From the N.C. Department of Environment and Natural Resources
RALEIGH – Requirements of a state plan approved recently by the U.S. Environmental Protection Agency to address mercury in North Carolina’s waterways have already been met by most of the state’s wastewater treatment facilities.
Last week the EPA signed off on a statewide mercury TMDL, or total maximum daily load, developed by the N.C. Division of Water Quality. In conjunction with this plan, the division created a permitting strategy for those entities that discharge treated wastewater into the waters of the state, to ensure that statewide mercury reductions continue to be met and to prevent mercury hot spots in waters that receive discharges. At present, 99 percent of the permitted facilities have already met the state’s new permitting requirements. Staff with DWQ developed this plan following a study conducted with the Division of Air Quality to track ways that mercury enters the state’s rivers and lakes.
The DWQ and DAQ investigation showed that 98 percent of mercury in waterways comes from air deposition – air currents carry mercury around the globe until it is deposited into waterways or onto land surfaces where it can be carried into waterways by stormwater. Only two percent of mercury in the water is a result of direct discharge from industrial and municipal wastewater treatment plants. Additionally, scientific studies have shown that most of the mercury in the water comes from sources outside of North Carolina’s jurisdiction. Currently, approximately 84 percent of mercury air deposition comes from sources outside of North Carolina. About 16 percent of mercury air deposition comes from sources inside North Carolina; that number is expected to decrease to 3 percent by 2016.
“This plan is an important step in North Carolina’s progress in addressing this worldwide problem,” said DWQ Director Chuck Wakild. “Solving this problem will require perseverance at the state, regional, national and international levels. North Carolina has been a leader in achieving wastewater plant improvements, and the state’s Clean Smokestacks Act has reduced toxic mercury air emissions from coal-fired power plants by more than 70 percent since 2002. It is our hope that this plan will safeguard the progress we have made in-state and spur greater attention to this problem beyond North Carolina’s boundaries.”
The DENR study into mercury issues was prompted by a statewide advisory by the Department of Health and Human Services concerning consumption of fish high in mercury by pregnant women and children. The federal Clean Water Act requires North Carolina to develop a TMDL for a pollutant that causes water quality impairment to a water body within the state. The DWQ plan estimates that a 67 percent reduction in mercury loading from all sources when compared to 2002 baseline levels is needed in order to meet fish tissue targets. As of today, North Carolina wastewater sources have achieved their share of this reduction. Though air emissions are not subject to the water quality permitting strategy, officials with the Division of Air Quality expect that North Carolina air sources will meet their share of the reductions by 2016.