Canyon Bridge Network Rebuilt After Slides

Few can forget the images of US Highway 101 buried under a 12-foot-deep pool of mud, trees, cars and pieces of houses from a massive mudslide that roared down saturated Santa Barbara County hillsides in January 2018.

As devastating as that extreme weather event was to the primary corridor through the area, even greater damage was inflicted on smaller, parallel route. A swath of destruction named the Montecito Debris Flow overwhelmed six Caltrans-maintained bridges along a seven-mile stretch of State Route 192, an east/west corridor extending from Santa Barbara to Carpinteria. The effort to restore this route to its prior condition would take almost two years.

The methodical rebuilding of the bridge system in the coastal mountains followed the 12-day closure and cleanup of US 101 after the mudslide struck. Following torrential rains, tons of mud and debris rushed down from the mountains that had been stripped of vegetation by the Thomas Fire just one month earlier. That wildfire was the third largest in modern California history.

The path of destruction was deadly and destructive. The Montecito Debris Flow took the lives of 23 persons, injured 167, and damaged 400 homes. The 12-day closure of US 101 and subsequent cleanup efforts were documented extensively by local and national media, and Caltrans’ response drew Twitter praise from local resident Oprah Winfrey.

After that effort, Caltrans turned its attention to the enormous task of planning to rebuild or repair the bridges. This process began with a methodical look at how to approach each of these six structures.

The project team, which included design and geotechnical engineers as well as Caltrans staff representing structural designers, management, stormwater, and maintenance divisions, was able to quickly develop a schedule for demolition and construction for these six bridges. Caltrans design engineers were able to produce bridge plans in a matter of weeks.

The Montecito Creek Bridge was heavily damaged. The rebuilding effort including an extensive removal and relocation of adjacent utilities before the new bridge could be reconstructed. A major high-pressure gas line that ran parallel to the bridge was damaged, putting services to the community at risk.

The gas line was adjacent to bridges at Montecito Creek and the farthest eastern bridge, Arroyo Paredon. Bridge repairs could not be worked on simultaneously at both locations without cutting off gas service to area residents.

Caltrans remained sensitive to the devastated Montecito community, and established a goal of maintaining utility service for neighbors struggling to put the pieces back together. The Department and utility companies worked to maintain gas service to the public by beginning the rebuilding effort at the Arroyo Paredon Bridge, because fewer utility complications allowed construction to begin sooner.

The Arroyo Paredon Bridge was completed and reopened in May 2019, with Lash Construction of Santa Barbara serving as the primary contractor. Although the estimated cost to rebuild the bridge was $10 million, all work was completed for slightly more than $4 million, representing a substantial savings under the emergency contract.

The construction of the Montecito Creek Bridge was more complicated due to the multiple utilities connected to the bridge. Before construction of the new bridge could begin, utility lines had to be removed and temporary lines installed away from the structure. A heavy rainy season also delayed construction and ongoing utility work.

When dry weather returned, the Caltrans-led construction team was able to make steady progress. The Montecito Creek Bridge reopened to the public with a celebratory ribbon-cutting in November 2019.

The Romero Canyon Bridge and the Toro Canyon Bridges were completed in January 2019, followed by the opening of the San Ysidro Creek Bridge in April 2019. The Toro Creek Bridge project was finished in February 2020. The contractor for the five remaining bridges was Security Paving of Sylmar, at a cost of $20 million.

“The Caltrans District 5 team was challenged by Mother Nature, first with a major fire, followed by the flooding of US 101 and the destruction to six bridges along State Route 192,” said Caltrans District 5 Director Tim Gubbins. “I am proud of the sustained effort by our staff and how they were able to meet this extraordinary challenge over the last two years. We are pleased that the full opening of Highway 192 helps with the healing for the community of Montecito.”

Source: Jim Shivers, Public Information Officer, Caltrans District 5