Hey, Work’s On in the Mines!

Hey, Work’s On in the Mines! is a Chapter 2 side quest in The Witcher 2: Assassins of Kings, available in Vergen on Iorveth’s path. Work in the dwarven mines has ground to a halt because monsters have overrun the shafts, and Alderman Cecil Burdon will pay whoever gets the picks swinging again. It naturally overlaps with the main quest Subterranean Life, which takes Geralt down into the same tunnels.

Underground, Geralt finds that the miners broke into ancient passages dug by creatures from far below, and rotfiends are now pouring in through them. Killing them is only half the job; each breach has to be collapsed with a bomb so nothing else crawls out. Bring at least three bombs before heading down.

Walkthrough

Stock up on at least three bombs (grapeshot does the job), then enter the mining shafts in Vergen; the quest starts as you go down, usually during Subterranean Life.
Kill the two rotfiends at the first tunnel and throw a bomb into it to seal it.
Clear the rotfiends in the room before the second tunnel and seal it with another bomb.
Find the third tunnel hidden behind the bullvore and the immortelle bushes and collapse it.
Return to Cecil Burdon at his house in Vergen (check both rooms) for your reward.