Prevention of Significant Deterioration and 

Title V Greenhouse Gas Tailoring Rule Step 3 

and GHG Plantwide Applicability Limitations 

Response to Comments 

Supplement for Tailoring Rule Methodology
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Prevention of Significant Deterioration and 

Title V Greenhouse Gas Tailoring Rule 

Step 3 and GHG Plantwide Applicability 

Limitations

Response to Comments

Supplement for Tailoring Rule Methodology

Air Quality Policy Division

Office of Air Quality Policy and Standards

U. S. Environmental Protection Agency

Research Triangle Park, NC 27711

June 2012
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GHG Plantwide Applicability Limitations – Response to Comments

Supplement for Tailoring Rule Methodology 

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Prevention of Significant Deterioration and Title V Greenhouse Gas Tailoring Rule Step 3 

and GHG Plantwide Applicability Limitations

Response to Comments – Supplement for Tailoring Rule Methodology

This document is a supplement to the Prevention of Significant Deterioration and Title V 

Greenhouse Gas Tailoring Rule Step 3 and GHG Plantwide Applicability Limitations –

Response to Comments document. The purpose of this document is to describe the key

components, for purposes of the Tailoring Rule Step 3 rulemaking, of the data sets and 

methodology the EPA used in the Tailoring Rule as the basis for the estimates of administrative 

permitting burdens.

The most thorough exposition of most components of the data and methodology that the 

EPA used in the Tailoring Rule is found in a technical support document (TSD) entitled: 

“Summary of Methodology and Data Used to Estimate Burden Relief and Evaluate Resource 

Requirements at Alternative Greenhouse Gas (GHG) Permitting Thresholds” (March 2010), 

included as Attachment C to the “Regulatory Impact Analysis for the Final Prevention of 

Significant Deterioration and Title V Greenhouse Gas Tailoring Rule: Final Report” (May 2010) 

(“Tailoring Rule Summary of Methodology”). In this document, the EPA estimates the number 

of newly constructed “anyway” sources, the number of modifications, and the number of hours 

needed to process those types of permits.

In addition, the EPA developed estimates of newly constructed GHG-only sources in a 

TSD entitled: “Technical Support Document for Greenhouse Gas Emissions Thresholds

Evaluation” (March 29, 2010), included as Attachment B to the “Regulatory Impact Analysis for 

the Final Prevention of Significant Deterioration and Title V Greenhouse Gas Tailoring Rule: 

Final Report” (May 2010) (“Tailoring Rule TSD for New GHG-only Sources”).

In the Tailoring Rule, we generally described how we estimated administrative burdens 

as follows:

[W]e estimated the administrative burdens to the permitting authorities at the 

various threshold levels for PSD or title V applicability as follows. First, for a 

particular threshold level, we estimated the number of GHG-emitting sources that 

would be subject to PSD requirements because they would undertake new 

construction or modification, and the number of existing sources that would be 

subject to title V requirements. Second, we estimated the average additional

administrative burden and cost of each PSD permitting action and each title V

permitting action for the GHG-emitting sources. Third, we multiplied those two

estimates, and the product is the additional administrative burden at the particular 

threshold level.

Tailoring Rule, 75 FR 31534/col. 3.
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a. Sources of Data Sets

In the Tailoring Rule, we estimated the amount of the permitting actions by relying 

primarily on the data sets in the NSR ICR, as well as, to lesser extents, the data sets in the Title V 

ICR and GHG Mandatory Reporting Rule. This section describes these three sources of data. 

This section also mentions, for purposes of comparison and to respond to commenters, another 

possible source of data, which is the RACT-BACT-LAER Clearinghouse. In addition, this 

section notes our current informal efforts to track GHG permitting in the States.

i. NSR ICR

We developed our estimates based on the overall number of PSD permitting actions 

included in the NSR ICR. The NSR ICR identifies the information the PSD permit applicants 

must provide to the EPA or to state or local permitting authorities to obtain a PSD permit. Under 

the Paperwork Reduction Act, the NSR ICR must meet certain requirements and be approved by

the Office of Management and Budget. Moreover, the NSR ICR must be renewed periodically.

The NSR ICR also identifies the amount of time that permit applicants may be expected 

to spend completing their applications, and the amount of time that the permitting authority may

be expected to spend processing the applications. The NSR ICR documents also contain 

information about the total numbers of permits and total numbers of minor sources. All this 

information is based on data provided by the sources and the states.

