ORAL ARGUMENT NOT YET SCHEDULED

_______________

IN THE UNITED STATES COURT OF APPEALS

FOR THE DISTRICT OF COLUMBIA CIRCUIT

_______________

No. 10-1413

_______________

 

SIERRA CLUB,

Petitioner, 

v.

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY,

Respondent.

_______________ 

ON PETITION FOR REVIEW OF FINAL ACTIONS BY THE

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

_______________ 

BRIEF OF RESPONDENT

_______________ 

OF COUNSEL:

BRIAN DOSTER

SCOTT JORDAN

U.S. Environmental Protection Agency 

Office of General Counsel

1200 Pennsylvania Avenue, N.W. 

Washington, D.C. 20460

Dated: April 6, 2012

IGNACIA S. MORENO

Assistant Attorney General

JESSICA O’DONNELL

U.S. Department of Justice

Environment & Natural Resources Division 

Environmental Defense Section

P.O. Box 7611

Washington, D.C. 20044

(202) 305-0851

USCA Case #10-1413 Document #1367679 Filed: 04/06/2012 Page 1 of 73
i 

CERTIFICATE AS TO PARTIES, RULINGS, AND RELATED CASES

Pursuant to Circuit Rule 28(a)(1), Respondent United States Environmental 

Protection Agency (“EPA”) states the following:

A. Parties, Intervenors, and Amici

All parties to this case are listed in petitioner’s brief. 

B. Rulings Under Review

Petitioner seeks review of the United States Environmental Protection 

Agency’s (“EPA’s”) final rule, “Prevention of Significant Deterioration (PSD) for 

Particulate Matter Less Than 2.5 Micrometers (PM2.5)---Increments, Significant 

Impact Levels (SILs), and Significant Monitoring Concentration (SMC),” 75 Fed. 

Reg. 64,864 (Oct. 20, 2010) (“Rule”) (JAXX-XX).

C. Related Cases

A petition for review of the rule by the State of Texas and the Texas 

Commission on Environmental Quality (collectively “Texas”), No. 10-1415, filed 

Dec. 20, 2010, also is pending before this Court. Texas’s petition is currently 

stayed pending action by EPA in response to Texas’s administrative petition for 

reconsideration, which EPA granted to address Texas’s claims that EPA provided 

inadequate notice and opportunity to comment on three discrete aspects of the 

Rule. The undersigned counsel is not aware of any additional related cases 

USCA Case #10-1413 Document #1367679 Filed: 04/06/2012 Page 2 of 73
ii

involving substantially the same parties and the same or similar issues pending in 

this or any other court. 

Dated: April 6, 2012 Respectfully submitted,

 IGNACIA S. MORENO

 Assistant Attorney General

 /s/ Jessica O’Donnell 

 JESSICA O’DONNELL

 United States Department of Justice

 Environment & Natural Resources Division

 Environmental Defense Section

P.O. Box 7611

 Washington, D.C. 20024

 Tel: 202-305-0851

 Jessica.O’Donnell@usdoj.gov

Of Counsel:

BRIAN DOSTER

SCOTT JORDAN

United States Environmental Protection Agency

Office of General Counsel

1200 Pennsylvania Avenue, N.W. 

Washington, D.C. 20460

 

 Counsel for Respondents

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iii

TABLE OF CONTENTS

JURISDICTION........................................................................................................... 1 

STATUTES AND REGULATIONS........................................................................... 2 

STATEMENT OF ISSUES ......................................................................................... 2 

STATEMENT OF THE CASE AND FACTS ............................................................ 3 

I. STATUTORY BACKGROUND ....................................................................... 3 

II. REGULATORY BACKGROUND ................................................................... 6 

 A. PSD Regulations..................................................................................... 8 

 B. EPA’s Longstanding Policy of Allowing the Use of 

 Screening Tools to Implement the PSD Review Process...................... 11 

 C. SILs and SMC under the Challenged Rule ........................................... 14 

 1. PM2.5 Significant Impact Levels................................................... 14 

 2. PM2.5 Significant Monitoring Concentrations..............................18

STANDARD OF REVIEW......................................................................................... 20 

SUMMARY OF ARGUMENT................................................................................... 23 

ARGUMENT............................................................................................................... 26 

I. THE CAA AFFORDS EPA DISCRETION TO PROMULGATE 

 SILs AS MEANS TO “DEMONSTRATE” THAT A SOURCE

 WILL NOT “CAUSE, OR CONTRIBUTE TO” A VIOLATION OF THE 

 NAAQS OR INCREMENTS............................................................................ 26 

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A. EPA Reasonably Interprets CAA Section 165(a)(3) to

 Allow the Use of SILs to “Demonstrate” that a Source 

 Will Not “Cause, or Contribute to” a Violation of the 

 NAAQS or Increments. .........................................................................26

 B. EPA Agrees that SILs Should Not Be Used to Exempt a

 Source Whose Emissions are Shown to Cause a Violation 

 of the NAAQS or Increment. ................................................................ 32 

II. EPA’s ADOPTION OF SILs IS SUPPORTED BY ITS 

 INHERENT AUTHORITY UNDER ALABAMA POWER TO 

 CREATE DE MINIMIS EXEMPTIONS........................................................... 36 

A. EPA’s Reasonably Interprets Section 165(a)(3) to Allow

 the Use of SILs as De minimis Thresholds.............................................38

B. EPA’s Interpretation of Section 165(a)(3) to Allow the 

 Use of SILs to Demonstrate Compliance with NAAQS

 and Increments Furthers the Legislative Design. .................................... 42 

