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Utah State engineers design solutions to repair nation's tallest dam

LOGAN — A team of 15 engineers, technicians and students built a model one-fiftieth the size of the spillway at the nation's tallest dam, replicating the crippled chute damaged by floods earlier this year.

The February failure of Oroville Dam's spillway in California put the safety of the nation's dams under scrutiny, but also provided a team of experts at Utah State University the opportunity to engineer the best — and safest design — of a new spillway for a critical source of water in the Sacramento Valley.

"It is a pretty significant dam in California," said Michael Johnson, a project leader and research professor who specializes in experimental hydrology.

The spillway began to break apart on Feb. 7, damage that grew worse as dam operators were forced to continue releasing water after the emergency spillway's release began to erode a hillside.

Fearing for the safety of downstream residents, emergency officials evacuated nearly 200,000 people — elevating concerns both in California and across the nation over the aging nature of the country's water infrastructure.

As earthen dams and spillways go, there was nothing in the structural design at Oroville that immediately gives clarity to cause of the failure, Johnson said. A team of forensic engineers are continuing to probe what went wrong, he said.

Oroville Dam, at 770 feet, was completed in 1968 and included many of the design features in place at dams throughout the country.

USU's research laboratory is no stranger to building physical models of dams, but this is its largest and has been done at the request of the California Department of Water Resources based on previous work the lab did on the power turbines at Oroville.

At 100 feet long and 60 feet wide, the model simulates a prototype dam and spillway of more than 4.4 million square feet.

Its "mountains," made of 20,000 pounds of concrete, replicate the actual topography at Oroville to simulate flows in the California drainage, with mapping accomplished with a laser scanner mounted on aircraft.

"To build the topography was no small job," Johnson said. "But we have some of the best brains in the world working on this project because we all benefit from what goes on (there).

The Sacramento Valley is one of the most productive agricultural regions in the country.

Those fields depend on water from places such as Oroville Dam and the success of the model built at the Utah lab.

The model, constructed in 40 days, supplies just over 7,030 gallons per minute and simulates a flow of up to 277,000 cubic feet per second — which Johnson said is akin to a 100-year flood event.

Construction and subsequent operation of the model is happening on an accelerated timeline so the information can be used in the replacement spillway's design — with an eye toward having everything functioning by the start of California's wet season in November.

Mac McKee, who oversees the lab, said researchers and students there have participated in the construction of 20-plus models of dams along the Lower Colorado River, which flows from west Texas down to the Gulf of Mexico.

With each project — like Oroville spillway replication — engineers gain additional information about the complex design world of dams and related infrastructure.

This particular project is costing the lab $277,000, McKee said.

"What it is buying is a lot insurance that the structure will function as designed. Beyond that, it is the recognition it brings to the university and this water lab," improving the discipline of engineering, he said.

"We're discovering new stuff that brings enlightenment and improvement in how engineering is done, and that changes the world in a good way," McKee said.