I started RVing in California when dumping gray on the ground was still legal ;)
Then when big drought hit CA about 15 years ago, they actually start asking the residents to use household gray water for lawns watering.
still trying to figure it out? try to ask if marijuana is legal.
Gray water is perfectly safe for dumping and it is actually holding it for more than 24 hr that allows for bacteria growth.
All CA campgrounds allow for washing dishes in tubes or taking campshowers and dump the water around.
I think the main issue with RV dumping at campgrounds was kitchen debris coming with it and that is why whole issue started.