The headquarters of the affluent Garrahan Mining Company not only emphasize the affluence of the Garrahan family, but also the mining history of Appalachia, burrowing deep underground beneath the exclusive township of Bramwell. Unlike the Hornwrights, who opted to erect the seat of their corporate power in downtown Charleston, the Garrahans stayed on the southern edge of Mount Blair, with the company headquarters lying in the shadow of their Mega Mansion.
The lobby of the headquarters is sunken beneath the surface of the ground, with glass panels letting in sunlight to illuminate the interior. The main lobby is below ground, accessible either through the doors in the atrium, which deposits the player character right in the lobby, or through the monorail tunnel, which delivers the player character down the tunnel to the station inside the headquarters, or a third option of going through the parking lot, which leads to the break room and security checkpoint in the research wing.
The lobby has several points of interest. On the ground floor, on the western face, is the cafeteria and the conference room. Just up the stairs is the admin department, with a locked safe (level 3) controlled by a terminal (level 2) and the Garrahan estate access key on the desk. Directly opposite the entrance to the lobby is the CEO Vivian Garrahan's office, with the somber musings on the challenge she issued to Hornwright and the dire straits the company ended up in when they failed. The office also contains a bobblehead spawn point and a steamer trunk.
On the eastern face, by the CEO's office, is the control room for Garrahan activities. Right next to it is the corridor which leads to the development laboratories, where the excavator power armor was created. The fabrication and testing room to the east contain two power armor stations, three spawns for Excavator armor components, with a magazine spawn point to cap it all off. There are also weapons, armor, and chemistry workbenches inside.
The testing, control, and assessment lab to the west contain a tinker's workbench and a power armor frame spawn point. Just next to it is the control room where the power armor was registered and a small excavated cavern where it underwent iterative development. The northern end of the corridor leads to the mezzanine and break room, which then goes to the parking lot beyond.
- 《查爾斯頓先鋒報》：人類機器大對決 - 在執行長辦公室前面的接待區，終端機旁。
- 哈洛德·福斯特的研發全像卡帶 - 在研發部門有修補工作台的區域的桌上。
- 市民中心隔間鑰匙 - 執行長的辦公桌下。用於Watoga Civic Center。
- 葛拉罕大廈門禁鑰匙卡 - 執行長的辦公桌上，用來打開葛拉罕大廈的電梯。A second one can be found in the side office in the nearby Admin area.
- 挖掘機動力裝甲設計圖 - 在專案經理的終端機內，礦工奇蹟任務流程拿到。
- Plan: Chemistry workbench - Inside the R&D lab, on a desk with an auto-miner, to the right of a chemistry workbench.
- Plan: Tinker's workbench - Inside the R&D lab, to the left of a tinker's workbench.
- Potential power armor mod plan - Inside the R&D lab, on a desk with a broken terminal in the southwestern corner.
- Potential Vault-Tec bobblehead - Inside the CEO's office, back shelves.
- Potential magazine - Inside the middle of the R&D lab, between the power armor stations, on a counter.
- 動力裝甲底盤和T系列裝甲部位在研發部門的動力裝甲工作台。Multiple power armor pieces can also spawn on the counters in the middle of the room.
- Fat Man - On the monorail line. Climb to the monorail platform outside the main building and then onto the station roof. Drop onto the monorail line and follow it away from the headquarters building. It will spawn just before a break in the line.
- Fusion core - In a fusion generator in the carpark, behind a Picklock 0 door.
《查爾斯頓先鋒報》：宏恩萊特獲勝！- 無法撿起的筆記，beside the terminal on the CEO's desk.
The Garrahan Mining Headquarters appears only in Fallout 76.