The Blue Slide

Have you ever noticed, as you drive between Brookdale and Ben Lomond, those iron pipes sticking out of the hillside? That's to stop the Blue Slide.

The slide was so named because it was composed of blue clay. It was aptly described in 1937:  "Its special blue clay ingredient makes it dangerous and unmanageable." 

And for many years it was unmanageable, depositing tons of debris onto Highway 9 during heavy rainfalls, cutting off the towns of Brookdale and Boulder Creek.

In 1936, there was a determined effort to halt the "annual avalanche at the 'blue slide.'" The state highway crews were assisted by Works Progress Administration (WPA) crews to cut the hillside back. The debris and rock was hauled out and used in the construction of the final segments of the San Lorenzo Valley's new hiking and bridle trail between Felton and Boulder Creek, a project sponsored by the chamber of commerce and expected to serve "thousands of summer vacationists."

However, the work did not stop the Blue Slide. In 1940, more tons of debris from the slide was used by state highway crews to level off the highway near Brook Lomond and to level off the ground for a parking area at the park in Ben Lomond.

In 1941, the Blue Slide "took the greatest skid in its history" when it dumped a 300-foot "mountain" on the highway, along with trees and power lines.

It wasn't until 1970 that the slide was tamed. Granite Construction of Watsonville was awarded an almost $300,000 contract to repair portions of Highway 9 including the Blue Slide area. "Washed out highway sections and embankments will be restored, and bin-type retaining walls built. In addition, drainage facilities will be replace[d] and rock slope protection will be installed." The work, which began in January, had to be postponed when the rains began as, you guessed it, the rains washed out the repairs.

Work was completed in the summer of 1970. The Blue Slide was subdued but not completely harmless. Slides at that spot, though not as damaging as in the past, continue to occur.

Image: Eleanor Fraser Collection, San Lorenzo Valley Museum.