Fixing the Most Dangerous Dam in the World

[00:01] Mosul Dam rises 370 feet or 113 meters above 

[00:09] the tallest dams in the Middle East. The dam was 

[00:16] never really stopped. That’s because ever since 

[00:22] has literally been dissolving, nonstop, below 

[00:29] water started flowing through the foundation of 

[00:35] a year later, the volume of seepage was measured 

[00:42] I usually hate to use the olympic-sized 

[00:46] it makes sense because it was enough 

[00:52] And the issue is that, once a process like this 

[00:58] for the past 40 years or so, the problem at 

[01:04] some of the most preeminent engineers across the 

[01:09] and, of course, armed conflict. Failure of a 

[01:15] towns along the Tigris River would be fully wiped 

[01:20] wave would be so massive that even major parts of 

[01:27] submerged. In 2006, the US Army Corps of Engineers 

[01:34] in the world.” That was 20 years ago, and Mosul 

[01:40] And the story of how it got there is fascinating. 

[01:55] Mosul Dam is an earthen embankment dam 

[02:00] built to generate hydropower and store water 

[02:05] is on the west side of the dam with four turbine 

[02:11] sticking up from the plant that absorb changes in 

[02:16] The dam has an outlet structure through the 

[02:21] radial gates here. And an auxiliary spillway with 

[02:27] spillway gates and fuse plugs if you want to learn 

[02:32] The dam itself is impressive, but the rock that 

[02:38] and in many ways, far from ideal. The geology 

[02:45] a sedimentary rock that is widely used 

[02:49] and drywall. What it’s not widely used 

[02:55] the consensus of experts involved on Mosul 

[02:59] all around, a terrible idea. One 

[03:04] “the decision to locate such a major and important 

[03:10] the Mosul Dam site was fundamentally flawed.” 

[03:15] That’s because of a critical property of gypsum,  

[03:18] one that it doesn’t share with many other types 

[03:24] You might be familiar with limestone caves and 

[03:30] subsurface. Some of these can be quite dramatic 

[03:36] Cave in Kentucky. They’re formed because the 

[03:42] as long as it’s a bit acidic, which rainwater 

[03:48] years, that water kind of carves away the earth 

[03:54] is roughly 200 times more soluble in water than 

[04:00] sugar or salt that dissolves almost instantly, but 

[04:07] are accelerated to human timescales in gypsum. 

[04:13] because dissolution isn’t a linear process. 

