The entire service area for Corpian Well Drilling Inc. of Boscobel, Wis., lies within the Driftless Area. Although the area was not ground level by historic glaciers, it did experience glacial runoff when they melted. The inundations not only carved out rivers and streams, but percolated down through permeable limestone, creating a formation known as karst that weaves through unpredictable strata. Working in karst is about as tough as water well drilling gets.
Mike Beinborn, owner of Corpian Well Drilling Inc., describes the formation’s conditions: “Karst throws you so many curve balls. A lot of guys won’t drill in this. You think you know the formation — you drill through a lot of lime rock with large crevices and voids, then soft sandstone, some shale. But you move 10 feet over, same elevation, same aquifer, it’s completely different. Suddenly there is no soft shale, or there is no soft sandstone.”