UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

DEC 1 8 2008 

THE ADMINISTRATOR 

MEMORANDUM 

TO: 

FROM: 

RE: 

Regional Administrators 

Stephen L. Johnson, Administrator 

EPA's Interpretation of Regulations that Determine Pollutants Covered By 

Federal Prevention of Significant Deterioration (PSD) Permit Program. 

INTRODUCTION 

In this memorandum, I am establishing an interpretation clarifying the scope of 

the EPA regulation that determines the pollutants subject to the federal Prevention of 

Significant Deterioration (PSD) program under the Clean Air Act (CAA or Act). Under 

Title I, Part C of the Act, the PSD program preconstruction permit requirement applies to 

any new major stationary source or modified existing major stationary source of 

regulated air pollutants located in an area that is either attaining the National Ambient Air 

Quality Standards (NAAQS) or unclassifiable. Under the federal PSD permitting 

regulations, only newly constructed or modified major sources that emit one or more 

"regulated NSR pollutants," as that term is defined in 40 C.F.R. 52.21(b)(50), are subject 

to the requirements of the PSD program, including the requirement to install the best 

available control technology (BACT) for those regulated NSR pollutants that the facility 

emits in significant amounts. This memorandum contains EPA's definitive interpretation 

of 40 C.F.R. 52.2 1 (b)(50) and is intended to resolve any ambiguity in subpart (vi) of that 

paragraph, which includes "any pollutant that otherwise is subject to regulation under the 

Act." As of the date of this memorandum, EPA will interpret this definition of "regulated 

NSR pollutant" to exclude pollutants for which EPA regulations only require monitoring 

or reporting but to include each pollutant subject to either a provision in the Clean Air 

Act or regulation adopted by EPA under the Clean Air Act that requires actual control of 

emissions of that pollutant. 

As a matter of practice, EPA has not historically applied the PSD program to 

pollutants that are subject only to monitoring and reporting requirements. EPA may 

mandate monitoring and reporting by regulation to gather information about emissions 

for several purposes, including establishing emissions baselines or informing decisions 

regarding whether to establish controls or limitations for a particular pollutant. Although 

EPA has not required that PSD permits contain emissions limitations for pollutants 

subject only to monitoring and reporting requirements, the EPA Environmental Appeals 

Internet Address (U L) http'lhiww.epa.gov 

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Board (EAB or Board) recently determined that prior EPA actions are insufficient to 

establish a binding interpretation that section 52.21(b)(50) covers only pollutants subject 

to regulations that require actual control of emissions. In re: Deseret Power Electric 

Cooperative, PSD Appeal No. 07-03 (EAB Nov. 13,2008). The Board's decision has 

contributed to uncertainty regarding the scope of the PSD program. Permitting 

authorities, applicants, and other interested parties do not currently know whether 

pollutants for which EPA has only established regulatory requirements to monitor and 

report emissions are covered by the PSD program and whether sources must consider 

these pollutants when assessing whether they are major sources that must apply for a PSD 

permit. 

I respect the EAB decision in Deseret, which was thorough, thoughtful, and based 

on the permitting record before the Board. This memorandum is not intended to 

supersede the Board's decision, which was issued in accordance with authority delegated 

to the EAB by the EPA Administrator. See 40 C.F.R. 5 124.2; 40 C.F.R. 5 124.19; 57 

Fed. Reg. 5320 (Feb. 13, 1992). The purpose of this memorandum is to build on the 

Board's Deseret opinion and address ambiguity in EPA's regulations that remains after 

the EAB concluded the Agency did not previously establish the interpretation that 

pollutants subject solely to monitoring or reporting requirements are not "regulated NSR 

pollutants" that require emissions limitations based on levels that can be achieved using 

BACT. Deseret slip op. at 9. This memorandum is intended to reduce ambiguity by 

setting forth an initial interpretation of EPA's regulation at 40 C.F.R. 5 52.21(b)(50). 

The EAB encouraged EPA offices to consider whether to undertake an action of 

nationwide scope to address the interpretation of the phrase "subject to regulation under 

the Act," which is used in the regulatory definition of "regulated NSR pollutant." See 

Deseret slip op. 63-64. This memorandum is intended to accomplish that purpose, thus 

relieving individual EPA Regional Offices of the burden of resolving an issue which 

affects the entire national permitting program. Immediate issuance of this interpretation 

of EPA's regulation is needed to ensure the continuing operation of the federal PSD 

permitting program and to resolve ambiguity and reduce confusion among permitting 

authorities, the regulated community, and other interested stakeholders. This 

memorandum reflects my considered judgment and explains existing regulatory 

requirements. The interpretation adopted in this memorandum is consistent with the 

historic practice of the Agency and with prior statements by Agency officials, including 

the Administrator, the EAB, and the General Counsel. EPA has not previously issued a 

definitive interpretation of the definition of "regulated NSR pollutant" in section 

52.21(b)(50) or an interpretation of the phrase "subject to regulation under the Act" that 

addressed whether monitoring and reporting requirements constitute "regulation" within 

the meaning of this phrase. 

The interpretation in this memorandum applies to all PSD permitting actions by 

EPA Regions (and delegated States that issue permits on behalf of EPA Regions), under 

the federal PSD permitting program governed by 40 C.F.R. 5 52.21. I request that the 

Regional Offices implement the attached interpretation immediately in federal PSD 

permitting actions. In addition, Regional Offices should take immediate steps to inform 
delegated States of this interpretation. I also encourage Regional Offices to promptly 

communicate this interpretation to state and local agencies that implement EPA-approved 

PSD programs under their State Implementation plans.' 

I. BACKGROUND ON THE EAB'S DESERET DECISION AND THE NEED 

FOR THIS CLARIFICATION OF THE PSD REGULATIONS 

A. The Deseret Decision 

On November 13,2008, the EAB issued a decision in In re Deseret Power 

Electric Cooperative, PSD Appeal No. 07-03 (EAB 2008). The case involved an appeal 

of a PSD permit that Region 8 had issued on August 30,2007, to Deseret Power Electric 

Cooperative (Deseret) authorizing it to construct a new waste-coal-fired electric 

generating unit near its existing Bonanza Power Plant, in Bonanza, Utah. The Board 

issued an order and opinion remanding the permit because it found that Region 8 

erroneously believed it was required to follow a historic agency interpretation concerning 

the scope of the phrase "subject to regulation" used in the regulatory definition of the 

term "regulated NSR pollutant," 40 C.F.R. 52.21(b)(50), and the Clean Air Act (section 

165 and 1 69).2 The Board found that the permitting record failed to set forth "sufficiently 

clear and consistent articulations of an Agency interpretation to constrain the authority" 

of the Region in the manner explained in the Region's response to public comments. The 

Board also considered additional Agency documents cited in the briefs submitted by 

various parties and concluded that these Agency actions also were insufficient to 

unequivocally establish the specific interpretation of the phrase "subject to regulation" 

that Region 8 believed it was bound to apply in issuing the permit. 

