There's a Dahl chest in Pity's Fall, behind some electric fences. It's in the bottom floor of a large room with multiple levels, where you fight a lot of enemies.
The mission objective at this point is "Get to the engine room".
It looks like it only requires a single switch because there's just one red light above the door.
Best Answer
If you stand at the entrance to Pity's Fall and look up you will see a Red cable. It leads up to one of the catwalks west. Most players will jump up onto it for a slam switch.