DESCRIPTION: Linn County plans to improve Quartzville Road in Linn County, Oregon. The improvements will include widening the shoulders to provide a pedestrian/bicycle travel lane, pavement overlay, and constructing new parking areas, restroom facilities, and information kiosks.
Several landslides within the project limits impacted the stability of the roadway. The planned improvements include taking steps toward mitigating five landslides located at ±MP 5.4, ±MP 5.8, ±MP 6.1, ±MP 6.7, and ±MP 8.3. These mile points (MP) are referenced from the intersection of Quartzville Road and Old Huffard Drive, which is located ±0.5 miles north of the intersection with Highway 20. The slides are uphill of Green Peter Reservoir.
SERVICE: Foundation Engineering was retained by the Linn County Road Department to complete a geotechnical investigation and site reconnaissance for each landslide and provide slide mitigation options. Our scope of work included exploratory drilling, laboratory testing, engineering analyses, and development of landslide mitigation recommendations. A range of mitigation options were evaluated including overexcavation and replacement, construction of buttresses, construction of retaining walls, and drainage improvements, including the installation of slope drains.