Experimental helicopter water drops at Regents Slide were scheduled but ended up being during recent rains, which appears to have done something. The upper, dirt portion of the slide is moving on its own every day. I think some tens of thousands of yards came off over the weekend.
Here’s a recent summary I sent to my institution a month ago.
Caltrans geotech has heavily-instrumented the upper portion of the slide due to its continuous movement. The movement has made it very hazardous to remove so equipment has been put on and pulled off the working bench repeatedly over the past few months. The attached photo shows the upper slide as of February 3rd, circumscribed in orange dashed lines. The original slide is on the back (south) side of a rocky, resistant ridge and well below this upper area. Debris from that rockslide can be seen 500 feet down on the highway on the right side of the photo.
The plan has been to start above the rockslide section and cut it out using a working bench. The cut material gets pushed over the edge, gradually working downhill back to the highway. The upper slide section was destabilized by that process and started “rotating”, slipping downhill and outward, pushing over the resistant rocky ridge below. The arrows in the photo are my attempt to depict that rotation. The weight of the upper area to the left is causing the material to slide downhill but it is encountering the resistant material below. That is causing it to actually move horizontally and outwards to the right and to push out into the air, calving off like a glacier reaching the ocean or a lake. You can see there are two new slide sections at the horizontal arrows where the dirt is flaking off and falling down to the highway.
Excavation is on hold while it rains. There is a presumption that as the soil gets heavier with water, the material will accelerate (not catastrophically fail) and reveal exactly where the slip plane is behind the slide. That will allow them to have a better defined plan moving forward. You can see their graded slope in the upper left of the photo. They need to keep that slope behind the slip plane as they work their way down to the right.
Changes over the last month involve more dirt being pushed off the bench onto the slide (head) and the lower right (toe) calving off down to the highway. Also see attached two photos I took during the rain last week. Beneath the remaining vegetation there are fissures criss-crossing the moving section. It acts like a glacier, slipping off the top of the lower part of the larger slope, calving off the mountainside about 400′ above the highway. Impossible to put equipment on it when it’s wet. They monitor it daily and pull off when it accelerates and jump back on when it slows down.
That’s the latest from ground zero,
Mark
Here are the photos Mark references:
March 12, 2025 by Mark Readdie
March 14, 2025 by Mark Readdie
And from yesterday, March 18, which shows the recent drop:
Something I forgot to mention probably because I recycled a month old update. In addition to the two excavators and two other dozers, there are an additional two D8 dozers that have been retrofitted to wireless operation because Caltrans is pushing Papich to keep pushing dirt over the slip-plane crack but having an operator in the machines is too dangerous. The scale and complexity of this slide has pushed Caltrans into new technological territory in order to keep making progress. Perhaps a photo of all the equipment working on the slide would provide some scale. I’ll have to see if I can get that this week.
Maybe the top down approach isn’t going to work. Just a thought. Afte 2 years of failure, it seems a new approach should be taken.
My intention here is to provide a factual update so folks can have as much information as possible to set their plans and expectations. I appreciate what we are all going through for the last year in all the various ways. Hopefully a bit more info from the site can be helpful to you. -Mark
My guess is that the natural slope is fairly close to 1:1 (1 1/4:1?). Mark, what is the natural angle of repose range for the relevant materials, both natural and unconsolidated/fill under the range of conditions expected (including seismic activity)? Are any arrangements for subsurface drainage being done or planned? What kind?
Thanks for this Mark. I’m glad to hear some equipment is moving dirt. I’ve been picturing shipping containers set up to protect excavators at highway level working from both sides. Some material could be removed and trucked away. I’d love to see some drone footage!
avalanche technique. Dynamite the slide. Haul the dirt away. Pave the road.
This road is cursed. Build a byway around it. Rebuild the coast ridge road.
These are temporary fixes.
Nature bats last…
I tend to agree with Tierra. What is the cost per vehicle count to maintain this road? How does it compare with other highways in this respect?
Have they ever considered using explosives?
call trans is a virtual back hole leading to no where. AI (artificial Intel) would likely offer much more in solutions. It would be programmed to combine all previous landslide/rebuilds into a scenario most closely representing this one.
Internationally, there is likely a history of rebuilds similar to Sur’s..in that archive there a chance of finding a scenario closely resembling ..What’s my guess for a perfect fix? Begin at the bottom..grade, in a curved shape, tier it so the slope itself will offer enduring supportive strength..it will require drainage, more rebar then our minds can imagine, and concrete out the ying-yang.. That’s only one half, for the upper reaches far above the lower road, will need to be stabilized just as aggressively. Perhaps with a design as Esalen used to stabilize the slope rising steeply above the bathhouse.
What Im imagining is entirely an uneducated approach..just reaching a little ways into my dream state.
