ADOT's geotechnical investigation on US 89 landslide enters final stages

We have heard from a lot of people who want to know when US 89 is going to reopen…

While we don’t have any sort of a timeline to give you yet, we can report that the geotechnical investigation is entering its final stages. Once complete, the information gathered will help engineers uncover the best long-term solution to restore the landslide damaged US 89 highway.

After receiving environmental clearance, heavy construction started Tuesday. Crews are working to cut a pathway down the slope to the base of the mountain slope.

That access path will allow the geotechnical engineers to dig pits, approximately 20-40 feet long and 10-15 feet deep, which will provide critical information regarding any movement that may be present at the base of the slide. The excavation work is necessary because it will lead to recommendations by the geotechnical team on what options are available within the site to realign the roadway or rebuild the existing roadway.

“This is the final piece of the puzzle we’ll need to wrap up this geotechnical investigation,” said Steve Boschen, ADOT deputy state engineer of design. “Prior to this, our drilling crews were only able to access this area via helicopters.

ADOT’s goal is to repair this critical section of highway and restore connectivity throughout the region as soon as possible. But before we can start the repairs, we need to determine the cause of the landslide and assess the safety of the slope.”

ADOT’s geotechnical investigation at the US 89 landslide site is the first phase of the solution. Crews are monitoring the stability of the slope and the ultimate repair of the highway will be based on the results of the geotechnical investigation. Efforts also continue on exploring the use of Navajo Route 20 as a temporary detour route while US 89 repairs are addressed.