' The EPA regulation setting forth PSD program requirements for State Implementation 

Plans also includes the same definition of this term at 40 C.F.R. 4 5 1.166(b)(49). 

Because the same language is used in this regulation, Regional Administrators may also 

apply the interpretation described in this memorandum prospectively when reviewing and 

approving new submissions for approval or revision of state plans. Because the EAB 

determined that the interpretation adopted in this memorandum was not previously 

established by the Agency, this interpretation does not apply retroactively to prior 

approvals of State Plans by EPA Regional Offices. To the extent approved State 

Implementation Plans contain the same language as used in 40 C.F.R. 4 52.21(b)(50) or 

40 C.F.R. 4 5 1.166(b)(49), States may interpret that language in state regulations in the 

same manner reflected in this memorandum. 

The statute and regulation use similar but not identical language. The regulation 

defines a regulated NSR pollutant to include "Any pollutant that otherwise is subject to 

regulation under the Act" and requires BACT for "each regulated NSR pollutant." 40 

C.F.R. 55 52.21(b)(50), (j). The Clean Air Act requires BACT for "each pollutant 

subject to regulation under this Act." CAA $8 165(a)(4), 169. The United States Code 

refers to "each pollutant regulated under this chapter," which is a reference to Chapter 85 

of Title 42 of the Code, where the Clean Air Act is codified. See 42 U.S.C. $5 

7475(a)(4), 7479(3). For simplicity, this memorandum generally uses "the Act" and the 

Clean Air Act section numbers rather than the U.S. Code citation. 
More specifically, the primary issue before the Board was whether the permit had 

to include BACT limits for carbon dioxide (C02) under the definition of a "regulated 

NSR pollutant" and statutory language in sections 165 and 169 that make the BACT 

requirement applicable to "each pollutant subject to regulation" under the Act. The 

Petitioner (Sierra Club) argued that this statutory language was unambiguous and subject 

to only one interpretation as a matter of law, leaving the Agency, and hence the Region, 

no discretion to interpret the phrase. Petitioner argued that the act of promulgating a 

"regulation" in the Code of Federal Regulations that required power plants to monitor 

and report, but not control or otherwise limit, C02 emissions clearly rendered C02 a 

pollutant "subject to regulation" for purposes of the PSD program and thus required that 

the PSD permit in that case contain an emissions limitation for ~02.~ 

Region 8 and the Office of Air and Radiation (OAR), represented by Regional 

Counsel and the Office of General Counsel, argued that the statutory phrase "subject to 

regulation under this Act" is ambiguous and therefore subject to reasonable interpretation 

by the Agency. Moreover, the offices contended that EPA had historically interpreted the 

phrase "subject to regulation" to include only those pollutants "subject to a statutory or 

regulatory provision that requires actual control of emissions of that pollutant," thus 

excluding pollutants (like C02) for which only monitoring is required. The Region and 

OAR argued that Region 8 followed this longstanding interpretation and thus properly 

did not include BACT limits for C02 in the PSD permit for Deseret. 

The Board rejected Petitioner's argument that the Act compelled only one 

interpretation of the phrase "subject to regulation" and found "no evidence of a 

Congressional intent to compel EPA to apply BACT to pollutants that are subject only to 

monitoring and reporting requirements." Deseret slip op. at 63. Thus, the Board agreed 

with the Region and OAR that the statutory phrase "subject to regulation under this Act" 

is ambiguous. However, as discussed above, the Board also concluded that the Region's 

reason for not including a BACT limit for C02 in the permit - that it was bound by a 

historic interpretation of the phrase "subject to regulation" - was not supported by the 

administrative record for the permit. Id. Thus, the Board remanded the permit to the 

Region to "reconsider whether or not to impose a C02 BACT limit in light of the 

Agency's discretion to interpret, consistent with the CAA, what constitutes a 'pollutant 

subject to regulation under this Act."' ~d.~ The EAB also encouraged EPA offices to 

consider whether to undertake an action of nationwide scope to address the interpretation 

of the phrase "subject to regulation under the Act." Id. at 63-64. 

B. Implications of the Deseret Decision for the PSD Permitting Program 

The appeal also involved the question of whether the monitoring regulations that EPA 

issued pursuant to section 821 of the Clean Air Act Amendments of 1990 were issued or 

are enforceable under the Clean Air Act. That issue is not addressed in this 

memorandum. 

4 The Board rejected Petitioners' other challenge to the permit based on the alternatives 

analysis for the permit. Id. at 2 1-23. 
As a result of the Board's decision, states, regulatory agencies, industry and the 

public would benefit from clarification regarding how EPA interprets this key phrase 

"subject to regulation" in the PSD program's regulatory definition of "regulated NSR 

pollutant." Currently, roughly 275 sources obtain PSD permits nationwide per year. 

Approximately 50 of them obtain PSD permits issued by EPA or delegated states 

implementing the federal PSD program at 40 C.F.R. 5 52.21. The remainder are issued 

under approved State Implementation Plans. The Deseret decision has led to confusion 

for sources applying for PSD permits under 40 C.F.R. 5 52.21 because they currently do 

not know if they should include a BACT analysis with their PSD permit application for 

carbon dioxide or any other pollutant for which only monitoring regulations exist. The 

Board's decision has also caused confusion among delegated permitting agencies which 

are unsure how EPA interprets its regulations, which they are implementing on EPA's 

behalf. 

Moreover, as discussed in detail below, because the term "regulated NSR 

pollutant" is found in the definition of "major stationary source" at 40 C.F.R. 5 

52.21(b)(l)(i)(a), there is also confusion as to which sources must apply for PSD permits, 

since newly constructed or modified "major stationary sources" must obtain PSD permits. 

There is currently uncertainty regarding the pollutants that must be considered when 

determining major source status. Thus, while the Deseret case decision was about 

whether a major stationary source obtaining a PSD permit based on its emissions of other 

pollutants was required to install BACT for an additional pollutant, it has created 

questions for hundreds of thousands of smaller sources that must determine whether they 

are "major sources'' that must obtain PSD permits if they experience a major 

modification or construct a new facility. This confusion potentially extends to source 

categories that have never had to obtain PSD permits in the past. 

