Crews will begin a $20 million project Monday to remove radioactive deposits along the West Branch of the DuPage River at McDowell Grove Forest Preserve near Naperville.
The work will complete the DuPage Forest Preserve District's portion of the toxic waste cleanup that has covered more than 7 miles of waterways over roughly seven years.
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The northern portion of McDowell Grove will be closed through November as crews remove materials contaminated with thorium, a radioactive chemical.
"We're very excited about concluding the remediation, which has been a diligent effort," said John "Ole" Oldenburg, DuPage Forest Preserve director of natural resources. "We want to get it cleaned up, get the public back in and enjoying the river, as well as seeing the aquatic biology begin to recover."
The radioactive material came from an old gas light-manufacturing plant in West Chicago. The thorium is a byproduct of work that went on there starting in the 1930s. The dangers were unknown at the time and the material was used as soil filler in West Chicago until the plant closed in 1973.
"The soil found its way through erosion and stormwater into Kress Creek, then eroded into the river. Through sediment transport, it became deposited in the river banks and flood plains," Oldenburg said.
In addition, the West Chicago plant produced uranium at the federal government's behest during World War II as part of the storied Manhattan Project that created the world's first nuclear weapons. Some of that uranium runoff was discovered in nearby homes.
Most of West Chicago, the West Branch and Kress Creek have been decontaminated, and the old factory site is now being used as a way station for excavated thorium that is barreled up and shipped to a federal depository in the western United States.
For its part, the forest preserve has completed decontamination within portions of Warrenville Grove and Blackwell forest preserves, both near Warrenville.
While the radioactive deposits at McDowell Grove are buried under layers of clean sediment and are not considered a danger to human health, workers will temporarily alter the flow of the river to expose its banks and then bore down to remove contaminated soils.
Workers also will reconstruct the river channel in a more free-flowing shape, then enhance it with plantings. Ultimately, officials said, the project will increase oxygen levels and improve aquatic habitat for fish and invertebrates.
The closed area will encompass McDowell Grove's main entrance and parking lot on Raymond Drive and will continue north to Warrenville Road. All trails through the area, including the underpass at I-88, will be closed, as will the preserve entrance, parking lot and picnic area.
Visitors will be able to access a portion of the West Branch Regional Trail by entering McDowell Grove from the south. From the Regional Trail, visitors will be able to reach select mowed turf trails within McDowell Grove. Paddlers who wish to enter the river will need to use the put-in site at Fawell Dam, which they can reach via an access road off Raymond Drive.
District officials said the closures will not affect the 360 Youth Services 10K run, scheduled for April 15. But Oldenburg warns that when workers begin digging in late April, visitors need to heed fences and locked gates.
"Some people don't believe our signs when we say 'Stay out,' but it's so critical," he said. "There will be no way to get across the river."
Cleanup: River channel will also be reconstructed