PHOENIX — Cutting back the mountain slope and constructing a gravity buttress wall is part of the proposed solution to repair US 89 near Page, which was damaged in a Feb. 20 landslide. The repairs, at an estimated cost of $40 million, could take more than two years to complete.
Almost immediately after the February landslide forced the closure of US 89 south of Page, the Arizona Department of Transportation began assembling a team of geotechnical experts to examine the stability of the mountain slope that carried the damaged highway and searching for options available to reopen the roadway.
After an exhaustive geotechnical investigation that included geologic mapping, subsurface exploration and monitoring, laboratory tests and slope stability analyses, the final report has been submitted. The 463-page report concludes the recent landslide was a reactivation of a small portion of an ancient landslide, but little to no new movement has occurred since testing began.
The active landslide is approximately 135 feet below the roadway and measures approximately 1,200 long at the base of the slope.
The report listed several alternatives for the ultimate repair of US 89, but the construction of a landslide buttress and upslope lane adjustment was considered the most geotechnically feasible preferred alternative. The buttress, a wall-like support structure composed of rock, would be built at the base of the slope and the highway travel lanes would be moved farther to the east by creating a new cut into the existing slope in the Echo Cliffs.
“The recommendation is to move the road 60 feet, and take the rock from the cut and put it at the base of the hill to form a rock buttress to lock in the recent slide,” said Steve Boschen, ADOT deputy state engineer of design. “The right-of-way and environmental process will be our biggest challenge, but we will streamline that as much as possible so we can benefit the traveling public and especially the Bitter Springs and Marble Canyon communities.”
In addition to the buttress, the report reviewed several other alternatives, including:
- Repaving and reopening the highway along its current alignment would be the quickest and easiest way to restore mobility in the area, but would come with the greatest risk to the general public.
- Retaining wall structures are a common tool for repairing roadways damaged by landslides, but due to the depth and geometry of the landslide, it is not technically or economically practical to construct a retaining wall at this site.
- Rerouting the highway above the current alignment, higher on the mountainside, was considered, but significant grading would be required.
- Permanently closing the highway and building a new highway in another location was considered. Construction of a new remote route would take years of study planning, design and extensive land acquisitions.
At a later date, ADOT will formally request additional federal aid to fund the repair of US 89 through the Federal Highway Administration’s Emergency Relief program, which reimburses state and local jurisdictions for the repair or reconstruction of highways, roads and bridges damaged in natural disasters and catastrophic failures.
ADOT previously was awarded $35 million in federal aid to pave Navajo Route 20 and establish it as a shorter detour route for motorists until repairs are complete on US 89.
In an effort to restore mobility to the area as soon as possible, ADOT has worked with the Navajo Nation, Navajo Division of Transportation, Bureau of Indian Affairs and the Federal Highway Administration to move forward with paving Navajo Route 20, a 44-mile-long tribal route, which is a mostly dirt road that stretches from Bodaway-Gap to LeChee. N20 runs parallel to US 89 and will significantly reduce travel time for motorists heading to and from Page and the Lake Powell.
Construction started in late May on N20 and is scheduled to be completed in August. The route will eventually serve as the interim bypass for drivers and will be designated Temporary US 89 (US 89T) once paving is complete.
The current detour established for drivers is using US 160 (Tuba City exit) and State Route 98, which is approximately 115 miles long and 45 miles longer than the direct US 89 route. Drivers also have the option to take US 89A north to Marble Canyon toward Fredonia to reconnect to US 89 in Kanab, Utah.
US 89 has been closed north of Bitter Springs and south of Page since Feb. 20 due to a landslide that buckled pavement on the mountain slope in the Echo Cliffs.
ADOT has launched a range of communication tools, including a Web page (azdot.gov/us89) dedicated to keeping the public informed about the status of the closure and alternate travel routes, complemented by up-to-date video and photos of the roadway damage on US 89.
For more information about ADOT projects and programs across Arizona, see the agency's latest blog posts.