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Cape Cove Landslide

Cape Cove Landslide
Florence, Oregon

This landslide has repeatedly caused extended closure of Hwy 101 about 10 miles north of Florence, Oregon. The landslide is about 250 ft wide and occupies a steep slope that extends about 600 ft above the roadway. GRI performed a geologic reconnaissance and mapping of the landslide and surrounding area and completed five borings to evaluate slope stability for an area of potential future movement north of the landslide. A 150-ton crane was required to lift the track-mounted drill rig and a track-hoe excavator onto the densely forested hillside. GRI installed, monitored, and maintained inclinometers and groundwater piezometers in each boring with a data acquisition system for remote data collection. Using the field and instrumentation data, the geologic conditions and the configuration of the landslide and potential failure surfaces were modeled and slope stability analyses were performed for existing conditions. GRI provided a report summarizing recommendations for short- and long-term mitigation measures with preliminary construction costs for the various alternatives.

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