The EPA developed the first NSR ICR shortly after the enactment of the PSD and 

nonattainment NSR permitting programs. The EPA has renewed the NSR ICR every three years 

since then. The renewal process provides for two notices in the Federal Register, which give the 

public two opportunities to comment. 

Prior to the promulgation of the Tailoring Rule, the most recent renewal of the NSR ICR 

had occurred in 2008, so that it was information in the 2008 NSR ICR that served as part of the 

data sets for the EPA’s administrative burden estimates in the Tailoring Rule.

The EPA is currently in the process of renewing the NSR ICR. In this renewal, the EPA

identified the number of permit applications, minor sources, and time spent as the same as the 

2008 ICR, except that the EPA adjusted the number of permit applications to account for, among 

other things, tribal and GHG permitting.

The EPA published the two Federal Register notices containing the NSR ICR on 

November 25, 2011 (76 FR 72700-72702) and April 17, 2012 (74 FR 22779-22780), and 

allowed 30-day comment periods for each notice. The EPA did not receive any comments on the 

NSR ICRs during those comment periods. Thus, no one has contested the amounts of permitting 

activity, including the numbers of minor sources, and the permitting authority time spent on 

processing permits.
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ii. Title V ICR

As with the NSR ICR, the EPA has developed an ICR for Title V permitting, which we 

call the Title V ICR. The EPA developed the first in 1995, after enactment of Title V in the 1990 

Clean Air Act Amendments, and has renewed it periodically since then. The Title V ICR 

contains data concerning the amounts of Title V permitting activity and the time States spend 

processing Title V permits. In promulgating the Tailoring Rule, the EPA relied on the data in the 

Title V ICR that was renewed in 2009. Since then, the Title V ICR was renewed on June 13, 

2012. http://www.reginfo.gov/public/do/PRAViewICR?ref_nbr=201204-2060-016# The EPA 

published the two Federal Register notices for this renewal on December 14, 2011 (76 FR 

77820) and April 25, 2012 (77 FR 24702-24703). This renewal contained essentially the same 

data as in the version of the ICR relied on in the Tailoring Rule, except that in this renewal, the 

burden estimates were increased because the number of sources in Indian Country and the Outer 

Continental Shelf as well as Deepwater Port sources was increased. No one commented on the

ICR during the two public comment periods for this renewal.

iii. GHG Reporting Requirements

In 2009, the EPA signed what we call the Mandatory GHG Reporting Rule (MRR). 74 

FR 56260–56519 (October 30, 2009). The 2009 Final MRR included reporting of GHGs from

various facilities and suppliers. The source categories in the 2009 Final MRR cover

approximately 85 percent of U.S. GHG emissions through reporting by direct emitters as well as 

suppliers of fossil fuels and industrial gases.

b. Methodology and Assumptions – Numbers of Permits

The EPA estimated the numbers of newly constructed sources, which included both 

“anyway” sources and GHG-only sources; as well as modifications, which also included both 

“anyway” sources and GHG-only sources. These estimates are discussed immediately below.

i. Newly Constructed Major Sources – Add Additional GHG (“anyway” new sources)

In the Tailoring Rule Summary of Methodology, the EPA described the methodology for 

estimating the number of sources in the category entitled “Newly Constructed Major Sources –

Add Additional GHG,” which we call “anyway” new sources, as follows:

The August 2008 ICR for the New Source Review (NSR) program estimates that 

282 PSD and 519 non-attainment NSR permits are issued annually. EPA’s initial 

burden analysis concentrated solely on the 282 annual PSD actions. If a source is 

major for a pollutant for which an area is designated non-attainment, all 

significant emissions or significant emissions increases of pollutants for which the 

area is in attainment are still subject to PSD review. Thus, some of the facilities 

applying for nonattainment permits may also undergo PSD actions at the same 

time. Although there is no way of accurately predicting which of the 519 

nonattainment actions might also coincide with a PSD action related to GHG 

emissions, we believe it is likely that most will since they typically involve large 
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emission sources; thus, it is assumed all nonattainment actions from the ICR 

annual estimate will also need a PSD permit. Therefore, in this final analysis, to 

more accurately depict the number of PSD permitting actions occurring annually, 

it is assumed that all 801 permitting actions above involve a PSD action. We 

estimate that 70% of these permit actions are modifications, or 560 of the 801, 

based on feedback received from the National Association of Clean Air Agencies 

(which estimated that some 65% of these permitting actions involve 

modifications); other commenters on the proposed tailoring rule (who generally 

said that most permitting actions involve modifications); and EPA program staff 

experience...

