Massive Rancho Palos Verdes Landslide in California

hi everyone today I'm going to cover the massive landslide in the area of Rancho Palace Verdes California this is in Southern California according to the mayor of this city it's the largest active Landslide currently ongoing in the United States in the continental US that is and it's it's just massive now stories like these fascinate me if you're new to the channel I'm an engineer I'm licensed as both a professional geologist and a professional engineer in several States so these stories are extremely interesting to me so I'm going to break down what's going on what are the root causes and what's going to be done to perhaps remediate this situation although I think they've got their work cut out for them here the other thing I want to cover is just the societal aspect from a governing standpoint when is it reasonable to keep pouring money into something that appears essentially as unsustainable so I'll cover that as well now let's start with this evacuation area that was put out by City officials this was as of August 31st 2024 it's a large area it encompasses approximately 450 to 500 homes so let's look at this geological map so here's where we're located this area here that's in Gray it's it's classified as quaternary Landslide deposits so material that's moved in the last 10,000 years so just to give you an idea of where we are in Southern California here's a Google map and then here's a Google Earth image we'll zoom out just give you a perspective where this is basically west of Long Beach and you see from this footage there's been significant movement in fact this Landslide overall is moving at a rate of 3 to four feet a month or 50 ft a year which is astounding you can see this individual's driveway is about 10 ft above the roadway now maybe 20 ft actually you see these scarps these large cracks forming quite a large area essentially a mile long and a mile wide now this map shows the rate of movement the green is where the movement slowed down and that is the shallower landslide material and the material shown here in red is the deeper Landslide material it's part of an ancient landslide that up until now hadn't been moving so it's recently been reactivated there's also areas where the landslide toe is pushed out into the sea approximately 500t although they are getting ready to do underwater measurements to determine exactly how far that toe extends from the shoreline so you can see this material here for reference this point of land here is called Inspiration Point and you see the debris from the the toe of the landslide moving out offshore so back in 2017 the city officials initiated some remediation work they refer to these as hydrog it's the insulation of two horizontally drilled dewatering Wells to extract water underground in the Portuguese B Landslide now the Portuguese bin Landslide is a smaller Landslide area as part of this overall alamira slide complex the ancient Landslide so they decided they needed more borings to determine where they should best put these horizontal drains because it was a buildup of water groundwater that was creating excess po water pressures that was the initi for these slides and in fact it's what's causing them to perpetuate and what they found was the area that they were getting ready to remediate the upper slide was at a depth of 165 ft but this much deeper more ancient slide is at a depth of 330 ft so from my research this Landslide movement at least the upper one goes back to 1956 When government officials were doing roadway work along krenshaw the extension of krenshaw and uh just from what I gather they probably cut the toe off a portion of the slope and once you do that and get movement it can go on for for a very very long time and then once these cracks open up they're prone to filling with water from from rainfall or other water leaks in the area as particularly if uh utilities are ruptured and it just further propels the movement of the slope now the these horizontal drains that they were planning to put in cost about $5 million each and to put that in perspective the overall City budget's about 35 million a year here's a closeup of this Landslide cross-section so they realize they need to do more borings they're planning to do a different type of remediation and that is through basically dewatering Wells vertical Wells so they want to do these additional nine borings to make sure that they're adequately characterizing where the high po water pressures are located so make sure they go deep enough for these relief Wells and they're studying this here over about the next month they're trying to decide should they use smaller casing they're cheaper to install and when they Shear off from continued movement they could essentially redrill or ream that smaller casing out or should they go in with more expensive larger diameter casing and then once you do that you may be maxed out on the size that you could use to enlarge such a well so kind of a oneandone scenario and then if once it shears off you have to replace it all together so they're conducting this subsurface investigation as we speak and this isn't really happening quick enough for the homeowners and I feel for them you know it's uh it's a sad situation you know a number of these people have had their electrical power cut off they've had their gas cut off I think uh upwards of people have had their gas cut off and now around 200 people have had their power cut off it's uh uncertain right now how long those outages will continue the electricity has been turned off for fear of a spark causing a wildfire so presumably once they're out of the fire season then perhaps some of these people can get their power restored but that's uh really up in the air at this point you can see they have some above ground utilities I believe these are sewer lines and they've had leaks of these due to slope movement and rupture in one recent incident there was 10,000 gallons of raw sewage that Spilled Out quite quite the mess so let's look at some of these areas right now that are currently impacted you see this this road section here this is right in the middle of the most rapidly accelerating portion of the slide which is a deeper seated slide at a depth of 330 ft now on August 20th 2024 the city of Rancho Palace veres had a city council meeting and uh they discussed the technical aspects of what was going on what they plan to do and then they had residents speaking up about their concerns and questions about what's going on so interestingly the mayor of this city is an engineer and you don't typically see government