Borallus was a Colonial outpost.
When considering the Fleet's next stop, after their exodus from the Twelve Colonies, Sire Uri propositioned that Borallus should be their place of resupply. According to Uri, whose argument was that Carillon was too far away, "everything we need is there".
Unfortunately, being a logical place to resupply, Adama stated that a Cylon task force would undoubtedly be waiting for them there. (Saga of a Star World)