Wisconsin DNR Mercury Rule NR 446 Now In Effect

Wisconsin's revised Mercury Rule (NR 446) requiring coal-fired power plants to reduce air emissions of mercury became effective December 1, 2008. The rule regulates emissions from coal-fired power plants from seven utilities in Wisconsin. Under the rule, the state’s large coal-fired power plants must achieve a 90% mercury emission reduction through one of two compliance paths.


90% reduction by 2015: Under the mercury rule, large coal-fired power plants must either meet a 90% mercury emission reduction or limit the concentration of mercury emissions to 0.0080 pounds of mercury per gigawatt-hour by January 1, 2015.

Multi-pollutant option: Large coal-fired power plants also have the option of choosing a multi-pollutant alternative. The multi-pollutant alternative requires the affected power plants to achieve nitrogen oxides (NOx) and sulfur dioxide (SO2) reductions beyond those currently required by federal and state regulations. Under the multi-pollutant approach, additional time is allowed to achieve the 90% mercury emission reduction standard.

Smaller coal-fired power plants (> 25 MW and < 150 MW) must reduce their mercury emissions to a level defined as Best Available Control Technology (BACT). Wisconsin’s four major utilities, Dairyland Power Cooperative, We Energies, Wisconsin Power & Light Company and Wisconsin Public Service Corporation, were already required to reduce their mercury emissions 40% by January 1, 2010 under previous rules. Mercury emissions expected from the application of the new rule will reduce coal-fired power plant mercury emissions from 3,200 lbs down to 500 lbs per year.

Caltha LLP assists Wisconsin industries in applying for and complying with WDNR air emission control permits.


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