Aside from the physical damage they cause, sinkholes create scary visuals and serious hazards. It’s frightening to imagine the ground beneath us suddenly collapsing and forming a void in the ground. But indeed, it happens more frequently than most would anticipate.

In August 2019, a dropout sinkhole was discovered beneath an existing transformer pad near the intersection of Salem Road and Lewman Way at the River Ridge Commerce Center in Jeffersonville, Indiana. This world-class business and manufacturing park contains more than 6,000 prime acres of land under development along the Ohio River. To save the transformer and prevent further damage and safety risks, the owner called on SME to provide a quick response and geotechnical engineering solutions.   

Measuring approximately 15 to 16 feet deep, this dangerous sinkhole was surrounded by tall grass, and virtually unnoticeable from a distance. Based on a decade-long relationship rooted in trust, River Ridge Development Authority reached out to SME’s Senior Project Engineer Wes Hemp, PE, PG, LEED AP, for help. 

When Wes arrived to the site, he could see that only the ends of the transformer pad were still supported, as the dropout sinkhole undermined most of the soil supporting the pad. The upper 8 feet of the profile consisted of clay soils. The sidewalls of the sinkhole were in danger of collapsing and completely undermining the transformer pad. 
Due to the severity of the dropout sinkhole, quick repair was needed. 

SME mobilized to the site immediately to observe site conditions and provide general direction on a course of action. Formal remedial recommendations were provided within only 48 hours of our initial site visit. 

Recommendations consisted of:

  • thoroughly cleaning the sinkhole via conventional excavation and hydrovac excavation, 
  • plugging the sinkhole with appropriately-sized crushed aggregate (to permit subsurface drainage while stabilizing the sinkhole),
  • and construction of a concrete cap spanning the exposed limestone bedrock surface prior to re-setting the transformer pad. 

SME also provided general guidance and consulting during the remedial phase.  To the owner’s delight and great relief, the transformer was saved, remedial expenses were minimized as a result of quick action, and the hazard was mitigated.