C. The SILs Identify Levels below which a Source’s 

 Impact is Truly De minimis and thus Requiring a 

 Cumulative Impact Analysis Would Yield Information

 of Only Trivial Value.............................................................................. 43 

III. EPA PROPERLY USED ITS DE MINIMIS AUTHORITY TO

 ADOPT SIGNIFICANT MONITORING CONCENTRATIONS.................... 44 

A. Petitioner’s Challenge to EPA’s Authority to Adopt 

 SMCs is Time-Barred. ............................................................................ 47 

B. EPA’s Interpretation of Section 165 (e)(2) is a Permissible 

Construction of the Statute......................................................................49

C. The SMC Implements the Legislative Design By 

 Exempting Data that Is Not Accurate Enough to Serve any

 Useful Purpose. ....................................................................................... 51 

D. The SMC Reflects the Level at Which Regulatory Benefits

 are Truly De minimis. ............................................................................. 53 

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CONCLUSION............................................................................................................ 56 

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TABLE OF AUTHORITIES

CASES

*Alabama Power v. EPA, 

 636 F.2d 323 (D.C. Cir. 1980)......................................... 2, 22, 36, 49, 50, 51, 53

Alaska Dep't of Envtl. Conservation v. EPA, 

 540 U.S. 461 (2004)............................................................................................22

Am. Electric Power Co. v. Connecticut, 

 131 S. Ct. 2527 (2011)........................................................................................22

Burlington Truck Lines v. United States, 

 371 U.S. 156 (1962)............................................................................................20

*Catawba County, N.C. v. EPA, 

 571 F.3d 20 (D.C. Cir. 2009)..................................................... 20, 21, 27, 28, 40

Chevron, U.S.A., Inc. v. NRDC, 

 467 U.S. 837 (1984)............................................................................... 21, 22, 27

City of Waukesha v. EPA, 

 320 F.3d 228 (D.C. Cir. 2003)............................................................................20

Davis County Solid Waste Management v. EPA, 

 108 F.3d 1454 (D.C. Cir. 1997)..........................................................................35

Envtl. Def. v. Duke Energy Corp., 

 549 U.S. 561 (2007)............................................................................................22

*Envtl. Defense Fund ("EDF") v. EPA, 

 82 F.3d 451 (D.C. Cir. 1996), amended by, 

 92 F.3d 1209 (D.C. Cir. 1996)................................................................ 22, 39, 44

Entergy Corp. v. Riverkeeper, Inc., 

 556 U.S. 208 (2009)......................................................................... 21, 28, 31, 41

*Authorities chiefly relied upon are marked with an asterisk.

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In re N. Mich. Univ. Ripley Heating Plant,

 PSD Appeal No. 08-02, 2009 WL 443976 (EAB Feb. 18, 2009)......................10

*In re Prarie State Generating Co., 

 13 E.A.D. 1 (EAB 2006).............................................................................. 13, 28

Kokechick Fishermen's Ass'n v. Sec'y of Commerce, 

 839 F.2d 795 (D.C. Cir. 1988)............................................................................41

*Medical Waste Inst. & Energy Recovery Council, 

 645 F.3d 420 (D.C. Cir. 2011)..................................................................... 47, 48

Motor & Equip. Mfrs. Ass'n v. Nichols, 

 142 F.3d 449 (D.C.Cir.1998)..............................................................................47

New York v. EPA, 

 443 F.3d 880 (D.C. Cir. 2006)............................................................... 39, 40, 50

NRDC v. EPA, 

 571 F.3d 1245 (D.C. Cir. 2009)..........................................................................21

Ober v. Whitman, 

 243 F.3d 1190 (9th Cir. 2001) ............................................................................22

Ohio v. EPA, 

 997 F.2d 1520 (D.C. Cir. 1993)..........................................................................22

Public Citizen v. Young, 

 831 F.2d 1108 (D.C. Cir. 1987)............................................................. 37, 40, 50

*Sur Contra La Contaminacion ("SURCCO") v. EPA, 

 202 F.3d 443 (1st Cir. 2000)........................................................................ 31, 32

United States v. Mead, 

 533 U.S. 218 (2001)............................................................................................21

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STATUTES

5 U.S.C. § 706(2)(A) ................................................................................................20

21 U.S.C. § 376e(b)(5)(B) .......................................................................................40

42 U.S.C. §§ 7401-7671q .......................................................................................... 3 

42 U.S.C. § 7407(a) ................................................................................................... 4 

42 U.S.C. § 7407(d)(ii), d(iii).................................................................................... 5 

42 U.S.C. § 7409(b)................................................................................................... 3 

42 U.S.C. § 7410(a)(1)-(2), (l)................................................................................... 4 

42 U.S.C. § 7410(a)(2)(C), (D).................................................................................. 4 

42 U.S.C. § 7411(a)(4).........................................................................................5, 39

42 U.S.C. §§ 7470-7479 ............................................................................................ 5 

42 U.S.C. § 7470..................................................................................................4, 41

42 U.S.C. § 7470(3).................................................................................................41

42 U.S.C. § 7473....................................................................................................4, 5

42 U.S.C. § 7475......................................................................................................44

42 U.S.C. § 7475(a) ................................................................................................... 5 

42 U.S.C. § 7475(a)(3).............................................. 2, 4, 5, 8, 26, 27, 29, 37, 38, 40

42 U.S.C. § 7475(a)(7).............................................................................................44

42 U.S.C. § 7475(e)(1) ............................................................................................... 6 

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42 U.S.C. § 7475(e)(2).................................................................... 1, 6, 9, 25, 44, 51

