Well, I misread your thread and badly worded my reply, sorry. What I was trying to say, the valve should still be where you released the gas in Claires game. However, in Chris\' game, since the first floor is flooded (and frozen), you can access the area where the valve is through the room where Steve and Claire activated the crane and hit the pipe in the first place.
[edit]Also, if you needed to turn off the electricity, you don\'t need the valve anymore if you are at this point. Just use the handle on the power machine thingy.