What was found
AIRCRAFT WAS GROUNDED: THE FLIGHT CREW REPORTED THAT THERE IS A MILD ODOR PRESENT WHEN PACK 1 IS ON. THE ODOR SUBSIDES WHEN PACK 1 IS TURNED OFF. IT DOES NOT SMELL ELECTRICAL OR MECHANICAL (OIL). MAINTENANCE FOUND A HEAVY OIL BURNING SMELL WITH BOTH PACKS ON WITH THE APU AS THE BLEED SOURCE. MAINTENANCE FOUND OIL LEAKING FROM THE APU SURGE AIR DUCT JUST PRIOR TO THE SURGE VALVE WHICH WAS RUNNING DOWN ON THE RIGHT HAND APU ACCESS DOOR. MAINTENANCE REPLACED THE APU PER TASK CARD 26L31049003 AND ACCOMPLISHED A DECONTAMINATION OF THE ENVIRONMENTAL CONTROL SYSTEM PER TASK CARDS 26L00021013, 26L00021014. A SATISFACTORY LEAK / OPERATIONAL CHECK WAS ACCOMPLISHED WITH NO ODORS NOTED.