Scientists with the U.S. Army Corps of Engineers were inspecting the Martis Creek Dam, which sits just outside Truckee, Calif., and about 35 miles upstream from Reno. It is one of 10 dams in the United States that has “urgent and compelling” safety concerns, according to the Corps, which owns the dam. Data from the most recent evaluation revealed that, not only does the dam have significant leakage, it also lies in close proximity to not two, but three fault zones.

Introducing the Polaris Fault.