What was found
(AIRCRAFT NOT GROUNDED) (EMERGENCY DECLARED) DURING DESCENT ECAM Y PUMP LO PR SHOWED UP. PERFORMED ECAM ACTIONS AND WE GOT A SECOND ECAM Y SYS LO LVL. PERFORMED ECAM ACTIONS AND GOT LANDING NUMBER THROUGH FLYSMART. / UPON ARRIVAL OF A/C DURING GROUND CREW OPERATION OF CARGO DOORS FOUND HYD FLUID LEAKING FROM #2 ENG FAN COWL AREA. WITNESSED HYDRAULIC FLUID COMING FROM #2 ENG PUMP DELIVERY CHECK VALVE AREA. REMOVED AND REPLACED O-RING FOR CHECK VALVE I.A.W MM 29-13-36-000-001-A AND MM 29-13-36-400-001-A. OPS AND LEAK CHECK OF YELLOW HYDRAULIC SYSTEM GOOD IAW AMM 29-13-00-710-002-A. A/C OK FOR SERVICE.