This may be a case of “New Technology is not necessarily better than old technology.” Taum Sauk Dam (Missouri, 2005).
And then there is systems design. But we’ll get to that.
The plant consisted of an Upper Reservoir situated atop Proffit Mountain contained by a kidney-shaped rockfill dike, a Lower Reservoir and Powerhouse impounded by a concrete gravity dam, and a 7,000-foot-long concrete and steel-lined tunnel that connected the two.
Built in the 1960s it took off-peak power and pumped water to the upper reservoir, and then used that water to generate hydroelectric power during peak hours. When it was built there were 2 “float” type shutoffs to keep the pumps from overfilling the reservoir, as primary and backup. For some reason I have a vision of a giant toilet-tank fill valve. But when the reservoir was maintained in 2004, that system – which had worked since the 1960s – wasn’t high-tech enough and so it was replaced with 2 pressure traducers which would sense when the water level was too high. In theory.
On Sunday, September 25, 2005 an engineering tour of the site discovered water flowing over the reservoir. The transducers had broken free. When they were replaced they were not calibrated for the new position. And new “fail-safe” probes were added. It wasn’t enough, and the dam failed on December 14th.
On December 14, 2005, the Upper Reservoir of the Taum Sauk Pump Storage Plant failed by overtopping during the final minutes of one of its pumping cycles. As a result, the reservoir’s 4,300 acre-feet volume of stored water was released from a 656-foot-wide breach in 25 minutes, traveling down Proffit Mountain toward the Black River with a peak discharge of 273,000 cfs. Before it reached the river and flowed into the Lower Reservoir where it was entirely contained, the flood destroyed 281 acres of Johnson’s Shut-Ins State Park and ripped the superintendent’s home from its base.
No life was lost, but about $1 billion in damage was done.
Here is how Public Radio remembered the event, in 2015. Ten-year anniversary of reservoir breach that flooded Johnson’s Shut-ins state park.
The wall of water followed the Black River and swept through Johnson’s Shut-ins State Park, depositing tons of rock, boulders and sediment along the way. It also damaged the park’s lone residence, which housed park superintendent Jerry Toops, his wife, and their three children. They, too, were swept away, but all survived with only minor injuries.
You should click thru for the images; there are only 3, but worth a look. An aerial view of the devastation down the side of the mountain. The residence of the Park Superintendent after the flood. A photo of a boulder carried 1.5 miles by 1.3 billion gallons of water. I wish they had more info on the boulder; it looks to be a cube of rock about 5 feet on a side, more or less.
As for the systems design… (from the link at top.)
The “fail safe” Warrick probes failed to report the critical high water level in the reservoir because the probes had been incorrectly set at a higher elevation than the low point on the parapet. This was further compounded by system programming that required both probes to trip the pumps off-line. There was no program in place to maintain calibration of the sensors against actual reservoir levels, and no program to evaluate the actual crest elevation around the reservoir rim with respect to shut down triggers within the system programming.
What could go wrong? They were using High Tech™ sensors! So much better than that antiquated system from the 60s. Which never failed to shut down the pumps.
Anyway the reservoir was reconstructed out of roller-compacted concrete, and the rebuilt power station was opened in 2010. Along the way the owner of the generator paid some hefty fines.