Given the confusion resulting from the Board's conclusion that the documents 

relied on by the Region and OAR did not establish a "sufficiently clear and consistent 

articulation of an Agency interpretation" of "subject to regulation," id. at 37, the Agency 

believes that the best path forward is to establish a clear interpretation of its regulations at 

this time. Immediate issuance of this interpretation is appropriate to ensure consistent 

implementation of the PSD program by Regions and delegated states, and to eliminate 

ambiguity and confusion among permitting authorities, the regulated community, and 

other stakeholders. As discussed in more detail below, the Agency may adopt this first 

clear, binding interpretation in this memorandum because the EAB held that documents 

cited by the Region and OAR had not established an interpretation and the interpretation 

set forth in this memorandum is consistent with, and a further elaboration of, those prior 

statements on the matter. The Agency's exercise of its discretion to interpret what 

constitutes a pollutant subject to regulation is detailed below. 

EPA'S INTERPRETATION OF THE TERM "REGULATED NSR 

POLLUTANT" IN 40 C.F.R. 5 52.21(b)(50) 
EPA interprets the definition of "regulated NSR pollutant" in 40 C.F.R. 8 

52.21(b)(50) to exclude pollutants for which EPA regulations only require monitoring or 

reporting but to include each pollutant subject to either a provision in the Clean Air Act 

or regulation promulgated by EPA under the Clean Air Act that requires actual control of 

emissions of that pollutant.5 This interpretation is supported by the language and 

structure of the regulation and sound policy considerations. Furthermore, this 

interpretation is consistent with past practice in the PSD permitting program, EPA's prior 

statements regarding pollutants6 subject to the PSD program, and is permissible under the 

Clean Air Act. 

A. Language and Structure of 40 C.F.R. 6 52.21(b)(50) Support Limiting Its 

Applicability To Pollutants That Must be Controlled Under Clean Air Act 

Regulations 

The structure and language of EPA's definition of "regulated NSR pollutant" at 

40 C.F.R. 52.21(b)(50) supports an interpretation that it covers only those pollutants 

subject to a statutory or regulatory provision that requires actual control of emissions of 

that pollutant. The portions of the definition pertinent to this memorandum read as 

follows: 

Regulated NSR pollutant, for purposes of this section, means the following: 

Congress could require control of emissions through a statutory provision that directly 

imposes actual controls or limitations on a particular pollutant or that requires EPA to 

write regulations to control or limit particular pollutants. As discussed further below, in 

the latter circumstance, EPA does not interpret the PSD requirements to apply to such a 

pollutant until EPA promulgates the regulation required by the Act. 

This memorandum does not seek to further define the specific nature or scope of any 

individual "pollutant" that is subject to such controls. Any ambiguity as to whether some 

part, component, or constituent of a substance or category of substances is controlled 

under a regulation should be resolved in the context of interpreting the individual rule 

that gives rise to the issue. See, e.g., Regulating Greenhouse Gas Emissions Under the 

Clean Air Act, Advance Notice of Proposed Rulemaking ("ANPR), 73 Fed. Reg. 44354 

(July 30,2008) at 44420-421 (describing the various consequences that could arise given 

the definition of the "pollutant" that EPA may establish in a regulation of one or many 

greenhouse gases). For example, in adopting the New Source Performance Standard 

(NSPS) for municipal solid waste (MSW) landfills, EPA was explicit that it was 

regulating only MSW landfill emissions collectively, and not the individual components 

of those emissions. 56 Fed. Reg. 24468,24470 (May 30, 1991) ("The pollutant to be 

regulated under the proposed standards and guidelines is "MSW landfill emissions."); id. 

at 24474 ("The EPA views these emissions as a complex aggregate of pollutants which 

together pose a threat to public health and welfare based on the combined adverse effects 

of the various components. . . . The EPA thus views the complex air emission mixture 

from landfills to constitute a single designated pollutant."). 
(i) Any pollutant for which a national ambient air quality standard has been 

promulgated and any constituents or precursors for such pollutants identified by 

the Administrator. * * * 

(ii) Any pollutant that is subject to any standard promulgated under section 11 1 of 

the Act. 

(iii) Any Class I or I1 substance subject to a standard promulgated or established 

by title VI of the Act; 

(iv) Any pollutant that otherwise is subject to regulation under the Act; 

40 C.F.R. Cj 52.21(b)(50), as amended, 73 Fed. Reg. 28321 (May 16,2008). The 

definition also excludes hazardous air pollutants from the PSD program in accordance 

with section 112(b)(6) of the Act and discusses a transition period established in 2008 for 

addressing condensable particulate matter. 

As reflected above, the first three parts of the definition describe pollutants that 

are subject to regulatory requirements that mandate control or limitation of the emissions 

of such pollutants.7 40 C.F.R. Cj 52.21(b)(50)(i)-(iii). Consistent with the text of the Act, 

the fourth part of the definition of "regulated NSR pollutant" covers "[alny pollutant that 

otherwise is subject to regulation under the Act." 40 C.F.R. Cj 52,21(b)(50)(iv). 

Dictionary definitions illustrate that the term "regulation" (used in the fourth part 

of the definition) is susceptible to more than one meaning. This term can be used to 

describe a rule contained in a legal code, such as the Code of Federal Regulations, or the 

act or process of controlling or restricting an activity. The primary meaning of the term 

"regulation" in Black's Law Dictionary (gth Ed.) is "the act or process of controlling by 

rule or restriction." However, an alternative meaning in this same dictionary defines the 

term as "a rule or order, having legal force, usu. issued by an administrative agency or 

local government." The primary meaning in Webster's dictionary for the term 

"regulation" is "the act of regulating: the state of being regulated." Merriam-Webster's 

Collegiate Dictionary 983 (loth ed. 2001). Webster's secondary meaning is "an 

authoritative rule dealing with details of procedure" or "a rule or order issued by an 

executive authority or regulatory agency of a government and having the force of law." 

Webster's also defines the term "regulate" and the inflected forms "regulated" and 

"regulating" (both of which are used in Webster's definition of "regulation") as meaning 

"to govern or direct according to rule" or to "to bring under the control of law or 

constituted authority." Id. In the context of construing the Act, the EAB observed in the 

Deseret case that a plain meaning could not be ascertained from looking solely at the 

word "regulation." The Board reached this conclusion after considering the dictionary 

definitions of the term "regulation" cited above. Deseret slip op. at 28-29. 

The interpretation of the phrase "subject to regulation" in section 52.21(b)(50)(iv) 

that EPA is adopting in this memorandum is directly supported by the primary meaning 

of the term "regulation" used in the dictionaries described above. Each of these 

definitions uses the word "control" or incorporates it through reference to a definition of 

' Class I or I1 substances are specific categories of ozone depleting emissions. 
a similar word. Furthermore, in construing similar language in the Act, the EAB 

recognized that "subject to regulation" may be read to mean "subject to control" by virtue 

of a regulation or otherwise. Deseret slip op. at 33. 

