A stretch of Minnesota Highway 13 in Mendota Heights near Lilydale Regional Park is estimated to be closed until Nov. 1 for repairs after the slope underneath the roadway failed due to heavy rains back in early June.

Repairs have officially started on the highway, which will include a subsurface drainage system and a retaining wall, according to Chris Hoberg, a maintenance operations engineer at the Minnesota Department of Transportation.

The slope failure happened June 3 and the highway was subsequently closed to traffic the same day. Hoberg said MnDOT had to study the area at first to figure out the root cause of the issue, but they ultimately determined that saturated soil caused by rainfall undermined part of the road.

“We had heavily saturated soils, water moving through the granular soils underneath the roadway, and that created more pressure than the slope was able to to handle and so that caused the failure.”

The drainage system being built will be able to drain the soil underneath the highway and divert water into a storm sewer system to prevent subsurface water from accumulating to that level of a failure again.

A 240-foot-long retaining wall will also be built.

“Just because of the terrain on site there, this is an area where the roadway needs to be built on an embankment. It needs to have a retaining structure to hold that soil in place so the roadway can sit on it,” Hoberg said.

Hoberg added that there have been failures before in the area, so MnDOT will be connecting this repair with adjacent ones to create a more robust system. He said this will stabilize this section of Highway 13 for the long term.

Contractors started mobilizing repair equipment and materials to the site on Sept. 9 and construction activities began Sept. 11. Hoberg said repairs are currently progressing well and they are on target for their November reopen date.

The roadway is currently closed between Wachtler Avenue and Sylvandale Road, and signed detours are in place.

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