A 12-minute catastrophe
At 5:09 AM on December 14, 2005, a section of the upper reservoir at the Taum Sauk Pumped Storage Power Station failed. A combination of design flaws and malfunctioning sensors led to the reservoir overfilling. Water poured over a 900-foot section of the parapet wall, rapidly eroding the rockfill embankment beneath. Within minutes, the wall collapsed, unleashing approximately 1.3 billion gallons of water down the side of Proffit Mountain. The entire reservoir emptied in about 12 minutes, creating a flood with an estimated peak flow of 289,000 cubic feet per second.
The deluge descended with incredible force, sending a 20-foot-high wave of water, rock, and uprooted trees toward the East Fork of the Black River and into Johnson's Shut-Ins State Park. The flood scoured a path 2.6 km long, up to 240 meters wide, and 6 meters deep, stripping away all soil and vegetation down to the ancient bedrock. This newly carved canyon exposed Proterozoic-era rocks for the first time in over a billion years.