Frequently Asked Questions
Why was the road closed?
Was the road failure caused by an earthquake?
No, it was not caused by an earthquake.
What caused the cracks in the road?
There are several factors contributing to the slope's instability (see "What have you learned so far?" below). Wet soil conditions experienced in the spring of 2019 caused an increase in the weight of the soil leading to an unstable condition, resulting in a slope failure. Part of the why is unknown - why did this road failure happen now? Sometimes a series of events can come together to cause a failure.
What steps have been taken to date?
- We developed an investigation plan. See Facebook video.
- We reviewed the known geology and surrounding topography.
- Soil borings were taken to determine soil classification, properties and layers.
- Instrumentation was placed in the soil boring holes to detect, measure and identify the depth of movement.
- We installed additional instrumentation to measure groundwater depth and saturation levels.
- We created an investigation and monitoring plan for additional areas near the main failure.
What have you learned so far?
- Heavy snows and rainfall have saturated the soil.
- The soils are susceptible to failure and cannot support the hillside (and roadway) when saturated.
- The Yellow Medicine River has been eroding the toe of the slope, which holds the slope up. The river is located at the bottom of a steep embankment below this section of the road.
- The embankment continues to move, approximately one inch per day, at the main crack. There is a three-foot displacement from one side to the other.
- There is significant movement at 50 to 100 feet beneath the road surface.
Will the road be opened in 2020?
No, there will be no repairs or construction during 2020. With a problem of this size, it's important that we take the time that is needed to understand what's happening with the soils and slope movement.
Where are you in the process?
We've analyzed the data that's been collected and we're working to developed recommendations for the road. Conversations with local governments, Upper Sioux Community, DNR and landowners are taking place this spring. Input from all stakeholders and the general public will be gathered during the spring/summer of 2020 before a decision is made.
Has the bridge that crosses the Yellow Medicine River near 600th St. been monitored, too?
The bridge is safe, but yes, we have monitored and analyzed the bridge.
NOTE: This page will be updated as new information or concerns are received and evaluated.