Tunnel Debate Reignites As Residents Press Council For Renewed Support In Marin County

MILL VALLEY, CA — The long‑running debate over reopening the Alto Tunnel resurfaced at the Mill Valley City Council meeting, drawing numerous speakers both for and against the idea of restoring the former rail tunnel as a bicycle and pedestrian link between Mill Valley and Corte Madera.

Warren Wells, policy and planning director for the Marin County Bicycle Coalition, asked the council to update and reaffirm its 2000 resolution supporting further study of the tunnel’s reuse. He said reopening the tunnel would connect nearly 10 miles of multi‑use path from Sausalito to Terra Linda, offering a continuous, low‑stress route separate from car traffic.

“We are here to ask that you update that quarter‑century‑old council resolution to reflect the work that has been done to date, and renew the request that the outstanding issues be evaluated by the county,” Wells said.

Supporters emphasized safety for families and commuters currently using Camino Alto and Horse Hill Lane, which they described as steep and uncomfortable routes shared with heavy traffic. One Mill Valley resident said reopening the tunnel would allow his young children to bike to schools and parks without adding to congestion on Highway 101.

Opponents focused on cost, engineering risks and neighborhood impacts.

John Palmer, a Scott Valley resident and homeowners association leader, argued the project would require a full reconstruction rather than a simple reopening, citing tunnel collapse and homes built above the alignment. He suggested total costs could reach $100 million or more once inflation, easements and related work are considered.

“There are alternatives which could be improved,” Palmer said, pointing to the Horse Hill route as a lower‑cost option.

While councilmembers did not deliberate on the item, which was raised during general public comment, several acknowledged the scale of the decision. Councilmember Stephen Burke noted the council would need to balance competing priorities and limited staff capacity when considering if and when to bring a tunnel resolution back for formal discussion.

The city clerk reported receiving 21 written comments on the Alto Tunnel topic prior to the meeting.