The Taum Sauk Hydroelectric Storage Plant, one of the largest stand-alone pumped storage plants, overflowed causing catastrophic flooding.
The Taum Sauk Hydroelectric Storage Plant in Missouri was engineered to take power from other sources during part of the day and supply energy during other hours. The facility was made of four parts: a 55-acre reservoir at the top of a mountain, a 7000-foot-long tunnel, a powerhouse with two reversible pump-turbine units, and a lower reservoir formed by a dam. The plant produced 350 megawatts by releasing water through the plant into a 400-acre lower lake. Then, at night, the water was pumped back into the upper pool to store energy for the following day when demand would be high again (like a giant battery). The process was directed by remote control in St. Louis, 120 miles away.
In December of 2005 however, a catastrophic failure of the upper reservoir released more than a billion gallons of water in less than 15 minutes. This caused a serious flood that injured nine people and created widespread environmental damage. The Federal Energy Regulatory Commission (FERC) determined that water ran over the top of the reservoir because of water level meters that gave inaccurate readings about how high the water actually was. They also determined that AmerenUE, the utility company that runs the plant, knew about the problem but had not yet managed to repair it and had not reported the problem to the commission. AmerenUE was required to pay $10 million dollars in fines and another $5 million dollars in improvements to the area around the plant. They also had to adopt a better safety program that included hiring a Chief Dam Safety Engineer to oversee the operation. This is another example of the huge responsibility held by engineers to think seriously about safety in all of their work.
The newly rebuilt and recertified dam opened again in April of 2010. The new reservoir is made entirely of roller-compacted concrete, and it includes a spillway to handle overflow and a video system to help in monitoring the water level.
Read more about the Taum Sauk Disaster.