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Highway 67 is sliding away; MnDOT's trying to figure out how to stop it

For a while, part of the road was slipping away at about an inch a day.

For a while, part of the road was slipping away at about an inch a day. Minnesota Department of Transportation

The Upper Sioux Agency, full of wispy prairie grasses, bluffs, and the occasional bald eagle circling overhead, is about as starkly pretty as Minnesota state parks get. It’s just outside of Granite Falls and a hop, skip, and a jump away from the Yellow Medicine River.

But these days, the park is basically divided in half, with a 16-mile detour between the visitor center and the campgrounds. That’s because in April, officials with the Minnesota Department of Transportation (MnDOT) found the section of Highway 67 that spans the park six inches lower than it should have been.

An ugly, lightning bolt-shaped crack split the road and sunk a swath of pavement into the earth. And week after week, it kept sinking, about an inch a day, turning the crack into an impassable fissure. Highway 67 was slipping from its moorings, like a chunk of layer cake sliding down a floe of runny icing.

MPR reported that this road has been graded on its current alignment since the ’40s, but this has never been an issue before along this particular hillside. By the end of the month, MnDOT had closed it off.

“The next day, we were out there with an investigation plan,” soil engineer Cody Brand says. Workers probed down as far as 80 feet to find the extent of the damage. What they discovered wasn’t exactly heartening.

The hillside was crumbling as far as 50 feet down, weakened by the river lapping at the base and sopping wet soil from all the rain and snow we’ve seen this year. It’s been one of the wettest 12 months on record for our state, and it’s effectively turned the once-solid ground into useless mush.

The entire Midwest has been drenched this year, flooding out roads, farms, and homes. Southern Minnesota is one of the regions taking the brunt of the punishment. It’s consistent with warnings from the National Climate Assessment, which predicted climate change would increase both temperatures and heavy rain events in the region, and “amplify existing climate-related risks” to its “people, ecosystems, and infrastructure.”

No one weather event is the direct consequence of climate change, but scientists agree we’re seeing more “5-year” and even “100-year” storms and floods that we used to. The Department of Natural Resources, which documents these “mega-rain” events, noted that the 18 years between 2000 and 2017 have seen “nearly three times” as many mega-rains as the 27 years previous.

Our present—as well as our future—is poised to be wild and wet, and that leaves our state (and its infrastructure) vulnerable.

While MnDOT works to find the weak point, Highway 67 keeps sliding away. Thankfully, it isn’t sinking as quickly as an inch a day anymore, but Brand says the road is now three feet from where it should be, and counting. There’s no telling, he says, how many more inches the road itself can take.

It’s too soon to say what exactly MnDOT’s going to do about it. No matter what, that decimated pavement is going to have to go, and the department will have to stabilize the hillside somehow.

That might mean providing drainage so the ground can dry out and firm up. It might mean protecting the base from the lapping waters of the river. It might mean installing a pillar—like a dowel inserted into a wobbly wedding cake—to keep the whole thing from crumbling. Brand hopes to have an answer soon.

Meanwhile, if climate predictions are any indication, we should gird our collective loins for more of the same.