DESCRIPTION: Realignment is currently underway for a 5‑mile long section of the Coos Bay - Roseburg Highway (OR 42) in rural, southwest Oregon. The new realignment follows the Middle Fork of the Coquille River through a geologically complex valley with steep slopes and extensive areas of slope instability.
SERVICE: Foundation Engineering completed a geotechnical investigation for the project. The work included a preliminary investigation and evaluation of slope stability for alternative alignments. LIDAR, aerial photos, geologic mapping, and subsurface exploration were used to identify potential landslides and evaluate the risks associated with each alignment alternative.
The investigation identified the environmental and geotechnical project constraints. Landslide mapping and slope stability analysis identified the potential landslide risks and associated mitigation costs. Based on the findings ODOT selected an alignment that closely followed the existing road.
Once the alignment was selected, Foundation Engineering completed subsurface investigations including 14 helicopter access borings, in addition to several test pits and borings completed with conventional methods. This subsurface information was used to develop the basis for the design of rock and soil slopes and landslide mitigation. We provided project management, landslide mapping, subsurface exploration, landslide and ground water monitoring, evaluation of slope stability risks, rock slope design, landslide mitigation design, and earthwork. The project is currently under construction and our team is providing construction assistance and consultation.