The geotechnical investigations and report are complete for the US 89 Bitter Springs Landslide south of Page, Arizona. ADOT published a news release with the results of Kleinfelder’s geotechnical investigation and a link to their geotechnical report. The recommended mitigation for the 1,200 foot long, 135 foot deep landslide is to cut into the uphill slope and move the road approximately 60 feet and to use the resulting material to construct a gravity buttress at the toe of the slide. Other options considered but rejected were rerouting the road, some form of active stabilization using a retaining wall, and simply closing the road. The repairs are estimated to cost $40M and take approximately 2 years to complete. The video below shows an interview with Steve Boschen, Deputy State Engineer for Arizona describing the alternatives that were considered. [Source: Check out the full ADOT Press Release and download the report via Arizona Geology Blog. Image: ADOT]
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On March 21, 2008 a landslide caused the closure of Arizona State Route 87 between Payson and Phoenix near mile post 224. So far there are no official estimates as to the size, but based on aerial photos, it appears to be at least 50,000 sq-ft in plan. The offset at the head scarps was approximately 2-meters (6.6-ft) according to AZGS Geologists on site. It appears to have been a rotational slide as the toe of the landslide heaved the southbound roadway up by as much as 1-meter (3.3 ft). There was an existing soil-nail retaining wall on the slope that was destroyed by the slide as well. Lateral deformations can be seen in photos of the median barrier and the roadway striping. The deformations extended into the northbound lanes as well. More photos and links after the break. (Photo by ADOT)