Federal work crews have stationed a drill rig on the crest of the dam to retrieve core samples. A focus of the investigation – which is part of the USBR’s regular Safety of Dams programme – is to determine how the dam would perform under a variety of conditions and assess the longevity of the infrastructure components from the core of the dam. The work is expected to take two weeks to complete.

The 172m high Hungry Horse dam, located on the south fork of the Flathead river, is a variable-thickness concrete arch structure, with a crest length of 644.7m. At the time of its completion, the dam was the third largest dam, and second highest concrete dam, in the world.