First get on the bus and head to the power station. You don't have to turn on the power (just use a turbine instead).

Now you need to drop down into that gap in between the metal walkways.

Here is the tricky part: You see those nail looking things coming out of the concrete?

There should be three of them, go to the first one and move very slowly until you reach the end of the nail thing without falling.

Zombies should pile-up straight in front of you!