Um. First off do a survey of the camp now. Tell them what each additional service will cost and how much of that they will have to pay. Maybe even take a deposit to be given back at the end of the event. Also, put up a sign inside the porta potty reminding them. Attach with duck tape, that comes off enough for the company to be okay with it. (Remember to take it off at the end of the event.) That's where I'd start.
The Lady with a Lamprey
"The powerful are exploiting people, art and ideas, and this leads to us plebes debating how to best ration ice.
Man, no wonder they always win....." Lonesomebri
Get a Taint, you pathetic cur!