Master Sgt. Kenneth Estes, 97th Medical Operations Squadron NCO in charge of bioenvironmental engineering, prepares to add Phenol Red Solution to a water sample, July 16, 2013, during a routine water sampling. Members of the 97th MDOS bioenvironmental engineering flight routinely monitor for the presence of drinking water contaminants. The base receives its drinking water from the City of Altus water treatment plant. (U.S. Air Force photo by Senior Airman Kenneth W. Norman / Released)