Board Game Arena

My friend was playing with marine world expansion, and claimed that with archeologist played, each boarder space bonus he gained by placing excavatoin site should trigger the archeologist's ability twice. Is it true?

I'm fairly certain excavation site nullifies any placement bonuses so no, border spaces would not trigger archeologist (or any other) type of bonus. Correct me if wrong but this was my experience during a recent alpha MW game.

You are thinking of Reconstruction.
For Excavation Site and Archeologist I would say yes. Because Archeologist triggers when you gain a border placement bonus, not when you cover it.