The Springwater Corridor Bike Path is a heavily utilized bicycle commuting thoroughfare extending along the east bank of the Willamette River in downtown Portland. The path was constructed on the lower terrace of the river bank adjacent to an existing private rail road. The bank’s alluvial soils are continually subjected to transient raising and lowering of the river level and erosional forces which combine to create localized landslides. In the spring of 2012, an approximate 80-foot long section of the bank failed and resulted in the loss of approximately 4 feet of asphalt and shoulder.
The City of Portland Parks and Recreation contacted GeoStabilization International to evaluate potential solutions not only to stabilize the remaining unstable slope, but also reconstruct the path and shoulder that had failed into the river below. The potential stabilization options were also required to adhere to strict environmental regulations and meet the goals of the City of Portland Greenway Code. The initial phase of the project was also limited to construction related activities above Ordinary High Water Level to allow project commencement prior to Corps of Engineer permit acquisition.
Geostabilization’s engineering group developed a repair plan consisting of a Launched SuperNail® and high strength galvanized mesh reinforced slope along with a Geosynthetically Confined Soil BioWall® on a Launched SuperMicropile™ supported pile cap. The Soil Nail Launcher™ was identified as an ideal tool for the environmental and in-water work restrictions. The Soil Nail Launcher™ had the ability to install the Launched SuperNails® while working from the existing trail platform. By launching the nails rather than drilling, no drill cuttings were produced. The facing of the BioWall® consisted of geosynthetic bags filled with topsoil and faced with a turf reinforcement mat. Over 700 live willow stakes were planted within the facing bags to provide a native aesthetic that met the goals of the City of Portland Greenway Personnel.
Geostabilization’s crews successfully completed this challenging project while maintaining full public access during normal commuting hours and weekends. The City of Portland Parks and Recreation plans a second phase of bank stabilization work after Corps of Engineers permit acquisition to further enhance the native vegetation and wildlife habitat below the foundation of the BioWall®.
Gonowabie Road is a historic logging road now serving vacationers and homeowners who enjoy the beauty and tranquility of Crystal Bay in Lake Tahoe.