during the phase of the main mission in which you destroy the generators, there is a teleportation matrix that can be found by the entrance to the robot assembly area. When entered go to the far right corridor and Maggie will be there. Speak to her and the eleveator you are in will go defaulty thanks to her and youll wind up in the waste disposal.
You can find it in a footlocker called Military Footlocker in the Waste Disposal of ZM
it’s easy to miss but it’s just right of the room with the first support sentry.