The Oregon Department of Transportation will repair a landslide and the Sheep Creek bridge on Highway 20 beginning in the summer.
The landslide and bridge are located at milepost 56.6, about 25 miles east of Sweet Home.
“Those of you who drive U.S. 20 between Sweet Home and the Oregon 126 junction know that there are some rough patches of road in that area, especially this time of year,” said Jerry O. Wolcott, project leader with ODOT Area 4. “U.S. 20 has a number of large landslides in this area. Given the geological features in the area, building the highway and avoiding contact with all slides was impossible.”
Sheep Creek Bridge was built with the easternmost abutment set on an active landslide, Wolcott said. When the bridge was built, this abutment was designed to accommodate slide movement and be adjusted as the earth moved around the bridge.
In 1993, 2006 and again in 2011, ODOT adjusted the abutment to accommodate the movement, Wolcott said. Historically the movement had been about an inch a year. However for about the past four years the movement has been about 6 to 7 inches a year. The bridge now needs to be repaired and reset to accommodate further movement. This will be done in two phases, first the landslide repair and then the bridge repair.
Phase One of the project will install a “picket fence” of large steel pile, placed in a series of four foot wide holes then filled with concrete. This “fence” will be located above the bridge and will redirect the slide away from the bridge.
ODOT will select a contractor this spring. The cost is estimated at $1.87 million.
The project won’t change the need for the bridge to continue to accommodate earth movement, but it will redirect and reduce the slide activity so that the impact to the bridge is consistent and predictable and therefore more manageable.
Phase Two will repair slide damage to the bridge and then reset the bridge. ODOT officials anticipate a final design in early 2016 and have no cost estimate yet.
Work on the first phase will take place in the summer. The bridge repair will happen the following summer in 2016.
Due to the shortened weather window, both phases of construction will take place during the middle of the summer as weather permits. All of this work will take place during daytime hours.
During the summer, drivers can expect short delays as equipment and piles are moved and placed.
During summer 2016, the highway will be closed for a short time while the end of the bridge is replaced.
With no detours available at the bridge, drivers should make alternate travel plans during the complete closure period.
“We will know more about the length and timing of the closure later as the plans are finalized,” Wolcott said. The public will receive advance word of the closures and will have plenty of time to make alternate plans.
Wolcott is planning to contact City of Sweet Home officials to set up an informational presentation about the project.
More information is available on the web at http://www.oregon.gov/ODOT/HWY/REGION2/Pages/US-20-Sheep-Creek-Bridge-Phases-1-and-2–.aspx