42 U.S.C. § 7475(e)(3).............................................................................................29

42 U.S.C. § 7475(e)(3)(D).............................................................................. 6, 9, 29

42 U.S.C. § 7476 ........................................................................................................ 4 

42 U.S.C. § 7479(1)................................................................................................... 5 

42 U.S.C. § 7479(2)(C) .............................................................................................. 5 

42 U.S.C. § 7607(b)(1).........................................................................................1, 24

42 U.S.C. § 7607(b).................................................................................................46

42 U.S.C. § 7607(b)(1).................................................................................. 1, 47, 48

42 U.S.C. § 7607(d)(9)(A).......................................................................................20

CODE OF FEDERAL REGULATIONS

40 C.F.R. § 50.13 ....................................................................................................... 3 

40 C.F.R. Pt. 51, App. S...........................................................................................35

40 C.F.R. Pt. 51, App. W.............................................................................. 9, 10, 11

40 C.F.R. § 51.165(b) ........................................................................... 15, 35, 36, 48

40 C.F.R. § 51.165(b)(2)................................................................. 12, 16, 28, 29, 36

40 C.F.R. § 51.165(b)(3) ..........................................................................................29

40 C.F.R. § 51.166 ..................................................................................................... 6 

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40 C.F.R. § 51.166(i)(5).................................................................. 13, 14, 46, 48, 55

40 C.F.R. § 51.166(i)(5)(i)(c) ........................................................................... 18, 45

40 C.F.R. § 51.166(k) ................................................................................................ 8 

40 C.F.R. § 51.166(k)(2)................................................................. 15, 34, 35, 36, 42

40 C.F.R. § 51.166(l)(1)............................................................................................. 9 

40 C.F.R. § 51.166(m) ............................................................................................... 8 

40 C.F.R. § 51.166(m)(i) ........................................................................................... 9 

40 C.F.R. §§ 51.166(m)(1)(iii), (iv)........................................................................... 9 

40 C.F.R. § 52.21 ....................................................................................................... 6 

40 C.F.R. § 52.21(i)(5).......................................................................... 13, 14, 46, 48

40 C.F.R. § 52.21(i)(5)(i)(c) ............................................................................. 18, 45

40 C.F.R. § 52.21(k) ............................................................................................8, 34

40 C.F.R. § 52.21(k)(2)......................................................................... 15, 35, 36, 42

40 C.F.R. § 52.21(m) ................................................................................................. 8 

40 C.F.R. § 52.21(m)(1)(i)......................................................................................... 9 

40 C.F.R. § 52.21(m)(1)(iii), (iv)............................................................................... 9 

FEDERAL REGISTERS

44 Fed. Reg. 3274, 3283 (Jan. 16, 1989).................................................................12

45 Fed. Reg. 52,676 (Aug. 7, 1980).............................................................. 1, 13, 45

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45 Fed. Reg. at 52,705 .............................................................................................45

45 Fed. Reg. at 52,706 .............................................................................................45

45 Fed. Reg. at 52,707 ................................................................................ 16, 17, 45

45 Fed. Reg. at 52,708 .......................................................................... 16, 17, 45, 48

45 Fed. Reg. at 52,709 ...................................................................................... 45, 48

45 Fed. Reg. at 52,710 .......................................................... 1, 13, 18, 19, 45, 48, 52

45 Fed. Reg. at 52,733-34........................................................................................47

52 Fed. Reg. 24,672, 24,713 (July 1, 1987)................................................ 12, 15, 28

61 Fed. Reg. 38,250 (July 23,1996).........................................................................13

61 Fed. Reg. at 38,291 .............................................................................................13

61 Fed. Reg. at 38,292 .............................................................................................13

61 Fed. Reg. at 38,293 .............................................................................................13

70 Fed. Reg. 68,218, 68,266 (Nov. 9, 2005) ...........................................................10

72 Fed. Reg. 54,112 (Sept. 21, 2007) ........................................................................ 5 

72 Fed. Reg. at 54,116 ............................................................................................... 5 

72 Fed. Reg. at 54,139 .......................................................................... 14, 15, 28, 30

72 Fed. Reg. at 54,141 .......................................................................... 10, 18, 45, 54

72 Fed. Reg. at 54,142 ...................................................................................... 18, 54

75 Fed. Reg. 64,864 (Oct. 20, 2010)......................................................................1, 6

75 Fed. Reg. at 64,865 ............................................................................................... 7 

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75 Fed. Reg. at 64,866 .................................................................... 7, 8, 9, 12, 15, 18

 

75 Fed. Reg. at 64,867 .........................................................................................8, 18

 

75 Fed. Reg. at 64,868 ............................................................................................... 5 

 

75 Fed. Reg. at 64,890 .............................................................................................13

 

75 Fed. Reg. at 64,891 ...................................................................................... 11, 14

 

75 Fed. Reg. at 64,892 .............................................................................................33

 

75 Fed. Reg. at 64,893 ...................................................................................... 16, 43

 

75 Fed. Reg. at 64,894 ................................................................................ 16, 17, 33

75 Fed. Reg. at 64,895 .............................................................................................45

 

75 Fed. Reg. at 64,896 .......................................................................... 19, 45, 53, 54

 

75 Fed. Reg. at 64,897 ................................................................................ 19, 48, 54

 

75 Fed. Reg. at 64,899 .............................................................................................35

 

75 Fed. Reg. at 64,900 .............................................................................................35

 

75 Fed. Reg. at 64,901 .............................................................................................35

 

