Paper No. 153-2
In December, the EPA released new national regulations on the disposal of coal combustion residues (CCRs) that addresses risks to water resources from disposal of coal ash in storage ponds.1
While the new regulations address the direct discharge of effluents from coal ash ponds under the National Pollution Discharge Elimination (NPDES), they do not consider the potential for coal ash effluents to leak and migrate to associated surface water or underlying groundwater. Previous studies following the 2008 coal ash spill at the Tennessee Valley Authority (TVA) Kingston Fossil Plant have shown that boron, strontium and their isotopic fingerprints were good indicators of coal ash effluents migration in the environment.2,3
Seepages and shallow groundwater discharge were collected in May 2015 from around coal ash ponds at the TVA Cumberland and Gallatin Fossil Plants in Tennessee. The groundwater discharge was elevated in chloride, sulfate, manganese, and iron compared to the lake water at both plants. Boron, which is known to leach from coal ash during storage in coal ash impoundments, presented significantly elevated concentrations in the discharges (5 – 36 mg/L) relative to background concentrations in local waters (~0.05 mg/L). Toxic elements, such as arsenic and selenium, were also present in some of the groundwater discharge (up to 5 ppb for arsenic and 10 ppb for selenium), which could impact aquatic life in the rivers receiving the groundwater discharge. The high boron, coupled with high chloride, sulfate and arsenic, provide strong evidence that coal ash effluents are being leaked to surface water via seepages through the coal ash pond holding walls and shallow groundwater conduits. Given the large number of coal ash impoundments through the US, these results raise the question of the potential environmental risks of these coal ash ponds to the environment.
1 USEPA, Federal Register 2015, 80, (74), 21301-21501.
2 Ruhl, L.; Vengosh, A.; Dwyer, G. S.; Hsu-Kim, H.; Schwartz, G.; Romanski, A.; Smith, S. D., Environ. Sci. Tech. 2012, 46, (21), 12226-12233.
3 Ruhl, L. S.; Dwyer, G. S.; Hsu-Kim, H.; Hower, J. C.; Vengosh, A., Environ. Sci. Tech. 2014, 48, (24), 14790-14798.