Went out with some friends for a couple of hours on Sunday morning and picked up trash from a little section of a greenway multi-use path. I bike commute along that path, and it had been bugging me, so I recruited a couple of friends and then contacted the city. They have a well-designed volunteer coordinator, who set us up with grabbers, trash bags, gloves, masks, waivers (so we don't sue them, obviously!) and they pick up the bagged trash later, asking only that we not leave it blocking the paths. I put up a post on NextDoor, inviting other folks to join us, but I figured if it was just the three of us that was fine.
Turns out 5 adults with intent can pull a LOT of garbage out of a creek/greenway in two hours. The place looked a ton better, we piled up .. I dunno, a dozen full-sized trash bags worth of stuff, and it felt so nice to actually DO something to make the place a little cleaner! Plus, not only did we pick up every piece of plastic that we found, we also found a prairie dog skull that everyone thought was cool!