At issue is a precarious, cracking stretch of the roadway just above Slide Ranch, between Stinson Beach and Muir Beach.
Proposed is a 523-foot-long, 20-foot-high but mostly buried retaining wall anchored by metal piles sunk 15 feet into the downslope hillside, with just 8 feet of the wall "exposed at the top that would reveal only natural wood lagging," according to a summary of the project issued by Caltrans. A 5- to 8-foot-wide bench area would be provided at the bottom of the retaining wall to allow for construction and wall maintenance.
The project at milepost 7.7 near Slide Ranch includes replacement of drainage inlets and culverts, addition of a metal pipe drain, installation of a metal beam guard rail, and installation of cable railing along the retaining wall.
In addition, "the roadbed would be reconstructed and resurfaced in the areas where slope failure has caused extensive cracking and buckling of the roadway," a Caltrans announcement said.
The project site is bordered on the upslope by Mount Tamalpais State Park, and on the downslope by the Golden Gate National Recreational Area.
The downslope would be planted after completion of the six-month project, scheduled to begin in April 2012.
Headed toward Stinson Beach past Slide Ranch, a similar but smaller downslope project is planned at milepost 8.
The plan follows completion in 2007 of a four-month, $25 million road reconstruction project that closed a stretch of road north of Slide Ranch to Panoramic Highway. A similar project also shut the road in 2005. The road closures were an inconvenience for motorists, disrupted commerce and riled merchants. Plans now call for one lane of the roadway to remain open to traffic during construction of the 2012 project.
Winter storms batter the narrow, winding road, causing parts of it to buckle, break off and slide down the hill at a pace that surprises even veteran observers.
In November 2007, after completion of the last project, Caltrans spokesman Bob Haus doubted there would be a need for more work anytime soon.
"We are hoping this is the last major work we will have to do for quite awhile out there," he said at the time.
Read more West Marin stories at the IJ's West Marin section.
Contact Nels Johnson via e-mail at firstname.lastname@example.org