Palos Verdes LANDSLIDE UPDATE, JULY 9, 2024
PVP Watch and the City of Rancho Palos Verdes (RPV) are very concerned about the recent increase in land movement around Portuguese Bend and its adverse impacts along Palos Verdes Drive South (PVDS) and surrounding neighborhoods.
Accelerated movement in the Portuguese Bend Landslide complex has expanded to more than 680 acres as reported at the July 2 City Council meeting and is impacting homes and infrastructure. Two homes have been red-tagged so far. Streets and utilities (gas, water, electric, sewer, storm drains, etc.) were also affected. Around 8 miles of public trails were closed. The historic Wayfarers Chapel was disassembled.
Where are the slides?
The Ancient Portuguese Bend Landslide Complex was formed over 120,000 years ago and occupies 1,100 acres. It is made up of five separate slides, four of which are in Rancho Palos Verdes and one in the City of Rolling Hills:
Abalone Cove Landslide (AC)
Portuguese Bend Landslide (PB) including Ancient (AnPB) and Active (AcPB)
Flying Triangle (FT)
Klondike Canyon Landslide (KC)
Beach Club Landslide (BC)
Portuguese Bend landslide complex.
Long-time residents are probably familiar with the gradual land movement near the Portuguese Band in past decades.
How much is the land moving?
PRV consultant reported that GPS data showed unprecedented increases in movements in the Landslide Complex since October 2022. Recent land movement rates are approximately:
7-11 inches per week in the Abalone Cove Landslide,
9-12 inches per week in the Portuguese Bend Landslide, and
2-7 inches per week in the Klondike Canyon Landslide.
The middle of the landslide complex is moving the fastest, at over 13 inches per week.
These movements are much higher than those recorded in the past.
probable cause of the increased movements.
The RPV Geologist reported that 2022-23 rainfall was 193% of average. 2024 continues to be wetter than average with 23.19 inches, 170% of average. The resulting moisture likely caused the unprecedented increase in land movements.
Damages caused by the land movements.
These movements manifest at the ground surface as scarps, fissures, sinkholes, cracks, shears, and thrusts. The total area of the active Landslide Complex has expanded by approximately five acres.
Palos Verdes Drive South in the Portuguese Bend area. PVP Watch photo.
The Abalone Cove Landslide area has expanded approximately 180 feet farther west at Narcissa Drive and on the York property at 6001 PV Drive South (PVDS), quickly deforming the Narcissa Drive curve and is the same movement that caused major bulging of the parking lot at the Wayfarer’s Chapel property.
Wayfarer’s Chapel parking lot. PVP Watch photo
The Portuguese Beach Club experienced deformation along Seawall Road and 4 to 5 feet bulging across the beach. The seafloor has lifted above the sea level.
Portuguese Beach Club. PVP Watch photo.
Portuguese Point is being overridden by the landslide, resulting in failure of the historical rock wall along the Olmsted Trail and loss of beach access to Abalone Cove via Olmsted Trail.
Photos courtesy of the City of RPV.
Miles of hiking trails have been closed.
Photos courtesy of the City of RPV.
PVDS – The road has cracked and become very uneven. The “ski jump” is worsening.
The “ski jump”, Palos Verdes Drive South in the Portuguese Bend area. PVP Watch photo.
Seaview Neighborhood – Two homes have been red-tagged. Water and sewage lines had to be installed above ground to avoid breakage.
Seaview neighborhood, RPV. PVP Watch photo.
Red-tagged home in the Seaview neighborhood, RPV. PVP Watch photo.
Seaview neighborhood, RPV. PVP Watch photo.
Seaview neighborhood, RPV. PVP Watch photo.
Los Angeles County Sanitation District crews are repairing a section of sewer line near the Seaview neighborhood damaged by land movement. The line is now above ground. As of now, there are no known sewage leaks.
RPV’s actions to reduce the land Movements.
