It is located just before crouching to go through a hole in the metal gate. There will be a damaged metal catwalk leading to a small room, where the document can be found, next to a dead patient in the Sewer.
"Already weak, cold. It's still bleeding but it doesn't hurt anymore and I almost have quiet. I can't hear the Walrider anymore. Maybe the therapy is wearing off, I can't remember the dreams. Said I could earn my release from this place by submitting to the therapy. Lies. Of course they were lying. It was not therapy. We were sacrificed to conjure a demon. Please, let there be no dreams. The only hel..."