F.E.A.R. 2: Project Origin

This achievement is for the Reborn campaign.

After going into the sewers you will see big rusty looking hatches where infected enemies will come out. There are nine of these, five in the main room where you first encounter them, and four in the cylindrical room shortly after it. Simply go up to every one that is open and press X to pull the level and close them up. (There will be a green light if it is still open).

Here's a video outlining all nine locations.

After dropping down into the sewers, proceed through the narrow tunnel and hatch 1/9 will be straight ahead.

Continue up the small set of stairs, turning left at the top. Follow this all the way to the end and drop down to the right to find hatches 2/9 and 3/9.

Turn around and follow the water to the left. Continue straight ahead over the debris to find hatches 4/9 and 5/9.

Now proceed through this area and you’ll reach another narrow tunnel. At the end of this tunnel you’ll see a circular opening leading to the next area as well as another narrow tunnel leading to the left.

Head through the circular opening and follow the walkway to the right to find hatch 6/9.

Head down the stairs to the left and at the bottom you’ll find hatch 7/9.

Drop down to the left and go straight ahead to find hatch 8/9.

Turn back around and head the other direction, past the taxi and over some piles of debris. Go up the small stairs and follow this around to reach a set of metal stairs. At the top of these you’ll find hatch 9/9.