Devil's Slide

Devil's Slide Tunnels Project

October 1, 2010 UPDATE:
Caltrans Celebrates the Devil’s Slide Tunnel “Punch Through” (PDF)

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The coast between Pacifica and Montara is unsurpassed in scenic beauty. Carved out of the steep cliff sides, Route 1 hugs the coastline for much of the distance between these two towns. In one part, the road crosses the aptly named Devil's Slide region, a steep, unstable geological formation. This section of road has a long history of closure due to rockslides and land slippage. One of the longest road closures happened in 1995. It lasted 158 days, and cost almost $3 million to repair.

Following many years of public input and careful evaluation of alternatives, Devil's Slide will be by-passed by two inland tunnels, providing a safe, dependable highway between Pacifica and Montara. This is the Devil's Slide Tunnels Project.

The project calls for construction of two tunnels beneath San Pedro Mountain, each 30-feet wide and 4,200-feet long. At the northern end, a 1,000-feet bridge will span the valley at Shamrock Ranch. A re-alignment of Route 1 at the southern end will provide safe transition into and out of the tunnel. Approximately one-quarter mile south of the tunnel is the site of an Operations and Maintenance facility. An earthen embankment and vegetation-covered roof will help the facility blend with natural surroundings.

Throughout the public input and evaluation phases, lasting over 30 years, concerns about effects on wetlands, wildlife, plants, noise, and visual impacts received highest priority – click on the links, above right, to see more information.

The bypassed section of Route 1, together with 70 acres of State right of way, will be available for public access and recreational use following the planned tunnel opening in early 2012. Caltrans will monitor and improve the state of wetlands, wildlife, and plants until independent resource and regulatory agencies determine mitigation work has met its success criteria.