EPA received a number of modeling analyses from various groups, including both industry and environmental groups. In some cases, EPA and commenters modeled the same or similar policy scenarios, sometimes using the same model, but obtained substantially different results due to differences in the assumptions employed. In these cases, model-input assumptions can be better understood by comparing and contrasting the modeling performed. The NODA shares these analyses and seeks additional comment on the models and assumptions used.

Administrator Mike Leavitt has outlined five guiding principles that provide context for additional inquiry and that narrow the focus of the Agency's deliberations. The five principles will ensure that the final mercury rule: (1) concentrates on the need to protect children and pregnant women from the health impacts of mercury; (2) stimulates and encourages early adopters of new technology that can be adequately tested and widely deployed across the full fleet of U.S. power plants utilizing various coal types; (3) significantly reduces total emissions by leveraging the $50 billion investment that CAIR will require; (4) considers the need to maintain America's competitiveness; and (5) comprises one of many agency actions to reduce mercury emissions.

In Dec. 2003, EPA proposed two alternatives for controlling mercury. One approach would require power plants to install controls known as "maximum achievable control technology" (MACT) under section 112 of the Clean Air Act. If implemented, this proposal would reduce nationwide mercury by 14 tons or about 30 percent by early 2008. Currently, nationwide mercury emissions from power plants are about 48 tons per year.

A second approach would create a market-based "cap and trade" program that, if implemented, would reduce nationwide power plant emissions of mercury in two phases. Beginning in 2010, the first phase would reduce power plant mercury emissions by taking advantage of "co-benefit" controls - mercury reductions achieved by reducing SO2, and NOx emissions under the Clean Air Interstate Rule. In 2018, the second phase of the mercury program sets a cap of 15 tons. When fully implemented, mercury emissions would be reduced by 33 tons (nearly 70 percent).

This rule, when combined with Bush Administration actions to reduce NOx and SO2 emissions from power plants, make diesel a clean- burning fuel, regulate nonroad diesel vehicles, and implement the most-protective ozone and fine particles standards, will ensure that the next decade will be among the most productive periods of air quality improvement in our nation's history.

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EDITOR'S NOTE: EPA will take comments on this action for 30 days after publication in the Federal Register. For more information on the NODA, visit: http://www.epa.gov/mercury/control(under)emissions/ noda.htm; on the Clean Air Mercury Rule, visit: http://www.epa.gov/ air/mercuryrule/; and on the Clean Air Interstate Rule, visit: http:/ /www.epa.gov/interstateairquality/.

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