Vernon County CTH SS Reconstruction

Challenge

The rural stretch of roadway in Vernon County, Wisconsin, between Pea Vine Road and STH 56 isn’t just another back road. Residents rely on it for daily travel, farmers depend on it to move equipment and goods, and emergency responders count on it when every minute matters. It also serves as a critical bypass around the City of Viroqua, carrying regional traffic and providing a reliable route when flooding impacts in-town streets.

But years of pavement deterioration, repeated slope failures, and deep longitudinal cracking have taken their toll. Entire sections have slowly crept downhill, creating hazardous conditions and forcing crews into a cycle of ongoing repairs to keep the road passable.

The steep slopes along the downhill side of the roadway, combined with a history of severe storm events, raised concerns about the potential for a major roadway failure. In 1978, similar conditions led to the complete loss of a portion of the road and forced its closure. A long-term solution was needed to improve overall conditions while addressing multiple slope stability concerns throughout the one-mile corridor. 

Solution

SEH partnered with the Vernon County Highway Department to evaluate the corridor and develop a reconstruction strategy that addressed both performance and slope stability. The project included extensive geotechnical investigation, including soil borings conducted throughout the entire alignment to better understand subsurface conditions. The analysis revealed slope stability factors well below acceptable safety thresholds, confirming the need for targeted subgrade and embankment improvements. In response, the team designed solutions that removed six to nine feet of unsuitable soils in critical areas and replaced them with engineered base aggregate reinforced with geogrid. These improvements significantly increased stability and reduced the risk of future roadway movement.

Drainage Improvements and Community Benefits

To further protect the corridor, all existing culverts were reviewed and upsized to better accommodate watershed flows during heavy rain and flood events. Riprap slopes were installed at culvert outfalls to reduce erosion, and stone ditch checks were placed at regular intervals to slow water velocity and protect the embankment. The County is now positioned for future federal funding thanks to the 60 percent shelf design plans completed during the project.

A Road the Community Can Rely On

The completed reconstruction has transformed a problem-prone roadway into a safer, more reliable route for a predominantly agricultural community that depends on it daily. Since completion, the County has received positive feedback from residents who now experience fewer closures, improved safety, and greater confidence in the roadway’s ability to withstand future storm events.