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. Currently, the reservoir is in a state of disrepair. The hydroelectric generators no longer operate and the water has become stagnant.
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.
Poseidon Reservoir has a chance to spawn 3 Legendary ghouls upon entering the main building on Very Hard difficulty.
The Poseidon Reservoir appears only in Fallout 4.