Furthermore, the placement of the word "regulation" after the phrase "subject to" 

in the context of the fourth part of the definition supports reading section 52.21(b)(50)(iv) 

to describe an act or process rather than a rule in a code. The use of the singular 

"regulation" without an article (such as "a" or "the") preceding the word is more 

naturally read to describe an "act or process," which supports the application of the 

meaning from Black's Law Dictionary (gth Ed.) that emphasizes "controlling by rule or 

restriction." EPA did not choose to use the plural "regulations" or an article before the 

word, which would have produced language such as "subject to regulations under the 

Act" or "subject to A regulation under the Act." A regulation that used these phrases 

(instead of the one EPA chose) would be more consistent with the dictionary meanings 

that describe a regulation as a "rule" such as would be contained in the Code of Federal 

Regulations. 

Likewise, the combination of the general language in the fourth subpart with more 

specific provision in the first three subparts of the regulation is meaningful. Each of the 

identified categories is a class of regulations that require actual control or limitation of 

emissions of pollutants and none involve only monitoring and reporting of pollutant 

emissions. The use of the word ''otherwise" in front of phrase "subject to regulation" 

establishes a link between the first three parts of the definition and the fourth, suggesting 

that the four parts of the definition should be read in concert. Specifically, the placement 

of the fourth part of the definition after the first three parts identifying regulations that 

require controls supports reading the fourth part to cover the same type of regulatory 

requirements addressed in the first three parts of the definition. 

Courts have recognized that "[wlhere general words follow the enumeration of 

particular classes of things, the general words are most naturally construed as applying 

only to things of the same general class as those enumerated." See American Mining 

Congress v. US. EPA, 824 F.2d 1 177, 1 189 (D.C. Cir. 1987). Accordingly, the general 

language including pollutants "otherwise subject to regulation," as used in the fourth part 

of the regulated NSR pollutant definition, can be read to apply to the same general class 

of pollutants enumerated in the first three parts of the definition -- pollutants that are 

subject to a promulgated regulation requiring actual control of a pollutant. 

In the Deseret opinion, the EAB declined to apply this principle (known in legal 

terms the ejusdem generis canon of interpretation) in the absence of any analysis or 

statement of intent in the preamble to the 2002 rulemaking in which EPA adopted the 

definition of the term "regulated NSR pollutant." Slip Op. at 45-46. EPA has prepared 

this memorandum, in part, to provide the analysis and statement of intent that were 

lacking in the record of the Deseret permit. For the policy reasons discussed in this 

memorandum, EPA reads the definition of "regulated NSR pollutant" to apply only to the 

same general class of regulated pollutants as those enumerated in the first three parts of 

the definition. Since the phrase "subject to regulation" does not have a clear meaning, as 
the Board recognized in interpreting the statutory text of the Act in the Deseret opinion, it 

then follows, with this additional analysis and statement of intent regarding the 

regulation, that the principle of ejusdem generis can be applied to the general language in 

section 52.21 (b)(50)(iv) of EPA's PSD regulations. 

B. Important Policy Considerations Support The Interpretation Adopted Here 

I believe that EPA's various responsibilities under the Clean Air Act are most 

effectively implemented by making PSD emissions limitations applicable when the 

Agency promulgates a regulation restricting pollutant emissions based on a considered 

judgment by the Administrator (or the Congress) that particular pollutants should be 

subject to control or limitation. Requiring such limitations automatically for pollutants 

that are only subject to data gathering and study would hstrate EPA's ability to 

accomplish several objectives of the Clean Air Act. The Agency's interpretation of the 

scope of the PSD program set forth in this memorandum remains broad, covering any 

pollutant subject to control through regulations established under the Act that apply in a 

particular area. However, this broad application of the PSD program should not be 

without reasonable boundaries that make the NSR program and other Act programs 

effective, yet manageable, for EPA and the states to administer. 

The administration of emissions control programs under the Act requires reasoned 

decision-making that is often informed by review of emissions data. Section 114(a)(l) of 

the Act authorizes the Administrator to require various persons to gather and report 

emissions data for a number of purposes. 42 U.S.C. § 7414(a)(l). These include 

developing an implementation plan or emissions standards for specific source categories 

under sections 11 1, 112 or 129 of the Act; determining if any person is in violation of any 

standard or requirement of an implementation plan or emissions standard; or "carrying 

out any provision" of the Act. The latter may include information gathering for research 

under provisions of the Act that direct or authorize EPA research on various matters. 

Although there are exclusions in section 1 14(a)(l) regarding certain title I1 requirements 

applicable to manufacturers of new motor vehicle and motor vehicle engines, section 208 

of the Act authorizes the gathering of information related to those areas. 42 U.S.C. § 

7542. 

An interpretation of the PSD regulations that makes the substantive requirements 

of the program applicable to individual pollutants based solely on monitoring and 

reporting requirements (contained in regulations established under section 114 or other 

authority in the Act) would lead to the perverse result of requiring emissions limitations 

under the PSD program while the Agency is still gathering the information necessary to 

conduct research or evaluate whether to establish controls on the pollutant under other 

parts of the Act. This would frustrate the Agency's ability to gather information using 

section 114 and other authority and make informed and reasoned judgments about the 

need to establish controls or limitations on individual pollutants. If EPA interpreted the 

requirement to establish emissions limitations based on BACT to apply solely on the 

basis of a regulation that requires collecting and reporting emissions data, the mere act of 
gathering information would essentially dictate the result of the decision that the 

information is being gathered to inform (whether or not to require control of a pollutant). 

I prefer an interpretation that allows the Agency to first assess whether there is a 

justification for controlling emissions of a particular pollutant under relevant criteria in 

the Act. This interpretation permits the Agency to provide notice to the public and an 

opportunity to comment when a new pollutant is proposed to be regulated under one or 

more programs in the Act. It also promotes the orderly administration of the permitting 

program by providing an opportunity for EPA to develop regulations to manage the 

incorporation of a new pollutant into the PSD program, for example, by promulgating a 

significant emissions rate (or de minimis level) for the pollutant when it becomes 

regulated. See 40 C.F.R. 8 52.21(b)(23). Furthermore, an interpretation that preserves 

the Agency's ability to gather information to inform the Administrator's judgment 

regarding the need to establish controls on emissions without automatically triggering 

such controls in no way limits the Agency's authority to require controls on emissions of 

a particular pollutant when the Administrator determines they are warranted. This 

interpretation preserves the Administrator's authority to require control of individual 

pollutants through emissions limitations or other restrictions under various provisions of 

the Act, which would then trigger the requirements of the PSD program for any pollutant 

addressed in such an action. 