75 Fed. Reg. at 64,902 .............................................................................................15

 

75 Fed. Reg. at 64,904 .............................................................................................15

75 Fed. Reg. at 64,906 ............................................................................................ 15

75 Fed. Reg. at 64,993 .............................................................................................17

 

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xiii

GLOSSARY

CAA

EDF

EPA

JA

NAAQS

NRDC

NSR

PM2.5

PM10

RTC

PSD

SILs

SIPs

SMC

μg/m3

Clean Air Act

Environmental Defense Fund

United States Environmental Protection Agency

Joint Appendix

National Ambient Air Quality Standards

Natural Resources Defense Council

New Source Review

Fine particulate matter (particulate matter 2.5 micrometers and 

smaller in diameter)

Coarse particles (particulate matter 10 micrometers and smaller 

in diameter

Response to Comment

Prevention of Significant Deterioration

Significant impact levels

State implementation plans

Significant monitoring concentration

Micrograms per cubic meter

 

 

 

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1 

JURISDICTION

This case involves a challenge to the United States Environmental Protection 

Agency’s (“EPA’s”) final rule, “Prevention of Significant Deterioration (PSD) for 

Particulate Matter Less Than 2.5 Micrometers (PM2.5)---Increments, Significant 

Impact Levels (SILs), and Significant Monitoring Concentration (SMC),” 75 Fed. 

Reg. 64,864 (Oct. 20, 2010) (“Rule”) (JAXX-XX). Petitioner invokes this Court’s 

jurisdiction under Clean Air Act section 307(b)(1), 42 U.S.C. § 7607(b)(1), which 

requires that petitions for review of final action of EPA be filed within 60 days of 

the date of publication in the Federal Register. 

While Petitioner purports to challenge the validity of the above-noted Rule, 

one of their four claims in fact challenges final action taken by EPA long ago. See 

infra argument III.A. Specifically, Petitioner claims that EPA’s de minimis waiver 

of preconstruction monitoring requirements specified in Clean Air Act section 

165(e)(2), 42 U.S.C. § 7475(e)(2), is unlawful; at base, this claim challenges 

regulations EPA issued in 1980, 45 Fed. Reg. 52,676, 52,710 (Aug. 7, 1980) 

(JAXX-XX). Because Petitioner failed to challenge these regulations within 60 

days of their issuance, Petitioner’s instant challenge to these regulations is timebarred under section 307(b)(1), 42 U.S.C. § 7607(b)(1), and this Court lacks 

jurisdiction to hear it. 

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STATUTES AND REGULATIONS

The pertinent statutes and regulations are set forth in a separate addendum.

STATEMENT OF ISSUES

1. Whether EPA has discretion under section 165(a)(3) of the CAA, 42 

U.S.C. § 7475(a)(3), to develop methods and tools that a permit applicant may use 

to “demonstrate” that it does not “cause or contribute to” violations of the NAAQS 

and PSD increments.

 2. Whether EPA reasonably adopted, under the de minimis authority 

recognized in Alabama Power Co. v. EPA, 636 F.2d 323, 360-61 (D.C. Cir. 1979), 

“significant impact levels” as screening techniques that relieve permit applicants of 

the need to expend resources on modeling of a proposed project combined with the 

emissions from other existing sources when the permit applicant shows that the air 

quality impact of the emissions added by its construction is de minimis and that 

additional analysis is not needed to make the demonstration required to obtain a 

permit.

3. Whether the relevant data and analysis in the record support EPA’s 

finding that the particular significant impact levels promulgated for PM2.5 represent 

the level below which the burdens of requiring a cumulative air quality analysis 

yield a gain of only trivial value.

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4. Whether the Court can hear Petitioner’s untimely challenge to EPA’s 

exercise of its de minimis authority recognized in Alabama Power to establish 

“significant monitoring concentrations” as a screening tool to exempt proposed 

sources from pre-construction monitoring requirements.

5. If Petitioner’s challenge to EPA’s establishment of significant 

monitoring concentrations is not time-barred, whether EPA properly invoked its de 

minimis authority to establish a significant monitoring concentration for PM2.5. 

6. Whether the relevant data and analysis in the record support EPA’s 

finding that the particular significant monitoring concentration promulgated for 

PM2.5 represents the level below which the burdens of regulation yield a gain of 

only trivial value. 

STATEMENT OF THE CASE AND FACTS

I. STATUTORY BACKGROUND

The Clean Air Act (“CAA” or “Act”), 42 U.S.C. §§ 7401-7671q, requires 

EPA to set National Ambient Air Quality Standards (“NAAQS”) at levels requisite 

to protect public health and welfare. 42 U.S.C. § 7409(b). EPA has established 

both an annual and a 24-hour PM2.5 NAAQS. The annual PM2.5 NAAQS is 15 

micrograms per cubic meter (μg/m3

) and the 24-hour PM2.5 NAAQS is 35 μg/m3. 

40 C.F.R. § 50.13. 

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Once EPA establishes a new or revised NAAQS, States are required to 

develop and submit for EPA approval state implementation plans (“SIPs”) that 

contain emission limitations and other control measures to ensure that the relevant 

NAAQS is achieved and maintained. 42 U.S.C. §§ 7407(a), 7410(a)(1)-(2), (l), 

7475(a)(3). The CAA’s Prevention of Significant Deterioration or “PSD” 

provisions are among those that must be addressed by SIPs. 42 U.S.C. 

§ 7410(a)(2)(C), (D). 

