After you hit the ground, run over and knock down the scaffolding on the left.Then run to the right, you will be beset by another brain slug. Follow its direction all the way to the left, then from the beam of light back to the left and back to where it attached itself to you.
Continue to the right and drop down to the platform below, continue past the lift and two switches along the lower path. Jump across to the hanging girder and then hop across the next two until you reach solid ground again.
As you move forward, you will walk over a button on the ground. The switch triggers a time delay release of a crate from a claw hanging from the roof infront of you. As you activate the button, hold back on the control pad to slow your walk down. Wait for the crate to drop in front. Keep behind it until you see a circular saw coming your way. When it is almost upon you, jump onto the crate and over the saw.
Jump up to the raised platform on the right and jump again to have the demonic growth release you from brain slug control. Wait for the saw to come back to the section just below you, then jump across and hop over to the safety of the closest suspended girder.
On this girder you will need to run back and forth between either end to tilt the girder enough to enable you to jump to the next girder to the left. Once you have reached the second girder, grab the third girder and pull it back as far as you can. Jump onto it, it will swing across allowing you to jump onto the platform on the left. Continue up the ramp until you reach the elevator again.

