Lower Emissions Limits Proposed for Cheswick Generating Station

Updated: Sep 12


And that’s just what’s happened in Pennsylvania regarding Reasonably Available Control Technology (RACT) for large coal-fired power plants so we wanted to help break things down.


You can get all the details and background on our recent blog about Pennsylvania’s illegal RACT determinations for those plants required by the decision of the U.S. Court of Appeals for the Third Circuit in its decision Sierra Club v. EPA.


But the long and short of it is this: The U.S. Environmental Protection Agency (EPA) occasionally revises the National Ambient Air Quality Standards (also known as NAAQS) for ozone or oxides of nitrogen, a precursor of ozone.  


In Sierra Club, the court determined that an emission limit for NOx that was lower than the one set by the regulation was both economically and technically achievable because selective catalytic reducer-equipped Pennsylvania plants themselves – as well as SCR-equipped plants in nearby states –  regularly achieved lower NOx emission rates.


In the order following its decision, the court required DEP and EPA to re-evaluate RACT limits for the coal plants’ NOx emissions so that those limits would satisfy the Clean Air Act’s RACT standard.


How does this relate to us locally? On Dec. 2 the Allegheny County Health Department (ACHD) published notice of its re-determination of RACT for the Cheswick Generating Station, which was also required by the Sierra Club decision.   


This proposed re-determination will:

  1. decrease Cheswick’s emission limits for NOx from 0.12 pounds per million British thermal units (lb/MMBtu) to 0.090 lb/MMBtu under normal operating conditions

  2. decrease emissions limits for NOx from 0.35 lb/MMBtu to 0.27 MMBtu under all operating conditions, including startups, shutdowns, and malfunctions and,

  3. eliminate an exception to Cheswick’s NOx emission limit that purported to apply when the inlet temperature of the plant’s selective catalytic reducer (which is used to control NOx emissions) was below 600 degrees Fahrenheit

“The Cheswick Generating Station is scheduled to cease operations in April 2022, so these decreased emission limits – although required by law – will have only a limited impact on local air quality,” GASP senior staff attorney John Baillie explained.


ACHD is nevertheless accepting comments on the new limits through Jan. 11.


GASP continues to follow this issue and will keep you posted.


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