Although this issue has been raised in the context of C02 emissions, EPA's 

interpretation of whether PSD requirements are triggered by monitoring and reporting 

requirements has broader implications. While the timing of this memorandum was 

influenced by the uncertainty in the PSD program concerning whether permits must 

contain emissions limitations for C02 and whether additional smaller sources must now 

apply for permits when they construct or modify, the adoption of this interpretation is 

also necessary to preserve EPA's ability to collect emissions data on other pollutants for 

research and other purposes such as evaluating the need for emissions controls or 

limitations. The current concerns over global climate change should not drive EPA into 

adopting an unworkable policy of requiring emissions controls under the PSD program 

any time that EPA promulgates a rule under the Act that requires a source to gather or 

report emissions data under the Act for any pollutant. This consideration is the same 

whether the substance at issue is COz or other substances that may emerge and require 

evaluation to inform a reasoned decision concerning whether controls should be 

established for such substances under the Clean Air Act. Furthermore, as discussed 

above, the interpretation adopted here in no way limits EPA's ability to make a 

considered judgment that controls on a particular pollutant are warranted under the 

criteria in other parts of the Act and thereby invoke the requirements of the PSD program 

for that particular pollutant. 

C. This Interpretation is Consistent with the Agency's Past Practice and Statements 

The interpretation adopted in this memorandum is consistent with the historic 

practice of the Agency and with prior statements by Agency officials, including the 

Administrator, the EAB, and the General Counsel. 
As a matter of practice, EPA has not issued PSD permits containing emissions 

limitations for pollutants that are only subject to monitoring and reporting requirements. 

PSD permits issued by the Agency (and delegated states authorized to issue federal 

permits on EPA's behalf) have only contained emissions limitations for pollutants subject 

to regulations requiring actual control of emissions. EPA staff have reviewed permits 

issued under this program and have not identified any federal PSD permits that establish 

limitations on the emissions of pollutants that were only subject to monitoring and 

reporting requirements established under the Act at the time the permit issued. Since 

1993, EPA has had regulations in place requiring monitoring and reporting of carbon 

dioxide emissions. See Acid Rain Program: General Provisions and Permits, Allowance 

System, Continuous Emissions Monitoring, Excess Emissions and Administrative 

Appeals (final rule), 58 Fed. Reg. 3590 (Jan. 11, 1993). I am not aware of any PSD 

permits containing emissions limitations for carbon dioxide issued by either the Agency 

or its delegates since that time. During at least part of this time period, EPA made clear 

that it considered C02 to be an air pollutant under the Act. See Memorandum from 

Jonathan Z. Cannon, General Counsel to Carol M. Browner, Administrator, entitled 

EPA 's Authority to Regulate Pollutants Emitted by Electric Power Generation Sources 

(April 10,1998) ("Cannon Memo"). 

In Deseret, the EAB expressed some doubt as to whether this had been EPA's 

practice based on the lack of any specific evidence of this practice in the record of the 

Deseret permit. Slip op. at 53-54. Ln the absence of a definitive statement (which the 

EAE3 found did not exist) that monitoring and reporting regulations alone do not trigger 

substantive PSD requirements, one must look to individual permits issued under the 

federal PSD program to identify this practice. The record of permits compiled to support 

this memorandum is sufficient to demonstrate that EPA has not in practice issued PSD 

permits establishing emissions limitations for pollutants that are subject to only 

monitoring and reporting requirements. 

Furthermore, the EAB observed that broad statements in the 1998 memorandum 

cited above by the Agency's then General Counsel suggest that the Agency has not, as a 

matter of practice, treated carbon dioxide as a "regulated" pollutant under any provisions 

of the Act, including those establishing the PSD program. Slip op. at 53-54. The Cannon 

memorandum described SOz, NOx, mercury, and C02 emitted into the ambient air as 

pollutants within the terms of the Act, but found that only SOz, NOx, and mercury were 

"already regulated" under the Act. Id. The General Counsel noted that "[wlhile C02 

emissions are within the scope of EPA's authority to regulate, the Administrator has 

made no determination to date to exercise that authority under the specific criteria 

provided under any provision of the Act." Id. At the time of this statement, EPA had 

already promulgated regulations requiring recordkeeping and monitoring of C02 

emissions. See 58 Fed. Reg. 3590 (Jan. 11, 1993). 

The EAE3 also observed that in 1978 EPA initially articulated an interpretation of 

the phrase "subject to regulation under this Act," as used in sections 165 and 169 of the 

Act. Deseret slip op. at 39, 52. In the preamble to the 1978 Federal Register notice 
promulgating the initial PSD regulations after the 1977 Amendments to the Act, 

Administrator Costle said the following: 

"[Slubject to regulation under this Act"' means any pollutant regulated in 

Subchapter C of Title 40 of the Code of Federal Regulations for any source type. 

This then includes all criteria pollutants subject to NAAQS review, pollutants 

regulated under the Standards of Performance for new Stationary Sources 

(NSPS), pollutants regulated under the National Emissions Standards for 

Hazardous Air Pollutants (NESHAP), and all pollutants regulated under Title I1 of 

the Act regarding emissions standards for mobile sources. 

43 Fed. Reg. 26388,26397 (June 19,1978);'see also 42 Fed. Reg. 57479,57481 (Nov. 

3, 1977) (same interpretation reflected in proposed rule). 

The interpretation set forth today is not inconsistent with the preamble statements 

made by Administrator Costle in 1978 because the specific categories of regulations 

identified in the second sentence of the passage quoted above are all regulations that 

require control of pollutant emissions. In addition, the interpretation in the 1978 

preamble said only that the PSD BACT requirement applies to "any pollutant regulated in 

Subpart C of Title 40 of the Code of Federal Regulations," but it did not amplify the 

meaning of the term "regulated in." The EAB observed in a footnote to the Deseret 

opinion that one could argue that the 1978 interpretation meant that any type of provision 

relating to a pollutant (including a monitoring or reporting requirement) that was 

promulgated in subchapter C would trigger PSD requirements for that pollutant, but one 

could also argue that this statement applied only to the then-current Subpart C and not 

necessarily to future additions to that Subchapter. Deseret slip op. at 42, n. 43. However, 

even if the 1978 interpretation is construed to apply to future additions to subchapter C, it 

is still not clear that a monitoring or reporting requirement added to subchapter C would 

make that pollutant "regulated in" subchapter C because of the alternative meanings of 

the term regulation, regulate, and regulated discussed earlier. Thus, the Agency's 1978 

interpretive statement on the meaning of "pollutant subject to regulation under this Act" 

did not specifically address the issue of whether monitoring or reporting requirement 

makes a pollutant "regulated in" the described part of the Code of Federal Regulations. 

