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An interview with the geotech engineer that designed the foundation for the 4-lane I-70.
No surprises - vertical cliff faces are inherently unstable. Limestone has a natural pattern of vertical and horizontal fracturing that is infiltrated by snow melt during the day and then freezes overnight, so-called ice jacking, that gradually pries loose blocks of rock on the face of the cliff.
My own observation - there have been significant rockfall incidents after the 4-lane was built in 2004, 2010 and now 2016- every 6 years. Even with proactive rock scaling and barrier building by CDOT, there is so much cliff face area next to I-70 that the natural cycle of ice-jacking and large rainfall events will continue to produce rockfall events with regularity. As mentioned in the article, of more concern is the geologic history that shows a major cliff collapse that completely blocked the canyon and river 4,000 years ago. It just so happens that the Dotsero volcano erupted 4,000 years ago also. Earthquakes trigger large landslides like the Hegben event in Montana in 1959. Chances are very low that it will happen again anytime soon, but maybe it is worth pouring a lot of money into an alternate route for the periodic rockfall closures, and as an insurance policy for the "big one".
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