"When Wisconsin Public Service Corp. completed its purchase of Wisconsin Fuel & Light in 2001, it also assumed responsibility for WF&L's legacy of contamination left behind after decades of manufacturing gas in Wausau.
Today, that legacy lives on. Thousands of manufactured gas plants, or MGPs, heated coal or fuel oil to produce the gas that lit street lights, heated homes and fueled industry. And some of them, including the WPSC site in Wausau and Lincoln Wood Products in Merrill, now are toxic waste sites.
The sludge left behind by gas production, known as coal tar, is a complex mixture of hundreds or thousands of chemicals such as benzene and napthalene -- both known carcinogens. Every major community had at least one plant, according to Allen Hatheway, a Missouri geological engineer who is an MGP expert.
Sixty years after the gasworks gave way to electricity-generating power plants, not all of the MGPs have been found. Of 44 sites known by the Wisconsin Department of Natural Resources -- stretching from Janesville in the south to Ashland in the north, and Wausau and Merrill in between -- nine of the sites are considered clean."