The 240 remaining annual permit actions—labeled in Table 2-1 as “Newly 

Constructed Major Source-Add Additional GHG”—are assumed to be 

construction of new major sources as determined by emissions of one or more 

NAAQS pollutants. Due to the size and emissions of sources currently subject to 

the PSD permitting program, it is believed all of these newly constructed major 

sources will exceed each of the GHG thresholds we considered, including the

100,000 tpy CO2e, and will also need to include GHG-related requirements in the 

PSD permit. 

Tailoring Rule Summary of Methodology, 3-7 (footnotes omitted).

ii. Newly Constructed Major Sources

This category includes newly constructed sources whose emissions of non-GHG 

pollutants are too low to trigger PSD applicability, but whose emissions of GHGs meet or exceed 

the GHG PSD applicability threshold, and therefore do trigger PSD applicability.

As explained in the technical support document for the proposed Tailoring Rule, to 

estimate the number of these sources, the EPA identified the various categories of sources that 

emit GHGs, ranging from the electric generating sector and many subcategories in the industrial 

sector to the commercial and residential sector. The EPA then calculated the number of existing 

sources in those categories. The EPA primarily relied on data from the U.S. GHG Inventory and 

the GHG Mandatory Reporting Rule. The EPA then –

appl[ied] growth rates in the number of units or facilities in a source category to 

the number of existing facilities at the different thresholds. Growth rates were 

available from a variety of sources including Economic Census data, EIA energy

survey data, and various EPA regulatory impact analyses and information 

collection requests which require source population estimates. In some cases there 

was sufficient information to distribute new sources to different thresholds based 

on emission information specific to the new sources....Otherwise EPA assumed 

the same size and threshold distribution for new units as for existing units...

“Technical Support Document for Greenhouse Gas Emissions Thresholds Evaluation” (July 7, 

2009), Attachment B in “Regulatory Impact Analysis for the Proposed Greenhouse Gas 
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Tailoring Rule: Final Report” (September 2009), at 9. See 75 FR 31535/col. 1 (noting that the 

EPA used this approach in the final Tailoring Rule).

The EPA calculated that the number of sources in this group, at the Tailoring Rule 

thresholds (100,000/75,000) is 2, at the 50,000/50,000 threshold is 3, and at the 25,000/25,000 

threshold is 10 (although at the statutory threshold of 100 or 250 is 19,649). Tailoring Rule 

Summary of Methodology, at 5, Table 2-1. 

For purposes of the present Tailoring Rule Step 3, the number of sources in this group is 

too small to have a meaningful impact, and as a result, we will not further discuss this group or 

the EPA’s methodology in estimating the number of sources. We note, however, that the 

methodology for this group is particularly complex because, among other things, it has numerous 

subcategories, each of which requires a growth estimate, and many of those are based on 

different sources of data. As a result, if in the future the EPA found it necessary to reassess its 

overall methodology, reassessing this component would involve additional complexities.

iii. Current Modifications – Add Additional GHG (“anyway” modifications) 

This category includes major modifications at major sources that are triggered by

increased conventional pollutant emissions, but that also exceed the threshold level for GHGs.

In the Tailoring Rule Summary of Methodology, the EPA described the methodology for 

estimating the numbers of these sources as follows:

The August 2008 ICR for the New Source Review (NSR) program

estimates that 282 PSD and 519 non-attainment NSR permits are issued 

annually.... Although there is no way of accurately predicting which of the 519 

nonattainment actions might also coincide with a PSD action related to GHG 

emissions, we believe it is likely that most will since they typically involve large 

emission sources; thus, it is assumed all nonattainment actions from the ICR 

annual estimate will also need a PSD permit. Therefore, in this final analysis, to 

more accurately depict the number of PSD permitting actions occurring annually, 

it is assumed that all 801 permitting actions above involve a PSD action. We 

estimate that 70% of these permit actions are modifications, or 560 of the 801, 

based on feedback received from the National Association of Clean Air Agencies 

(which estimated that some 65% of these permitting actions involve 

modifications); other commenters on the proposed tailoring rule (who generally 

said that most permitting actions involve modifications); and EPA program staff 

experience. Further, 80% of these modifications are expected to involve 

combustion activities with GHG emission levels exceeding the statutory

thresholds and any of the significance levels we considered, up to an [sic: and] 

including the 100,000 tpy CO2e level, thus requiring the inclusion of GHG related 

requirements in a PSD permit. This equates to 448 modifications annually. We 

believe that any of the modifications that would be subject to PSD due to the 

conventional emissions would also be large enough to increase GHGs by at least 

100,000 tpy of CO2e.
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Tailoring Rule Summary of Methodology, at 3-6 (footnotes omitted).

iv. Minor Modifications Becoming Newly Major

This category includes (i) modifications previously considered minor that become major 

modifications due to GHG emissions occurring at existing major sources, and (ii) modifications 

at newly major GHG sources due solely to emissions exceeding the significance level threshold 

for GHG.

