As Iraqi forces continue their battle against ISIS in Mosul, there's another problem lurking just 25 miles away from the embattled city: the Mosul Dam, a structure the US Army Corps of Engineers has called the "most dangerous dam in the world," per a piece by Dexter Filkins in the January 2 New Yorker. It's not the dam itself that has both American and Iraqi officials worried: It's that the structure is built on void-prone gypsum rock, which needs constant cement injections; without that fortification, the ground underneath the dam will be whisked away and the dam will sink and crumble. When the dam was being built, experts assured then-leader Saddam Hussein the gypsum problem could be managed, and the Mosul Dam was completed in the mid-'80s—but structural problems were immediately evident. After the US invasion in 2003, Americans tried to spur the Iraqis to further fortify the dam, but they were (and still are) met with runaround. "The Americans are exaggerating," the dam's director scoffs. "This dam is not going to collapse. Everything is going to be fine."
Most of the dam's workers fled when ISIS took over the dam and the Mosul grout plant in 2014, and even though Kurdish forces retook the dam, grouting stopped for anywhere from three weeks to 18 months, based on conflicting stories. Now there's the extra pressure that will likely be put on the retaining wall as winter snow melts in the spring. And if the dam does break down? There could be a "catastrophe of Biblical proportions" in the form of an enormous wave towering up to 100 feet above the Tigris River and sweeping up all within a hundred miles. It would submerge much of Mosul, which would be hard to evacuate due to its ISIS stranglehold. Baghdad would also feel the effects within days from a 16-foot-high wave slamming into it. And the entire country would likely be left without power and see most of its wheat fields flooded. Total death toll: up to a million and a half people. "It's a nuclear bomb with an unpredictable fuse," an Iraqi-American civil engineer says. Read more of Filkins' piece on this looming disaster at the New Yorker.