The federal Environmental Protecting Agency is considering whether to designate the Neponset River from Hyde Park to Lower Mills as a place so polluted it requires federal funds and expertise to help clean it up.

The Neponset, from its confluence with the Mother Brook in Hyde Park to the Lower Mills dam, "contains sediment contaminated with elevated levels of polychlorinated biphenyls," according to the EPA, which is holding a public meeting on possible Superfund designation at 6:30 p.m. on Monday at the Mildred Avenue Middle School auditorium, 5 Mildred Ave., in Mattapan.

State environmental officials actually asked for the designation for the 3.7-mile stretch of the Neponset, one of the oldest industrial waterways in the US, along which mills were built after Dedham authorized a tax to build British North America's first canal in 1639 to power a town grist mill. Factories followed, making everything from chocolate to industrial centrifuges.

Some of the factories along the Hyde Park stretches of both the Mother Brook and the Neponset dumped PCBs into the water. In 2007, the state diverted the Mother Brook where it flows under Hyde Park Avenue to clean up PCBs in that area - and end their continued flow into the Neponset (the cleanup then led to a lawsuit only settled last year on which of the current landowners had to pick up the bulk of the costs for the work).

A 2004 study by the US Geological Survey found PCB levels in the river were particularly high in sediment behind dams on the river, in particular the dam at the former Tileston & Hollingsworth paper mill off River Street at the Hyde Park/Mattapan line (now the Shops at Riverwood) and at the dam at the former chocolate factory in Lower Mills.