In brief, the purpose of the PSD program is to protect the public health from 

adverse effects of air pollution notwithstanding attainment and maintenance of air 

quality standards, including ensuring that construction of new or modified sources 

in attainment areas does not lead to significant deterioration of air quality, while at 

the same time ensuring that economic growth will occur in a manner consistent 

with the preservation of clean air resources. 42 U.S.C. § 7470. Thus, the PSD 

provisions require EPA to establish “increments” (discussed below) for the various 

NAAQS pollutants and ensure that aggregate permitted pollution increases in 

attainment areas do not cause significant deterioration in air quality. 42 U.S.C. 

§§ 7473, 7476.

The PSD provisions also set forth procedures and requirements for 

preconstruction review and permitting of new or modified sources of air pollution 

that plan to locate in areas that are classified as “attainment” or “unclassifiable” 

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with respect to a particular NAAQS. See, generally, 42 U.S.C. §§ 7470-7479.

1

Under CAA section 165(a)(3), to obtain a construction permit, a proposed 

facility subject to PSD review must demonstrate that emissions from construction 

or operation of such facility “will not cause, or contribute to, air pollution in excess 

of any (A) maximum allowable increase or maximum allowable concentration for 

any pollutant in any area to which this part applies more than one time per year, 

[or] (B) national ambient air quality standard in any air quality control region.” Id.

§ 7475(a)(3). The “maximum allowable increase” of an air pollutant that may 

occur above a defined baseline concentration is known as the PSD “increment.” 

75 Fed. Reg. at 64,868 (JAXX); 72 Fed. Reg. 54,112, 54,116 (Sept. 21, 2007) 

(JAXX); see 42 U.S.C. § 7473. 

 

The permitting requirements apply to “major emitting facilities,” (hereinafter 

“facilities”), including new or modified sources that emit 250 tons per year or 100 

tons per year for certain source categories of any air pollutants. Id. §§ 7475(a), 

7479(1), (2)(C), 7411(a)(4).

For purposes of determining whether emissions from a proposed 

facility will cause or contribute to an exceedance of either any increment or 

 

1

 An “attainment” area is one where the air quality meets the NAAQS for a 

pollutant; an “unclassifiable” area is one that cannot be classified as meeting or not 

meeting the NAAQS for a pollutant. 42 U.S.C. § 7407(d)(ii), (d)(iii).

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NAAQS, section 165(e) requires the permitting authority or the proposed 

facility to conduct an ambient air quality analysis including: 

continuous air quality monitoring data . . . gathered over a period of 

one calendar year preceding the date of the application for a permit . . 

. unless the State, in accordance with regulations promulgated by the 

[EPA] Administrator, determines that a complete and adequate 

analysis for such purposes may be accomplished in a shorter period. 

42 U.S.C. § 7475(e)(1), (2). 

Section 165(e)(3) further authorizes EPA to promulgate regulations 

regarding the ambient air quality analysis required for PSD review, including rules 

that “specify with reasonable particularity each air quality model or models to be 

used under specified sets of conditions for purposes of this part.” Id.

§ 7475(e)(3)(D). 

II. REGULATORY BACKGROUND

Over time, EPA has promulgated comprehensive regulations and guidance 

setting forth detailed requirements for States to implement the PSD program. See

40 C.F.R. § 51.166. EPA also has established corresponding regulations for 

federal implementation of the PSD provisions in States that lack an EPA-approved 

PSD program in their SIP. 40 C.F.R. § 52.21. The final rule at issue here, 

“Prevention of Significant Deterioration (PSD) for Particulate Matter Less Than 

2.5 Micrometers (PM2.5)---Increments, Significant Impact Levels (SILs), and 

Significant Monitoring Concentration (SMC),” 75 Fed. Reg. 64,864 (Oct. 20, 

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7 

2010) (“Rule”), supplements these regulations to implement the PSD provisions as 

applied to fine particle pollution—also known as “PM2.5.”2

Specifically, the Rule does three things: First, it establishes “increments” for 

PM2.5, which serve to limit aggregate pollution increases in attainment and 

unclassifiable areas to prevent significant deterioration of air quality in areas that 

are meeting the NAAQS. See 75 Fed. Reg. at 64,865 (JAXX). Second, it 

establishes “significant impact levels” (“SILs”) for PM2.5 that may be used in 

various ways in evaluating the impact that a proposed new source or modification 

may have on the PM2.5 NAAQS and increments. Id. at 64,865-66 (JAXX-XX). 

Generally speaking, the SILs EPA adopted in this Rule are screening tools that 

may be used to identify de minimis circumstances where it may be unnecessary for 

a PSD permit applicant to conduct a more in-depth cumulative impact analysis of a 

proposed source’s impact. Third, the Rule establishes a “significant monitoring 

concentration” (“SMC”) for PM2.5. Id. at 64,866 (JAXX). The SMC is a screening 

tool to identify de minimis circumstances where either a proposed source’s impact

or the existing ambient concentration of PM2.5 is de minimis and thus the collection 

of preconstruction monitoring data would not yield meaningful information for the 

 

 

2

 The “2.5” in this acronym refers to the size of fine particulate matter, i.e., 2.5 

microns or less. Other EPA regulations implement the PSD provisions as applied 

to relatively more coarse particulate matter up to 10 microns (“PM10”).

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8 

analysis. See id. at 64,866-67 (JAXX-XX). Sierra Club challenges only those 

provisions of the Rule relating to the PM2.5 significant impact levels and significant 

monitoring concentration.

