Transcript — The Wild Story of the Taum Sauk Dam Failure

[00:00:00] were nearly finished filling the upper reservoir end of the daily cycle. Water rose to the top parapet wall that ran along the top of the dam. shut off, but the other kept running, and soon, minutes, those splashes turned into a steady the embankment on the other side. The rockfill and wider. The pump finally shut off, but it already been undermined. The wall tipped over, and mountainside headed directly toward a state park. considered a model of modern engineering, And what the investigations found would change

[00:01:05] Grady, and this is Practical Engineering. pumped storage plant was unlike really any other size. South of St. Louis in the Ozark Mountains, talked about pumped storage on the channel before, of its time. Built by Union Electric, whole plant is basically a battery. It’s which is normally not a good thing for a only about how much electricity you can produce,

[00:02:02] coal plants in the Missouri area could that production up and down to accommodate Union Electric proposed a clever solution, for its time. Two reservoirs were constructed: and another near the top of Proffitt Mountain, hydroelectric plant with two reversible turbines. reducing the output of thermal power plants, lower to the upper reservoir, usually overnight. that stored potential energy created from on the grid by reversing the system to generate power out that you put in. Some of that water energy in the pumping and generation. But, with an

[00:03:05] enough to justify the enormous cost of building that doesn’t produce any of its own electricity. the upper reservoir. It’s just such an unusual a ring dike or ring levee, perched on top way to build a dam. We typically construct them can form the sides and back of the reservoir. to build the dam all the way around, increasing there are no valleys at the tops of mountains, pumped storage facility. The power available multiply gravitational acceleration, the density

[00:04:02] difference in height, called head. We can really output needed for a specific duration, you can in height between the two reservoirs in a pumped which reduces the size of all the infrastructure, Missouri provided a perfect location for the of height between the upper and lower reservoirs. the highest mountain in Missouri, Taum Sauk, reservoir until there was too much pushback it to a slightly lower peak nearby. And they construction, forcing the engineers to realign it that unique kidney bean shape. The original dam

[00:05:04] just dumping a long pile of rocks around the well as an embankment if you have a good source require a lot of compaction, and it doesn’t settle rockfill doesn’t do well is hold back water. panels were installed all along the inside of A tunnel connected a morning glory inlet through was set into a basin 20 feet or 6 meters below the for a vortex to form as it was drained each day. remotely with no on-site technicians required, the many decisions that would prove disastrous.

[00:06:00] operated on average around 100 days per year, electricity demands were more variable between markets in the 1990s opened up the possibility Those 100 days per year went up to 300, often twice per day, nearly every day of the year. upper reservoir had dealt with leaks essentially projects were implemented throughout its life to of filling and draining were only making things beside the reservoir to capture some of the of 2004, Ameren decided to bring out the big to install a geomembrane liner to cover the

[00:07:00] problem, but it caused a few new ones too. Institute of Electrical and Electronics the plant an “Engineering Milestone” infrastructure. On the day before the ceremony, upper reservoir and witnessed water pouring dam. The operators quickly switched from back down. They chalked up the issue to high caused the overtopping, but just to be safe, level sensors. And what they saw was concerning. the reservoir, there was a valid concern that But the reservoir needed level sensors installed So, instead of mounting those sensors directly

[00:08:04] length, the engineers tried something different. top and bottom of the embankment slope. The cables, minimizing the number of penetrations underdesigned. Those conduits were buoyant, the reservoir filled and emptied each they had become dislodged and deflected, that were lower than the actual water level. decided to reprogram the control system on the pumps. The original design called for between the top of the wall and the maximum distance would be enough to avoid issues until

[00:09:01] the annual maintenance period when the they would never get the chance. someone observed the reservoir overflowing, in the early dawn when no one was around to notice. water quickly eroded down through the dam, cubic feet of water down the steep mountainside stripping away trees and rocks as it surged. when the park was practically empty, but the park whom was only seven months old) were swept away the entire family survived the event, but not The wave of water flowed into the lower reservoir,

[00:10:03] day, so there were no major downstream impacts. Federal Energy Regulatory Commission, events of this kind, a series of small oversights, disaster, combined to cause hundreds of millions family I mentioned. First was the embankment. wasn’t quite as rocky as the engineers who mixed into the fill, resulting in more settlement soil in the embankment’s foundation were also even worse. From construction to failure, two feet or 600 millimeters lower than where consideration when the level sensors were replaced

[00:11:04] sensors unattached and free to move around, there actual elevation of the water in the reservoir. to provide a backup that would automatically shut were installed in a location that was actually embankment wall. If the water hit those sensors, And they were incorrectly programmed in a way the pumps shut off. That first site visit when those failsafe sensors, but no one thought to important elevations like the top of wall and couple feet of margin and postpone a permanent on-site during those last few minutes of

[00:12:04] levels against the electronic measurements, after the enormous red flag of seeing it was overtopping. And the owner hadn’t notified there was no oversight for how Ameren responded. all happened well before the facility an off-channel reservoir, there were only two water being pumped in. With enough freeboard for control system, the designers never envisioned a top. Unfortunately, when you rely on complicated go wrong goes way up. These types of events are coined by Charles Perrow. The idea is that,

[00:13:04] when the safety measures themselves add to more likely, even expected. In other words, control system, a spillway is dead simple. Once They’re not failproof - I’ve talked about several are a lot fewer ways that things can go wrong. the failure, the largest penalty they’ve fund to improve the area around the project, that those funds have been mismanaged. The to a 177 million dollar settlement, much park, which held a reopening ceremony in 2010.

[00:14:02] Park was undergoing renovation, crews were Taum Sauk. To avoid a relicensing process, the same size as the original project. Rather embankment, Ameren and their consultants was built using roller-compacted concrete, earth-moving equipment and compacted into address both the settlement and leakage still taking advantage of the material from the and processed into aggregate for the concrete, the remote site. Maybe most importantly, is the largest roller-compacted concrete dam 2010, was rededicated as an IEEE milestone,

[00:15:05] award of Excellence in the Constructed Project. the professional community. The regulator, FERC, dam safety in the wake of the collapse. They put guidance document specifically addressing the that was circulated to the owners. They to have an internal dam safety program and a for overseeing it, a role Ameren didn’t have far as Hawaii to bolster their dam safety demonstrated the need for overflow spillways, control systems meant to avoid overfilling. the electrical grid, you know the importance of

[00:16:04] of power become a large part of our portfolio, supply and demand are only becoming more the only large-scale way to do this economically, are among the riskiest structures that humans they do, those failures usually come with and the environment. And because they don’t tragically. But, with battery storage becoming interesting to see how the economics of pumped the US will have more than 400 gigawatt hours 100 Taum Sauks. We’re right at the beginning of batteries have a lot of technical differences in

[00:17:05] with their own environmental challenges and lot different than building a major reservoir at keeps evolving, those differences in risks are how we store power, and at what cost. over again is the destructive power of water. It’s education and my career, and so I pay a lot of For example, major flooding recently hit parts of natural disaster when it comes to flooding, infrastructure is helping or hurting, a push to control the narrative after a disaster,

[00:18:01] story - the casualties, preventive measures, can subtly, or not-so-subtly, I like to use Ground News, today’s sponsor. and adds context to make reading the news on the flooding was covered by 230 outlets; not give you a comprehensive viewpoint. Every for political bias, factuality, and ownership of news monitoring organizations. For this story, outlets lean left, 40 percent are center, media conglomerates 73 percent of the outlets also have a feature called the Blind Spot by one side of the political spectrum:

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