In the Tailoring Rule Summary of Methodology, the EPA described the methodology for 

estimating the numbers of these sources as follows:

According to the NSR ICR, approximately 74,591 minor permitting 

actions occur annually, including the following: 30% involve new minor sources, 

new synthetic minor sources, and synthetic-based modifications; 30% involve true 

minor modifications; 20% involve netting based minor modifications; and 20% 

involve minor/administrative permit revisions.We believe that a number of 

projects that could have taken limits or netted out of PSD review and thereby

obtain a minor permit will now be required to apply for a major PSD permit, 

depending on the significance threshold set for GHG. These projects are identified 

in Table 2-1 under “Minor Modifications Becoming Newly Major.” Combining 

the number of synthetic-based modifications (7,459) and netting-based 

modifications (14,909) identified in the ICR, approximately 22,368 of these 

actions could potentially become major modifications subject to PSD review if 

their associated GHG emissions increases exceed the selected GHG significance 

level option. We did not count ‘new minor sources’ and ‘new synthetic minors’ 

because we have already accounted for them as potential major GHG sources if 

their PTE emissions exceed the selected GHG major source threshold option. 

Based on staff review of samples of minor source permits, it is estimated 

that 80% of the current minor modification actions likely involve combustion 

sources – totaling 17,894 actions of the total 22,368 minor modification actions.

Some of these actions may trigger the requirements of the PSD program 

depending on their GHG emission increases and the selected GHG significance 

threshold. In the absence of any experience involving GHG sources and any 

sufficient quantitative data from commenters, we determined the number of these 

actions on the following basis: We assumed the following percentage of the total 

17,984 actions would move to a major modification status due to GHG increases 

for each of the GHG significance level options considered in this analysis: 50% at 

25,000 tpy CO2e; 10% at 50,000 tpy CO2e; 5% at 75,000 tpy CO2e; and zero at 

100,000 tpy CO2e. To determine these percentages, we considered the relative 

emissions of CO2 emissions to NOx emissions at the current major modification 

significance level threshold for NOx (40 tpy). For example, for an average natural 

gas combustion boiler (a common industrial combustion unit that is part of many

modification projects), a 40 tpy NOx emissions would coincide with a 56,000 tpy
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CO2e level. Since many combustion related projects keep just under the 40 tpy 

NOx level to avoid major modification status, we assume that the CO2e emissions 

for a similar project will be around the 50,000 tpy CO2e level. Based on the 

relationship in combustion-related emission levels between NOx and CO2e just 

described, we believe it is reasonable to expect that all these currently minor 

modification projects involving combustion units will exceed the 100 tpy GHG 

significance level under the baseline scenario. This is because we do not believe 

that the sources at which these projects occur will be able to structure their 

operations so as to limit their GHG emissions to less than 100 tpy GHGs. 

However, at higher GHG significance level options, we assume that a decreasing 

proportion of projects will be significantly large enough, or they may emit GHGs 

close enough to the GHG significance level to be able to limit their operations or 

net-out for GHGs like they can for NOx. 

Tailoring Rule Summary of Methodology, at 8-10 (footnotes omitted).

The EPA estimated that at the 100,000/75,000 level, there would be 895 annual permit 

actions in this group of “minor modifications becoming newly major.” Tailoring Rule Summary

of Methodology, at 5 (Table 2-1).

v. Modifications at Newly Major Sources.

This category includes existing but newly classified major sources for GHGs that 

undergo modifications for which they will then be subject to PSD permitting requirements.

In the Tailoring Rule Summary of Methodology, the EPA described the methodology for 

estimating the numbers of these sources as follows:

[A]n existing, but newly classified major source for GHG, may undergo a 

modification for which it will then be subject to PSD permitting requirements. 

