Could Adamantine have found a Pre-CR underground structure that it had intended to repurpose, that only some of the colonists knew about? Maybe just the ones who had been involved with the initial installation? One of the things Corian had told Karime was that colony history/lore said at least some of the separatists had been part of the terraforming crew. Vi had also told her that census records for that point in the colony’s development were currently inaccessible due to the alien virus issue. (A lot of older data had been locked out of the active system to hopefully keep it safe, which was useless, since that wasn’t how the virus was transferred, which they didn’t know then, but anyway. Their systems colony-wide were completely shit-creeked and I don’t know who was going to fix it except it sure as hell wasn’t me.) So there was no way to know how many humans had actually left the main colony to come here.