ODOT’s I-5: Iowa Street Viaduct Replacement Project in Portland will reportedly cut into 6 ancient landslide surfaces according to a PSU Geology Professor. The existing bridge structure is over 50-years old and deteriorating and will be replaced. It appears that the slope adjacent to the bridge is where the landslide surfaces will be encountered, and the contractor has recently begun clearing trees in preparation for the work. A temporary highway will be constructed by cutting into the hill. The hill will be stabilized by a retaining wall on the order of 40-ft tall. I have not found any descriptions of the type of retaining wall proposed. News video below gives a good overview of the site.