I ended up figuring it out shortly after I made my comment but I didn't wanna post twice so quickly. I was up to the point where you explode the two turbines being guarded by a fiend, so before obtaining any keys. I was confused by the water pit behind the fenced area that opens because I kept thinking I had to shoot a grenade into the pipe to continue - I didn't understand the significance of that area opening up otherwise unless it was already open before and I just didn't notice. Was it just to show you the pipe connected to the exhaust in the next room over, which causes the wall to explode?
It took me a long to discover the elevator in the room that takes you down to what I think was the gold key. The map also started to make more sense there as some sort of facility where they were maybe investigating these monsters and stuff like that. In retrospect, I feel like an idiot for missing the elevator but the space to squeeze through was so narrow that I thought it was a simple break in the barrier, not a potential passageway.