Transportation

Months after Twin Cities highway closed, repairs to reopen it are set to begin

A landslide of soil on a hillside beneath a highway
Rain-saturated soil on a hillside in Mendota Heights, Minn., gave way in early June, undermining a section of State Highway 13 near Lilydale Regional Park. The highway has remained closed as the Minnesota Department of Transportation researched the best way to address the problem.
Minnesota Department of Transportation

It’s been more than three months since a state highway in the Twin Cities unexpectedly closed after saturated soil on a hillside gave way, undermining the pavement.

But the end of the closure may be in sight. The Minnesota Department of Transportation says work is set to begin this week to repair that stretch of Highway 13 in Mendota Heights.

“Our target is to have the roadway open by Nov. 1,” said MnDOT maintenance operations engineer Chris Hoberg.

Hoberg said contractors will follow a plan that aims to fix the damage caused by the slope failure — and prevent another from happening.

“We’re going to put in a trench drain system to help when water is moving downslope, subsurface, through the soil — that trench drain will capture that and disrupt the process that led to this particular failure,” he said. “And then we need to install a retaining structure to be able to build the road back in its current place.”

A slope failure along a highway that has undermined the pavement
A look at damage to State Highway 13 in Mendota Heights after saturated soil on a hillside gave way in early June, undermining a section of the road.
Minnesota Department of Transportation

Slope failure

The closure — which started late on June 3 — affects a stretch of Highway 13 where it traverses bluffs above the Mississippi River and Lilydale Regional Park.

Hoberg said the ground beneath the highway gave way after heavy rainfalls in spring.

“None of them were particularly significant in their own right, but collectively, that added up to a whole lot of water saturating the soil underneath the roadway. And it just became too much for the slope to handle,” he said. “It burst out, undermining the roadway there.”

After the slope failed and the highway was closed, MnDOT spent much of the summer working to understand the forces at work — performing soil borings, using sensors and gathering other data.

A telephoto image of  a road with orange signs indicating closure
Crews inspect the site of a slop failure along State Highway 13 in Mendota Heights on June 4.
Andrew Krueger | MPR News file

“We needed to study it and understand it and make sure that we knew what had caused the issues out there before we go and spend a bunch of money to make a repair,” Hoberg said. “We want to make sure that we’re solving the problems.”

That was followed by design work for the retaining wall — it’ll be about 240 feet long — and the drain system. Now, work is set to begin.

Hoberg said that stretch of Highway 13 has been a problem spot in the past; this new project will connect two previous repairs. But he said the work this fall “should do a great deal to stabilize it moving forward. It’s intended to be a long-term repair and really address the root cause of the issue.”

Until the repair is complete, the highway remains closed between Wachtler Avenue and Sylvandale Road in Mendota Heights. A detour is posted.