I read this on game informer. Unofficially confirmed (like everything else Half Life related) but i thought it was interesting.
http://www.gameinformer.com/b/news/archive/2011/06/15/half-life-3-hints-surface.aspx
http://www.gameinformer.com/b/news/archive/2011/06/15/half-life-3-hints-surface.aspx