Quarantine Zone

Head to the marked locations to find the gates leading to the quarantine zone. After checking the second gate with the bulldozer, find nearby fuel canisters and load them on the bulldozer. Turn on the bulldozer and watch the scene. The quest will be complete afterward.

Enter the quarantine zone. You'll find an M72 rocket launcher and lots of ammo in the alley past the bulldozer. You can also enter Nick's house to find Postacrd #7. Follow the straightforward path until you reach the next island to the east. Be careful since there's a lot of infected in the next area, with a screamer. Make your way to the medical area and take out the thug, ram and wrestler.

Before heading to the docks, grab the last secret file in the middle of the wooden crates near the workbench to the southeast corner.

Go downstairs to reach the dock entrance. Enter it to reach the next area.