PRESSURE HOSE USED TO SET DUKE JACKS AT HEADGATEWAS UNDER GOOSENECK OF HEADGATE ON THE BOTTOM. MAN PULLED ON THE HOSE. THE SHUTOFF VALVE ON THEEND CAUGHT ON SOMETHING & WAS INADVERTENTLY TURN ED ON. PRESSURE CAUSED HOSE TO WHIP & STRIKE MANON FOREHEAD CAUSING A LACERATION.