In early January 2005, Santa Barbara County received 23.7 in. of rain over three days, wrecking havoc on the slopes supporting Highway 154. One section, known as Painted Cave and located on a steep 1.5H:1V slope, was particularly bad off. Trapped water had blown a hole beneath it and took whole sections of asphalt down the mountain.
Caltrans officials' first priority was to avoid another landslide blow out. So, contractors installed a drain pipe underneath the road that extended down the four-acre mountain slope to the ravine below. Once the slope was rebuilt, Caltrans officials needed a product that would provide protective vegetation and could be applied quickly and safely.
Bruce Berlin of S & S Seeds in Carpinteria, Calif., offered such a product. Caltrans accepted Berlin's proposal to use Profile Product's Flexterra Flexible Growth Medium (FGM) for the project. Flexterra is a hydraulically applied FGM made of Thermally Refined wood fibers, crimped, interlocking fibers and performance enhancing additives that are engineered to perform under extreme conditions. Flexterra is the only FGM that requires no cure time to be effective - a very attractive benefit to Caltrans officials given the imminent threat of more rain forecasted.
Berlin recommended Flexterra based on its proven performance on steep slopes. Upon application, Flexterra creates an intimate bond with the soil surface to form a continuous, porous, absorbent and erosion-resistant blanket that allows for rapid germination and accelerated plant growth.
"Flexterra's soil-bonding characteristic and longevity of up to one year provided reassurance that it could perform in the short term and, in the longer term, provide protection if adequate germination didn't occur," said Peter New, landscape architect for Caltrans' District 5.
In March, KCI Environmental, based in San Luis Obispo, Calif., hydroseeded six tons of Flexterra with a native seed mix to ensure soil stabilization and to provide a medium for vegetative establishment.
Caltrans has reported that the application of Flexterra to Painted Cave's steep mountain slope has kept the slope stable and encouraged vegetation growth without "tenting" or lifting the material – as so often occurs with erosion-control blankets.
"Flexterra accommodated the time constraints of the application and provided workers with a medium that could be applied safely," said Berlin. "Because it also provided erosion-control effectiveness on saturated soils and compatibility with native vegetation, Flexterra was good match for this project."