Did you know that Surface Tension originally started with Boot Camp? There's concept art remaining for this iteration of the map. It had the same opening as seen in the "changelevel" area of Alien Research Lab (C2A4) to C2A5. Judging by the concept, it is likely that not much of the chapter was too different from the later version. You still went onto the Cliffside and ended up in the Military Camp section. It is unknown to how much the map differed in the early/mid 97 version of the chapter to the late 97 version of the chapter (how much differed beyond Cliffside) as late 97 marked the point where they started heavily revising HL. It is possible that Surface Tension went mostly unchanged (sans the new opening) until after E3 1998. It would be replaced by the Dam sometime in April of 1998, ValveVisit.avi would of documented the Dam as it was being worked on.
Snapshot of ValveVisit.avi that shows the development of the Dam.
Also, for reference... This photo always gets lumped into the Boot Camp section, but this is likely the outside of the Tripmine building.
and for shits and giggles, here's what the Cliffside looked like at this point:
Every damn time i see *something*.avi i remember those creepy videos. How do you call them... death files? Cuz pretty much all of them are .avi files if it's the videos we are talking about.