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What was the most expensive landslide to fix in the United States?

The Thistle, Utah, landslide cost in excess of $200 million dollars to fix (1984 dollars – adjusted for inflation this would be more than $400 million in 2010 dollars). The landslide occurred during the spring of 1983, when unseasonably warm weather caused rapid snowmelt to saturate the slope. The landslide destroyed the railroad tracks of the Denver and Rio Grande Western Railway Company, and the adjacent Highway 89. It also flowed across the Spanish Fork River, forming a dam. The impounded river water inundated the small town of Thistle. The inhabitants of the town of Thistle, directly upstream from the landslide, were evacuated as the lake began to flood the town, and within a day the town was completely covered with water. Populations downstream from the dam were at risk because of the possible overtopping of the landslide by the lake. This could cause a catastrophic outburst of the dam with a massive flood downstream. Eventually, a drain system was engineered to drain the lake and avert the potential disaster.

Gradually, the Thistle landslide reached a state of equilibrium across the valley, but fears of reactivation caused the railway to construct a tunnel through the bedrock around the slide zone. Also, the highway had to be realigned around the landslide. When the lake caused by the landslide was drained, the residual sediment partially buried the town and virtually no one returned to Thistle. This landslide is still moving at present, although at a fairly slow rate. State officials continue to monitor this landslide.

Learn more: photos of this landslide

Source:

University of Utah, 1984, Flooding and Landslides in Utah—an Economic Impact Analysis, University of Utah Bureau of Economics and Business, Utah Dept. of Community and Economic Development, and Utah Office of Planning and Budget, Salt Lake City, Utah, 123 p.

Tags: Landslides, Liquefaction, Maps, Precipitation, Soils