Old mining tunnels threaten highways

Tailings pile
A short drive on the Iron Range reveals the legacy of more than a century of iron mining. This mining rock waste pile rises over the horizon next to Highway 169 east of Chisholm
MPR Photo

Minnesota transportation officials are concerned underground tunnels could undermine U.S. Highway 169 near Chisholm in the Iron Range.

Miners pursuing iron ore dug the tunnels decades ago.

A hole that opened in the highway's median in 2007 drew attention to the problem. Now, a team from the Minnesota Department of Transportation is looking at what can be done to prevent a wholesale collapse.

Assistant district engineer Duane Hill says the team has gathered a lot of information and is working on a plan to mitigate the danger. They hope to have it ready this spring.

The team is most concerned about tunnels running beneath one 1-mile stretch of highway on the southern edge of Chisholm and another 1-mile section just west of town.

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