BORON AS AN INDICATOR FOR CONTAMINATION OF SHALLOW GROUNDWATER ASSOCIATED WITH COAL ASH PONDS IN NORTH CAROLINA

Coal is the major source of electricity in the United States. Six hundred coal fired power plants produce 136 million tons of Coal Combustion Residuals (CCRs) annually. CCRs are comprised of fly ash, bottom ash, and flue gas desulfurization materials that remain after burning. Over half of the generated CCRs is stored in surface impoundments and landfills. Previous studies have shown a direct impact on the water quality of surface water associated with CCRs in several North Carolina lakes and rivers. This study utilizes water quality data of monitoring wells surrounding thirteen coal ash ponds in North Carolina (2010-2012) published by North Carolina Department of Environment and Natural Resources (NC-DENR). Given that boron is a sensitive tracer for CCR effluents, we use it to monitor possible contamination of shallow groundwater. The data show large boron variations, from background levels (~50 ppb) typical to regional groundwater up to 4940 ppb. Seven of the thirteen sites had boron concentrations exceeding the background levels, which indicates recharge of CCRs effluents into the shallow groundwater. The elevated boron levels are clear evidence of coal ash contaminations in groundwater surrounding the ponds. However, the monitoring wells are located within the 500 m perimeter of the coal ash ponds and do not indicate whether CCR contamination has impacted aquifers used for drinking water in the surrounding areas. Further testing is needed to delineate the extent of contamination but this initial survey suggests significant leakage of coal ash effluent to the local aquifers.