County Sewer Mainline

The county sewer mainline is a sewage tunnel running underneath the Capital Wasteland.

Layout
The tunnel can be accessed from either inside the sewer waystation or a sewage grate along the Potomac, just north of a raider camp under the west point of the Key Bridge. It goes under Grayditch and Arlington Cemetery, but has no access points there. It is the home of Gallo, as well a number of feral ghouls and radroaches, and contains a large number of workbench items.

Gallo's home
Nearby the waystation access point (the right path after entering via the waystation) is a hostile ghoul named Gallo, whose room is located past several traps in the northwest region of the sewers. In Gallo's footlocker his storage key can be found which is used to access a storage closet nearby. Gallo's room also contains a small Nuka-Cola collection, a safe, as well as a pen of radroaches. There is a bed here too, and quite a few shelves.

If Gallo is killed, it can be used as player housing (though the Lone Wanderer cannot technically own it). It also contains 40 railway spikes and a Stealth Boy hidden in a box on a bottom shelf, along with some chems and ammunition.

Gallo's storage closet contains the following workbench items:

Sewer management main room
The sewer management main room is located in the central region of the mainline. It is occupied by a number of radroaches and feral ghouls. The storage closet can be accessed from a terminal behind a locked gate nearby. A number of chems, ammunition, and workbench items can be found inside.

Sewage tunnels
The sewage tunnels that compose most of the mainline are littered with the remains of dead mercenaries and wastelanders. These are often marked by the presence of feral ghouls nearby. Boxes of ammunition can be found near (or under) many of the remains.

Notable loot

 * Nuka-Cola Quantum in a safe.
 * Two pre-War books with Gallo's Nuka-Cola collection.
 * A Stealth Boy hidden under a box in Gallo's storage closet.
 * A copy of Tales of a Junktown Jerky Vendor, carried by Gallo.
 * Big Book of Science next to the terminal used to access the sewer management main room.
 * Two pre-War books also near the terminal.
 * Two smaller than normal Nuka-Cola trucks as seen in the photo of Gallo's collection.
 * Gallo's storage key in a footlocker by Gallo's bed.
 * Five Nuka-Colas on a shelf, for the quest Zip's Nuka Fix.

Appearances
The county sewer mainline appears only in Fallout 3.

Bugs
In a small room with a staircase near the exit to the Capital Wasteland, the player might find themselves swimming down the staircase rather than walking, having an oxygen meter displayed and the ability to "drown."