The design of the wall at Topanga and PCH is not intended to stop earth movement, only to keep the hillside in one piece.
By Carolanne Sudderth/Special to The Malibu Times
Despite delays, the work is almost done. Caltrans officials estimate that the concrete barrier holding back earth and rubble at the intersection of the Topanga Canyon Boulevard and Pacific Coast Highway will be finished by the end of the month.
The seven-section retaining wall and slope stabilization system looms above the abandoned gas station. Work was started in March of last year.
“At this point, we’re about 99 percent complete,” said Jeanne Bonfilio, Caltrans public information officer. The next step will be taken by Southern California Edison, which will move its light standards back from the roadway to allow the creation of a right turn lane onto Topanga Canyon.
“Once those are installed, we have some striping work to do, but we hope to be complete by mid- to late-December,” Bonfilio said.
Originally slated for completion in September, the project is almost three months behind schedule. Construction Office Chief Dan Freeman dismissed this as “just normal construction delays. Sometimes you run into different materials. We had to go back and check with our geo-technical people.”
The wall consists of six levels in three locations-a series of benches designed to catch debris from higher up-“just so it would have a place to land so it wouldn’t hit PCH,” Freeman said. “The slopes in the whole section aren’t real stable from natural erosion, and some of those hillsides are kind of moving toward the ocean.”
The technical term for the construction is “tie-back wall.” The theory is that although it may not prevent the land from moving, it will keep it in one piece.
The geology of the area behind the wall consists of a great deal of fractured material. The idea, Freeman said, is to anchor the wall into solid material. The process is necessarily site-specific. In this case, some 340 rods and cables ranging from 120 feet to 200 feet long “were pushed through the stuff that’s been folded and pushed back by the normal seismic movement, and go back into the solid area behind that and ground that in with concrete.”
Although California is subject to natural forces ranging from mudslides to seismic movement, the purpose of this particular wall is to keep rocks from tumbling onto the highway, or in worst-case scenarios, onto the roofs of passing cars. “This isn’t going to hold back that material from falling down the hillside,” Freeman said. “This isn’t going to hold back that thrust. That’s continental plate, and that’s huge, but what this will do is hold back that fractured material.”
For now, Caltrans is playing the waiting game. “We’re just waiting for utility poles to be relocated so we can widen out the road to make the right turn lane. And whenever they get that work scheduled, we should be out of there,” Freeman said.