Where is the Alto Tunnel and what is its history?
The Alto Tunnel was built in 1884 and is located in Marin County along the former Northwestern Pacific Railroad right-of-way, connecting Mill Valley and Corte Madera. The tunnel is 16-feet wide and 20-feet high, approximately 2200 feet (0.4 miles) long, and served as a single-track rail tunnel for nearly ninety years. In 1958, there was a substantial upgrade to the northern portal, which remains intact and in good condition today. The tunnel remained open until 1971, when substantial bulkheads were added at each portal to prevent entry. In 1975, a plug extending approximately 125-feet was added near the north end of the tunnel and in 1981, there was a collapse at the southern portal. The southern portal area was stabilized in 1982 with gravel and earth fill, which remains today. The middle 1600-feet of the tunnel remains sealed off. Read the MCBCs letter to the County, 3/31/09 On Tuesday, November 18, 2008, the Marin County Board of Supervisors approved of a $225,000 contract with Land
