Playable on: E1M3
Here is where the toxic byproducts generated elsewhere are converted into clean energy, in effect allowing the Phobos base to power itself.
A mid-episode E1 map I originally built a few months ago, had some monster placement done by 40oz, and then more recently I revised it to reshape and retexture some stuff as well as adding a lot of optional areas to explore.
Update Sept 26, 2011: Adjusted the monster placement a bunch to better fit the e1m3 slot, added a secret exit, made a couple of minor visual adjustments, and filled in all the secrets and optional parts! Could probably still be refined further, but it's done-ish for now :P