If you weren't allow to dump it on the ground, were you told what you could do with it? Were you near a water source? What did they have as toilet facilities, a hole-in-the-ground privy, or a contained unit? If it was a privy, I would have considered dumping it there. Why draw a line between gray water and black water if you're letting black water enter the ecosystem? <img src="/images/graemlins/crazy.gif" alt="" />

The only thing that comes to mind is to take an empty 5-gallon jug or bucket with a tight-fitting lid (and one of those bucket openers), and dump it all in there, and empty it at an RV dump site (or take it home).