Grand Coulee Dam: Pouring the Concrete
On December 6, 1935, the first bucket of concrete was poured onto the dam site. To prevent the possibility of cracking, concrete was poured into hundreds of 50 foot square blocks every 72 hours. After each pour, workers would scrub the concrete with wide brushes to remove scum. Millions of cubic yards were poured, and in February 1938, the foundation was completed 14 months ahead of schedule.