They Built a Dam So Big It Won’t Cool for 125 Years

In the middle of the Great Depression, in a desert canyon where summer temperatures pass 43 degrees Celsius, the United States government decided to pour more concrete in one place than had ever been poured before. If Hoover Dam had been cast as a single continuous mass, the heat generated by curing concrete alone would have taken over a century to fully dissipate, and the dam would have cracked itself apart from the inside as it cooled unevenly over that time. It was built anyway, in five years, largely on schedule, in one of the most dangerous work environments of the era. This video covers how Hoover Dam got built: the flood and water-supply crisis across the American Southwest that made a dam on the Colorado River politically unavoidable, the block-pour method engineers invented to solve the impossible cooling problem by dividing the dam into thousands of separate interlocking concrete columns, each threaded with its own network of cooling pipes carrying refrigerated river water, and the five-stage construction sequence that diverted an entire river through hand-dug tunnels before a single block could be poured. We also cover the human cost the postcard photos never show. Officially 96 workers died during construction, from falls, explosions, and carbon monoxide poisoning in tunnels working around the clock in a canyon that regularly exceeded lethal working temperatures, with unofficial estimates running higher once heat-related deaths are counted. Despite the danger, the Depression-era workforce, and a canyon nobody had built anything this size in before, Hoover Dam was finished roughly two years ahead of its revised schedule and close to budget, a rare outcome for a megaproject in any era. Part of an ongoing series on the megaprojects that shouldn't have been possible. Previous entry: the bridge an earthquake made a metre longer while it was still being built. Next: the tunnel boring machine that got stuck under Seattle for two years. 0:00 Cold open 0:45 The problem 3:00 The solution on paper 6:30 Building it, step by step 11:30 What almost went wrong 13:30 Verdict Link Subscribe now -    / @overbuilt-e9h