Part 31

Go back down the ramp and through one of the newly opened doors with a "SURFACE ACCESS" sign.

Enter the room with the first aid station to be knocked out, robbed of weapons, and dragged to section c2a3e.

In section c2a3e, after regaining control, quicksave and run forward, jumping onto boxes to reach a side ledge without getting squished. The trash compactor moves much faster, so you'll have to really rush to make it to the ledge.

Wait until the trash compactor stops moving, then quicksave and quickrestore to ensure its two halves are displayed properly.

Use the compactor's halves to cross the room and grab the crowbar from the ledge on the other side.

Climb down the nearest ladder and use your flashlight to find a grating on the floor.

Bash the grating out and drop into a large pipe, moving along it to reach the "Residue Processing" chapter.

After falling out of the pipe into water in section c2a4, turn right and exit the water.

Go through a short tunnel to a large outdoor area where two headcrabs will teleport in. To avoid them, enter running and swerve left into the water, then run-hop across the water to a silo-like structure with a ladder.

Go to the right of the silo to find a valve wheel. Start it turning and immediately run up the ladder.

Quickly drop onto the wooden platform inside the silo before it lowers too far. If you take some damage, play on as a first aid station is coming up soon.

Ride the platform until it stops, then crouch-walk into the rusty pipe opening and move along until section c2a4a loads.

At the end of the pipe in section c2a4a, bash out the grating. Watch as a security guard kills headcrabs. Follow him, grabbing his pistol after he is eaten by barnacles. Be sure to get the bullet clip on the floor near the start of the curving hallway.

Use the crowbar to bash the three barnacles the guard leads you to.

Use the first aid station on the wall past the barnacles if needed.

Go down the hallway to the left of the first aid station to find another bashable barnacle near the top of winding stairs.

Move to the bottom of the stairs to find an HEV station, watching out for two headcrabs in the small area to the right.

Return to the room where you dropped from the pipe and find the ladder on the side of the hazardous waste vat. Climb it and jump to the large chunk of gunk ahead.

Take a running jump at the pipe entrance past the gunk, crouching right before you land.

Follow the pipe to a ledge in a room full of waste vats with mashers. Cross the room using the two mashers ahead. Jump to the nearest masher as it rises from the sludge, then jump to the second masher before the first reenters the sludge. Immediately jump onto the big pipe past the second masher. You may take some toxic damage, but you can heal it soon.

Walk along the big pipe, then turn right and jump to another nearby big pipe. Follow it to the big waste mixing vat, crouching when necessary.

Before crossing the vat, drop to the lower floor and use the first aid station. You can also go through a door to an area with two headcrabs and an HEV station. Use the HEV station and first aid station until you have 100 health and 100 armor.

Climb the ladder back up next to the mixing vat. Jump to the center part of the nearest mixer. Wait until the mixing arms line up between the two centers, then quickly jump across using them. The mixers are moving very fast, so try to jump from the end of the first mixer to the second mixer's center, crouching right before you land. If that's too hard, very carefully crouch-walk along one side of the tank until you reach the exit pipe, then crouch-drop into it.

Run forward to land on the open pipe's edge, crouch-walk into it, and move along until section c2a4b loads.

In the room with conveyor belts in section c2a4b, bash all wooden crates for health and ammo before riding the big slanty conveyor.

After dropping into water, turn around and enter the large underwater pipe with the "DANGER" sign.

Surface in the next room and get onto one of the side ledges.