Soledad Mountain Road Landslide Evaluation


La Jolla, California

Scope of Work:

  • Subsurface Exploration
  • Laboratory Testing
  • Geologic and Engineering Analyses
  • Expert Witness Services
  • Written Report

Ninyo & Moore evaluated the landslide on Soledad Mountain Road in La Jolla, California, for the City of San Diego. The project included an evaluation of the cause of the landslide, evaluation of conditions at homes involved in litigation, and providing support during litigation.

Project Challenge: The project presented issues for geotechnical investigation under a critical schedule to evaluate the causes of landslide reactivation, and to stabilize the hillside and re-open Soledad Mountain Road, a major artery, for traffic. Interim slide stabilization had to also occur prior to onset of winter rains. Our investigation had to begin immediately upon notification of the slide movement by the City.

Innovative Solution: To evaluate the geologic conditions and cause of landslide movement required mobilizing a number of geologists and engineers under short notice and a mix of subsurface evaluation techniques. Large-diameter borings were downhole logged by engineering geologists to evaluate landslide geometry and characteristics. Simultaneously small-diameter borings were used to obtain hundreds of samples for soil moisture and other testing in order to identify if water from existing utilities and other sources could have been a contributing factor to slide reactivation. Construction repairs utilized a combination of grading, reinforced concrete shear pins, geofabrics, and drainage improvements for stabilization.

Services: Ninyo & Moore's scope of services included review of available background information such as pertinent existing geotechnical literature, and topographic and geologic maps; and geologic mapping of the landslide. Our field evaluation included drilling and logging small-diameter borings, trenches, and test pits; downhole logging of large-diameter borings by a Certified Engineering Geologist; logging and sampling shear pin borings; and detailed evaluations of the homes damaged or destroyed in the landslide. Our laboratory tested over 2,500 samples in support of the evaluation.

NINYO & MOORE We transform today so our world is a better place tomorrow.