[04:19] which means more dissolving and so 

[04:23] Many dam failures have resulted from internal 

[04:28] rock carries away particles, leaving voids. This 

[04:34] which I covered in an earlier video. But 

[04:39] by designing filtration systems that 

[04:44] escape the subsurface, you can’t easily 

[04:49] The designers of the dam knew the 

[04:53] and they had a few ideas to address it. One was 

[04:58] the bottom of part of the reservoir. This would 

[05:03] at least in the dam’s immediate vicinity, 

[05:08] the total volume of the flow. However, the volume 

[05:14] layer would be fairly fragile to damage from 

[05:19] was to use a cutoff wall, basically a continuous 

[05:26] The problem was that there were no machines that 

[05:31] of the gypsum. The idea they landed on was 

[05:37] Mosul Dam’s design included a continuous concrete 

[05:43] It had one purpose: to provide access to the 

[05:48] pumps. Political and schedule pressures 

[05:53] before the grouting was complete, but 

[05:56] to the gallery tunnel to continue that process 

[06:02] they underestimated how serious and complex a 

[06:08] As soon as the reservoir filled up, the problem 

[06:13] pools of seepage in the intro, but it wasn’t 

[06:19] the dam as caverns formed in the geology below 

[06:25] those sinkholes started appearing closer 

[06:30] the solution cavities were migrating in the 

[06:36] operators have maintained a continuous grouting 

[06:42] bentonite, and water into the rock below 

[06:47] the voids. It’s basically a nonstop 

[06:53] because grout doesn’t fare well in flowing water 

[06:59] Recognizing the hazard they had created 

[07:04] with a backup solution. Since it was clear that 

[07:10] they would just build another dam downstream 

[07:16] when) Mosul Dam failed. Badush Dam 

[07:22] It would have a hydropower plant and store water 

[07:28] storage pool to protect downstream cities from 

[07:35] halfway finished before the geopolitical 

[07:43] In 2003, a US-led coalition invaded Iraq as 

[07:50] to the September 11th attacks. As a major piece 

[07:56] the coalition worried. Some early reports hinted 

[08:02] as an act of sabotage. But it didn’t take long to 

[08:09] They started coordinating with the US Army 

[08:14] whose report concluded that the risk 

[08:18] the “most dangerous dam in the world” quote 

[08:23] The truth is that the “danger” of a dam is 

[08:28] and it’s not a statistic that’s widely tracked, 

[08:33] a government agency was willing to say it means a 

[08:39] the situation seriously and started working with 

[08:45] the dam. That panel largely came to the same 

[08:52] Coalition forces had bases and equipment 

[08:57] concerning enough that they decided to 

[09:01] inundation area if the dam were to breach. At 

[09:07] was helping the new Iraqi government 

[09:11] including improving the grouting program at 

[09:16] considered a temporary solution, the consensus 

[09:22] to address the foundation problems beyond 

[09:27] Initial efforts by the US government to help at 

[09:33] A few notable examples: The winning contractor 

[09:39] grout) mixing plant design, and somehow 

[09:44] despite it being printed on the front page of 

[09:48] the concrete plants had already been delivered, 

[09:53] to try and convert them into grout mixing 

[09:59] with no ladders or braces. Some weren’t even 

[10:05] for the hoppers had no retaining walls, 

[10:10] and pumping equipment couldn’t even fit into 

[10:15] dam operations staff meant to run all this 

[10:20] a few weeks of training. The oversight 

[10:25] Millions of dollars had been spent on 21 

[10:31] Coalition forces continued efforts to improve 

[10:37] the US was withdrawing troops from the country 

[10:43] back to the Iraqi government. Unfortunately, that 

[10:49] continued to plague the region. In mid-2014, 

[10:56] and Daesh) took over several cities in Northern 

[11:03] Mosul Dam, which was still relying on nearly 

[11:09] safe. That August, ISIS seized control of Mosul 

[11:16] collapse. For more than a week, the dam was out of 

[11:22] what the militants might do (or what they might 

[11:28] Even short-term neglect presented a serious 

[11:34] by Kurdish and Iraqi forces, with the help of US 

[11:40] Iraqi hands, but the surrounding areas weren’t. 

[11:47] the disruption of the workforce at the dam, and 

[11:52] operation wasn’t being maintained. Equipment 

[11:58] used. Voids were going untreated, and concerns 

[12:04] Realizing that the Iraqi government was too 

[12:09] the US decided to stay involved as 

[12:15] the Army Corps of Engineers led a task 

[12:19] and the results were alarming. The US Embassy 

[12:25] saying that the dam had an “unprecedented risk 

[12:30] half-a-million and 1.5 million people along the 

[12:37] crisis unlike almost anything in modern history. 

[12:43] ongoing occupation by the Islamic State, making 

[12:49] able to evacuate to safer areas. Electrical 

[12:55] and poor communication would make things 

[13:00] The Iraqi government tried to downplay the alarm a 

[13:06] Resources said, quote, “The looming danger to 

[13:12] is present in all the world’s dams.” I don’t 

[13:17] actually supported by some kind of analysis, but 

[13:23] hilarious if it weren’t such a serious situation. 

[13:29] what we normally use, and multiplying it by the 

[13:34] of Engineers, you get an expected annual fatality 

[13:43] would anybody consider that acceptable. This is a 

[13:49] large dam projects. This green area generally 

[13:55] making a structure safer. Yellow, you have to be 

[14:01] the minister’s estimate of probability, and the 

[14:07] Mosul Dam would plot somewhere around here on 

[14:13] moniker doesn’t seem like hyperbole when you 

[14:18] Sean MacFarland, “If this dam were in the United 

[14:24] The urgency finally spurred action in 2016. 

