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Update on Regional Haze Rule Activity

Posted: June 2nd, 2020

Authors: Amy M. 
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The Regional Haze Rule (RHR) was promulgated in 1999 at 40 CFR Part 51, Subpart P.  The U.S. EPA developed the RHR to meet the Clean Air Act (CAA) requirements for the protection of visibility in 156 scenic areas (Class I areas) across the United States.  The goal of the RHR is to return visibility in these areas to natural conditions by 2064.  The RHR established visibility milestones for each planning period called the uniform rate of progress (a.k.a. glide path) at each Class I area.  States must make reasonable progress toward this goal during each planning period.  The first stage of the RHR required that certain types of existing stationary sources of air pollutants evaluate Best Available Retrofit Technology (BART).  The purpose of the BART evaluations was to identify older emissions units that contributed to haze at Class I areas that could be retrofitted with emissions control technology to reduce emissions and improve visibility in these areas by 2018.  The initial round of RHR state implementation plan (SIP) revisions that addressed BART requirements were due in December 2007.

What’s Happening Right Now?

States are currently in the process of developing SIP revisions for the second RHR planning period, following the 2017 U.S. EPA RHR revisions and 2018-2019 final guidance documents.  SIP revisions are required by July 31, 2021 and must address further controls that could be applied to stationary sources to reduce emissions of visibility impairing pollutants during the 2021-2028 period.  Some states have made more progress than others in the evaluation of what further controls are feasible in order to make progress on visibility improvement goals during this planning period.

The approach to selecting sources to be evaluated has varied from state to state.  Some states are selecting sources within certain industries that are large emitters of sulfur dioxide (SO2), nitrogen oxides (NOX), and particulate matter less than 10 microns (PM10).  For example, Washington focused primarily on combustion sources in industries such as power, pulp and paper, and refining.  Some states developed a threshold based on the facility’s emissions of visibility impairing pollutants in tons per year (Q) divided by their distance in kilometers to the closest Class I area (d) and selected the facilities above the threshold for evaluation.  For example, Oregon has selected all facilities with Q/d of at least 5 for evaluation and asked facilities to evaluate all emissions sources that are not classified as insignificant activities.  Wyoming selected facilities with a Q/d of at least 10 and asked facilities to evaluate units with the largest emissions of SO2, NOx, and PM10.  Some states performed a modeling analysis to determine the facilities with the largest impact on visibility impairment in Class I areas and selected sources above a certain threshold for analysis (e.g., the Southeastern States).  Finally, some states asked for evaluations on individual emissions units at facilities (e.g., Minnesota).

The pollutants to be evaluated also can vary from state to state.  For example, Washington requested an analysis of SO2, NOx, PM10, ammonia, and sulfuric acid mist.  Oregon is focusing on SO2, NOx, and PM10.  (Oregon is also focusing on allowable emissions, rather than actual emissions.)  The southeastern states have determined that SO2 emissions have the greatest impact on visibility impairment and are focusing on that pollutant.

What’s Involved in the Evaluation of Controls?

If your facility or a group of sources at your facility is selected for evaluation, a Four Factor Analysis will be required.  The four factors are:

  • The cost of control,
  • Time necessary to install controls,
  • Energy and non-air quality impacts, and
  • Remaining useful life of the source.

Note that unlike the BART analyses we conducted for the first planning period, the four factor analysis does not include air dispersion modeling.

Many of us are familiar with the first and third factors because we routinely evaluate technical and economic feasibility of controls and the associated energy and non-air quality impacts of potentially feasible controls as part of permitting exercises or state air quality improvement initiatives.  The U.S. EPA’s Control Cost Manual contains recommended procedures for developing capital and operating cost estimates for controls that are determined to be technically feasible.  Often the framework outlined in the manual is adjusted using a vendor’s equipment cost estimate or equipment cost data included in other similar facilities’ permit applications or in industry studies, rather than using the complex equations in the cost manual to size and cost control equipment.  Cost factors that should not be overlooked include the cost of new ductwork or fans, cost to replace a stack to accommodate a wet plume, cost of an unplanned shutdown (if required to install controls), and any cost required to demolish or move existing equipment to make space for new control equipment.  The annual cost of installing additional controls or improving existing controls is divided by the expected reduction in emissions to develop a cost per ton estimate.

The other two factors, time necessary to install controls and remaining useful life of the source, are important because the states are evaluating improvements that can be made in order to improve visibility in the 2021-2028 time period.  If it will take 10 years to install a control or if the emissions unit will be shut down between 2021 and 2028, the outcome of the analysis will be different than if an emissions reduction can be accomplished quickly and the emissions unit has 20 more years of life.  If a control technology is determined to be technically and economically feasible, a compliance deadline will be established based on the estimated time necessary to install controls.

Although states have not indicated they have a certain threshold in mind for determining whether additional control is cost effective, the fact that many Class I areas are well below the glidepath (visibility is better than many areas’ goal) for the second planning period is likely to mean that the cost per ton threshold is lower than it would be in a traditional permitting analysis.  When the U.S. EPA was evaluating whether NOx controls would be cost effective for non-electric generating unit sources for the 2017 Cross State Air Pollution Rule update, it used a threshold of $3,400/ton.  There have been several non-RHR related air regulatory programs in the past 10 years that have resulted in reductions in emissions of SO2, NOx, and PM10 and improved visibility in Class I areas, so the number of sources required to make emissions reductions during the second planning period may not be significant.  However, the fact that visibility is better than expected does not relieve the states from requiring a four factor analysis from selected facilities (it may allow for more flexibility in which sources are selected, though).

The four factor analysis approximates an evaluation of reasonably available control measures and does not have to be as stringent as a best available control technology (BACT) analysis.  U.S. EPA guidance also indicates that it is reasonable for states to determine that sources complying with various federal air quality regulations, those with recent BACT limits, those firing clean fuels, and combustion sources with SO2 and NOx controls that are at least 90 percent effective are not candidates for additional controls.

What’s Next?

States will utilize the results of the four factor analyses and projected 2028 emissions to conduct modeling against baseline emissions and determine the progress they expect to make improving visibility during the second planning period.  The control measures that will be implemented during the second planning period will be included in the RHR SIP revisions that are due next July.  Measures could include work practices, addition of controls on uncontrolled sources, improvements of less effective controls, year-round operation of existing controls, fuel changes, and operating restrictions.  Prior to incorporating control measures into the RHR SIP there will be dialogue between the states and the regulated community and an opportunity to provide comments on the draft SIP.

The U.S. EPA announced in January 2018 that it would revisit certain aspects of the 2017 RHR revisions in a notice and comment rulemaking. However, no action has been taken to date and the current rule and guidance documents are driving state actions for the 2021-2028 planning period.  Any future U.S. EPA rulemaking action will impact the next planning period, and ALL4 will be on the lookout for any regulatory changes.  If you haven’t heard how your state is handling regional haze evaluations, it is a good idea to check in with them and determine if your facility will need to take any action or provide any information as the state is working on their SIP.  If you need assistance completing a four factor analysis, please contact Amy Marshall or your ALL4 project manager.  We have completed analyses for various types of facilities in several states.


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