I have fought the "Boss" Ruffus, and have the red keycard the he dropped when I killed him.
I went back the way I came and used the keycard to enter the door by the beginning of this section.
In this area, one of the doors requires a "Passcode". Where do I find the Passcode? I have been all through the area and have only found two journal entries, one saying Colonel Nightly is insane and the other one about earthquakes. Neither of them mention a Passcode.