The main sections of the Boston-area Charles, Mystic and Neponset Rivers are in pretty good condition overall, but a few sections and some tributaries have received grades ranging from C- to F based on the prevalence of combined sewer overflows, E. coli and toxic algal blooms, according to the Environmental Protection Agency's 2022 Three Rivers Report Card. "A lot of investment has been put in to improve water quality, but it's still not enough -- the promise of the Clean Water Act has not been fully realized," says Andy Hrycyna of the Mystic River Watershed Association.