The Teton Dam failure in Idaho in 1976: a problem with the use of loess material in the construction of a large embankment dam

 The Teton Dam, built on the Teton River in Idaho failed on 5 June 1976 as it was filling. 94m high, it cost $100 million to build; built by the US Bureau of Reclamation- to provide hydropower.

Ian Smalley 1992. The Teton Dam: rhyolite foundation + loess core = disaster. Geology Today 8, (no.1) 19-22.

Ian Smalley, Tom Dijkstra 1991.  The Teton Dam (Idaho USA) failure problems with the use of loess material in earth dam structures.  Engineering Geology 31, 197-203.

Geotechnical problems with loess usually involve hydroconsolidation and subsidence- the problems are caused by the presence of the open metastable structure of ground materials. What the Teton Dam failure demonstrates very clearly is that there are geotechnical problems associated with remoulded loess- it is not only the open structure that causes geotechnical problems- it is the nature of the ground itself.  Problems arose within the field of soil mechanics because of an inclination to view ground materials as either cohesive (clayey) or cohesionless (sandy soils). Loess was a soil which was

essentially cohesive but definitely not sandy- loess occupied a sort of midway position. The problem at Teton was that it could not be satisfactorily compacted- the essential core lacked the required properties. In loess the primary mineral particles interact (after remoulding)- there is no capacity for compaction. The engineers at the Teton Dam failed to understand the special nature of loess ground- this contributed to the failure.