episodic/maps/personal/dario/wasteland_test.vmf
A wasteland-themed survival map where the player fights endless waves of enemies while trying to find six petrol canisters to fuel a chopper. This map was included in an update to Episode One in May of 2013 but later removed.
Huh, kinda weird that they would accidentally add this with an Episode 1 update in 2013 if it was an old survival mode they worked on in Episode 1 and 2's devcycle.
EDIT: Wait, could this potentially be a work in progress map for EP3? The context of the map is surviving waves of enemies until you fuel a helicopter, which kinda coincides with Gordon and Alyx planning to take a helicopter to Borealis at the end of EP2. Probably just extrapolating here but still.