I'm not sure if this is something that is known already and I am just stating the obvious but it seems clear that the Jughead bomb was buried where the Swan station was built.
I was watching an episode from season 2 the other day and Sayid was banging on a wall in the Sawn station. He explained to Jack that there a very thick wall of concrete that he could not break through. They crawled under the station and found more concrete. This matches Daniel's instructions to bury the bomb in concrete. Sayid went on to say that the last time he saw concrete poured like this was when he was in Chernobyl (the site of the worst nuclear power plant disaster in history). Maybe the DARHMA Initiative new that the Jughead bomb was buried there in the concrete and the infamous "incident" that Chang refers to has to do with the the Jughead bomb. That is why the Swan station was built there.