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Flexterra® FGM Case Study: Highway 154, California Roadway Project

Situation

Highway 154 is a gently curving two-lane mountain pass that takes drivers through canyons, grasslands, orchards and the foothills of the San Marcos Mountains in Santa Barbara County. Forty-five miles in length, Highway 154 is one of two main arteries going north from Santa Barbara, California. In early January 2005, the skies opened up and Southern California and Santa Barbara County received three solid days of rain. In this short period, Santa Barbara County received 23.7 inches of rain in addition to the 30 inches of rain that had already fallen in the three prior months, wrecking havoc on the slopes supporting Highway 154. One section in particular, known as Painted Cave, was located on top a steep, mountain wall on a 1.5H:1V slope. This section was undermined by trapped water that had built up on the uphill side, which then blew a hole beneath the highway, taking several sections of asphalt with it down the mountainside. One entire lane of the two lane highway was washed away.

Problem

With so much damage, much of the road had to be closed with no thru traffic allowed, inconveniencing many Santa Barbara residents and other travelers needing quick access north. Over $4,000,000 in emergency funds were appropriated to CalTrans to provide emergency repairs to this popular highway. Faced with a number of different options, CalTrans officials knew they needed to rebuild the slopes and determine how to establish vegetation as quickly as possible. “With the forecast calling for rain in the near future, our construction staff asked for erosion control solutions to be implemented immediately,” said Peter New, landscape architect for CalTrans’ District 5. 

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