Dam It

"'Just finished putting the Dam campaign that we streamed a while back into a L4D addon. It’s gray box, and some code features are missing but it’s playable from beginning to end. It also includes two standalone survival maps that never shipped.' - Turtle Rock co-founder Chris “MacMan” Ashton"Dam It is an unreleased Campaign for Left 4 Dead that was made by Turtle Rock Studios and it was later released on the augerresources.com that tells about the map and how the campaign stitches between Dead Air and Blood Harvest. It was released last November 7, 2016 and it was only exclusively available on the PC version of Left 4 Dead for free by downloading it on augerresources.com website. Alongside the campaign is two standalone survival maps that has never been shipped.

Glitches/Bugs
Due to this campaign was left unfinished during the development of Left 4 Dead, the whole map has tons of unfinished content and leftovers. But, despite all this, the whole map is still considerable to be playable from start to finish.

Here’s a list of known issues you may come across since they could not update the code changes from the final retail version of Left 4 Dead:
 * Fire, smoke and explosions do not trigger panic events in the hangars.
 * Zombies do not crawl all the time in the orchard.
 * Farm house mob does not spawn in the far side of the woods.
 * Covered bridge does not collapse with explosions.
 * Burned forest area is missing wandering fires.
 * The burning forest section has a burn trigger that stays on too long. If you move quickly you’ll take burn damage.
 * The dam spawn room is missing health kits and weapons.
 * The elevator models have an offset origin in the dam. Players can still get on and use them, but they are invisible and wall collision is missing.