Thursday, July 18, 2013

US Highway 89 Landslide - Solution Identified



Image courtesy of ADOT and taken from their Highway 89 web banner
Nearly five months after it occurred, the Arizona Department of Transportation (ADOT) has released the results of its long awaited geotechnical report on the cliff rupture. Readers will recall my previous postings on this blog about this major geologic and social event in northern Arizona.

I first reported on the event when I received an e-mail from a friend while traveling in Luxor, Egypt just a few hours after it happened. You can read that here. Reporting on this event from Egypt was one of the strangest blogging experiences I have ever had, not only because I had such limited time to write a blog but also because I was hearing up-to-the-minute news about an event happening at home while on the other side of the globe. I wrote a second piece about the event here, where I speculated that the slump might have occurred on road fill material only. That speculation was put to rest in a third posting here and my last posting went up here that described in more details what ADOT was up to with the testing.

Now the results of the study can be read here. A copy of the full 436-page study can be downloaded from that page. A summary is that five alternatives were considered but the chosen alternative is to cut back into the cliff an additional 60 feet and then use that material to form a rock buttress at the foot of the slide, some 135 feet below the current right-of-way. There are good graphic that visually describe the fix. The cost will be $40 million and it will take approximately two years to complete. $35 million has already been authorized for the pavement of Navajo Route 20 just o the south and east.

Kudos to ADOT for choosing what is likely the best all-around alternative for the affected communities.

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