Dow Chemical will begin removing pollution from a three-mile stretch of the Tittabawassee River near its Midland plant.
Dow already removed dioxin and furan contamination in the area; but there are five other chemicals that remain that can be harmful to wildlife.
The company just finished removing a dioxin-laced island in the river.
Dow also continues "interim" cleanups of land on the floodplain where people have homes. In some cases, that involves removed contaminated soil from people's yards; in other instances it might involve moving a firepit further away from the bank of the river.
Dow will eventually have to remove contamination from 24 miles of the Tittabawassee River, and five miles of the upper Saginaw River.
But that will take time. Mary Logan is project manager for the U.S. Environmental Agency.
"We haven’t predicted because we don’t know how fast we might sort of pick up steam as we move downstream, but it will be at least a decade," says Logan.
And the cleanup will also never be perfect.
"Any site where we've had a long history of an industrial presence," says Logan, "we're never going to be able to return the entire watershed - or this portion of it - to pristine conditions.
Some people in the region say the cleanup is taking too long.
They also dispute a University of Michigan study that found no increased risk of cancer in people who live along the rivers.
The state warns people not to eat too many fish from the Tittabawassee and Saginaw Rivers.
Advisories say some fish, especially bottom-feeding fish like carp, should not be eaten at all by children or pregnant women.
Dioxins and other contaminants can build up in the bodies of the fish, and eating too many of them is considered risky, even for healthy people.
Dow Chemical set up factories in Midland in the early 1900's. Its factories dumped untreated wastewater into the river for decades.