Rally Sewage Goes Where ??

[Distantdrummer]

Last Texas Vintage Rally had 103 units. But they were in a park. All had the opportunity to hook up to underground sewer or tanks I presume.

But what happens when there are hundreds of trailers parked in a field such as at an International Rally?
Is there some sort of field line run? If so how does it flow?
If not and everyone is boondocking there must be a hell of an aroma around the camp.
Is there a constant parade of folk pulling their blue wagons to some haunted dump site?
BTW how do you thouroughly clean out a blue wagon? Seems like those things would always be a bit stinky. Where do folks keep them?

I have no idea why this question popped into my head, but it did and now I cannot rest til I figure it out.