More than 1,800 volunteers have registered to head out on foot and by boat next weekend to pick up trash and debris along the Connecticut River and its tributaries in Vermont, New Hampshire, Massachusetts and Connecticut.
The annual "Source to Sea Cleanup" takes place on Saturday.
About 65 groups have already signed up for the effort.
Organizers say many businesses are forming employee cleanup groups, and some groups are joining the effort for the first time this year.
Last year volunteers pulled more than 51 tons of trash from about 60 miles of riverbanks and waterways.