A fissure has opened in the great dwarf-canal leading down from Thorin's Hall, threatening to flood the Vale of Thráin.
'Hurry! Take the mortar and make the repairs before the fissures expand. It's only a matter of time before the wall is breached.'
Enter Thorin's Hall to the north, then go west to the Hall of Merchants.
Tindr gave you some mortar with which to repair the cracks in the canal walls.
Tindr is in the courtyard outside Thorin's Hall.
The fissure was sealed. You should return to Tindr with news of your success.