Slip sliding away: the landslides of Palos Verdes
On the Palos Verdes peninsula, engineers try to hold back the forces of nature as the ground shifts beneath their feet
In the rainy early morning hours of Nov. 20, Palos Verdes residents received a menacing reminder that they live on a bed of geologic activity far beyond their control.
A 600-foot section of Paseo Del Mar in San Pedro below the White Point Nature Preserve suddenly dropped down the cliffside. It was the most damaging landslide on the Peninsula since the 17th and 18th holes fell to the beach in 1999 from what’s now Trump National Golf Club.
This month a consultant firm hired by the City of Los Angeles to analyze the causes of the slide cited an unknown source of groundwater as a main culprit. Excess water, together with a general slope of the land toward the sea, the makeup of the ground and coastal erosion, led to the failure, according to a report by the geotechnical and environmental consulting firm Shannon & Wilson Inc.
Little has been done to repair the estimated $62 million in damage done by the landslide.
“All government is in a hurt because of tax revenue,” said Richard Havenick, leader of an ad hoc landslide committee as part of the San Pedro Neighborhood Council. “It’s a terrible situation. If you have enough money you can spend it on shoring up the bluff.”
Geologists after the event placed sensors into nine shafts they bored into the ground. From the sensors they detected no significant movement since the slide. Yet because of the increased accumulation of groundwater that’s still unknown, the firm ruled the cliff only “marginally stable.”
The closest houses, while just a few hundred feet away, are said to be safe though efforts are still needed to shore up the 120-foot cliff. For now the city is struggling to come up with $7 million needed for what engineers deem “immediate improvements” to remove groundwater, install drains and stabilize the earth.
Last week the Army Corps of Engineers told Los Angeles city officials they would not be able to help fund rebuilding the road. Coastal erosion would need to be more of a contributing factor, said Vince Jones, Los Angeles deputy city engineer.
“We’re continuing to study the sources of irrigation,” Jones told a gathering of the San Pedro Neighborhood Council last week. “We are still not sure exactly how much water irrigation caused this problem.”
Many in the local community are upset at the slow pace of the cleanup and reconstruction of the popular cliffside thoroughfare. Claudia Kreis, who lives nearby, said dealing with land movement just goes with living on the Peninsula.
“We all have lots of cracks and things like that,” Kreis said. “We’ve chosen to live here and I think it’s one of the issues you don’t think about when you move here, but there is land movement.”
The White Point landslide represents only the most recent high profile slide on the hill. The continual shifting of the earth on the Peninsula through processes that began millions of years ago set the stage for today’s efforts against Mother Nature.
It costs taxpayers millions of dollars to keep landslides at bay. Like the flood levies that hold back the Mississippi River, engineers in Palos Verdes have employed various techniques like the ones planned at White Point to restrain the ground. Occasionally they aren’t so lucky. And when it’s deemed possibly someone’s fault, conflicts often ensue.
This is a story in essence that began 15 million years ago as the Earth entered a period of great volcanic activity. Over the next six million years, massive eruptions occurred over much of the earth’s surface. Where ash fell into the ocean it settled to the sea floor and formed layers.
Under pressure and other sediment those layers turned into clay called bentonite. And as the ocean receded and the continent shifted, the seafloor became the land where the bentonite clays now exist between layers of sedimentary rock that make up the California coast.
In areas such as Palos Verdes where the layers are dipping toward the ocean, these bentonite clays are like the icing of a wedding cake getting chipped away from beneath.
In the case of the White Point landslide, unusual amounts of groundwater saturated the bentonite layers, which together with coastal erosion and gravity caused the slide. It’s the bentonite clay that acts as the “slip plane” for almost every major landslide that occurs on the Peninsula, said Bob Douglas, professor emeritus of geology at USC.
“Along the cliff you often see this whole gradation, which is mostly clay with some volcanic ash,” Douglas said. “The PV peninsula is just a large chunk of the earth’s crust that’s been moved around. It was probably located much further south than it is now.”
Douglas has the fortune – or misfortune, as he puts it – of being a geologist living in Portuguese Bend, the most landslide-prone area on the Peninsula. Landslides here date back to prehistoric times. A series of de-watering wells removes an estimated 300 gallons of groundwater daily and sends it into the ocean to prevent further sliding. One of the wells needs to be replaced because land movement actually severed the hole.
