Is The Fragile Geology Of St. Anthony Falls Imperiled?

By Mike Mosedale, Minnesota Reformer:

In 1992, Greg Brick secured permission to access a rarely visited place on the Mississippi River not far from downtown Minneapolis: the vestigial remains of the Eastman Tunnel.

Brick is a geologist with a passion for exploring underground spaces, so he knew the disastrous collapse of the unfinished tunnel in 1869 utterly transformed St. Anthony Falls. What was once a natural, 50-foot high waterfall with an irregular limestone ledge became the highly engineered, concrete-encased structure you see when you walk across the Stone Arch Bridge.

Brick’s interest in accessing the tunnel was driven in part by an obscure curiosity. Could he use it to catch a glimpse of a very old, well concealed but critical piece of riverine infrastructure known as “the cutoff wall?”

The immense concrete dike, which runs deep under the riverbed, was constructed by the U.S. Army Corps of Engineers in the 1870s to prevent the Eastman Tunnel collapse from eroding St. Anthony Falls into oblivion — a potentially ruinous development for a young city dependent on water power.

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