From Ruin to Revival
A pastoral drive set in the picturesque San Marcos Mountains of Santa Barbara County, California defines the view one receives while on Highway 154 or San Marcos Pass. However, this idyllic scene was not the one seen by passersby after the winter rains of early 2005. Damaged mountain slopes, washed out roadways and crumbling craters of asphalt were the results of more than 30 inches of rain that fell in the span of two weeks in early January 2005. This was in addition to the 24 inches of rain that fell from approximately October to December 2004. With such significant damage and the threat of more rain ahead, the California Department of Transportation, or CalTrans, knew a fast solution was necessary.
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. Forty-five miles in length, Highway 154 is one of two main arteries going north from Santa Barbara, California to Los Olivos and connects drivers to Highway 101, the primary highway north from Santa Barbara that runs along the Pacific coast.
Normal rainfall for the area is 18 to 20 inches a year. Most of this falls from October through March with the rest of the year being generally dry. By the end of December 2004, 30 inches of rain had already fallen in the three prior months, thereby saturating the ground.
In early January, the skies opened up and Southern California and Santa Barbara County received three days of solid rain. In this short period, Santa Barbara County received 23.7 inches of rain, 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 and pulled down the mountainside by water that had built up on the uphill side. The trapped water blew a hole beneath the highway and took several sections of asphalt with it. One entire lane of the two lane highway was washed away.
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.
New said various conventional erosion control products, such as seed, straw with tack, bonded fiber matrix and fiber rolls, were considered to repair the damage. While some of these products could be used to repair some of the damage incurred on Highway 154’s more stable ground, the Painted Cave and other highway sections adjacent to unstable, steep mountain grades posed greater challenges because of the precipitous slopes directly above and below the roadway.
For Painted Cave, CalTrans officials’ first priority was to avoid another landslide blow-out. To accomplish this, contractors installed a pipe underneath the road that extended down the four-acre mountain slope to the ravine below to drain rainwater coming from the uphill side of the road. Once the slope was rebuilt and the pipe installed, CalTrans officials needed a product that would provide protective vegetation to the rebuilt slope and could be applied quickly and safely on the steep mountain slopes.
Bruce Berlin, erosion control product manager with S & S Seeds based in Carpinteria, California, offered such a product. CalTrans accepted Berlin’s proposal to use Profile Product’s Flexterra® FGM for the project. It is a hydraulically applied, flexible growth medium made of Thermally Refined wood fibers, crimped, interlocking fibers and performance enhancing additives that are engineered to perform under extreme conditions.
Berlin recommended this product based on its proven performance in providing erosion protection and seed germination on steep slopes. Another added benefit, Berlin explained, was that it was the only FGM that required no cure time to be effective. Upon application, it 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.
“With no curing time, the FGM was an attractive solution because it could be applied with threat of rain in the near future,” said New. “It’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.”
Because workers would apply the product on a steep mountain slope, hydraulic application via a hydroseeder was an essential component to providing workers with a quick and safe solution to stabilizing the slope. Additionally, Berlin informed CalTrans officials that the FGM would be compatible with the native plants that grew naturally on the slopes by allowing them to grow, unimpeded, through the FGM.
To reduce the slope length and prevent rilling, fiber wattles were installed at pre-determined intervals transverse to the mountain slope. Workers were also able to use the wattles to gain footing while rappelling down the mountain. In March, KCI Environmental hydraulically applied six tons of the FGM with a native seed mix onto the mountain slope to ensure soil stabilization and to provide a medium for vegetative establishment.
CalTrans has reported that Painted Cave’s steep mountain slope has remained stable with some outcropping of growth occurring.
“So far, Flexterra has performed adequately,” said New. “It has remained well-knitted together and the soil bonding is evident. We haven’t seen a high percentage of germination, which we suspect is due to inadequate rainfall following application. We’ll continue to evaluate the success of the FGM into this winter when we have more rain.”
Berlin also was optimistic that the FGM would provide the slopes with the stability and germination necessary to prevent further damage to the roads in future rain events.
“We’re banking that this will give CalTrans the protection they need to get through the coming fall rain season,” said Berlin. “On challenging situations, such as steep slopes, a FGM is effective and will save CalTrans money over the long term.”
Berlin continued, “A FGM accommodated the time constraints of the application and provided workers with a medium that could be applied safely. Because it also provided erosion control effectiveness on saturated soils and compatibility with native vegetation, it was good match for this project.”
For more information, contact Sarah Willnerd, Swanson Russell Associates, 1222 P. Street, Lincoln, NE 68508 (402)437-6411, firstname.lastname@example.org.
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