The interpretation adopted here (that pollutants subject to the PSD BACT 

requirement are only those pollutants for which the Agency has established regulations 

requiring actual controls on emissions) is also not contradicted by other Agency 

statements regarding the pollutants subject to the PSD program reflected in rulemakings, 

memoranda, and opinions of the EAB. OAR and Region 8 previously believed that these 

Agency actions had established a controlling interpretation that the PSD BACT 

requirement applies only to pollutants for which a statute or regulation required actual 

' Hazardous air pollutants are no longer covered by the PSD program due to an exclusion 

adopted in the 1990 Amendments to the Act. 42 U.S.C. 5 7412(b)(6). 
control of emission^.^ However, the Board did not agree that these statements had 

conclusively established this interpretation. The Board observed that the mere absence of 

inconsistency between these prior statements and the interpretation followed by Region 8 

in issuing the Deseret permit was insufficient to establish that interpretation as 

controlling. Slip Op. at 48. Nevertheless, the Board's analysis in Deseret illustrates the 

Agency's previous statements in rulemakings, memorandum, and EAB decisions are not 

inconsistent with the interpretation adopted in this memorandum. 

This Interpretation is Permissible Under the Clean Air Act 

This interpretation of the regulations is not precluded by the Act, and indeed is 

supported by reading the PSD provisions of the Act in the context of other provisions of 

the Act that require emissions controls and authorize collection of emissions data to 

inform a decision to establish such controls. In the Deseret case, the EAB concluded that 

the phrase "subject to regulation under this Act" used in the Act was ambiguous and 

susceptible to both interpretations advocated by the parties in that case. Slip Op. at 28- 

35. In this discussion, the Board concluded that the terms of the statute do not preclude 

reading "subject to regulations under this Act" to mean "subject to control" by virtue of a 

regulation or otherwise. Id. at 33. 

The language in sections 165(a)(4) and 169(3) of the Clean Air Act requiring 

technology-based emissions limitations for "each pollutant subject to regulation under the 

Act" is permissibly construed in context to call for emissions limitations under the PSD 

program only for those pollutants that are otherwise subject to controls on emissions 

based on an express EPA determination or Congressional directive that such control is 

appropriate. Given that this language appears in a section 165(a)(4) - a provision that 

requires actual controls on emissions - it is reasonable to conclude that Congress 

intended EPA to apply such controls to the pollutants that are controlled under other 

provisions of the Act. The fact that Congress specified in the Act that BACT could be no 

less stringent than NSPS and other control requirements under the Act indicates that 

Congress expected BACT to apply to pollutants controlled under these programs. See 42 

U.S.C. $ 7479(3). 

Given the way Congress drafted sections 165(a)(4) and 169(3) of the Act, it is 

apparent that Congress intended for EPA to determine the applicability of the BACT 

requirement on the basis of decisions to regulate particular pollutants under other parts of 

the Act. Other provisions in the Act that authorize the Administrator to establish 

emissions limitations or controls on emissions provide criteria for the exercise of the 

Administrator's judgment to determine which pollutants or source categories to regulate. 

Many of the criteria in the Act applicable to a determination by the Administrator to 

regulate pollutants or source categories are based on public health or welfare. See e.g., 

This understanding was the basis for the Agency's observations regarding when 

greenhouse gases would become "subject to regulation" that were contained in the 

recently-issued Advance Notice of Proposed Rulemaking on the use of the Clean Air Act 

to regulated greenhouse gas emissions. See ANPR, 73 Fed. Reg. at 44420 and n.96. 
42 U.S.C. 5 7408(a)(l)(A); 42 U.S.C. 5 741 l(b)(l)(A); 42 U.S.C. 5 7521(a)(l). Thus, it 

follows that Congress likewise expected that pollutants would only be regulated for 

purposes of the PSD program after the Administrator has promulgated regulations 

requiring control of a particular pollutants on the basis of a considered judgment applying 

the applicable criteria in the Act, after EPA promulgates regulations on the basis of 

Congressional mandate that EPA establish controls on particular pollutants, or after 

Congress itself directly imposes actual controls on a particular pollutant. 

Furthermore, Congress authorized EPA to gather emissions data under section 

114 and other provisions of the Act for various purposes, including informing decisions 

to establish controls on emissions. 42 U.S.C. 5 7414(a). The enactment of this provision 

is evidence that Congress generally expected that EPA would gather emissions data prior 

to establishing plans to control emissions or developing emissions limitations. Congress 

also included in section 307(d)(9) of the Act, which establishes a requirement for 

reasoned decision-making by authorizing courts to reverse Agency action that is arbitrary 

or capricious. 42 U.S.C. 5 7607(d)(9). Considering the PSD provisions in the context of 

these other sections in the Act that authorize gathering emissions data and require 

reasoned decision-making, it is fully consistent with Congressional design to decline to 

require BACT limitations for pollutants that are not yet controlled but only subject to data 

collection and study. 

E. Timing, Form, and Scope of Regulations That Invoke PSD Program 

Requirements. 

Because the first three parts of the definition of "regulated NSR pollutant" apply 

to a standard "promulgated" under various provisions of the Act, EPA interprets the 

fourth part of the definition to also apply to a pollutant upon promulgation of a regulation 

that requires actual control of emissions. Thus, EPA does not consider a pollutant to be 

"subject to regulation" until the Agency has promulgated a regulation that requires 

control of emissions of that pollutant. We do not interpret the fourth part of the definition 

to apply at the time of an endangerment finding or other determination that may be a 

prerequisite to issuing control requirements under certain provisions of the Act. For 

example, it is the promulgation of a NAAQS under section 109, not the listing of a 

pollutant under section 108 which is based in part on an endangerment finding, that 

makes a pollutant a "regulated NSR pollutant" under the first prong of 40 C.F.R. 

52.21(b)(50)(i). Similarly, it is the promulgation of a standard under section 11 1, not the 

listing of a source category based on an endangerment finding, that makes a pollutant a 

"regulated NSR pollutant" under the second prong. 40 C.F.R. 52.21(b)(50)(ii). This 

approach makes sense because decisions notpade until promulgation of the final 

regulations establishing the control requirements for a pollutant often are relevant to 

decisions EPA makes regarding implementation of the PSD program for that pollutant. . For example, until EPA issues the NSPS for a source category listed under section 

11 l(b)(l)(A), EPA has not made a final decision regarding how to identify or define the 

pollutant(s) that will be regulated by the NSPS. See, e.g., Municipal Solid Waste 

Landfills NSPS, 61 Fed. Reg. 9905,9912 (1996) ("Today's rulemaking under section 

11 l(b) establishes a new classification of pollutants subject to regulation under the CAA: 
"MSW landfill emissions."'). Indeed, EPA has promulgated PSD regulations for newly 

regulated pollutants concurrently with an NSPS in the past. See id. 

