Aliens: The Second Nukage v1.31 addon - Doom

THE SECOND NUKAGE - THE STORY
The story begins shortly after the Aliens fiasco on LB4-26, on the planet LB4-28. This planet, better known as either Dustball or Dirtclod by its inhabitants, is the site of one of the Colonial Marines' ammunition dumps, and they're having a sewage problem. It seems that the water system for the base (including the main power supply) was no longer flowing. Thinking that is was the result of some overgrown algae, a team of technicians was sent down to drain the system and unclog whatever was blocking the water supply. Strangely enough they never returned. A squad of Colonial Marines was sent to investigate and find the poor, lost technicians. The marines entered into the hydroelectric station and find it taken over by an unknown strain of xenomorphs - unknown because the Yutani-Weyland Corporation kept the whole incident on LB4-26 (or, at least what they could piece together about it) a secret. The marines were driven back and reinforcements were dispatched immediately to rush to their aid. One squad was sent to protect the entrance of the water system to make sure that none of the alien menace makes it into the base. The rest of them were sent into the water system to eradicate the xenomorphs. Twelve hours later all transmissions from the ammunition dump cease.

Here's where you come in. You were ordered on a routine patrol mission on the far side of the planet before the discovery of the xenomorphs. When you emerge from the radio distortions of the nearby mountains, you can't make contact with the marines at the base. Assuming the worst, you head back into The Second Nukage.