The beta began March 22nd, 2011 after the DLC unveiled earlier in February. Cold Stream is a community-made piece of content from the creator of the 2 Evil Eyes campaign.
It'll come with a new Steam Achievement; Stream Crosser, which is earned by completing the campaign on any difficulty. It officially releases for free via Steam this July 24th.
Left 4 Dead 2 Cold Stream releases July 24th
02 July 2012 | By Simon Priest