(airy music) - [Narrator] Excavating began in July of 1950 on the west end of the dam.

A total of four and one half million cubic yards of embankment was to be excavated, some 5% of the total excavation.

This work was completed in the autumn of 1952.

Moving the vast amounts of earth required a sizable fleet of equipment capable of hauling large amounts of earth.

In use was 25 50 ton twin engine rear dump trucks and 20 30 cubic yard bottom dump trucks.

Also in operation, a massive Marion 191 M electric power drag line whose 14 cubic yard bucket made it the largest shovel ever built on two tracks.

Two 10 hour shifts moved 75,000 cubic yards of Earth daily.

By 1958, work began on the powerhouse substructure.

More than 222,000 cubic yards of concrete was required.

This work employed 800 men working in three shifts around the clock, pouring 125 cubic yards of concrete every hour.

On August 2nd, 1958, with the embankment having narrowed the Missouri's channel, the core was ready to start closure operations.

With 8,800 cubic feet per second of water flowing past the Oahe Dam site, every available dump truck was called into operation With six heavy duty tractors dozing the shale into the river, dumping an average rate of 3,200 cubic yards per hour.

Western contracting completed the closure in 21 and one half hours.