Gordon Leon, a member of the Rancho Palos Verdes planning commission and a resident in the 92-home Portuguese Bend Community Association, said residents are fairly accustomed to dealing with land movement and the potential for slides.
“Our roof isn’t completely straight,” Leon said, pointing to a dip in the shingles. “I’ve got stress cracks in different areas of the house. It’s just something that we deal with. Most people here have the expertise to check.”
Due to past landslides, Portuguese Bend for decades was subject to a building moratorium which prevented development on 16 lots. A court decision about five years ago overturned the moratorium and this year construction began on the first homes located on the hill above the existing residences.
The case boiled down to a difference of geological opinion. The city of Rancho Palos Verdes said it wasn’t safe. The homeowners said it was. And the homeowners won. Jim York, who tried to develop on an adjacent lot subject to the past moratorium, said he’s spent millions of dollars on geology studies also to prove the city wrong.
The City of Rancho Palos Verdes remains in constant battle of its own to repair the cracks and the sharp dips on the nearby section of Palos Verdes Drive South. Entire sections of the road must be rebuilt every three months. This year repairs will cost an estimated $500,000. Carolyn Lehr, RPV city manager, said the city constantly monitors geologic activity.
“Every locale has its own unique phenomenon,” Lehr said. “We’re always monitoring any changes in our geologic areas so that we can be responsive with projects that will help to minimize those impacts. It’s one of the unique aspects of our city.”
City engineers are also working to shore up another section of the road further east called the Terapaca landslide about two miles from the San Pedro border. A fix is estimated at $19 million but so far the city has received state grant funding for just $9 million, said RPV Mayor Anthony Misetich.
“We have a shelf-ready plan, we just need to get the rest of the money to fix it so it won’t undermine our roadway,” Misetich said.
Lawsuits and foreclosure
Landslides have wreaked havoc throughout Palos Verdes over the years. In 1999, the 17th and 18th holes of what was then Ocean Trails Golf Club fell into the sea in a slide that would eventually contribute to the course being sold in foreclosure to Donald Trump in what would become Trump National Golf Club. A landslide geologist reportedly stood on the 18th tee box watching his subject matter occur before his eyes.
In Palos Verdes Estates, city officials worked for decades to resolve litigation arising from landslides. In 1981, a landslide caused by a sewer main leak that occurred over several years destabilized ten properties along the cliffside. Settlements resulted in the city owning the homes. Some were demolished. Others were left vacant, while the city manager and police chief now occupy the rest.
At this point the expense of maintaining the properties might not be worth it, said Christi Hogin, an attorney handling the cases for the city.
“The city has made a sound choice by finding this particular use,” Hogin said. “But even this use can’t be necessarily sustained forever, given that there has been some movement.”
Allan Rigg, PVE public works director, said city planners purposefully chose not to put approve homes in landslide-prone areas like the cliffsides of Lunada Bay and Christmas Cove.
“We have a lot of rocky bluffs which you really don’t have landslides on, which is where the majority of our bluff homes are located,” Rigg said.
The city, of course, would not be liable if a home was damaged from a slide that occurs naturally.
“There are some things that are acts of God and not the city,” Hogin said. “We’re not responsible for every bad thing that happens.”
Water drainage is essential to minimize the chances of a slide, said Stephen Jacobs, a geology consultant.
“You’ve got the slope condition where bedding dips out,” he said. “You also have slopes where bedding of the underlying strata is not necessarily relevant. You have soils that underlie the slope – when they get wet they expand, when they are dry they contract. These have a tendency to creep down the slope. The soil types really need to be kept under control with regard to drainage or moisture.”
Jeff Miller, president of the South Coast Geologic Society, works to inform the general public about the geology in their area and what to look out for as a home-owner.
“Our goal is to reach out to the public and make sure they understand what’s going on from a geologic perspective in Palos Verdes,” Miller said. “Landslides have been occurring in Palos Verdes for a long time before development, and landslides will continue to occur in Palos Verdes. The most important thing is to be as prepared as you can be. It doesn’t mean the whole place is going to slide away.”
For more information about possible landslides in your area visit the web site for the U.S. Geological Survey. ER