The County sewer mainline is a sewage tunnel which 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 Arlington Memorial bridge. It goes under Grayditch and Arlington Cemetery, but has no access points there.
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).
Gallo's storage closetEdit
Gallo's storage closet contains the following workbench items:
It also contains 40 Railway Spikes and a Stealth Boy hidden in a box on a bottom shelf, along with some chems and ammunition.
Sewer management main roomEdit
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.
Sewer management storageEdit
The sewer management 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.
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.
Also in the tunnel between the sewer management main room and Gallo, there's a strange skull with glowing eyes stuck on a metal rod, with two smaller rods crossed just under it. This is a subtle reference to the Khans from Fallout and Fallout 2.
The county sewer mainline appears only in Fallout 3.
pc xbox360 ps3 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". [verified]