On May 30, 2003, Groundhog autonomously descended into the abandoned Mathies Mine near Pittsburgh, PA. The 1500-pound vehicle was equipped with laser range sensors, a night vision camera, gas detectors, sinkage sensors, and a gyroscope. 308 meters into the rapidly decaying mine, Groundhog encountered a broken ceiling beam that draped diagonally across the robot's path. The robot made the appropriate decision to retreat. During the retreat the robot rebooted more than once for some fault that is not yet clear. This was close enough to the portal that the team intervened by communicating via a faint wireless link. A communication loop ensued, which was cleared by our PA DEP safety monitor who physically entered a short distance to hit a reset button, enabeling the robot to emerge.