About four years ago some clown at our yard showed up at 6:00 on a Tuesday night, probably intentional, and sanded under spot lights until many boats in the yard were covered in green! It took me 8 hours to get my boat clean and I was six boats away. It was a pretty windless night.
Needless to say he no longer stores at our yard for the winter, not by his own choice... Use a vacuum and tent off your boat for the courtesy of others around you, please..
Most yards, at least up here, go by EPA rules, even for the DIY, which means recapturing ALL dust so it never even hits the ground.
I don't know any yard up here that still allows a sander to knowingly hit the bottom of a boat without a vacuum connected to it. I work in about 10 different local yards.. This however is not just an EPA issue but an issue of common courtesy & decency to you neighbors.
Common courtesy dictates tenting and vacuums on sanders or what ever it takes to keep dust off the ground and other boats. I have seen brand new tan canvas, just installed a few days before a launch, virtually destroyed by bottom paint dust.. The guy who just paid 5k for the new canvas was NOT a happy camper and neither was the canvas guy or the boat yard....
I think it is fair for boaters who use sanders with no vacuum, and no tenting, to know what other boaters go through, as I & many others have, when they do so. It can make an AWFUL mess for others and is simply a rude practice when there are ways to prevent this dust from affecting others.
Once dew settles on bottom paint dust, cleaning it off the deck requires some caustic chemicals and often some form of light acidic cleaner. I was still finding hints of green months later.
I spent more time cleaning the mes off my boat than the guy did sanding his... Kind of ironic that he caused me more work that he actually did...