Part 18

Sneak-shoot the crab in the coolant basin room.

Use the wheel on the panel to the right of the window to drain the coolant basin.

Crouch-walk down the corridor to a room with a bullsquid.

Sneak-shoot the bullsquid with your pistol.

Look near the dead guard for armor items and .357 ammo.

Enter the room's small lift and use its button panel to go down a floor.

Sneak-shoot the headcrab around the corner to the right.

Heal at the first aid station if needed.

Use your flashlight to find the short hallway leading to the coolant basin floor.

Find the ladder in the basin's back right corner.

Climb the ladder and carefully crouch-push the two coolant barrels off the side without falling.

Climb back down the ladder.

Start pushing coolant barrels into place to form a bridge across the gap.

Push two barrels onto the large drainage grille in the center of the floor.

Push the other two barrels over next to the grille, one on each side, to create a line.

Go back the way you came, ride up the lift, and go to the room with the wheel.

Turn the wheel again to refill the basin.

Look through the window to check if your barrel arrangement is usable.

If usable, go back through the hole in the coolant room door and down the hall to where you killed houndeyes earlier.

Go to the broken bridge.

When you step on the bridge, two vortigaunts and an alien grunt will teleport in on the other side. Run back to the doorway.

Get out your pistol and use the flashlight to shoot them from a safe distance.

Go back to the bridge and quicksave.

Try jumping across using the coolant barrels.

Once across the bridge, turn left and sneak-shoot the bullsquid visible through a window with your pistol.

Get out your shotgun and look for a door opened by a button panel to its right.

As soon as the door opens, double-barrel the vortigaunt standing just past it.

Go through the door, turn right, and move slowly along the left wall until a vortigaunt teleports in ahead of you.

Quickly charge and double-barrel the vortigaunt, then back up.

If another vortigaunt appears, blast it. If not, charge around the corner and blast it.

Get out your assault rifle and quicksave.

Go through the room's back door and forward to where you can see two marines shooting at an unseen foe. Shoot them both.

Turn right and go to the back wall.

Use the nearby first aid station.

Shoot the alien grunt near a railing on a higher floor at the other end of the area, past crates and barrels, with your pistol, using the flashlight to see.

After the grunt falls, move forward and jump onto the overturned coolant barrel.

Turn left and jump onto a crate, then turn right and jump onto another crate.

Run forward and drop down near a door.

Check the floor next to the dead marine for ammo and AR (Assault Rifle) grenades.

Get your pistol out and crouch-walk through the door.

Use the flashlight to see a headcrab on the floor ahead after turning a corner. Shoot it.

Crouch-walk to the next corner and quickly shoot the headcrab at the top of the first set of stairs.

Crouch-walk up the stairs and sneak-shoot the headcrab at the top of the second set of stairs.

Past the stairs, walk carefully by the flaming pipe on its right side.

Go through the doorway and cross the room to find another doorway.

Get out your shotgun and quickly blow away the vortigaunt to the right of that doorway with a double-barrel blast.

Move past the vortigaunt to the control room.

Go through its door and drop down to its lower floor, where you'll find the body of the bullsquid you shot through the window earlier.

Look next to the window to find a control console.

Use both of the large red levers on the console to restore power.

Climb up the ladder and leave the control room.

Turn right past the control room door to find a railing you can crouch-jump over to shortcut back to the bridge.

Quicksave and recross the bridge using the barrels.

Go down the hall and back to where section ba_power1 reloads.

Return to the radio room and get the secret ceiling vent area's ammo canister if you didn't get it before.

Go down the passage to the left of the radio to get onto the access lift's upper platform.

Use the platform's button panel to raise the lift to your level.

Cross the lift to the platform on the other side.

Get out your shotgun and quicksave.

Run down the dark hall to where you can turn a corner.

When you do, two vortigaunts will teleport in. You can retreat and shotgun them as they come to you, or move far enough in front of the nearby wind.