If we have leftover dishwater (or cooking water, such as used for
boiling pasta), we often pour it in the road or a non-traffic area.
However, we got a pop up camper last year so if necessary, we can drain
to a outside waste container that can be dumped at a station later.
However, we rarely have that much water and still dump it outside.

As for camping, don't worry about it. They always have room. One year I
couldn't get there til friday, and wound up on 1st street near the
frontage road. It was a LONG walk, but I was there!

John