Now head down the sewer hall and find yourself being hunter. Be ready to dodge attacks from a monster and before you head to the northern room, be prepared. At the back of that room, hit the switch to operate the lift. There's a four minute waiting period in which time the monster who was attacking you will emerge. Run away as fast you you can and dodge attacks as you go along. You can wait for the time to run out or attack it. If you're attacking then use the Nitrous Oxide in the area and freeze the creature and damage it as much as you can. Run when the freeze wears off and use the second and third nitrous in the process in order to kill it. Otherwise, just bide your time.
The next area has another merchant and a shooting gallery. So stock up and get around the mining tunnels by killing off enemies until you get to a cavern. Once its cleared head north and press a switch that sens a mine cart to you. Now head up hill to the south and another kill switch. Pick off your enemies with a shotgun and then grab the dynamite from the cart and blow them all up. From there, two giant creatures will attack you. One of the giants is a pansy so no worries. Climb the ladder and get to the zipline. Operate the lever at the other side and let off a lava at one of the giants. With one down and one to go, just keep popping bullets until it croaks. When it's on its knees, vault on top of it and hack away.
When you're done, head to the eastern doorway and get to a multi-level cavern with insects. Take them out bit by bit before heading to the slope and a small cave with a switch. This switch opens half of the door to the south and then head back out to the other cave where the second switch it. Geting to the gate, dodge falling blocks and start running. Pull the switch to your left and activate the lift in the center of the room
The new area has another merchant, once done get to cracking. Shoot at the first two you find to set them on fire. Do the same with the others or taken them out with a blitz move. Now note the locked door to the east before getting to the wooden shed to the south. Crank it up and reveal a ladder to an underground passage. Inside the tunnel are more enemies so be careful and head to the maze. Watch out for traps and get ready to climb the ladder north again. Once up head to the western corner and take them out one by one and then grab the Key to the Mine from the pedestal. More enemies ensue, kill them and get to the east door.