A. PSD Regulations

As noted above, section 165(a)(3), 42 U.S.C. § 7475(a)(3), requires that a 

new source or modification proposing to locate in an attainment or unclassifiable 

area demonstrate that its emissions will not cause or contribute to any violation of 

the applicable increment or the NAAQS. For this demonstration, EPA’s preexisting PSD regulations generally require sources to submit for review and 

approval a source impact analysis and an air quality analysis, which consist of an 

analysis of existing air quality that would be affected by the proposed source and a 

showing that the proposed source’s allowable emissions would not cause or 

contribute to a violation of any NAAQS or increment. 75 Fed. Reg. at 64,866 

(JAXX); 40 C.F.R. § 51.166(k), (m); 40 C.F.R. § 52.21(k), (m). 

The source impact analysis is primarily a modeling analysis designed to 

show that the allowable emissions increase from the proposed source, in 

conjunction with other emissions increases from existing sources, will not result in 

a violation of either the NAAQS or the increments. 75 Fed. Reg. at 64,866 

(JAXX). EPA has published guidelines for conducting this modeling analysis in a 

document called the Guideline on Air Quality Models (the “Guideline’), which is 

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9 

incorporated in the Code of Federal Regulations. 40 C.F.R. Pt. 51, App. W. 

EPA’s PSD regulations require modeling to be based on the Guideline. 40 C.F.R. 

§§ 51.166(l)(1), 52.21(l)(1). The Guideline implements CAA section 

165(e)(3)(D), 42 U.S.C. § 7475(e)(3)(D),

3

The air quality analysis must assess the ambient air quality in the area that 

the proposed project would affect. 75 Fed. Reg. at 64,866 (JAXX); 40 C.F.R. 

§§ 52.21(m)(1)(i), 51.166(m)(1)(i). Consistent with section 165(e)(2), 42 U.S.C. 

§ 7475(e)(2), this analysis must contain air quality monitoring data that is 

representative of the air quality in the area affected by the proposed source for the 

one-year period preceding receipt of the PSD permit application. 75 Fed. Reg. at 

64,866 (JAXX); 40 C.F.R. §§ 51.166(m)(1)(iii), (iv), 52.21(m)(1)(iii), (iv). Where 

data representative of air quality in the area already exists, the applicant may 

submit that available data; otherwise, the source owner or operator must install and 

operate monitors to collect the necessary data. 75 Fed. Reg. at 64,866 (JAXX); 

New Source Review Workshop Manual, Prevention of Significant Deterioration 

by identifying air quality models and 

modeling techniques that should be applied in the review of PSD permit 

applications. 40 C.F.R. Pt. 51, App. W, § 1.0.a. 

 

3

 40 C.F.R. Pt. 51, App. W, Preface (explaining how the Guideline was 

published to satisfy requirements of the 1977 amendments with respect to 

consistency in the application of air quality models). 

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10

and Nonattainment Area Permitting, at C.18-C.19 (Draft Oct. 1990) (hereinafter 

“NSR Workshop Manual”) (JAXX-XX);4

EPA’s Guideline recommends using monitored data to determine one 

component of the background concentration used in an air quality modeling 

exercise. 40 C.F.R. Pt. 51, App. W, Table 8-2 n.9 (“Generally, the ambient 

impacts from non-nearby (background) sources can be represented by air quality 

data unless adequate data do not exist.”); id. § 8.2.3.f. (referencing § 8.2.2

In re N. Mich. Univ. Ripley Heating 

Plant, PSD Appeal No. 08-02, 2009 WL 443976 (EAB Feb. 18, 2009).

5 of the 

Guidelines which describes air quality data from monitors); 72 Fed. Reg. at 54,141 

(JAXX) (discussing this topic but referencing § 9.2 prior to a revision that moved 

this content to § 8.2).6

 

4

 This document is referenced in the Guideline on Air Quality Models. 40 

C.F.R. Pt. 51, App. W, Preface n.2. EPA developed the NSR Workshop Manual 

for use in conjunction with New Source Review workshops and training, as 

guidance for permitting authorities to be used in implementing the PSD 

requirements of the New Source Review Program. See id. (Preface). 

 Another component of the background concentration is 

established by explicitly modeling the impact of “nearby sources.” 40 C.F.R. Pt. 

51, App. W, §§ 8.2, 8.2.3.b; 72 Fed. Reg. at 54,141 (JAXX); see also 40 C.F.R. Pt. 

5

 Section 8.2.3.f. of the Guidelines actually references § 89.2.2. This appears 

to be a scrivener’s error, as the Guideline does not have a § 89 or a § 9.2.2.

6

 EPA renumbered the sections of Appendix W in 2005, and moved the 

content of § 9 to § 8. 70 Fed. Reg. 68,218, 68,266 (Nov. 9, 2005). The proposed 

rule to establish SILs and SMCs appears to reference the older § 9.2 and § 9.2.3.f, 

which are presently located at § 8.2 and § 8.2.3.f. respectively.

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51, App. W, Table 8-2 (describing three types of source emissions data that are 

needed to complete a cumulative impacts analysis on a PSD permit application). 

B. EPA’s Longstanding Policy of Allowing the Use of Screening 

Tools to Implement the PSD Review Process

A fundamental principle of the air quality modeling discipline is that a 

modeling analysis should begin with relatively simple estimating techniques that 

provide conservative estimates of air quality impact and then progress toward more 

refined and precise techniques as needed. 40 C.F.R. Pt. 51, App. W, §§ 2.2, 4.2.1, 

4.2.2. The Guideline observes that “use of screening techniques followed, as 

appropriate, by a more refined analysis is always desirable.” 40 C.F.R. Pt. 51, 

App. W, § 2.2.c. With respect to PSD permit review specifically, the Guideline 

states: 

The purpose of [screening] techniques is to eliminate the need of more 

detailed modeling for those sources that clearly will not cause or 

contribute to ambient concentrations in excess of either the National 

Ambient Air Quality Standards (NAAQS) or the allowable prevention 

of significant deterioration (PSD) concentration increments. If a 

screening technique indicates that the concentration contributed by the 

source exceeds the PSD increment or the increment remaining to just 

meet the NAAQS, then the second level of more sophisticated models 

should be applied.

