After a gas well accident in which a worker lost a leg at a plant, north of Pittsburgh, we were asked to investigate the root cause. The injured well tender had been initiating a “post-fracking” procedure-blowback operation to release pressure in the capped well-at the time of the mishap. When the main valve was opened, the pipe ruptured due to water hammer. The pipe, set off center, broke loose and whipped around, striking the well tender. O’Donnell engineers, conducting the evaluation on behalf of the worker, found that the pipe did not fail because of faulty material or construction.