Once the player clears out the Scum Pits and searches around a bit, the player will find an access hatch in the giant albino ant queen's lair. It has a complicated electronic lock on it, so a decent lock pick skill with an electronic lock pick will open unlock the hatch. This port leads to Sub-Level-1-Classified. The discovery of this is significant since it fleshes out the Hoover Dam pre-War history a bit (makes FOA happy), gives a bit of history about the centaurs and floaters (again, FOA interest), and gives the player access to a great science lab. Not only can the player use it, but the scribes would be tickled to use it and will. This will positively affect Hoover Dam's future growth and prosperity.
Character type completion breakdown
Combat boy, Diplomacy Boy, Science Boy - Player must to kill the critters in the area first.
Stealth Boy - If the player is really stealthy, they can sneak to the hatch and lock-pick it.