This reservoir not only distributed water from Lake Cochituate to the surrounding farmlands and towns, but was also a source of hydroelectric power, used by Poseidon Energy for its research facilities scattered about the Commonwealth. On October 22, 2077 there was a mass email sent to the entire staff detailing a change in their policies regarding Bring Your Child to Work Day. Normally, they wouldn't allow children into the plant; however, they decided to change the policy to allow two children at a time. If the worker were to bring in more than two children, they would have had to leave them with a caretaker outside the factory while the other two were taken on a quick tour. Currently, the reservoir is in a state of disrepair, and is far more dangerous than it was before the War, with a pack of feral ghouls having moved in.
A series of catwalks on the north side of the facility lead up to a maintenance area containing an armor workbench. A catwalk connecting to the room leads up around some central pillars.
The facility opens to a managerial office on the right, which contains a terminal that opens the doors on the ground that lead further in to the facility, as well as another armor workbench. A network of catwalks lead all over the room. On the ground floor in the southwestern room is a weapons workbench. The locked doors on the southeast end of the plant lead down in a room with some holding tanks, as well as a chemistry station.
- A robot model kit (parts) is found in the Railroad cache; by going into the broken pipe on the south side of the plant and following it to an enclosure. The parts are on a coffee table.
- The Poseidon Reservoir safe key is in the corner of the managerial office's roof, accessed by going up the catwalks and dropping down.
Poseidon Reservoir appears only in Fallout 4.
- Poseidon Reservoir terminals; Terminal
- Fallout 4 Vault Dweller's Survival Guide Collector's Edition p.353-354: "[5.01] POSEIDON RESERVOIR
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."
(Fallout 4 Vault Dweller's Survival Guide Map)