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DEP’s New, Re-Evaluated RACT II Limits for PA Coal Burners Means Ozone, NOx Emissions will ‘Finally Be Regulated Properly’

From time to time, the U.S. Environmental Protection Agency (EPA) revises the National Ambient Air Quality Standards (also known as NAAQS) for ozone or oxides of nitrogen, a precursor of ozone.  

When EPA revises a NAAQS for ozone, states with areas that do not attain the newly revised standard must evaluate major sources of oxides of nitrogen – also referred to as NOx – to determine that the emission controls in place at such sources within nonattainment areas meet what’s known as Reasonably Available Control Technology, or RACT, standard set forth in section 172 of the Clean Air Act.   

At this point, you may be asking, “Why is ozone concerning?” According to the EPA, ozone is the main ingredient of smog. Ozone irritates the lungs and can cause or contribute to breathing problems, especially in people with asthma and other lung diseases.  High ozone levels can also harm certain plants, including tree species native to Pennsylvania.

But now let’s get back to RACT: Because all areas of Pennsylvania are included in the Ozone Transport Region created by section 184 of the Clean Air Act, Pennsylvania must re-evaluate RACT for all of its major sources of NOx any time the NAAQS for ozone is revised.  

What is RACT? EPA defines RACT to be “the lowest emission limitation that a particular source is capable of meeting by the application of control technology that is reasonably available considering technological and economic feasibility.” 

Also according to the EPA, a determination of “economic feasibility” is not based on a source’s ability to afford to install and operate a particular emission control, but rather on evidence that similar sources in fact use the control. A state may implement RACT either on a case-by-case basis or by a generally applicable regulation.

Here’s where things get a little more complicated: In 2008, the EPA revised the NAAQS for ozone. Pennsylvania is still working on getting its RACT re-evaluations right to meet that standard.

And here’s another thing: When the EPA and the Pennsylvania Department of Environmental Protection (DEP) developed rules to implement RACT for the 2008 ozone standard, they acquiesced to the operators of coal-fired electric generating units that are equipped with selective catalytic reducers (SCRs) by coming up with a regulation that set limits on the plants’ NOx emissions high enough that such plants did not need to run their SCRs to meet the limit.  

Selective catalytic reducers control NOx emissions effectively but are costly to run once they are installed, so operators of plants that are equipped with them have resisted requirements that they be operated at all times.  

Last August, the U.S. Court of Appeals for the Third Circuit struck that regulation down in Sierra Club v. EPA, 972 F.3d 290.  

“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,” GASP senior staff attorney John Baillie explained. 

He continued:

“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.”

There are at least five coal-fired electric generating units that are equipped with selective catalytic reducers still operating in Pennsylvania:  

  • Cheswick Generating Station in Allegheny County
  • Conemaugh Generating Station in Indiana County
  • Homer City Generating Station in Indiana County
  • Keystone Generating Station in Indiana County and 
  • TalenEnergy Montour in Montour County.  

Although these plants are some of the largest NOx emitters in the state, Pennsylvania is only now properly applying RACT to them in the wake of the Sierra Club decision and order: Notice of the first re-evaluated RACT determination for one of these plants – the Keystone Station – was published in the Pennsylvania Bulletin on Sept. 11.  

Since then, DEP has also published re-evaluations for the Conemaugh Station (on Oct. 2), and the Homer City Station (on Oct. 16).

In those notices, DEP has proposed to decrease the allowable rates of the plants’ NOx emissions, which are expressed in terms of pounds per million British thermal units ( which is written like this: lb/MMBtu) on a daily average basis, as follows:

Emissions Unit Proposed NOx Emission Limits
Conemaugh (both units) 0.070 lb/MMBtu (normal operating conditions)
Conemaugh (both units) 0.270 lb/MMBtu (all operating conditions)
Homer City (Units 1 and 2) 0.080 lb/MMBtu (normal operating conditions)
Homer City (Units 1 and 2) 0.450 lb/MMbtu (all operating conditions)
Homer City (Unit 3) 0.070 lb/MMBtu (normal operating conditions)
Homer City (Unit 3) 0.270 lb/MMBtu (all operating conditions)
Keystone (both units) 0.080 lb/MMBtu (normal operating conditions)
Keystone (both units) 0.300 lb/MMBtu (all operating conditions)

 

“All operating conditions” include:

  • emissions during start-up, shut-down, and malfunction
  • operation pursuant to emergency generation required by [the grid operator] including any necessary testing for such emergency operations
  • and during periods in which compliance with this emission limit would require operation of any equipment in a manner inconsistent with technological limitations, good engineering and maintenance practices, and/or good air pollution control practices for minimizing emissions. 

The subsection in the regulation that imposed the 0.012 lb/MMBtu limit that was struck down by the Sierra Club Court does not, on its face, permit any such exceptions, but another regulation allows sources to apply for authorization of “source-specific RACT” for facilities that are unable to comply with RACT limits.

Data from EPA’s Air Markets Program Database for the first six months of 2021 shows that these plants’ NOx emissions regularly exceeded the rates allowable under “normal operating conditions” and sometimes exceeded the rates allowable under “all conditions.”  

Possibly, this is because the plants are still formally subject to the 0.12 lbs/MMBtu limit and not required to operate their selective catalytic reducers. The proposed new limit should mean that the plants will be required to operate them going forward, which would help reduce ozone pollution in Pennsylvania and neighboring states.  

“Thirteen years after the NAAQS for ozone was revised in 2008, some of the largest sources of ozone-causing NOx emissions in the state will finally be regulated properly,” Baillie said. “It’s also entirely possible that further emission reductions could be on the way: Pennsylvania has yet to implement RACT for the 2015 revisions to the NAAQS for ozone. Let’s hope it takes DEP fewer than 13 years to get it right this next time.”

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