The Michigan Department of Environmental Quality said Friday it had accepted Dow Chemical Co.'s plan for cleaning up properties contaminated with dioxin released from its chemical plan in Midland.
About 1,400 properties in the city, most residential but some vacant, are believed polluted from airborne emissions of dioxin over much of the 20th century. Dioxin is a group of toxic byproducts from industrial processes that the World Health Organization says may impair the human immune and nervous systems and damage organs such as the liver. The U.S. Environmental Protection Agency is evaluating the potential cancer risk.
After negotiations that began in the mid-1990s, Dow and the Department of Environmental Quality agreed on a cleanup framework in February. Dow later submitted a detailed five-year work plan, which the state agency has approved.
Beginning this month, Dow contractors will collect soil samples from properties with willing owners and measure their dioxin content. Those with dioxin levels greater than 250 parts per trillion will be eligible to have a 1-foot layer of soil removed and replaced with fresh soil and landscaping.
"We think that will remove the contamination that's of any significant level," said Jim Sygo, the department's deputy director.
The 250 ppt standard is less stringent than Michigan's statewide cleanup threshold of 90 ppt. But the law allows local variations based on soil conditions and other factors. In the Midland area, regulators concluded 250 ppt was strong enough to meet cancer risk requirements for people exposed to the soil, Sygo said.
"We have reached an important milestone in the road to resolution," Dow spokeswoman Carrie Houtman said. "Dow is committed to working with residents to ensure that everyone understands if, and how, the implementation of this work plan could impact them. Now that the five-year plan has been approved by DEQ, we anticipate soil testing to begin as early as next week."
Michelle Hurd Riddick, a member of an advocacy group called the Lone Tree Council that has long pushed for a cleanup, said environmentalists were "optimistic that progress is being made in a community that historically has not wanted to deal with dioxin for decades." But she said the 250 ppt standard was too weak.
Dow, whose corporate headquarters is in Midland, acknowledges its dioxin emissions have polluted city neighborhoods downwind of the plant as well as a 50-mile section of the Tittabawassee and Saginaw rivers and Lake Huron's Saginaw Bay.
The EPA is overseeing cleanup of the rivers. Dow plans to begin with a 3-mile segment of the Tittabawassee near the plant, then move downstream. The EPA says a couple of years will be needed to settle on a plan for the next 24 miles.