Senior Airman Shaquille Robinson, an intel analyst assigned to the 89th Attack Squadron, pours gravel next to a housing foundation to support its piping in Rapid City, S.D., Dec. 10, 2016. Piping installed in uncompacted ground can develop negative pitch causing stress on the pipe, laying the pipe on a gravel bed will resolve the issue. (U.S. Air Force photo by Airman 1st Class Donald C. Knechtel)