Dams are paradoxes, both loved and hated, serving as symbols of peace, and weapons of war. The latest news about the Mosul Dam, the fourth largest dam in the Middle East and located in Iraq, provides a good example. Like the vast majority of dams, the Mosul Dam had the typical mission of "controlling" water resources for agriculture and flood prevention.
The problem with Mosul Dam was the site geology got in the way of a good engineering project. The bedrock is gypsum, which is 100 times more soluble than limestone, leading to sinkholes and caves, not good things to try to pile a bunch of water near or store water on top of in large quantities. Of course, geotechnical engineers rarely let "geology" get in the way. All it will take is money and grout - and a lot of both.
But now with the human geography of the Middle East shifting with the advent of "populist" Springs, the control of nature, and the structures built to exert control, become targets to win. In this New Yorker article, Mosul Dam is considered a "bigger problem than ISIS". And this Al Jazeera article promotes the collapse of Mosul Dam would be "worse than a nuclear bomb." Even the Canadians are concerned as discussed in this CBC article and video where millions of Iraqis are at risk of flooding if the dam foundation were to collapse without its daily "injection" of the magic grout keeping the gypsum foundation from disintegrating.
America's love affair with dams has lead to something like 75,000 scattered across the US by the US Army Corps of Engineers, the federal Bureau of Reclamation, energy companies, and states that have the foresight to invest in water on their own like Wyoming. As Norman Smith discussed, many of the proposed dams met their mission. Others, however, were not so lucky and failed, either by washing away, or were "leakers" meaning they never held water, or they barely held water. In at least one case outside the US, Smith describes the untimely demise of a dam design engineer when a king discovered that all of the water in his newly constructed dam leaked under the dam.
In the US, perhaps the most famous dam failure is the St. Francis Dam in California. The history and forensic engineering analysis of this catastrophic failure where a dam "tipped"over due to "hubric" overfilling is well documented by J. David Rogers in his incredible book, article, and presentation.
And then there are the dams like the Mosul Dam where the foundation of either the reservoir, dam abutments, or both, lead to the failure of the dam mission. Anchor Dam located in north central Wyoming is infamous for "leaking". I grew up in Wyoming and knew some of the contractors to the federal Bureau of Reclamation who constructed parts of the dam. Yet even with all of the information collected by the Bureau of Reclamation geologists and engineers, lots of myths and misinformation were shared with the public by prominent academic and government scientists. The misinformation lead to my paper to dispel some of the confusion regarding why the dam served as a money pit for so long (and continues to do so today).
One of my graduate students revisited the Tumalo Dam located in central Oregon. The dam was constructed over 100 years ago yet never held water due to sinkholes, presumably due to pirating of water by tubes and fractures in the volcanic rocks. Here is a video of someone from the area describing the turbid history. And here is the graduate student thesis exploring converting the "failed" dam site to managed aquifer storage and recovery.
But what about a dam that might rival Mosul Dam if it ultimately failed? Baker Dam in Washington state might fit this bill. Like the Tumalo Dam, the Baker Dam is almost 100 years old. And like the Tumalo Dam, much of the dam construction information was not documented, or in the case of Baker Dam, lost forever when a landslide destroyed the powerhouse where the documents were stored. Unlike Anchor and Tumalo dams, leakage occurred along the abutments following the initial filling of the reservoir, in part because no grout curtain was installed.
Seepage investigations indicate the possibility of the Baker Dam "failure". Concrete, Washington with a population of about 1,000, rests below Baker Dam, so while its failure would probably not rival a nuclear bomb in terms of lost life, the lost hydropower would likely be sorely missed in nearby Seattle.