PRV has initiated an Emergency Hydraugers Project involving the installation of two horizontally drilled hydraugers (dewatering wells) that will extract water below the ground in the Portuguese Bend Landslide complex to slow the land movement. The cost of the project is estimated to be approximately $10 million. RPV is funding this project through the Capital Improvement Fund. The city is actively pursuing reimbursement through federal disaster recovery funds made available when President Biden declared a federal disaster for several California counties, including Los Angeles County, in response to the winter storms between January 31 and February 9, 2024.
Illustration courtesy of the City of RPV.
One hydrauger will likely be installed near Burma Road to intercept water at higher elevations. The other well will be on the south end, at the toe of the landslide, and will relieve artesian pressure that forces groundwater to the surface without pumping.
Three test boreholes are drilled to determine the best locations for the two hydraugers.
Two more boreholes are planned but will require additional equipment. Hydraulic data is expected in six to eight weeks.
Location of the hydraugers will be decided based on the results of the test boreholes.
Photos courtesy of the City of RPV.
PVDS - RPV is developing plans to re-grade the area known as the “ski jump” near Altamira Canyon. Driving at the ski jump is becoming more difficult.
The “ski jump”, Palos Verdes Drive South in the Portuguese Bend area. PVP Watch photo.
Re-grading work is anticipated to occur this summer when traffic is lighter.
Costs to repair the slide section of PVDS have increased from $1M per year to an estimated $3.5M.
RPV recently approved restrictions on this portion of PVDS prohibiting bicycles, motorcycles, and other two-wheeled vehicles for safety reasons.
Wayfarer’s Chapel has been disassembled and stored for future re-assembly.
Wayfarer’s Chapel. PVP Watch photo.
Other efforts - Geologic Hazard Abatement District (GHAD).
GHADs are public agencies formed to provide a management structure and funding source to protect from landslides, erosion, liquefaction, and other geological hazards.
These GHADs are independent of the City. They levy assessments on property owners in their districts for landslide mitigation, including operating dewatering wells.
There are two (GHAD) within the Ancient Landslide Complex that were formed in 1981 and 1982. These are the Abalone Cove Landslide Abatement District (ACLAD) and Klondike Canyon Landslide Abatement District (KCLAD).
Abalone Cove Landslide Abatement District is outlined in pink.
Aerial photo copied from https://www.abalonecovelad.com/
Klondike Canyon Landslide Abatement District is outlined below.
Map from https://kclad.org/
Financial assistance loans to ACLAD and KCLAD.
Due to the severity of damages on properties within each of the two GHADs, the RPV City Council agreed to provide a financial assistance package which was approved at its July 2, 2024 meeting.
ACLAD received a $1.61 million loan and KCLAD received a $1.9 million loan. Both loans are at an interest rate of 2% for up to 12 years. Additionally, the City is offering in-kind services, such as geology, engineering, and project management to assist with the GHADs implementation of their respective projects.
The Assistance Packages are contingent on the GHADs’ landslide mitigation plans being endorsed by a licensed geotechnical engineering company.
We will update our readers on the mitigation actions by the two GHADs.
Summary
PVP Watch commends the City of RPV, its City Council, and its management and staff for their actions to minimize and mitigate the Portuguese Bent landslide and repair PVDS for the estimated 16,000 vehicles that travel on this road each day. These landslide problems will probably take a long time to resolve. PVP Watch will update our readers as we learn of new developments.
Stay informed.
For more information on the landside, readers are encouraged to visit the City of RPV website.
If you would to receive e-notifications on matters related to the landslide, subscribe to the City of RPV’s notifications.
This article is one in a series of articles that PVP Watch will continue to post to update our readers on the status of the landslides on the peninsula.
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Donations
We are a group of volunteers and donations keep PVP Watch alive. If you would like to help, please send us your check for $35 or more to PVP Watch, 5011 Rockvalley Road, Rancho Palos Verdes, CA 90275. Thank you.