Regional Haze Planning Steps

Step #1: Ambient Data Analysis

This step applies to states, tribes, and any local air quality agencies preparing a Regional Haze implementation plan to reduce emissions to make reasonable progress toward the national visibility goal in the Clean Air Act. The separate 2018 EPA Technical Guidance on Tracking Visibility Progress for the Second Implementation Period of the Regional Haze Program document addresses this step and can be found here. This step addresses 1) How to identify the 20 percent most anthropogenically impaired days and the 20 percent clearest days, and 2) How to determine baseline, current, and natural visibility conditions for each Class I area.

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Step #2: Determine Affected Class I Areas in Other States

This step addresses how a state determines which out-of-state Class Iareas "may be affected by emissions from the state." A state has the flexibility to use any reasonable method for quantifying the impacts of its own emissions on out-of-state Class I areas, and it may use any reasonable assessment for this determination. Determinations of affected Class I areas may be retained from the first implementation period; however, states should also consider whether any assumptions underlying previously determined linkages have changed. States reassessing their linkages for the second implementation period may make this determination based on the state’s recent emissions or anticipated emissions in 2028. The most common approach to assess which out-of-state Class I areas may be affected by aggregate emissions from a given state in the first implementation period was to use a photochemical transport model to track the contribution due to emissions from whole states to specific Class I areas. This determination is a suitable topic for interstate consultation, which should be documented.

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Step #3: Selection of Sources for Control Analysis

The step addresses how states select the emission sources for which an analysis of emission control measures will be completed. Selection of a source at this step does not necessarily mean emission controls will ultimately be required for that source. A state may consider estimated visibility impacts (or surrogate metrics for visibility impacts), the four statutory factors, the five required factors listed in the RHR (section 51.308(f)(2)(iv)), and any other factors that are reasonable to consider. IMPROVE data and the 2018 EPA technical guidance document can be used to develop light extinction budgets (i.e., pie charts showing the light extinction contribution from each ambient PM species) for single days and average budgets for the 20 percent most anthropogenically impaired days. It is recommended that states use estimates of 2028 emissions (resolved by day and hour, as appropriate) to estimate visibility impacts (or related surrogates) when selecting sources, rather than values of recent year emissions.

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Step #4: Regional Support for Characterization and Selection of Control Measures

This step addresses how a state should characterize (i.e., collect information on) the relevant factors (four statutory factors and visibility benefits) that are necessary to make reasonable progress. A state may also consider one or more of the five additional factors in the Regional Haze Rule (section 51.308(f)(2)(iv) – a state must consider these factors in source selection, the control analysis, or both), as well as the visibility benefit of an emission reduction measure. The Rule provides states with considerable flexibility to decide how to characterize the factors, but the approaches must be reasonable and documented.

The RHPWG Control Measures Subcommittee develops Four-Factor Analysis Protocol or Process and assembles a Control Measure Clearinghouse. The overall purpose of each RHPWG subcommittee in its subject area is to:

1. Interact and coordinate with other appropriate WRAP Work Groups for Regional Haze SIP preparation tasks.
2. Develop principles or protocols to guide RH SIP preparation tasks that are appropriate for western state circumstances.
3. Determine when and what contract work is needed and assist in preparation of contract tasks and evaluation of work products.
4. Keep pace of work on schedule for RH SIP preparation

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Step #5: Select Control Measures for Reasonable Progress

This step addresses how a state makes decisions about what emission control measures for a source are necessary to make reasonable progress. A state should make control decisions that are reasonably consistent among and across sources within the state. Consider measures adopted by other contributing states, including all measures that have been agreed upon through interstate consultation. It is recommended that states consider the time necessary for compliance as part of their determination of what compliance deadlines for selected control measures are reasonable. The regulations preclude considering the fact that a control cannot be installed and become operational within the implementation period in determining whether a measure is necessary to make reasonable progress.

The RHPWG Control Measures Subcommittee develops Four-Factor Analysis Protocol or Process and assembles a Control Measure Clearinghouse. The overall purpose of each RHPWG subcommittee in its subject area is to:

1. Interact and coordinate with other appropriate WRAP Work Groups for Regional Haze SIP preparation tasks.
2. Develop principles or protocols to guide RH SIP preparation tasks that are appropriate for western state circumstances.
3. Determine when and what contract work is needed and assist in preparation of contract tasks and evaluation of work products.
4. Keep pace of work on schedule for RH SIP preparation

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Step #6: Regional Modeling of LTS to set 2028 Reasonable Progress Goals

In this step, States will determine the visibility conditions in 2028 that will result from implementation of the LTS and other enforceable measures to set the Reasonable Progress Goals (RPGs) for 2028. The relationship between the LTS and the RPGs for the clearest and most impaired days is a key concept in the regional haze program, as the two RPGs provide a way for the states to check the projected outcome of the LTS against the goals for visibility improvement.

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Step #7: URP Glidepath Check

This step addresses how a state compares the RPGs to the baseline period and the Uniform Rate of Progress (URP) glidepath. The rule requires:

1. Comparing the 20 percent most anthropogenically impaired days and the 20 percent clearest days in 2028 at the in-state Class I area to 2000-2004 conditions.
2. Determining the URP that would achieve natural conditions at the in-state Class I area in 2064.
3. Comparing the 2028 RPG for the 20 percent most anthropogenically impaired days to the 2028 point on the URP glidepath for the in-state Class I area.

If the RPGs are above the URP glidepath, the guidance offers examples approaches to meeting the Rule requirement to make a “robust demonstration” that no further control measures would be reasonable to require. If a state’s RPG is above the URP glidepath, the state must calculate the number of years it would take to attain natural visibility conditions if visibility improvement were to continue at the rate of progress selected by the state as reasonable for the implementation period.

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Step #8: Additional SIP Requirements

This step addresses a few additional rule requirements, including consultation with other states, tribes (if applicable), and consultation with FLMs. The second implementation period SIP should include a progress report addressing the period since submission of the progress report for the first implementation period.