From Halopedia, the Halo wiki
Ballast is a human Inner Colony world, governed by the Unified Earth Government. Ballast was the homeworld of Spartan Frederic-104. Vallejo is a city on the world, where the car manufacturing company Kabord was originally based out of.
During the Human-Covenant War, the world was attacked by the Covenant. During the course of the battle, it is rumored that the UNSC Defense Force succeeded in defeating the Covenant, although it is possible that the rumor was created by the Office of Naval Intelligence to raise morale. The colony was apparently still intact during the Battle for Earth, as evidenced by active transports from the colony to the Quito Space Tether.
After the war, as part of Project ALOHA-19, an Acheron Security A.I. memory matrix containment and display module was shipped from Havenwinter on Ballast to UNSC Transit Dock L22 on Luna, and from there to an Outpost Discovery on Earth.
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