The categories of regulations described in the first three parts of the definition of 

"regulated NSR pollutant" indicate that a requirement to control emissions of a pollutant 

can have more than one form. This can include a direct emissions limitation, such as the 

NSPS, or ambient standards, such as the National Ambient Air Quality Standards that 

limit emissions upon promulgation through the PSD permitting criteria. See CAA $ 

165(a)(3); 40 C.F.R. 52.21(k)(l). The NAAQS also require development of emissions 

limitations or other restrictions on emissions in state plans for attaining those standards. 

Furthermore, EPA has recognized that pollutant emissions may also be controlled 

through restrictions on the production and import of substances that can be released into 

the atmosphere. However, because information gathering requirements do not impose 

any restriction on the release of a pollutant into the air, the Agency does not interpret 

these types of regulations in isolation to make a pollutant subject to regulation. When 

monitoring and reporting requirements are developed to facilitate enforcement of a 

regulation requiring control of pollutant emissions, the control requirement triggers the 

PSD requirements, not the monitoring provisions established to ensure compliance with 

that control requirement. 

Furthermore, when an individual pollutant must be controlled under a regulation 

contained in the State Implementation Plan of a single state, EPA does not interpret 

section 52.21(b)(50) to require regulation of that pollutant under the PSD program 

nationally or in other states that have not determined the need to regulate that pollutant to 

protect the NAAQS in that other state. Several parties have argued in briefs to the EAB 

and public comment on PSD permits that EPA's approval of regulations applicable only 

in an individual state makes pollutants regulated in only that state subject to the PSD 

program in other states. However, the establishment of State Implementation Plans under 

the Act reflects the principle of "cooperative federalism" on which the Act is based. See 

Ellis v. Gallatin Steel Co., 390 F.3d 461, 467 (6th Cir. 2004). While Congress allowed 

individual states to create some regulations that are more stringent than federal 

regulations to apply within its borders, 42 U.S.C. $ 7416, Congress did not allow 

individual states to set national regulations that impose those requirements on all other 

states. See State of Connecticut v. US. EPA, 656 F.2d 902,909 (2d Cir. 1981) (finding 

that while a state is free to adopt air quality standards more stringent than required by the 

NAAQS or other federal law provisions, Congress "carefully drafted" the Act to preclude 

those stricter requirements from applying to other states.). Consistent with this legal 

precedent, EPA does not interpret section 52.21(b)(50) of the regulations to make C02 

"subject to regulation under the Act" for the nationwide PSD program based solely on the 

regulation of a pollutant by a single state in a SIP approved by EPA. 

The latter aspect of this interpretation is consistent with one previously adopted 

by EPA when promulgating its regulations addressing the application of the New Source 

Review program to and its precursors. 73 Fed. Reg. 28321,28330 (May 16, 

2008). That rule provides an option for individual states to regulate ammonia as a PM2.5 

precursor under the non-attainment NSR program for a particular PM2.5 non-attainment 
area after making a demonstration that ammonia emissions are a significant contributor to 

that area's ambient PM2.5 concentrations. EPA explained in that rule that if this option 

were invoked by one state, such an action would not make ammonia subject to the NSR 

program nationally or in other areas for which this demonstration had not been made. Id. 

EPA described this interpretation in the notice of proposed rulemaking and public 

comments on the rule did not contain any objections to this interpretation. 70 Fed. Reg. 

65984,66036 (Nov. 1,2005); 73 Fed. Reg. at 28330. 

PUBLIC PARTICIPATION CONSIDERATIONS 

I am mindful of the significant public interest in this issue and the benefit of 

receiving public input on this question. However, administrative agencies are authorized 

to issue interpretations of this nature that clarify their regulations without completing a 

public comment process, and I believe that such action is warranted in this case for the 

reasons discussed earlier. As described above, immediate claification of this issue is 

necessary to resolve confusion concerning whether certain sources should be seeking 

PSD permits and whether permits already under review must require limitations on 

pollutants subject only to monitoring and reporting requirements. The PSD permitting 

program has effectively become inoperative until EPA addresses this issue. A prolonged 

delay of permit reviews would contravene EPA's obligation under section 165(c) of the 

Clean Air Act to process PSD permit applications in a timely manner. 

EPA's authority to make rules and interpret them derives from the Clean Air Act, 

and section 307(d) of the Clean Air Act and the Administrative Procedure Act (APA) 

establish procedures for our exercise of rulemaking authority and exceptions to those 

procedures. Under one provision of the APA, 5 U.S.C. 553(b)(A), interpretative rules are 

exempt from notice and comment requirements. Section 307(d) of the Clean Air Act 

establishes procedures for, among other things, "the promulgation or revision of any 

regulations under part C of subchapter I of this chapter (relating to prevention of 

significant deterioration of air quality and protection of visibility)." However, that 

section of the CAA states clearly that it "shall not apply in the case of any rule or 

circumstance referenced to in subparagraphs (a) or (b) of subsection 553(b) of Title 5." 

Thus, section 307(b) of the Clean Air Act preserves the Agency's authority to establish 

interpretations of regulations promulgated under the Act without engaging in a notice and 

comment rulemaking process that is otherwise required for the promulgation and revision 

of PSD regulations. However, the adoption of an interpretation in this manner does not 

preclude subsequent action by the Agency to solicit public input on the interpretation. 

An interpretative document is one that explains or clarifies, and is consistent with, 

existing statutes or regulation. National Family Planning and Reproductive Health Ass 'n 

v. Sullivan, 979 F.2d 227, 236-37 (D.C. Cir. 1992). This memorandum explains and 

clarifies the meaning of the definition of "regulated NSR pollutant" in section 

52.2l(b)(50) of the existing NSR regulations, and does not alter the meaning of the 

definition in any way that would be inconsistent with the terms of the regulation. This 

interpretation explains that in applying the regulation, EPA will use a common meaning 

of the term "regulation" to describe the act or process of controlling or restricting an 
activity. The term "regulation" is susceptible to this reading without any change to the 

language in the rule. Furthermore, section 52.21(b)(50) enumerates specific categories of 

regulations that each require control of emissions of a pollutant before using general 

language that may be read, in accordance with accepted principles of legal interpretation, 

to refer to items with the same characteristics as the enumerated items. This reading is 

not inconsistent with the existing language in the regulation, and it is permissible under 

the Clean Air Act. 

