13 March 2015
Yeager Airport is located about 5 km east of downtown Charleston in West Virginia, USA. The airport is located on top of a hill, with steep slopes on several sides, including at the end of the main runway. In 2005 a project was initiated to increase safety at Yeager Airport by creating an over-run area at the end of the runway, including the installation of an EMAS, which is a concrete surface that is designed to bring aircraft to safe stop. In 2010 this successfully arrested an over-running regional jet:
The construction of the EMAS required that a new, large fill slope was built, retained by a reinforced slope. There is a very detailed and interesting presentation about the design and construction of the slope (NB this is a PDF); at the time this was apparently the largest reinforced slope in the United States (I’m not sure if this is still the case). This images, from the presentation, shows the completed structure at the end of the runway at Yeager Airport:
In Wednesday the Charleston Daily Mail reported that six residents had been moved out of their houses below the slope as movement of the slope had been detected in the EMAS. Yesterday this quickly developed into a very large-scale landslide. This image is from a gallery that is in a Charleston Daily Mail report from yesterday:
This is a massive, very deep-seated and rather complex failure. The scale is somewhat impressive. The failure is surprising in so much as the conditions appear to be dry, a fact that is supported by this image of the rear scarp, although as the comment below notes, there has been significant rainfall and snowmelt in recent weeks:
The slope reinforcement is clear to see in the image – the failure appears to have sliced through it. The images gives few indications as to what has gone wrong – whether this is a design failure or whether something happened at the toe of the slope to change the system. I do wonder if the rock below the reinforced slope has failed though – this might explain the interesting geometry of the collapse. Either way, this is going to be very expensive, and it will affect both the operations at Yeger Airport and the local residents for some time to come.