RETURN HOSE PLUGGED UP. TRIED TO CLEAR WITH PRESSURE WON'T CLEAR. TOOK HOSE OFF AT COLLECTOR. LIFTED WITH CRANE. TRIED TO BERAK HOSE WITH HAMMER. WOULDN'T CLEAR. SHOVED SHOVEL HANDLE UP HOSE T O DISLODGE. AIR TRAPPED ABOVE BLOCKAGE BLEW OUT AS MATERIAL RELEASED HOSE JERKED CAUSING INJURY.