The wastewater treatment plant is located directly east of Ulysses' Temple. After detonating the warhead near the water pipe, it can be reached by traveling along the top of the ruined building (the one lying on the side), turning around, and walking through a rocky path which leads to the wastewater treatment plant, which is accessed by a sewer grate. There is also a warhead left of the entrance which, when detonated, will have 2 lead-lined metal boxes under it.
Inside, past some tunnelers fighting several marked men, there is a room with two guards, a manager's terminal with an entry for the Nostalgia challenge, and a Ralphie poster for the Feel Like a Kid Again challenge.
- Pugilism Illustrated, interior office, behind the lockers.
- North-northeast of the entrance to the treatment plant and down a ledge are two NCR Ranger action reports. One of the reports is also labeled 'Addendum'. Both of the reports are part of the Nostalgia challenge added in the add-on.