I don't want to promise that they are, but it looks like the wasps are dead and/or gone from the back of my trailer. About three nights ago, I went outside and hosed down all of the stuff remaining in the trailer with lighter fluid and struck a match. As the fire would die down, I would spray on more juice, keeping it going until it was apparent that all the sticks, cardboard, grass, and anything else burnable was pretty much gone. I also used a rake and spade to move the chunks of sod around to try and expose as much to the blaze as possible. When it was all said and done, I hosed everything down with water to put out the fire and went to bed.
So far, over the past few days, I have seen no wasps flying in and out of the trailer. The sod was turned into mud when I hosed it down and so all the holes would have at least been covered, if not filled with dirt. I will not go so far as to say the war is over, but I think I can conclude that this particular battle has been won. Now, anyone need a trailer?