Although I believe it is appropriate under the circumstances to establish this 

interpretation without a public comment process, the public has recently had two 

opportunities to present their views to the Agency on this issue. First, on November 21, 

2007, the EAB granted review in the Deseret case on the issue of whether a PSD pennit 

must contain an emissions limitation for carbon dioxide and provided the opportunity for 

interested persons to submit amicus briefs. Deseret, Order Granting Review, PSD 

Appeal No. 07-03. Region 8 informed the public of the Board's decision to grant review 

and the opportunity to submit amicus briefs through publication of a notice in several 

newspapers and by directly mailing the notice to those persons who received a mailed 

notice of the draft PSD permit. Notification of Public Notice of Grant of Review, PSD 

Appeal No. 07-03 (Dec. 18,2007). One individual, twelve environmental organizations, 

and eight states joined in amicus briefs presenting reasons why they believed the Agency 

should support Sierra Club's position and establish emissions limitations on carbon 

dioxide in permits. Three businesses (including the permit applicant) and twenty-four 

organizations (representing industry sectors and other interests) joined in briefs to the 

Agency presenting arguments for not requiring emissions limitations on carbon dioxide 

in permits at this time. Second, on July 30,2008, in the Federal Register, EPA described 

what the Agency believed at the time to be its established interpretation of the PSD 

regulations in the Advanced Notice of Proposed Rulemaking on options for addressing 

greenhouse gas emissions under the Clean Air Act. 73 Fed. Reg. at 44400,44420, 

44498. The ANPR noted that this interpretation was under review by the EAB in the 

Deseret case. 73 Fed. Reg. at 44400. Thirteen entities submitted comments on the 

ANPR that included their views on whether the current PSD regulations require 

emissions limitations for greenhouse gases. 

In developing this memorandum, I have considered the amicus briefs submitted to 

the EAB and public comments on the ANPR. Thus, although EPA is not taking comment 

on this memorandum, this memorandum has already been informed by public views on 

the issued covered here. Many of the public submissions EPA has received advocate that 

the Agency should use the Clean Air Act to address greenhouse gas emissions, including 

using the PSD program immediately to require new sources to mitigate their emissions. 

Thus, many parties advocate that EPA should interpret the PSD regulation as broadly as 

possible in order to achieve the end result of requiring limitations on carbon dioxide 

emissions immediately for new and modified major sources. Other parties that submitted 

their views to the Agency recommend that EPA proceed more cautiously and consider 

the significant implications of applying the PSD program to carbon dioxide and any other 

pollutant that EPA may wish to study before establishing limits on such pollutant in PSD 

permits. 
With the ANPR, EPA is taking the next step in responding to the Supreme Court's 

decision in Massachusetts v. EPA. I believe the ANPR process is the appropriate forum 

for addressing the larger questions of whether greenhouse gas emissions endanger public 

health or welfare and whether EPA should utilize authorities contained in the Clean Air 

Act to regulate such emissions. The interpretation set forth in this memo addresses only 

the narrow question of whether EPA should require emissions limitation under the PSD 

program at the same time the Agency or Congress determines that is necessary to study 

the nature and extent of emissions of a particular pollutant. My determination that 

emissions limitations should not be required under the PSD program on the basis of 

monitoring and reporting requirements alone does not reflect a decision on the larger 

question of whether EPA's authority under the Clean Air Act should be used to address 

greenhouse gas emissions. If the Agency determines, after completing the process started 

by the ANPR, that it should establish controls for greenhouse gas emissions under the 

Clean Air Act, the interpretation established here would require PSD permits to contain 

limitations on carbon dioxide when, and if, EPA promulgates regulations establishing 

those controls. 

Furthermore, several members of the public are concerned about authorizing 

additional sources of carbon dioxide to construct out of concern that once built, such 

sources will forever emit carbon dioxide without limitation. However, the permitting of 

new sources without limitations on carbon dioxide at present does not foreclose limitation 

of such emissions in the future, if the Agency ultimately determines that control of such 

emissions is warranted after considering all of the implications of such an action through 

the process started with the ANPR. 

Some stakeholders argued that EPA should apply PSD to pollutants that are only 

monitored or reported because requiring a source to report emissions of a pollutant can 

provide an incentive for that source to reduce its emissions of the pollutant. While I 

recognize that monitoring and reporting requirements may sometimes have this effect, 

such requirements are primarily intended to gather information and do not ensure that any 

source will in fact control emissions. As stated above, I believe that a pollutant should 

not become subject to mandatory emissions limitations under the PSD program until the 

Administrator (or Congress) has decided that such pollutants should be directly 

controlled by regulation. The concerns discussed above about predetermining the result 

of the information gathering exercise are not changed by the fact that some sources might 

be motivated to voluntarily reduce emissions because of a mandatory disclosure of the 

nature and extent of their emissions. 

Since some Courts have limited an Agency's ability to change an established, 

authoritative interpretation of a regulation without engaging in a notice and comment 

rulemaking, the EAB in the Deseret case questioned whether subsequent EPA 

memoranda could change the interpretation set forth in the 1978 preamble. Slip op. at 52 

(citing Alaska Professional Hunters Ass 'n v. FAA, 177 F.3d 1030, 1033-34 (D.C. Cir. 

1999); Paralyzed Veterans of Am v. D.C. Arena L. P., 1 17 F.3d 579, 586 (D.C. Cir. 

1997)). However, these court decisions have also recognized that an Agency has the 
flexibility to establish an initial interpretation of a regulation without engaging in a notice 

and comment process. Furthermore, these cases do not necessarily require a rulemaking 

procedure when the Agency seeks to change its interpretation of a statute. 

I have evaluated the Agency's 1978 interpretation in light of the Board's analysis 

in Deseret to determine whether the interpretation announced in this memorandum would 

amount to a change in the 1978 interpretation that requires a notice and comment process. 

As explained above, my conclusion is that the 1978 interpretation did not specifically 

address the issue discussed in this memorandum. That interpretation said only that the 

PSD BACT requirement applies to "any pollutant regulated in Subpart C of Title 40 of 

the Code of Federal Regulations," but it did not amplify the meaning of the term 

"regulated in." As discussed earlier, it follows from the EAB's analysis in Deseret and 

the various dictionary meanings of "regulation" and "regulate" that the phrase "regulated 

in" used in the 1978 preamble is ambiguous. 

Furthermore, the 1978 interpretation was an interpretation of the statutory 

language and did not address the regulatory language that we now construe in this 

interpretative memorandum. The 1978 statement referred to the language in the statute 

which said "pollutant subject to regulation under this Act." The 2002 regulation I am 

interpreting here uses the phrase "pollutant that otherwise is subject to regulation under 

the Act" in a clause that appears among a list of specific types of regulations under the 

Act that invoke the requirements of the PSD program. As discussed above, the Agency 

interprets the language in section 52.2l(b)(50)(iv) in context with other parts of that 

definition. 

Thus, I do not believe the Agency's 1978 interpretative statement regarding the 

scope of the BACT requirement or the Board's opinion in Deseret precludes the Agency 

from issuing this interpretation of section 52.21(b)(50). The interpretation adopted in this 

memorandum is based on a reasonable reading of the terms of the regulation, is 

consistent with past Agency practice, and is not precluded by the Clean Air Act. 

Furthermore, for the reasons discussed above, it is not sound policy to trigger mandatory 

mitation under the PSD program on the basis of rules designed for