First tell the infected to come with you, you have to go to the ladder and climb up it.

Next you have your team-mates hit the small trash cans against the dumpster until they tip over.

Half way then a hunter needs to get behind the dumpster and start pushing the dumpster and tell a smoker or boomer to hit the trash cans and then the dumpster will start moving.

Once you get the dumpster over the hole - 2 things can happen one bad, one good. The bad is when the dumpster falls through the hole, the good is when it just gets stuck.

If you just can't do it, the person that becomes a tank can make a car.

Get over the hole, but then the tank can't attack. This way is so much easier to do, but you sacrifice the tank so I like the first one more.