Mercury TMDL

A statewide mercury TMDL was developed to estimate the proportions of mercury contributions to water and fish from wastewater discharges, in-state air sources, and out-of-state air sources, and to calculate appropriate reductions needed. Click HERE for more information on mercury in North Carolina.


Supplemental Information: 

Information on Mercury in North Carolina

Mercury TMDL

Mercury is a naturally occurring element. However, human activities have increased the amount of mercury that is available in the atmosphere, in soils and sediments, and in various water bodies. Anthropogenic mercury originates largely from air sources, such as coal-fired power plants and incinerators. Mercury in air falls as wet or dry deposition directly into waters, or onto adjacent lands, where it is washed off into surface waters when it rains. Some mercury is discharged in wastewater, although the amounts are usually very small compared to air sources. Most of the mercury found in the environment is in the form of metallic mercury and inorganic mercury compounds.

Mercury in Fish

Microorganisms in soils and sediments convert inorganic mercury to methylmercury. In this form, it is taken up by aquatic plants and animals. Fish that eat them build up, or bioaccumulate, methylmercury in their bodies. The highest concentrations of methylmercury are generally found in large fish that eat other fish. In North Carolina, the highest concentrations are usually found in largemouth bass and bowfin, and especially where mercury methylation rates are high.

Related Links

North Carolina Division of Air Quality Mercury Related Information

Mercury Regulations for Electric Generators (excerpts):

Other Statewide Mercury TMDLs

North Carolina Mercury TMDL Past Activitis and TMDL Schedule Archive

  • The TMDL process and schedule was presented to the Environmental Management Commission on September 9, 2010 as an information item.
  • An update of the TMDL process was presented to the Environmental Management Commission on July 14, 2011 as an information item.
  • An update on the Mercury TMDL was presented to the Environmental Management Commission Water Quality Committee on January 11, 2012 as an information item. 
  • An update on the Mercury TMDL schedule was presented to the Environmental Management Commission on March 8, 2012 as an information item.  
  • April 27, 2012  Draft Mercury TMDL available for formal public comment, Draft Post TMDL Wastewater Permitting Strategy and Reduction Options for Nonpoint Sources available for informal public comment
  • May 10, 2012  EMC meeting - mercury information item
  • May 14, 2012  Public meeting in Hickory, NC - INFORMATION BELOW
  • May 23, 2012  Public meeting in New Bern, NC - INFORMATION BELOW
  • June 18, 2012  Formal public comment on Draft NC Mercury TMDL ends
  • June - July, 2012  Revisions to the Draft NC Mercury TMDL as needed
  • July 12, 2012  EMC meeting
  • September 13, 2012  EMC meeting
  • October 12, 2012  EPA approved the NC Mercury TMDL