The Alpha Site is an off-world base established by the SGC. P3X-984 was first chosen as the location for the Alpha Site because its address was unknown to the Goa'uld, and the secrecy of the base had to be strictly guarded. It has been used as a destination for the evacuation of selected refugees when Earth has faced destruction from the Goa'uld or from an asteroid strike. It has also been used as a sanctuary for off-world races including the Rebel Jaffa following the destruction of Cal Mah by Yu and the liberation of the death camp of Erebus, and the Tok'ra refugees after their base in the Risa System was overrun by Anubis. It is protocol that off-world SG teams return to the Alpha Site in the event that Earth cannot be contacted. The Alpha Site also includes a full science lab which has been used in the development of alien technology such as the energy weapon used to neutralize the Kull Warriors.
When Anubis captured Jonas and accessed all his knowledge through the use of mind probe technology, the location of the Alpha Site was compromised. The SGC used a Tok'ra ship to transport the stargate to a planet with a completely new address, and Colonel Riley was placed in command of the new facility. However, despite precautions, Anubis discovered the location of the new Alpha Site, and the base was attacked by alkesh bombers and Kull Warriors. Colonel Riley ordered the evacuation of all personnel to the Beta Site, a secondary off-world base, and engaged the self-destruct which annihilated the facility and left the stargate horizontal but intact. At least 90 people were killed or missing following the destruction of the base, including Colonel Riley. An investigation suggested that operatives among the Rebel Jaffa or the Tok'ra who might have been captured by Anubis could have revealed the location of the base, but the source of the security breach that resulted in the attack was never officially determined.
Afterwards, the Alpha Site was relocated to P4X-650 where the new base was built inside a mountain, much like the SGC, and both Captain Sheffield and Colonel Pierce have served as commanding officers at the new facility. Although the stargate within the Alpha Site facility does have a DHD, most of the dialing and security protocols are still controlled by computer. The base relies on naquadah generators for much of its power, and it has at least one F-302 craft housed permanently on base. The Alpha Site served as a neutral location for the interrogation of Replicator Carter, which also made it the target of Fifth's Replicator ship. However, the facility was spared when Fifth was destroyed and Replicator Carter escaped through the Alpha Site stargate.
In addition to the Alpha Site, the SGC also established the Gamma Site, another off-world base used largely for scientific research.
Location: Red Rock Quarry, GVRD
Cross Reference: Artok, Ashrak, Beta Site, Delek, Gamma Site, Lieutenant Glenn, Major Green, Malek, M'zel, Naquadah Generator, Ocker, P3X-984, P4X-650, Colonel Pierce, Rebel Jaffa, Captain Shefield, Tok'ra
Episode Reference: Allegiance, Death Knell, Covenant, Endgame, Gemini