Drill crews and geologists affiliated with the US Bureau of Reclamation (USBR) will drill several test holes in Wanship dam in Utah this week to evaluate the potential for liquefaction of foundation alluvial materials during an earthquake.

USBR is conducting the field exploration programme at the dam under the authority of the Safety of Dams Act of 1978. This programme ensures that all USBR’s dams receive periodic examinations and evaluations to ensure early detection of any potential dam safety problems. Data gained from this exploration programme will be used to provide better input to risk assessments and performance parameters for the dam.

The work is being conducted in cooperation with the Weber Basin Water Conservancy District, and is anticipated to be finished in several weeks. Additional explorations may be required depending on the results of the initial investigations of the foundation, which consists of clay, silt, sand and gravel.

Wanship dam is located in Summit County, Utah, on the Weber river. The dam provides storage for irrigation water and year-round power generation. The dam, completed in 1957 as part of the Weber Basin project, is a zoned earth-fill dam. It is 53m high and 614m long and impounds a reservoir of 76.6Mm3.

Back in February 2006 repair work was undertaken on the dam’s spillway wall after a portion of the right wall collapsed due to movement and pressure of saturated soil. The dam itself was ruled structurally sound during the work, which was completed before the spring run-off.

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