Department of Environment & Conservation
Jim Fyke, Commissioner

Emory River Metals Study by the U.S. Army Engineer Research and Development Center

Environmental chemistry experts from the U.S. Army Engineer Research and Development Center (ERDC), located in Vicksburg, Mississippi, conducted a study to determine whether continued cleanup of the ash by dredging the Emory River would promote the release of metals within the ash and pose additional risks to the environment.  In May 2009, ERDC researchers collected ash and water samples from various areas of the spill and from the dredging operations.  In addition to extensive work to determine the presence and types of metals in the coal fly ash and waters, ERDC researchers constructed experiments designed to test the very extremes of environmental and operational conditions, including dredging, that would cause the ash to destabilize and release its contaminants.  It was under these extreme conditions that biological tests were performed to measure the potential effects on native fish and mussels.

ERDC’s results indicate the ash material possesses high stability and is largely resistant to high releases of toxic metals under extreme environmental conditions.  Of the metals released from the ash during this study, none exceeded EPA regulatory values, with the exception of selenium.  Extensive characterizations revealed that this behavior was attributed to the metals being present in relatively stable, less toxic forms, in the river.  Metals released from the ash were found mainly in their less toxic forms.  The only major exception to this was from the stilling pond, not the river, where the more toxic form of selenium (selanate) was measured in one water sample.

Standard toxicity tests from the above experiments showed no evidence for mortality of the native fish used in the tests.  Fish tissues did accumulate selenium, though its measured concentrations were below EPA screening values. While the long-term effects on fish due to metals released from the fly ash during dredging remain unclear, the reported chemistry and biological test results suggest a limited potential for toxicity related to fish. The study provides the basis for continued dredging of the Emory River for removal of the spilled fly ash.

Click here to view the Final Draft of the ERDC study entitled, "Evaluation of Metals Release of Oxidation of Fly Ash during Dredging of the Emory River, TN."

Click here to view supporting appendices.