"There's an oil spillage! There are climbable trusses that appear nearby enemy spawns. 6 of them are high enough to save you from the oil, while the other 3 trusses may not be trustworthy. If you are submerged in the oil, you'll be taking 8 damage every .2 seconds! The oil rises up pretty high, so be quick!"
A large oil drum will fall into the map. This drum will instant kill anyone who touches it. 9 trusses will spawn near enemy spawnpads. 6 of them will be safe from the oil while the other three may cut short. The oil rises after about 5 seconds and will continue to rise until the disaster ends.