These are the source maps for ETC1, which were kindly released by Dave J.
ETC2 is a single player mod set in the Half Life universe. The mod begins with Gordon being trapped and needing to escape from an "Earthquake Test Centre" ("E.T.C."). Everything of course goes to hell, resulting in Gordon needing to take on Vortigaunts, Gargantuas, Zombies and Soldiers!
I didn't this mod myself, it was made by DaveJ (creator of DE_DUST2). Seeing as the mod lacked a moddb entry, I saw fit to add one myself =] Be sure to visit the official page of the mod here Johnsto.co.uk
Special thanks to Diamond for providing extra media for this!