The Slippery Slope of Litigating Geologic Hazards:
California's Portuguese Bend Landslide
PART 3:
DAMAGES, LITIGATION AND MITIGATION
Slide Effects on Structures
The effects of the landslide have been progressive, first causing damage and then destruction of homes and other structures. Many roads in the area are buckled and broken, requiring repeated repairs. By 1961, more than 150 homes had been destroyed or seriously damaged by the slide. Since then, many additional homes have been affected to some degree, and Palos Verdes Drive has been constant need of repair. All underground utilities have been placed in above ground steel pipes with flexible couplings.
Albers v. County of Los Angeles
Affected homeowners filed suit in 1961 against the County of Los Angeles in a successful effort to obtain compensation for their losses, which amounted to nearly $10 million in 1960 dollars. The suit charged the county with liability based on negligence for the construction of Crenshaw Boulevard, which added weight to the upper slopes of the slide mass in the form of artificial fill. Although negligence could not be established, the county was found liable by the presiding judge using inverse condemnation.
Arguments by experts for the county brought several facts to light that were ultimately ignored in the judgment. These included: (1) the amount of artificial fill used in constructing Crenshaw Boulevard equaled only 0.5 percent of the total landslide mass in terms of weight, (2) the water added through septic system discharge and lawn irrigation probably caused groundwater levels in the slide mass to rise, and (3) detergents in the septic system effluent would be expected to have a negative effect on the strength of saturated bentonite clays.
Corrective Actions
An early attempt to prevent further slope movement was made by installing precast concrete pins through the slide mass in 1957. These pins, measuring 1.2 m (4 ft) in diameter and 6 m (20 ft) in length, extended 3 m (10 ft) into the underlying bedrock. Initially they slowed the rate of slope movement by 50 percent; however, after five months, the pins failed and movement accelerated.
The first of a three-phase stabilization project involved the installation of eight dewatering wells in the slide mass during the mid-1980s. Phase 2, completed during the late 1980s, included road relocations, surface drainage improvements, regrading the seaward side of the slide mass, and the addition of five more wells. In the early 1990s, revetments were placed at the base of the bluffs to protect them from wave erosion. Following the completion of this third phase, parts of the landslide was largely stabilized.
Questions for Part 3
- What information would be needed to evaluate the effect of septic system discharge and lawn irrigation on groundwater levels?
- How would the construction of Crenshaw Boulevard differ from the earlier construction of houses in terms of its ability to trigger a landslide?
-
What do the success of various corrective actions taken here suggest was (were) the cause(s) of the landslide?
REFERENCES
Ehlig, P.L., 1982, Mechanics of the Abalone Cove landslide, including the role of ground-water in landslide stability and a model for
development of large landslides in the Palos Verdes Hills; in Cooper, J.D. (compiler), Guidebook and Volume: Landslides and
Landslide Abatement, Palos Verdes Peninsula, Southern California; Assoc. of Engineering Geologists, Southern California
Section; Field trip number 10, p. 57-66.
Ehlig, P.L. 1987, The Portuguese Bend landslide stabilization project; American Assoc. of Petroleum Geologists Field Guide, Los
Angeles, p. 2-17-3-24.
James, L.B., and G.A. Kiersch, 1991, Failures of engineering works; in Kiersch, G.A., ed., The Heritage of Engineering
Geology; the First Hundred Years; Geol. Soc. of America Decade of North American Geology Project series, Centennial
Special Vol. 3, p.502-506.
Merriam, R., 1960, Portuguese Bend landslide, Palos Verde Hills, California; J. of Geology, v. 68, no. 2, p. 140-153.
Pipkin, B.W., and D.D. Trent, 1997, Geology and the Environment, 2nd ed.; West/Wadsworth Publishing, St. Paul, Minnesota, p.
206-208.
Proffer, K.A., 1992, Ground water in the Abalone Cover landslide, Palos Verdes Peninsula, southern California; in Slosson, J.E.,
Keene, A.G., and J.A. Johnson, eds., Landslides and Landslide Mitigation; Geol. Soc. of America Reviews in Eng. Geology,
vol. IX, Boulder, Colorado, p. 69-82.
Reiter, M., 1984, The Palos Verde Peninsula; Kendal/Hunt Publishing Co., Dubuque, Iowa, p. 26-33.
Shuirman, G., and J.E. Slosson, 1992, Forensic Engineering: Environmental Case Histories for Civil Engineers and
Geologists; Academic Press, Inc., San Diego, p. 112-119.
INTERNET SITES
Slope Stability, Triggering Events, Mass Wasting Hazards
http://www.tulane.edu/~sanelson/geol204/slopestability.htm
(includes a section on the Portuguese Bend Landslide)
USGS National Landslide Information Center
http://landslides.usgs.gov/html_files/nlicsun.html