officials having engineering backgrounds so it's appropriate here for him because he can relate to these technical aspects and communicate them uh clearly to people people who are affected by what's going on another thing that was of interest is he took some real shots at the the governor of California Nome for essentially not bothering to look into what's going on with the situation and he also the mayor commented that even the state geologist hasn't been to this city to see what's going on with this Landslide and I thought wow is this a a republican stronghold that uh I didn't know about in Southern California so I brought up this map it's it's all blue as you might expect you know most of California's blue at least the coastal areas in the southern tip of California so I think the mayor is just extremely frustrated this is a technical issue that can be addressed through gathering information performing an evaluation but most importantly they need Government funding at least that's what they're asking for to remedy this situation so again they're talking about these emergency installations of these hor Al drains in two different arrays then they're going to go onto these uh vertical Wells here pretty soon probably within the next month month and a half now what was mentioned at the city council meeting was that they're going to extend their moratorium on new construction in this Landslide area and I'm like that hasn't happened a long time ago that's that's kind of shocking so they're looking to extend it another 12 months months which only seems prudent so to give you an idea the average house price in this Rancho Palace veres area is $1.9 million so one of the things I was wondering about is whether insurance would cover these losses you know there's already people who have had to leave their home and in all likelihood won't be able to come back and it turns out I'll just read this from a search that I did and the question was is home and business insurance coverage for landslides the same as for mud flow and in essence neither one is covered under a typical policy a landslide is considered an earth movement event so like an earthquake it is excluded from the standard homeowners and business insurance policies however you can buy what's known as a difference in conditions policy which typically offers all-in-one coverage for landslides mud flows earthquakes and floods so how many of these 450 to 500 homeowners do you think had this extra insurance I would bet very few of them do but it also brings up a question why are lenders loaning money for people to buy houses in this area now I understand a lot of these houses were bought back in the 1960s and people have lived there since then and perhaps was unaware that at least geologically speaking their subdivision was right on top of a landslide I mean it's it's map like that on the geologic map now there are situations where people will consider those slides to be dormant and find out later they're not it's sort of like living next to a volcano take the people of Seattle living near Mount reneer is uh Mount reneer dormant it is for now but it won't be in perpetuity so this got me thinking you know the city officials have applied for funding to FEMA they're looking for various flows of federal funding to remedy this situation and you know aside from apparently government officials triggering this slide back in the 1950s they've been involved with various remediation efforts they've been involved with gring they've been involved with granting permits for people to build and and live in homes here so at what point do people say this just isn't sustainable we can't keep pouring hundreds of millions if not billions of dollars into a situation that isn't going to last very long and that reminds me of the situation with Hurricane Katrina and the resultant flooding back in 2005 in the City of New Orleans I mean it was a massive disaster and you can see that at the time of Katrina the population of New Orleans the City of New Orleans was around 450,000 and then that dropped to just above 200,000 after all the evacuations and it's slowly climbed and now's decreasing again but it's around 350,000 people right now so I remember at the time some people were discussing you know does it make sense for the federal government in particular to be spending billions of dollars to rebuild levies to put in other flood control measures uh to protect a city that's essentially 10 feet below sea level and the few voices that brought that concern up were quickly shouted down and accused of uh nasty motivations but I think it was a fair policy point I mean how sustainable is living in a city near the coast of the United States that's 10t below sea level and we've seen already that the flood control measures because of political pressures um money saving measures you name it failed miserably in 2005 so it was interesting to me at this city council meeting that you had affected homeowners deeply troubled by being put out of their house not knowing when they could go back I mean I I feel for these people and then you have other interest groups there's individual who spoke up about the road closure to two wheel Vehicles so they closed about a two mile stretch of roadway in the city because of cracking and and other distress of the roadway and this individual although very respectfully just said hey you know we don't really think it's right that you just close the road to essentially motorcycles and bicycles which is kind of interesting because you know I've covered the Teton Pass Landslide and that Landslide came to people's attention because a motorcyclist crashed on a large crack that opened up in the roadway so I think time is against these people in this area of California in terms of being able to stabilize this slope we're approaching the rainy season it's going to be highly likely that new rainfall this fall and winter is going to infiltrate these these scarps these open cracks that have opened up on this hillsides that subject to this Landslide and just further accelerate movement so I just don't see how they they've got the time to implement any remediation measures before they're going to be fighting the weather here so let me know what you think in the comments section I want to send a shout out to the channel members I really appreciate your ongoing Support also I'd like to send a shout out to those of you who provided super thans I'm going to roll credits for both at the end of this video I'm working on a lot of interesting stories and follow-ups on previous stories that done so please stay tuned for future videos [Music]