I thought this was quite a fun map and enjoyed playing it. There were a few nice little touches, such as the brush based floor numbers, that I haven't really seen before. The intro was good and I had no problems working out where to go next. The action set pieces (the elevator ambush, the teleporting vort's etc..) had plenty of useful cover and were enjoyable. I liked the little story scenarios, like the scientist running from the soldier. The ammo, health and suit charge was fairly well distributed. Plus I found a few semi-secret areas.

I played it through twice and have a few critical thoughts (mostly just nit picking)
-Could probably do with an autosave shortly after the intro. I died once on the second play through slipping off the rock face and the intros a little long to sit through mulitple times.
-The door leading outside at the start is orange coloured both inside and out.
-Didn't really like the wooden planks crossing the broken walkways, they're too 'unstable'. This might be my general dislike of the source physics though.
-Some of the music (in particular the elevator fight) is too loud. If you're using ambient_generics to play it maybe reduce the volume.
-The first vent by the crowbar just looks weird with the vent brush border around the vent prop. Maybe shrink the air duct to the size of the vent prop.
-The zombies playing dead by the big windows (where chopper crahses later) are moaning away before I enter. Maybe flag them as silent until 'aggressive'.
-The zombie bashing the door can be seen just standing still, the animation only triggers when you get closer. Maybe place the trigger before the player can see that area.
-Couple of the inaccessabe slide doors don't play a locked sound whilst others do. For consistency they all should.
-The am_double doors with glass panels have a cardboard/wood impact sound when struck with a crowbar!
-Few issues with the chopper area (I do appreciate how hard it can be getting the chopper to even function properly)
- the door with the green light opposite. The door itself can be walked through, also a green light general means pressing it will do something, which doesn't happen in this case. I was left briefly wondering if something had broken.
- on entering that area immediately to the right its possible to see under the building.
- the chopper fight is a little cliche. However my bigger issues were hitting the damn thing with the rocket launcher. When its far back in the corner more often than not my laser guided rockets would get close to it then zoom off in some random direction at the last second. I was beginning to wonder if I'd ever take it down! Also the ammo bin is convienently placed just round the corner from where the chopper lurks, so its too easy to peek round the corner, fire, duck back and resupply.
-The back tracking, while extending the play through slightly, was a little bland. No real changes to the layout or feel of the environment - just a few spawing head crabs.
- the ending was slightly confusing as after you press the button nothing happens. Its only when you walk out the room the map ends, but theres no real indication to do this. Personally I'd have the map fade out as soon as the buttons pressed.
-large areas of the map are too quiet - have you tried using soundscapes?
- it doesn't look like you used cube maps. Maybe give them a try? (easy for me too say, I can never get the reflections to look good myself).
-Looking at the file size, did you compile with both HDR and LDR?

Hmm, the list is longer than I intended. As I said, alot of its just being picky. I did like this map and will keep it. The workshop needs more single player maps (they only other one I've downloaded is Bravado), so nice job.