This category of PSD permitting activity is listed on Table 2-1 as “Modifications 

at Newly Major Sources.” With this new major source status, these facilities must 

apply for and be issued a PSD permit, if they undergo a major modification. See 

Appendix A for a list of newly major sources at different major source GHG 

thresholds. We estimate that 4% of these newly major sources will undergo 

modifications. This rate was obtained by dividing the current 560 annual PSD 

modification related permit actions (i.e., 70% of 801 actions identified in the NSR 

ICR) by the existing major source population of 14,700 major source title V 

permits. This represents our best available estimate of the rate of PSD 

modification activity at major sources, and we make the assumption that this rate 

will also apply for newly major GHG sources. We recognize that there is some 

level of uncertainty in applying this rate to GHG-only sources, particularly for 

sources in unconventional sectors such as commercial and residential categories, 

however we believe at higher GHG threshold levels, where large industrial 

sources predominate, that this modification rate provides a reasonable estimate of 

modification activity. As no data are yet available for commercial/residential 
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sources and because we cannot conclude that they will differ from industrial 

sources, we select the same 4% rate for modification activity.

Tailoring Rule Summary of Methodology, at 12-13.

The EPA estimated that at the 100,000/75,000 level, there would be 20 annual permit 

actions in this group of “modifications at newly major sources.” Tailoring Rule Summary of 

Methodology, at 5 (Table 2-1).

c. Methodology and Assumptions – Per-Permit Processing Time 

In addition, the EPA estimated the amount of permit-processing hours needed for the 

various types of permits. These estimates are discussed immediately below.

i. Anyway Sources 

In the Tailoring Rule Summary of Methodology, the EPA described the methodology for 

estimating the per-permit processing time for these sources as follows:

For permitting authorities, 50 additional burden hours are estimated to include the 

GHG requirements in a permit.20

20 A well-known gas with a familiar BACT process, such as NOx, requires an average of 20-30 

burden hours to be included in a permit. As less is known regarding GHGs and the BACT decision 

process, expert staff judgment set the burden for permitting authorities to add GHG to permits at 

50 hours. This is because determining BACT entails review and analysis of the available control 

techniques. For a well-known pollutant, the experience of the permitting authority allows it to 

efficiently consider the various options and narrow them down promptly to the one that should be 

considered BACT. Because no BACT determinations have ever been made, permitting authorities 

will need to invest additional time into reviewing the available technologies and selecting which 

one should be considered the best for the particular source. In the absence of any previous 

experience selecting BACT for GHG sources, we estimate that twice as much time will be 

necessary as for conventional pollutants.

Tailoring Rule Summary of Methodology, at 7 & n.20.

ii. GHG-Only Sources 

In the Tailoring Rule Summary of Methodology, the EPA described the methodology for 

estimating the per-permit processing time for these sources as follows:

In addition to sources becoming subject to PSD requirements because of 

GHG emissions related to modifications, new construction will occur that will 

require a PSD permit solely due to the source’s potential GHG emission levels, 

identified in Table 2-1 as “Newly Constructed Major Sources.” Based on the 

source data obtained from the GHG thresholds evaluation, these newly 

constructed major sources involve both industrial and commercial/residential 

facilities.The current NSR ICR notes that permitting authorities spend 

approximately 300 hours processing and issuing a new construction industrial 

source PSD permit. Sources spend almost 870 hours on average preparing for the 
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same permit. In the previous burden analysis, commercial/residential permits 

were assumed to require only 20% of the time necessary for an industrial permit. 

While it is still believed that these sources are less complex than their industrial 

counterparts in terms of numbers and types of emissions sources and control 

requirements, EPA now estimates the commercial/residential permits to take 70% 

of the time required to complete an industrial permit, resulting in approximately

210 hours and 866 hours for permitting authorities and sources respectively.This 

is based on comments received, which stated that we had significantly 

underestimated the amount of time needed. These commenters emphasized that 

commercial and residential sources will generally be located in populated areas, 

and therefore may elicit significant amounts of public input, which in turn will 

increase the amount of time needed compared to our initial estimates. However, 

the commenters generally did not provide quantitative information. As a result, 

we conducted further evaluation of the additional support and outreach activities 

for permitting authorities to assist with applicability determinations and emissions 

calculations, as virtually all commercial/residential sources will have no 

experience with the PSD permitting process. There are also many permit 

preparation activities that represent a fixed cost, such as preparation of notices 

and public hearings. Of the sources falling in this category, the number requiring 

PSD permitting will vary depending on where the thresholds for triggering PSD 

review (both major source and modifications thresholds) are established.

Tailoring Rule Summary of Methodology, at 10-11 (footnotes omitted). Specifically, the 

EPA estimated that the average permitting authority burden per GHG PSD permit type would be 

301 hours for industrial permits, because that is the amount of time needed for any other 

pollutant. Id., at 11, Table 2-2. This included estimates of time for activities ranging from 

attending pre-application meetings and answering respondent questions to approving the 

application and notifying the applicant of the permitting authority determination. Id.