What was found
CREW REPORTED GREEN HYDRAULIC RESERVOIR LOW LEVEL MESSAGE FOLLOWED BY SYSTEM LOW PRESSURE 30 MINUTES AFTER TAKEOFF. PER ECAM PROCEDURES, THE POWER TRANSFER UNIT & GREEN HYDRAULIC PUMP WERE SELECTED OFF. FLIGHT CONTINUED TO PHX WHERE CREW DECLARED AN EMERGENCY, LANDED WITHOUT INCIDENT & TAXIED TO GATE. MAINTENANCE FOUND NR 1 ENGINE CASE DRAIN HYDRAULIC LINE TO HYDRAULIC CONTROL UNIT LOOSE - TIGHTENED B-NUT IAW AIRBUS MAINTENANCE MANUAL 29-11-49.