What was found
THE M2 LAVATORY TOILET DRAIN O-RING SEAL WAS PINCHED AND CUT DURING ASSEMBLY OF DRAIN CAUSING WASTE WATER TO LEAK ONTO THE CENTER WING INTERSPAR UPPER SKIN PANEL. THIS RESULTED IN SEVERE CORROSION DAMAGE TO THE SKIN WITH A ONE INCH DIAMETER HOLE CORRODED ALL THE WAY THROUGH. *S/D* THE O-RING WAS REPLACED AND THE DAMAGED WING SKIN WAS CUT OUT AND REPAIRED. THIS WAS DISCOVERED DURING A 12C MAINTENANCE VISIT.