Hoover Dam is a concrete arch-gravity dam and was constructed between 1931 and 1936 during the Great Depression and was dedicated on September 30, 1935, by President Franklin D. Roosevelt. Hoover Dam impounds Lake Mead, the largest reservoir in the United States by volume when full. The dam's generators provide power for public and private utilities in Nevada, Arizona, and California. Hoover Dam is a major tourist attraction; nearly a million people tour the dam each year. The heavily traveled U.S. Route 93 (US 93) ran along the dam's crest until October 2010, when the Hoover Dam Bypass opened.
1 day after people: As generating plants cease to produce electricity, the last glow of artificial light on earth is still visible southwest of the United States. The Hoover Dam's generators are driven by the flow of water from Lake Mead, & the plant could remain operating unattended for months or even years. From space, the glitter of Las Vegas may be the only point of light on the surface of an otherwise dark planet.
1 year after people: The generators are about to be brought down by Quagga Mussel. These organisms multiply inside of the pipes, and eventually completely block the diameter of the pipe. The generators overheat and shut down, and Las Vegas goes dark forever. Without any active generators, no water moves through the dam, causing the Colorado River downstream will run dry. On the other side of the dam, Lake Mead begins to rise, eventually the water spill over the Hoover Dam.
10,000 years after people: The Hoover Dam is now one of the last structure of modern civilization still standing. But now, with the combination from series of events like rain, sandstorm, and earthquake have caused the massive dam to weakened. Finally, an earthquake cause the Hoover Dam to collapse after years of corrosion, erosion of concrete, and the cumulative effect of seismic activity.
Mistakes can be seen during the collapse of the Hoover Dam. (What exactly?)