Above: Devil's Slide Tunnels Project is 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 helps the facility blend with natural surroundings.