"Occasionally, some of them do find their way to the surface. We don't knoe how. But the Ocampa seal the tunnels afterwards."
Dilemma - Planet dilemma
Unless you have Biology, Exobiology, Geology and Integrity > 25 or Diplomacy, Leadership, Officer and Cunning > 32 all your personnel are stopped and this dilemma returns to its owner's dilemma pile.
Card logging info: Logged by openCards team at Jan 1st, 2008.
"Subterranean Barrier" is a backward compatible card form the Second Edition expansion Genesis - ST1E compatible (Copyright 2006 by Decipher).
See collectors infos for this card in the Second Edition section under the UCT-ID: ST2E 11 PF 5.
Also see here for all trade lists with any card fom "Genesis - ST1E compatible".