Plugging the river
The decision was made to intervene, or at least to survey the damage that had been done and decide whether any remedial action needed to take place. As simple as that sounds, the reality was anything but. There is a lot of water to consider, and stopping it was a daunting task.
The damming of the American Falls took 1000 trucks and 28,000 tons of rock. This nudged the flow of water over the Horseshoe Falls instead. Once the dam was in place, the engineers could take a good look at the bed and construction of the American Falls.