More than a mile long, the Grand Coulee Dam is the largest concrete structure in the U.S. In the fall of 2011, dam operators agreed to open the spillway just for American Experience. "It was very ...

Down the sloping ramp of the spillway, one of the eight fusegates — massive concrete blocks or buckets — had tipped and tumbled down, as is the intended design. The spillway activates at 10.5 ...