You must exit the room just before the checkpoint and you will end up outside again. It should only be a small platform I think... Then right under it a big pipe or something should come out and then you stand on it.
As the pipe thing goes back in then you will be able to crouch and go inside of it.
Make sure you do this part fast:
When you get into the room that the pipe leads to you have to shoot the red generator things on both the left and the right and then quickly blast the red generator in front of you before it goes up.
That should have crippled the mining operation.
After that you have to climb up onto one of those car things and jump into a little cave while riding it. It's dark in there.
I haven't actually played single player in a while, but this should help a little.