The easiest thing to do is just advertise a work party to clean up certain places. Kalamabama, his two sons, Alex and Zak, rvrtramp and I did this up in the canyon on the Kalama not too long ago. I haven't fished the Carbon, but I wouldn't mind getting to know the river and would be glad to help with a work party. All we did was set a time and place and then show up with a couple boxes of heavy duty bags.
We did talk it up at the various businesses on Kalama River Road and environs. This is probably the best thing you could do in advance of the clean-up. If you know or can find out the property owners affected, letting them know that there is a group of volunteers coming to clean up their property builds alot of goodwill.
Disposing of the trash can be another thing. We just decided to take care of it ourselves. Or, that is, Kalamabama volunteered to take it on himself to dispose of the trash we collected. Even if the group has to pony up for some disposal fees, it is worth the expense in my mind.
You just have to be willing to deal with the reality that slobs will continue to litter after you put in your time and money to clean up after them.
Anyway, I live alot closer to the Carbon than the Kalama, and I would be happy to lend my time and a few bucks to clean up some property owner's, or public site. Just post the arrangements and if I'm in town, I'd be happy to help.
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Tad