When a sinkhole opened up in Pennsylvania State Route 422 in 2019, Gannett Fleming partnered with PennDOT to accelerate investigation and design and ensure the roadway was fixed and reopened to the public as quickly as possible. The solution was a rather involved micropile supported reinforced concrete slab. The depth of the micropiles extended as deep as 180 feet to tag into competent bedrock. Gannett Fleming’s newsletter, Forces of Change, describes more about the project. One cool thing is that you can watch a time lapse video of virtually the entire construction process. Check it out.