Photo courtesy of Caltrans
Construction crews from Flo Engineering are actively working to restore access to State Route 27 in Topanga Canyon after a massive mudslide caused a closure of the highway.
The many powerful atmospheric river storms that have struck California since February have taken their toll on several highways and state roads. This has led to major landslides and a small section of an outer lane collapsed along the edge of a cliff in the Big Sur.
The California Department of Transportation (Caltrans) is well aware of the impact of these storms, which are increasingly becoming the norm, as these slides are occurring on a more frequent basis. The DOT has been on top of these storms and its emergency teams are rapidly dispatched to various sites, where they are assisted by local emergency services to close roads and protect lives.
Photo courtesy of Caltrans
More recently, a massive landslide at postmile 1.8 on State Route 27 in Topanga Canyon occurred, closing the road in both directions. The closure will be a long one, due to concerns about more landslides at the same location. Should all things go well, Caltrans hopes to reopen the road in the fall after the debris is removed and infrastructure is constructed to prevent future landslides at the same location.
Caltrans is taking no risks, nor is Flo Engineering Inc., the general contractor hired by the DOT to complete the emergency repairs and debris removal.
"A major landslide occurred adjacent to the current landslide in the 1940s," said Jim Medina, a Caltrans public information officer of District 7 [Los Angeles and Ventura counties]. "It's unknown how long the roadway was closed at that time. The landslide that occurred March 9 is twice as large — the visible face is about 300 feet above the roadway, but extends about 200 feet beyond that point into the brush. Due to present geological conditions and instability of the slope, material must be removed from the top down. Removing the ‘toe' of the slope will bring down the unstable earth and large boulders above as water is still percolating under the surface.
"A boulder that is about 10 feet high that is visible from the south side of the landslide is a safety concern," he added. "A crack has formed behind it that is about 5 to 10 feet wide, with the weight of the hillside pushing down on the boulder. A rough estimate of the landslide — just the visible face — is about 80,000 cubic yards and 9.2 million pounds. This is enough material to fill 5,500 dump trucks."
Necessary Repairs
The pace of repair operations are moving rapidly. Flo Engineering completed a trail to the top of the hill with tree trimmers cutting a path through thick brush.
"Flags are posted in various spots that will be used to coordinate with drone images to map location," said Medina "The brush is too tall and thick to clearly see."
One day later, drones were surveying the slide area and a loader was cutting through a toe section of the slide on the roadway to collect dirt, mud and rocks that will be used to build a berm to protect a creek from falling slide material. The berm was requested by the California State Parks.
Photo courtesy of Caltrans
This is an important milestone in the repair and clearing effort.
"Clearing some of the roadway will make room for loaders, bulldozers and excavators to begin clearing the slide at an undetermined time," said Medina. "The slide is still active and potentially dangerous, with soil clearly muddy and saturated. Our team from Geotechnical Services will begin mapping the slide. This will help us refine our recommendations and our initial calculations."
Caltrans and Flo Engineering are leaving no stone unturned and paying close attention to every detail associated with the operation.
For example, there were initial glitches with the temporary signals installed at Tuna Canyon Road and PCH (SR 1), including a wiring issue.
"The contractor has hard-wired the connections in this temporary signal and it seems to be working fine," said Medina. "Timing was a second issue. The signal was set for Eastern Standard Time, so the peak period was off and that's why we had such a short green phase. The unit has been reset for Pacific Standard Time, so we should be able to get a lot more vehicles through, especially in the morning. On Tuesday, seven vehicles and a bicyclist from Tuna Canyon were able to get through the intersection on single light at midday. The PCH green was timed at about 1:17, with the green for Tuna Canyon timed at a little less than half that time."
Lessons learned from previous landslides and severe storms are helping Caltrans navigate through this season's emergency woes.
Fortunately, no one was injured or killed by the Topanga Canyon landslide.
Assessing Situation
An April Caltrans press release highlighted the seriousness of the situation.
"Water continues to seep out from underneath the dirt, mud and rocks, indicating the mass may move at a given moment," said Medina. "A rainstorm over this past weekend, April 13-14, further saturated the unstable hillside."
At this point, SR 27 is closed from Grand View Drive to SR 1 (PCH).
"Temporary signal lights have been installed at Tuna Canyon Road and State Route 1 [Pacific Coast Highway]," noted the press release. "The signal provides a measure of safety for Topanga Canyon residents who need to access southbound PCH while SR-27 is closed. Caltrans is working with the county and elected officials to mitigate impacts to the community."
Caltrans has provided alternative routes and reminds drivers to "Be Work Zone Alert" and to "Slow for the Cone Zone."
On April 20, Toks Omishakin, secretary of the California state transportation agency, was joined by State Assembly member Jacqui Irwin and Los Angeles County Supervisor Lindsey Horvath at the Topanga Canyon landslide site to provide an update on work, commencing on a trail to the top of hill.
"The path will allow a Caltrans geologist to make a thorough assessment from atop the steep slope," noted the press release, which pointed out that several Caltrans representatives accompanied Toks, including Geologist Matthey Gaffney.
Photo courtesy of Caltrans
Medina, who has been in the thick of Caltrans' ongoing response to the landslide, responded to some questions about the actions the DOT took from day one and the latest updates.
Asked how quickly Caltrans was able to respond to the the disaster, Medina replied, "It was immediate. The slide occurred overnight on March 9 and the roadway was closed the next morning, when assessments began. A similar slide occurred adjacent to this slide in the 1940s. This landslide is twice as large and involves a very steep hillside."
There are concerns about other sections of road.
"But ‘[they are] not as bad," said Medina "Maintenance has taken advantage of the road closure by clearing boulders, rocks and debris along SR 27 further south of postmile 1.8, as well as clearing roadside brush in anticipation of fire season in September."
Caltrans has been dealing with several major landslides tin the past few months, and the state is ensuring it has the necessary resources required to handle each incident.
"Governor Gavin Newsom proclaimed a state of emergency [May 3] to help fund badly needed repairs of roads battered during this year's storms, including scenic Topanga Canyon Boulevard that was blocked by millions of pounds of debris," said Medina. "The governor's action comes two weeks after Caltrans officials said the massive, 300-foot-tall landslide that covered Topanga Canyon Boulevard in March with mud and rocks would not be cleared until fall, ‘if all things go well.' The proclamation enables Caltrans to request funding from the Federal Highway Administration's Emergency Relief Program, which could cover up to 100 percent of the repairs, according to the governor's office."
Flo Engineering was hired three weeks after the Topanga Canyon landslide.
The general contractor, which has crews and equipment on-site, is hard at work, ensuring that its people and DOT officials are safe at all times.
"Caltrans and the contractor are in constant contact, with regular site visits," said Medina.
The large mound of material on the road is a stunning and jaring sight.
"The boulders, dirt and mud are intimidating," said Medina, a veteran of many landslides. "Mother Nature can be a beast."
Flo Engineering teams are hard at and due to the complexity of the work, were unavailable for comment as of press time.
Due to the dangerous situation, Caltrans strongly urges pedestrians and bicyclists to avoid the work zone because a heavy-duty loader is moving boulders, dirt and mud. Progress will be slowed or delayed if people enter the work zone. CEG
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