s bringing all five of her children from 7 to 17 years old.”

Reopening the tunnel won't be easy. Neighborhood residents, who've enjoyed the solitude of hiking along the overgrown approaches, are organizing against the project. “It is a [public] right-of-way and it is not their private property, but a lot of people would like to see it left alone. Some people have a fear that homeless people would be living up there," said Peri.

Patrick Seidler, founder of the nonprofit Transportation Alternatives for Marin (TAM) and a vocal advocate for the tunnel project, allows that "change is difficult" for people. But he noted that studies by Rails to Trails Conservancy (PDF) show the same local residents who oppose the reopening of tunnels often turn out to be their biggest fans when the projects are completed.

An even bigger obstacle may be the cost. The price tag on the shorter, wider Cal Park tunnel between San Rafael and the Larkspur tunnel is already up to $22-24 million, according to Peri. Nobody knows what kind of shape the Alto Tunnel is in, but the current guess is that renovation costs would be comparable. The study is intended, in part, to develop a better estimate.

Seidler, who is also president of Wilderness Trail Bikes, says the tunnel project would be worthwhile even at a cost of more than $20 million because it would help to complete the greenway, which, in turn, connects the communities that sprang up along the old rail lines during the 19th century.

"The essence of bicycle transportation is that, to work to its potential, there needs to be a complete system," he said. "The rail lines are the most direct and efficient paths of travel between the towns."

The workshop is Wednesday at 6:30 p.m. at Edna Maguire School, 80 Lomita Drive, in Mill Valley.