News

Will County Watches Braidwood Water Levels

In late 2005, Exelon Corporation announced the escape of more than 3 million gallons of water contaminated with tritium, a low-level contaminant byproduct of nuclear power, at its Braidwood Generating Station in far southwest Will County. The water spilled from two defective valves on a blowdown line, just over the property line of the 259-acre Braidwood Dunes and Savanna Nature Preserve. The preserve is owned by the Forest Preserve District of Will County.

As a precaution, district executive director Michael Pasteris closed the preserve to ensure there were no health hazards for visitors. He reopened it 15 months later when a study revealed that the groundwater contamination was no longer a threat.

Cleaning up the leak, however, raises new concerns. Of the 30-some models proposed, Exelon’s chosen method, approved by the Illinois Environmental Protection Agency, calls for collecting contaminated water by pumping huge volumes underground from a lake on Exelon’s property to recapture the plumes of irradiated water. Groundwater then flows back into the pond to replace the water lost from pumping. This remediation could take up to five years to complete.

Forest Preserve staff are concerned that this pumping will lower groundwater levels on its property, potentially impacting the fragile plant communities at the Braidwood Preserve. The wetter plant communities, such as marsh and sedge meadow, have a close relationship with groundwater. Fluctuations in the water levels can have significant effects on species diversity and composition.

“We are collecting data on precipitation and local and regional groundwater elevations,” notes David Robson, district natural resources manager, “and data on groups and species of plants sensitive to hydrologic conditions.” Staff will analyze this data for the plant community’s responses to conditions. Indicator species, such as turtlehead and marsh St. John’s wort, only grow in wetland habitats and will react negatively if hydrologic conditions deteriorate, Robson explains. Simultaneously comparing conditions with nearby areas should allow staff to examine the causes of any changes.

The Forest Preserve District is working with Exelon to reduce the amount of water pumped from the pond and to design a long-term monitoring protocol.