In 2004, a sinkhole formed under a pier of the three-span bridge that carried northbound traffic on State Route 33 across Bushkill Creek. After attempts to fill the sinkhole and stop settlement of the pier failed, both the northbound and southbound structures were closed and eventually replaced. PennDOT surveyors later recorded movements of several inches on the new structures.
Schnabel was asked by PennDOT to join an expert team to investigate the subsidence of the new tandem bridge and define stabilization solutions. We took a holistic approach to the emergency investigation, using a suite of innovative technologies, ranging from sonic drilling to GIS 3D visualization, to decipher conditions in the complex karst geology. Our team worked with PennDOT to recommend and design stabilization measures and also provided field observations and monitoring during construction.