Marines from the decontamination platoon put a child pretending to be injured on a backboard during Exercise Silent Ghost outside St. Elizabeths East hospital in Washington, D.C. April 7, 2015. The exercise was a simulated chemical, biological, radiological, nuclear and high yield explosive incident. - Marines from the decontamination platoon put a child pretending to be injured on a backboard during Exercise Silent Ghost outside St. Elizabeths East hospital in Washington, D.C. April 7, 2015. The exercise was a simulated chemical, biological, radiological, nuclear and high yield explosive incident.