Devil's Slide
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Devil's Slide is a notorious stretch of California's Highway 1, along San Mateo County's coastline between Pacifica and Half Moon Bay. Construction of the road began in 1935. It is known for the landslides and erosion that often occur during winter storms, sometimes making the road impassable. The first major landslide destroyed much of the road in 1940, and a cycle of building and destruction has prevailed since.
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[edit] Natural setting
Devil's Slide is a name given to a steep, rocky coastal promontory located about midway between Montara and the Linda Mar District of Pacifica. The terrain is characterized by steep, eroded slopes with natural gradients ranging between 30 and 70%. There are small coastal valleys throughout along the major drainages within the Montara Mountain watershed. The soils in these valleys are deep and moderately well drained and have developed along the low terraces and alluvial fans of the stream channels.
The climate of the project area is Mediterranean with a strong maritime influence. The temperature range is narrow both seasonally and diurnally, while air moisture is relatively high. Extremely dense northern coastal scrub covers most of the locale, especially over San Pedro Mountain and along the steeper foot slopes of Montara Mountain. Small grassy openings and barren rocky areas are scattered throughout the scrub areas. The inland area holds other types of vegetation including, aquatic and coastal freshwater marshes/seeps, willow riparian scrub, coastal grassland, non-native forest, and pasture/ranch uses/non-native brushland. The endangered species Hickman's potentilla occurs on the slopes above Martini Creek at up to 130 meters in elevation.
[edit] History of the rebuilding conflict
A bypass has been proposed to the 600 foot long stretch. Beginning in 1958, California began the process to replace Devil's Slide with an inland route over Montara Mountain, known as the Martini Creek Bypass. The bypass bisected a section of Montara State Park, and was opposed by environmental groups. By 1975, 55% of the right-of-way had been acquired, when work on the proposed bypass was abandoned due to public opposition.
Most environmentalists supported a tunnel as a more environmentally sensitive alternative to the Martini Creek Bypass. A short railroad tunnel built in 1908 went through the area, but was destroyed during Prohibition, to keep it from being used by alcohol smugglers. The Sierra Club proposed building a tunnel to bypass the road in 1973. A Caltrans study in 1974 determined that a tunnel would be a viable alternative to the current road or a proposed inland freeway bypass. However, the state dropped the idea in the late 1970s.
A major slide in 1983 brought the problem to the public attention again. In 1985 Caltrans proposed the Martini Creek bypass as the preferred solution. However, the Sierra Club sued to stop construction, as California law requires that Highway 1 be restricted to 2 lanes in rural areas. The 101 foot wide road bed, complete with continuous uphill passing lanes, run-away truck ramps, and extra wide shoulders, would be the widest "2-lane" road in the state. Again the state decided to return to the status quo.
A five month outage caused by a slide in January 1995 again brought public scrutiny to the stretch of highway. In April, Caltrans documents were discovered that showed the agency had intentionally overestimated the costs of a tunnel, to support the freeway bypass. In July, the Federal Highway Administration ordered Caltrans to re-evaluate a tunnel to bypass Devil's Slide. On November 5, 1996, San Mateo County voters approved Measure T by 76%, changing the county's stated preference from construction of the bypass to construction of a tunnel. On November 9, Caltrans changed its position, supporting a tunnel as the best environmental, economic, and popular alternative to Devil's Slide.
Ground was broken for the new tunnel on May 6, 2005, with completion scheduled for 2011. [1]
[edit] 2006 Storm Damage
The Slide was closed on April 2, 2006 at 6:55PM for cracks in the road reminiscent of the 1995 failure. Longitudinal cracks along the length of the roadway in both lanes show a slow slippage of the roadbed towards the ocean. The road had already sunk considerably towards the ocean by that time. Extensive work needs to be done to stabilize the slide again, but Caltrans reopened the road during peak hours beginning on August 4, 2006 and was fully opened in September.
[edit] See also
[edit] Bibliography
- Biological Assessment, Species of Concern, Proposed Route 1 Devil's Slide Tunnel Bypass Project, San Mateo County, California Prepared by; Caltrans, Office of Environmental Planning, South. July, 1998.
- Michael Hogan and Ballard George, Air Quality and Noise Analyses for the Bypass Alternative, Devil's Slide Improvement Project, Caltrans District 4, prepared by Earth Metrics Inc., Burlingame, CA (1984)
- Devil's Slide Improvement Project, San Mateo County, California, Draft Second Supplemental Environmental Impact Statement, Caltrans District 4 (1999)
- Hovland, John H., Ph.D., P.E., A Study of the Feasibility of Stabilizing the Landslide Area Along Highway One, San Mateo County, California, by Dewatering, April, 1998
- Woodward-Clyde Consultants, Devil’s Slide Tunnel Study - Feasibility Report, October, 1996.
