Abstract:
DFI - S3 Conference 2026
Abstract
The Rancho Palos Verdes Landslide
By Randy Conrad, Malcolm Drilling Company Inc.
After unusually large amounts of rain in 2023 & 2024, the Portuguese Bend landslide in Rancho Palos Verdes, California accelerated its movement by a factor of 4 to 5 compared to prior years. The effected landslide area grew from 380 acres to 675 acres and damaged several residential properties.
This presentation highlights the efforts undertaken to slow down the currently largest and fastest moving landslide in the US. Initial investigation of the sliding mass started by investigating borings using sonic coring for up to 340 feet depth to collect continuous samples as well as the installation of many vibrating wire piezometers and shape array inclinometers to understand the various potential sliding planes.
Final mitigation measures included several dewatering, and depressurization wells up to 200 feet deep. This combined effort resulted in significant reduction in the rate of movement.