Pull the Plug

Pull the Plug is a quest in Fallout 4.

Quick walkthrough

 * 1) Talk to Sully Mathis to begin quest
 * 2) Fix the pipe leaks in the lake
 * 3) Start the pump
 * 4) Slay the mirelurks and speak to Sully

Detailed walkthrough
The pipes can be located by finding the bubbles on the surface and swimming down (water is irradiated).

After the player character fixes the pipes he can leave the zone and come back later to find out that the lake has been drained and occupied by raiders. At the very bottom of the dig site the player character will find Sully (tougher boss) and several mirelurks in pens which can easily be killed if the player doesn't open doors leading into their enclosures.