Saturday, June 01, 2013

Geotechnical assessment of US89 Bitter Springs landslide

ADOT has 8 videos posted on different aspects of the Bitter Springs landslide that closed US89 south of Page this winter.    The latest offers a status report and initial findings from the ongoing investigations.

Wayne Ranney's posted an excellent analysis of the situation at his Earthly Musings blog -

ADOT's contractors have found a shear zone between depths of 105 and 125 feet below the roadway, which puts it in the Chinle Formation, the clay rich unit that is the base of mega-landslides throughout the region.

Wayne raises the question of whether US89 can be rebuild across the giant landslides that cover the slope heading up through the "Big Cut" to Page.

ADOT is preparing to pave Navajo Route 20 (N20) as a detour at a cost of $28 million.     The question is whether the geotechnical investigations find that the challenges of rebuilding US89 can be overcome and if so, can the costs be justified.  If not, it would seem likely that N20 becomes the new primary corridor.

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