When a sinkhole roughly 20 feet long, 15 feet wide and 10 feet deep opened beside an Ohio Department of Natural Resources overpass in late 2016, conventional open-cut excavation wasn't an option. Removing the bridge would have taken months and cost millions. Instead, ODNR and its project partners developed a trenchless rehabilitation strategy. Engineers constructed an internal wall within the existing cobblestone storm pipe, then pumped more than 75 cubic yards of flowable fill into the subsurface cavity to stabilize the void. The storm sewer was bypassed throughout; an adjacent 30-inch water main remained operational. Once stabilized, the conduit was cleaned, inspected and relined. The project wrapped in under 90 days, representing an estimated 75% reduction in schedule and 700% cost savings over traditional replacement.