Lake County Widgeon Way Slope Repair

The County of Lake retained LACO to perform a geotechnical exploration and develop an engineered mitigation plan for a landslide endangering nearby structures, downhill properties, and State Highway 20 near Clearlake Oaks. The goal of the project was to reduce the risk of future sliding.

This project consisted of the following phases:

  • Quantitative slope stability evaluation of the slide and surrounding slopes using WinsTabl (version 3.0) software to determine the mechanism of failure and slide characteristics
  • A risk and cost analysis based on indications that the slope failure was caused by gravitational pressures or water flow
  • Preparation of design plans with specifications to support the construction bidding process
  • Bid assistance
  • Construction inspection
  • Monitoring slope conditions following repair

Our team found that elevated porewater pressures at the site appeared to be responsible for triggering the initial failure and subsequent reactivation of the slide mass. Repair design elements included diverting surface water, reducing slope grade, with future measures for subdrainage and face stabilization.

After the slide was stabilized, the County of Lake retained our services to install groundwater monitoring piezometers as a means to wirelessly monitor subsurface conditions in the vicinity of the slide, and to observe construction activities associated with the implementing of the recommended surface drainage improvements.

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