Hiroko Tabuchi reports for The New York Times

Floodwaters from two breached dams in Michigan on Wednesday flowed into a sprawling Dow chemical complex and threatened a vast Superfund toxic-cleanup site downriver, raising concerns of wider environmental fallout from the dam disaster and historic flooding.

The compound, which also houses the chemical giant’s world headquarters, lies on the banks of the Tittabawassee River in Midland, where by late Wednesday rising water had encroached on some parts of downtown. Kyle Bandlow, a Dow spokesman, said that floodwaters had reached the Dow site’s outer boundaries and had flowed into retaining ponds designed to hold what he described as brine water used on the site.

The Superfund cleanup sites are downriver from the century-old plant, which for decades had released chemicals into the nearby waterways. The concern downriver, according to Allen Burton, a professor of earth and environmental sciences at the University of Michigan, is that contaminated sediments on the river floor could be stirred up by the floodwaters, spreading pollution downstream and over the riverbanks.

“You worry about the speed of the current, this wall of water coming down the river,” he said. “It just has a huge amount of power.”

[Read more on why a third of Michigan’s Dams are still at risk.]

Mr. Bandlow of Dow said the company was “implementing its flood preparedness plan, which includes the safe shutdown of operating units on site,” which still manufactures plastics and other chemical products. He said only essential Dow staff remained on site to monitor the situation and “manage any issues as a result of the flooding.”

Mr. Bandlow did not provide information on the status of the cleanup sites.

Don’t miss stories like this Click for free EnviroPolitics Blog updates

Over the years the Dow complex has manufactured a range of products including Saran Wrap, Styrofoam, Agent Orange and mustard gas. Over time, Dow released chemicals into the water, leading to dioxin contamination stretching more than 50 miles along the Tittabawassee and Saginaw Rivers and into Lake Huron. Research has shown that dioxins can damage the immune system, cause reproductive or developmental problems, and cause cancer.

[Read about the new crisis Michigan is facing: flooding.]

There is also a tiny nuclear research reactor on the site, used to create material that can be used in product experiments. Overnight, Dow filed an “unusual event” report with the federal Nuclear Regulatory Commission warning of potential flooding at the site. But the reactor had already been shut down because of the coronavirus crisis, and there were no indications of flood damage on Wednesday.

If you liked this post you’ll love our daily newsletter, EnviroPolitics. It’s packed with the latest news, commentary and legislative updates from New Jersey, Pennsylvania, New York, Delaware…and beyond. Don’t take our word for it, try it free for an entire month. No obligation.