EFFECTS OF DOWNSTREAM TRANSPORT ON PHYSICAL AND CHEMICAL PROPERTIES OF COAL ASH 5 YEARS AFTER THE KINGSTON TVA SPILL

In December 2008, an unprecedented coal ash spill occurred from the Kingston Fossil Plant operated by the Tennessee Valley Authority (TVA) into the Emory and Clinch Rivers. Despite dredging efforts, approximately 382,000 m³ of ash remains within the river system, reaching 3 m thick within the lower Emory River. The spill also transported ash up to 5 km upstream. A Monitored Natural Recovery (MNR) remediation strategy is in place that requires sampling of the upper 15 cm of the riverbed to assess the concentration of ash and toxic metals, particularly As and Se, which are known to impact the invertebrate populations at other coal ash contaminated sites. We analyze three annual sampling events within the Emory River that occurred during the winters of 2012-2013. The first and third sampling event occurred after several moderate flows, whereas the second event occurred after a year long low flow period. To assess erosion and transport of residual ash we compare the percent total ash measured by polarized light microscopy (PLM), magnetic susceptibility (MS), anhysteretic remanent magnetization (ARM), and a suite of metals, including As and Se in discrete samples collected downstream and in cross channel profiles.

We document that TVA coal ash is composed of a diverse population of magnetic and non-magnetic particles that have both spherical and non-spherical form. MS and ARM are correlated with the total percent ash in all sampling events. Each sample set defines a single, linear trend between ARM and susceptibility, with the slope of the trend line increasing between 2012 and 2013. This suggests a slight fining of the magnetosphere assemblage with time. Elevated metals concentrations were observed in upstream samples with high percent ash. This is interpreted as erosion of the riverbed in the upper reaches of the Emory River. After the first sampling event, the total percent ash in downstream samples increased 3x yet total As decreased with each sampling event. We observed a better correlation of metal concentration and magnetic properties after periods of higher flows suggesting the importance of fluvial sorting. Peaks in metal concentrations originating from upstream samples where fluvial processes are active indicate that higher flow events will expose buried ash deposits that have not been sampled during MNR monitoring events.