Trunk highway 494 (I-494), managed by MnDOT, carries an average daily traffic count of over 290,000 vehicles. Since 2002, there has been a surface depression and subsidence on the edge of the road, adjacent to a near-surface storm sewer system of tunnels.
The sinkhole formed because of the ongoing migration of material into the stormwater system. For many years, the surface depression was handled through roadway patching. However, the rate of sinkhole development began increasing in 2013, and increased amounts of sediment began accumulating in the nearby Penn Avenue Lift Station, requiring more frequent maintenance by MnDOT to remove and dispose of the sediment.
MnDOT hired Barr to investigate the sinkhole and develop a solution for rehabilitating and eliminating its progression without disrupting nearby traffic patterns. Barr’s services included performing a desktop study of historical data, completing field investigations (geotechnical soil borings, laboratory testing of soil samples, and a tracer study), and developing a remediation design. Using our design, MnDOT completed construction in 2017.