[14:29] Iraq awarded a contract to an Italian company  

[14:32] to rehabilitate the structure, including a 

[14:38] grouting program. It was one of the most 

[14:43] with participation from the Iraqi government, 

[14:48] Italian military, and a number of international 

[14:54] engineers involved on the project, and 

[14:58] In the early days of the project, they were 

[15:03] to support the Iraqis who were operating 

[15:08] let them monitor the situation remotely while 

[15:14] The entire project had to happen near the front 

[15:20] continued to unfold in Iraq. Security forces 

[15:25] the dam and supply routes for materials and 

[15:31] but eventually, the project team was able 

[15:35] Over the next few years, all the grouting 

[15:40] piping, electrical systems and drill 

[15:45] Crews drilled more than 5,000 boreholes with 

[15:51] kilometers or 250 miles. 41,000 cubic meters 

[15:59] into the foundation along the entire length of the 

[16:05] inflate a rubber device called a packer using air 

[16:11] borehole and injection pipe. Or you just grout 

[16:17] Then you can pump grout at very high pressure 

[16:23] fissures. You just keep pumping until you reach 

[16:29] that you hold until the grout stops flowing. And 

[16:35] All this work was done using a sophisticated 

[16:41] depth, mix design, flow rate, and quantity of 

[16:46] track progress, identify issues, and visualize 

[16:53] delivery to batching to drilling and injection, 

[16:59] I love unique measurement units, and this project 

[17:05] the contractor would try to inject water into the 

[17:11] is the loss of water of one liter per minute 

[17:18] of 1 megapascal or about 145 psi. For all the 

[17:26] 98 percent had values below 3 Lugeons, a massive 

[17:34] The project finished in 2019. It was a 3-year 

[17:40] but Mosul Dam lost its most dangerous 

[17:45] the dam is in a much less precarious position. 

[17:51] Foundations Institute in 2022, highlighting 

[17:57] But this wasn’t like a typical construction 

[18:02] goal was to get the Iraqi government set up to 

[18:08] The rock below Mosul Dam may have a lot more grout 

[18:15] and there’s still a massive reservoir constantly 

[18:20] the rehabilitation project was training Iraqi 

[18:27] despite its magnitude, the project was sort of a 

[18:33] never been considered a permanent solution, and 

[18:39] improvement in the long-term prospects of the 

[18:46] Iraq is still planning for a more permanent 

[18:51] Badush Dam on the map, downstream from 

[18:56] the table if anyone can figure out how to come 

[19:00] Another option is that deep foundation cutoff 

[19:06] would provide a continuous barrier for seepage 

[19:11] These are used on a lot of dams across the 

[19:16] and depth as would be required at Mosul. In 2018, 

[19:23] 5 billion dollars, an almost unimaginable 

[19:29] and functions today. Whether the electricity and 

[19:36] capital is something that will probably 

[19:41] the government will keep pumping grout and Dinars 

[19:47] a flawed foundation, but now with much more 

[19:54] One of the trickiest  parts of Mosul Dam is that you can’t just see what the subsurface looks like. The Army Corps  

[20:01] of Engineers did a really detailed investigation, 

[20:06] on very limited observations from individual 

[20:12] a challenge for all kinds of engineering projects 

[20:19] My friend Brian at the Real Engineering 

[20:24] “The Anatomy of.” He’s putting everyday 

[20:29] so we can literally see inside. This is 

[20:35] up our favorite gadgets, and if you want to 

[20:40] You probably know about Nebula now, even if 

[20:44] built by and for independent creators. No studio 

[20:51] advertisements driving the content into a single 

[20:57] they’re excited about with as few barriers and 

[21:03] My videos go live on Nebula before they come 

[21:08] was specifically produced for Nebula viewers who 

[21:14] I know there are a lot of streaming platforms 

[21:18] monthly cost to keep track of, but I also know 

[21:23] there is a ton of other stuff on Nebula that 

[21:28] it dead simple: click the link below and you’ll 

[21:35] 30 dollars, for an entire year’s access 

[21:42] if you have subscription fatigue, but 

[21:45] you can get a lifetime membership. Pay once 

[21:50] last. If you’re with me that independent 

[21:55] I hope you’ll consider subscribing. Thank you