Prior to the Great War, Poseidon Reservoir distributed water to the surrounding farmlands and towns in addition to generating hydroelectric power for use in Poseidon's research facilities scattered throughout the Commonwealth. Since the War, the facility has fallen into disrepair and is inoperable.
Upon entering the facility the maintenance office is located on the right in a metal pod, inside the office is a terminal. On top of the office there's a hidden toolbox, accessible via a footbridge. Past the office, a stairwell can be used to access the lower level of the facility, the lower level consists only of a room containing a weapons workbench and some containers. In the southeast part of the facility lies the back area, behind one of the reservoirs a steamer trunk and safe is found.
The roof can only be reached via a stairwell located on the north side of the facility. On the roof a large metal pod with a armor workbench is located upon reaching the roof. On the east side of the facility another reservoir can be reached via a footbridge.
- Robot model kit parts in a Railroad stash (indicated by the railsign) via a brown pipe going into the lake, accessible via an underwater breach in the pipe, outside next to the factory.
- Poseidon Reservoir safe key - Inside, behind a large pipe in the upper west section corner (drop down from the catwalk). Opens the safe in room behind the security doors and a tool case in the main room.
- Cleansing the Commonwealth - This is one of the locations Knight Rhys will ask to cleanse of its inhabitants.
- Ghoul Problem
- Last Voyage of the U.S.S. Constitution - This is one of at least two destinations to which the Sole Survivor can be sent to retrieve the Poseidon radar transmitter.
- Learning Curve - This is one of the locations where you need to escort a scribe of the Brotherhood.
- Quartermastery - Scribe Haylen asks you to retrieve a haptic drive from this location.
- Randolph Safehouse - This is one of the possible locations that may need to be cleared out for Mr. Tims.
- Lost Soul - This is one of the possible locations that you may be asked to rescue a synth by the Railroad.
The Poseidon Reservoir appears only in Fallout 4.
- ↑ Fallout 4 Vault Dweller's Survival Guide, page 354 - "Poseidon Energy Reservoir not only distributed water to the surrounding farmlands and towns, but it was also a source of hydroelectric power. The power generated was used by Poseidon for its research facilities scattered about the Commonwealth."