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 riverbank adjacent to an existing private railroad. 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 approximately 80-foot-long section of the bank experienced slope failure, which resulted in the loss of approximately 4 feet of asphalt and shoulder.
The City of Portland Parks and Recreation contacted GeoStabilization International®, leading soil nail wall contractors throughout the United States and Canada, to provide designs to mitigate the landslide and provide slope stabilization. The city wanted solutions to stabilize the remaining unstable slope and reconstruct the path and shoulder that had failed into the river below. An important criterion was each option had to adhere to strict environmental regulations and meet the goals of the City of Portland’s Greenway Code. The project’s initial phase was also limited to construction-related activities above the Ordinary High-Water Level to allow project commencement before Corps of Engineer permit acquisition.
GeoStabilization’s engineering group’s repair plan, which was accepted by the city, was a soil nail wall constructed using launched SuperNails® combined with high-strength galvanized wire mesh to provide soil retention. Then, a Geosynthetically Confined Soil BioWall® was built on a launched SuperMicropile™ supported pile cap. The Soil Nail Launcher™ and soil nailing were identified as an ideal tool and method due to the environmental and in-water work restrictions. The Soil Nail Launcher™, one of GeoStabilization’s soil stabilization innovations, can shoot the SuperNails® into the slope while working from the existing trail platform. By launching the soil anchors rather than drilling, no drill cuttings were produced that could contaminate the surroundings.
Once the failed area was excavated, the crews launched the soil nails horizontally into the slope before the wire mesh was secured to the almost-vertical face with bearing plates. Then the micropiles were launched vertically and fitted with a steel-reinforced pile cap before the Geosynthetically Confined Soil® (GCS®) was constructed to regain the lost slope width. Finally, geosynthetic bags filled with topsoil and faced with a turf reinforcement mat were used to fabricate the BioWall®. Over 700 live willow stakes were planted within the facing bags to provide a native aesthetic to meet the City of Portland Greenway’s beautification goals.
Contact GeoStabilization International® at 855-579-0536 for our geohazard mitigation services and engineered soil repairs. Use our innovative technology for your slope protection, slope monitoring, and landslide prevention projects.
If you are interested in a no-obligation site visit to determine if our services fit your geohazard mitigation needs, call us at 855-579-0536 or fill out our contact form.