Id. § 2.2.a. The use of screening approaches is partly based on the 

recognition that more complex air quality modeling analysis requires more 

resources. Id. § 2.1.d.; 75 Fed. Reg. at 64,891 (JAXX) (“a screening tool 

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12

greatly improves PSD program implementation by streamlining the permit 

process and reducing the labor hours necessary to submit and review a 

complete permit application”).

Consistent with the Guideline, EPA has historically allowed the use of 

several types of screening tools to facilitate implementation of the preconstruction 

review process to reduce the permit applicant’s burden and streamline the 

permitting process for de minimis circumstances. 75 Fed. Reg. at 64,866 (JAXX). 

These tools include the SILs and SMCs, described generally below. 

Significant Impact Levels. The SIL, expressed as an ambient pollutant 

concentration (μg/m3

), has multiple uses. EPA initially promulgated SILs in 1979 

as the “significance levels” under which a source may be exempt from the 

preconstruction review requirements in Appendix S of Part 51. 44 Fed. Reg. 3274, 

3283 (Jan. 16, 1979). In 1987, EPA promulgated these SILs as a tool for showing 

that a predicted ambient impact resulting from the emissions increase at a proposed 

major new stationary source or modification would not cause or contribute to a 

violation of the NAAQS in an area that was not meeting the NAAQS. 52 Fed. 

Reg. 24,672, 24,713 (July 1, 1987) (promulgating 40 C.F.R. § 51.165(b)(2)). EPA 

also has interpreted this regulation to support using a SIL to show that an 

individual proposed source’s impact is de minimis and thus the source is not 

“culpable” for a violation of the NAAQS or increment that might be predicted in 

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13

an attainment area as a result of cumulative source impact analysis reflecting the 

impacts of other sources in the area. 75 Fed. Reg. at 64,890 (JAXX); 61 Fed. Reg. 

38,250, 38,293 (July 23, 1996); In re Prairie State Generating Co., 13 E.A.D. 1, 

103-09 (EAB 2006). Additionally, EPA guidance has provided for the use of the 

same SIL values to determine: (1) when a proposed source’s ambient impacts 

warrant a comprehensive cumulative source impact analysis that incorporates 

information on the air quality impact of the emissions of other sources besides the 

source seeking the permit; and (2) the size of the impact area within which the air 

quality analysis is completed. 75 Fed. Reg. at 64,890 (JAXX); 61 Fed. Reg. at 

38,293; In re Prairie State Generating Co., 13 E.A.D. 1, 103-09 (EAB 2006); see

also NSR Workshop Manual at C.24-C.31 (JAXX-XX). EPA proposed to codify 

some of these uses of SILs into the PSD regulations in 1996, 61 Fed. Reg. at 

38,291-93, but took no final action on that proposed rule. 

Significant Monitoring Concentrations. EPA initially promulgated 

Significant Monitoring Concentrations in 1980. 45 Fed. Reg. 52,676, 52,710

(Aug. 7, 1980) (JAXX). Using the SMC as a screening tool, sources may be able 

to demonstrate that it is unnecessary to gather preconstruction monitoring data for 

a particular pollutant at the discretion of the permitting authority. See 40 C.F.R. 

§§ 51.166(i)(5) and 52.21(i)(5); see NSR Workshop Manual C.16-C.18 (JAXXXX). Such a showing can be made by demonstrating that the modeled air quality 

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14

impact of emissions from the new source or modification or the existing air quality 

level in the area where the source would construct is less than a de minimis level,

expressed as an ambient pollutant concentration (μg/m3

). 40 C.F.R. 

§§ 51.166(i)(5), 52.21(i)(5); NSR Manual C.16-C.18 (JAXX-XX). 

C. SILs and SMC under the Challenged Rule 

1. PM2.5 Significant Impact Levels

 In the Rule, EPA for the first time adopted express language in regulations 

intended to authorize the longstanding practice of using “significant impact levels” 

as a screening tool for evaluating whether a comprehensive cumulative source 

impact analysis is necessary to demonstrate that a source will not cause or 

contribute to a violation of the NAAQS or increments. 75 Fed. Reg. at 64,891 

(JAXX); 72 Feg. Reg. at 54,139 (JAXX) (“If based on a preliminary impact 

analysis, a source can show that its emissions alone will not increase ambient 

concentrations by more than the SILs, EPA considers this to be a sufficient 

demonstration that a source will not cause or contribute to a violation of the 

NAAQS or increment.”); Response to Comment (“RTC”), EPA-HQ-OAR-2006-

0605-0059, at 67 (JAXX) (“The SIL is used largely as a screening tool to 

determine the level of air quality analysis that a proposed source or modification 

must undertake to satisfy the requirements for an air quality impact analysis.”). 

Specifically, under the provisions promulgated in this Rule, if the proposed source 

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15

shows through modeling that its projected emissions alone have an impact below 

the SIL, the source is deemed not to cause or contribute to any violation of the 

NAAQS or increments and is thereby exempt from doing a cumulative source 

impact analysis. 75 Fed. Reg. at 64,904, 64,906 (JAXX, XX); 40 C.F.R. 

