Cold Stream

Cold Stream is an upcoming DLC for Left 4 Dead 2. It was announced in a blog post on February 16, 2011. It will feature Cold Stream, a community made campaign from the creator of 2 Evil Eyes, as well as ports of additional Left 4 Dead campaigns. A release date has not yet been annouced, although it is expected to follow the release of Valve's next game Portal 2.

A beta was released on March 22, 2011 on Steam.

Beta
In Cold Stream the survivors from L4D2 follow the route of a Stream through forests and mountains.

One section of the stream is strong enough to drag unlucky survivors to a waterfall where they can be Incapacitated and left hanging on the edge.

In one new Addition to gameplay Players have to shoot exploding barrels to make a hole they can walk through, the explosion will attract a Horde.

There are new Cinematic sections such as the Military jets bombing the bridge or the rescue helicopter crashing into the woods.

Unfortunately in the Beta there is a glitch where instead of climbing down the ship's mast the computer controlled Survivors will jump down and die, this is really a problem in single player mode as the player will almost certainly be alone at the cresendo event in the scrapyard if they do that.