Buried Cutoff Wall Draws Attention In Twin Cities

A Mississippi River historian has been drawing attention in the Twin Cities region to a buried concrete cutoff wall, 140 years old, that has been protecting St. Anthony Falls. The wall, which is anchored in sandstone submerged in the river bottom, was built by the Corps of Engineers. 

But the question of who owns it now—and is therefore responsible for its maintenance—is not easy to answer. Construction of the wall began in 1869, after one of the most famous disasters in Minnesota history, when a tunneling project caused collapse of the sandstone riverbed and almost destroyed the falls. Completed in 1876, the wall is 6 feet thick at its base, about 40 feet tall and spans 1,850 feet across the river. It sits near the bottom of the horseshoe-shaped dam. 

The Corps often turns over major infrastructure projects to local entities after it has built them, leaving them with the responsibility of maintaining them. The Corps claims the city is responsible, but city entities are disclaiming ownership. Xcel Energy owns a lot of the infrastructure around the falls. The Corps completed a study of the wall in a 2015 paper that concluded the possibility of failure was remote.

According to the Minneapolis/St. Paul StarTribune, river historian John Anfinson has been urging public officials to examine the buried wall to assess its condition. But Corps officials say there is nothing to worry about. George Stringham, spokesman for the St. Paul Engineer District, explained that the wall is designed to prevent seepage in the soft, porous sandstone. Pressure is more or less equal on both sides of the structure, unlike a dam in which the pressure is much greater on one side. Stringham said it’s unlikely that the wall faces a serious structural threat anytime soon. 

According to the paper, the Congressional Research Service is investigating the legal process that would need to occur to require the Corps to analyze the wall’s condition.