I think it’s worth noting that this rotating, constantly moving upper slide is hanging 700 feet above the ocean, being held up by a series of rocky cliffs whose stability is unknown. Papich and their operators are on that upper bench, pushing dirt to the brink of the slip plane (and over it) under the spectre of Mud Creek’s catastrophic failure. Caltrans’s geotechnical engineer is doing the science trying to understand whether this is a creepy-crawly situation or a catastrophe waiting to happen, taking the operators lives and safety into his hands so that Caltrans can decide to keep working on the slide through the winter and the “landslide season”. I’ve been living with these operators for the past year, seeing and hearing the concern and anxiety they are managing every day they’re told to get in the tractor. To respond to the pressure to keep pushing dirt for everyone else’s sake, this is the most instrumented slide Caltrans has ever had. They can monitor how much it moves every day and make calculated predictions to inform when it’s “safe” or not to put heavy equipment on it.
At the same time, a team of landslide scientists now have funding to focus on better understanding this very situation, and to inform engineers throughout California on how to address the coastal highways, housing, etc. while increased rain intensity washes away the coastal mountains and bluffs and the ocean eats away at their foundations. I introduced UCSC professor Noah Finnegan to the Caltrans geotech and they will be working together with a direct link between the research results and engineering decisions for the future.
See link to article here:
https://news.ucsc.edu/2024/10/landslide-earthquake-prediction.html
Everyone is absolutely aware that right now nature has a home-run slugger up to bat and the engineering solutions for keeping these coastal highways open needs to level-up.
Thankfully the state will soon be cut off from federal funding due to the harboring of the illegals. Then we can stop dumping money we simply don’t have on a state or country level into a cursed highway that serves so few and has basically destroyed the community.
Thanks so much, Mark! Trying to MAKE something “feasible” that isn’t is a tough spot to be on. My father was a ‘dozer operator on the Ojai highway in the thirties, and having had a family narrowly escape an accident. Maybe that’s part of why I’m most concerned about the people who have to work in such a place. Killing people for political purposes by order, from a distance, people one doesn’t even know, may be the worst kind . . . Being their supervisor is VERY tough . . . Is it worth it to take the gamble? No “reward” is great enough in my book, although I’ve been in those shoes in the past.
When the competency of the rock is in doubt no amount of human competency is enough to overcome the reality of the infinite and changing factors that are so impossible for the human mind to juggle.
I suspect that the “ridge road” idea might be reasonable–I JUST DON’T KNOW! But I suspect that putting the road there in the first place under such conditions was a mistake.
Walter Trotter would have had highway cleared in a week with some dynamite and his dozer back in the day. No Coastal Commission back then to make stupid regulations and public access conditions to slow everything down. Dirt from slides have ended up in ocean here for millions of years but now has to be hauled away by giant trucks polluting the planet. Duh!!!
Unfortunately Regents Slide comes on the back of Paul’s Slide, which unnecessarliy kept the locals & public from transversing it when it was good and ready to do so, many months prior to when it opened to the public to now get to Lucia, which was now burned down (but still has cabins)! Cal Trans head person has lost credibility in my mind but I do understand how Regents is a different situation @ this time.
On another note, I hope CT has decided not to go ahead with the improvements @ Mud Creek (south of Gorda) to cause yet another disruption on the south coast for how damn long?
Thank you, Mark, for this informative explanation and update, and to Kate for posting it here. I 100% support the decision to prioritize the safety of the people working on this project. I know it is an enormous task to figure out how to make a more permanent solution to these increasingly common slides on the coast. Thank you to all involved for your expertise, determination, and caution in getting it done right.
A boy asked his doctor how to ask his girlfriend to marry him. “I’m afraid I’ll do it wrong,” said the boy.
“There ain’t no WRONG way,” said the doctor.
Change “doctor” to “old engineer” and make the question “How do I build a safe road in a place like this safely (especially for construction crews)?” “There ain’t no RIGHT way,” said the old (honest) engineer.
I’m sure the engineers and geologists on site have thought of everything and more that the commenters have thought of. From me: godspeed guys and once you’re done, I will drive along it and gawk in awe at the awesome problem you have solved.
I’m happy to hear that remote-controlled heavy equipment is being used.
It appears to me that the most competent rock sticks up in places between past accumulations of scree deposits covered by coastal, mostly drought-deciduous vegetation, as can be seen moving slowly toward steeper topography at the “sweetest” spot for failure–increasingly steeper terrain in the absence of any buttressing effect other than the occasionally more competent material, where it moves laterally as gullies develop at the junction. Just how “competent” IS the formational material. Apparently, it, too, has failed in the past, depositing large chunks of the most competent stuff as big boulders that separated (cracked) from the most competent stuff.
As one can see at the horizon, there appear to be some fairly large, almost level places. Would coring at those locations reveal highly competent formation (more so than the surrounding geophysical features) that might give insight into the type(s) of formations that might hold up better than designing a touist-type highway for “freeway” speeds? Organic engineering? Follow the best-suited formations rather than build highways on structural fills that are bound to fail “someday?”