MAINTENANCE CREW WAS REMOVING 55 GALLON DRUMS OF ROCK WASTE FROM CRUSHER PIT, AS CRANE BOOMED UP, BOOM STRUCK OVERHEAD I BEAM AND EXTENSION JIB ON SIDE OF BOOM THAT WAS HELD IN PLACE BY 5/16"" BOLT U-BOLTS BROKE LOOSE AND END OF JIB SWUNG DOWN STRIKING EE ON RIGHT SHOULDER.