What was found
AIRCRAFT WAS GROUNDED: APU BLEED SMELLY SOCK SMELL ON DESCENT, LANDING, UNTIL SHUTDOWN. MAINTENANCE FOUND RESIDUAL OIL IN THE APU PLENUM AND CLEANED THE APU INTAKE PLENUM. MAINTENANCE ALSO ACCOMPLISHED THE DECONTAMINATION OF THE ENVIROMENTAL CONTROL SYSTEM. A SATISFACTORY LEAK / OPERATIONAL CHECK WAS ACCOMPLISHED WITH NO ODORS NOTED.