MAC: Mines and Communities

EPA Issues Clean Water Mercury Listing Guidance

Published by MAC on 2007-03-09

EPA Issues Clean Water Mercury Listing Guidance


9th March 2007

The U.S. Environmental Protection Agency, EPA, is providing information on a voluntary approach for listing waters impaired by mercury from atmospheric sources under the Clean Water Act. States are required to list impaired waters at least every two years.

Under the new guidance issued Thursday, states that have in place a comprehensive mercury reduction program may put their waters impaired by mercury from air sources in a subcategory "5m" of their Clean Water Act Section 303(d) lists and defer development of Total Maximum Daily Loads, TMDLs.

"We believe that the 5m approach will help foster state mercury reduction programs that, together with our efforts at the national and international levels, will ultimately restore mercury-impaired waters," said Benjamin Grumbles, EPA assistant administrator for water.

The EPA, the states, and other stakeholders have been working to determine how best to address waters impaired by mercury, particularly where the primary source of the mercury is atmospheric deposition.

To date, over 8,500 water bodies in 43 states and Puerto Rico are listed under Section 303(d) of the Clean Water Act as impaired due to mercury.

State water programs have tools for addressing mercury discharges from water sources under the Clean Water Act, but they need to work closely with their air, waste, and toxics programs to address other sources of mercury.

U.S. mercury deposition results from domestic man-made sources and global sources, including natural, re-emitted, and man-made.

EPA has estimated that, on average, 83 percent of the mercury deposited in the U.S. originates from international sources, with the remaining 17 percent coming from U.S. and Canadian sources.

The mix of long-distance and local sources makes it difficult in some waterbodies to achieve water quality standards for mercury.

A number of states have developed or are in the process of developing Total Maximum Daily Loads, and there are currently approved mercury TMDLs for over 300 waterbodies in 20 states and the District of Columbia.

In addition, a number of states are moving ahead to address mercury sources within their control through comprehensive mercury reduction programs.

For more information on the new mercury guidance, visit:


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