§§ 51.166(k)(2), 52.21(k)(2). EPA also incorporated the PM2.5 SIL values into its 

preexisting regulation authorizing the use of SILs to determine whether a new or 

modified source causes or contributes to a NAAQS violation in a nonattainment 

area, 40 C.F.R. § 51.165(b).

7

EPA established the SILs for PM2.5 utilizing methods that would identify 

levels representing de minimis or insignificant impact on ambient air quality. 72 

Fed. Reg. at 54,139 (JAXX). The final SILs adopted by EPA were calculated by 

multiplying the PM10 SILs proposed in 1996 by the ratio of the PM2.5 NAAQS to 

the PM10 NAAQS, resulting in the following PM2.5 SILs:

 75 Fed. Reg. at 64,866, 64,902 (JAXX, XX). 

Averaging Period SILs (μg/m3

)

Class I Areas Class II Areas Class III Areas

Annual .06 0.3 0.3

24 hour .07 1.2 1.2

75 Fed. Reg. at 64,866 (JAXX).

 

7

 Petitioner does not and indeed cannot challenge EPA’s use of its de minimis

authority as reflected in 40 C.F.R. § 51.165(b) (see Pet. Br. 20 n.8 & 32 n.12), as 

EPA adopted this regulation in 1987 (52 Fed. Reg. 24,672, 24,713 (July 1, 1987)) 

and thus the time to challenge it under 42 U.S.C. § 7607(b)(1) has long since 

passed.

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16

EPA relied on past actions setting threshold de minimis values to conclude 

that the SIL values set here would also be de minimis. First, EPA calculated each 

PM2.5 SIL value such that the ratio of the PM2.5 SIL to the PM2.5 NAAQS was the 

same as the ratio of the previously established PM10 SIL to the PM10 NAAQS for 

each applicable averaging period. 75 Fed. Reg. at 64,893 (JAXX); see also 40 

C.F.R. § 51.165(b)(2). Using these ratios, the PM2.5 SILs are 2% of the NAAQS 

for the annual figures (annual PM2.5 SIL (Class II and III) of 0.3 μg/m3 divided by 

annual PM2.5 NAAQS of 15 μg/m3

) and 3.4% of the 24-hour NAAQS for the 24-

hour figures (24-hour PM2.5 SIL (Class II and III ) of 1.3 μg/m3 divided by 24-hour 

PM2.5 NAAQS of 35 μg/m3

). 

 EPA next compared the PM2.5 SILs to the PM2.5 increments consistent with 

the applicable averaging period. This comparison showed that the annual SIL was 

7.5% of the annual increment and the 24-hour SIL was 13% of the 24-hour 

increment. EPA then compared these percentages to the corresponding figures for 

the PM10 SILs, which are 5% for the annual and 17% for the 24-hour, and 

concluded they were comparable. 75 Fed. Reg. at 64,893 (JAXX).

Additionally, EPA looked back at the modeling and analysis done in 1980 to 

establish those earlier de minimis thresholds. This analysis and modeling (which is 

described in more detail at 75 Fed. Reg. at 64,893-94 (JAXX) and 45 Fed. Reg. at 

52,707-08 (JAXX-XX)) concluded that source impacts representing less than 5% 

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17

of the NAAQS and less than 35% of the increments were reasonably considered de 

minimis. 75 Fed. Reg. at 64,993 (JAXX); 45 Fed. Reg. at 52,707 (JAXX). The 

PM2.5 SILs established in this Rule compare favorably to that standard. The PM2.5

SILs at 2.0% (annual) and 3.4% (24-hour) of the NAAQS are both less than 5%. 

Similarly, the PM2.5 SILs at 7.5% (annual) and 13% (24-hour) of the Class II and 

Class III increments are both less than 35%.

Further, even in an area where multiple sources with de minimis impacts will 

be located, it cannot be assumed that the individual impacts of each source are 

additive. For example, four sources each consuming 12% of the increment would 

not necessarily consume 48% of the increment collectively. 75 Fed. Reg. at 64,894 

(JAXX). A given source’s greatest impact will be limited to the area nearest to it 

and during the specific times when the emissions are actually occurring, and the 

location and timing of a source’s impact will be different for different sources. Id.; 

see 45 Fed. Reg. at 52,708 (JAXX) (‘“[T]he source specific concentration [of the 

pollutant] occurs in only a limited area (often one point) and the temporal and 

spatial conditions which lead to maximum consumption [of the increment] by one 

source are seldom the same for other sources that may be making similar de 

minimis changes.”). 

Nevertheless, EPA expects permitting agencies to be cautious about using 

SILs where a number of de minimis impacts could collectively create air quality 

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problems. See RTC at 62 (JAXX) (“In short, it is not our intent that the SILs be 

used as a means of allowing known adverse air quality situations to be ignored just 

because they are small.”). If, for example, the cumulative effect of a number of de 

minimis impacts in an area can be shown to cause air quality problems that are not 

being addressed simply because no source’s impact is “significant” then the 

permitting authority must address the air quality problems, either by using lower de 

minimis levels, or by temporarily ceasing to use the de minimis concept altogether 

where it is known to allow the adverse conditions to worsen without remedy, or by 

taking some other step to address the problems. Id.

2. PM2.5 Significant Monitoring Concentrations

The Rule also added a significant monitoring concentration (“SMC”) for 

PM2.5 to the long-standing monitoring exemption provision (promulgated in the 

1980 PSD regulations at 45 Fed. Reg. at 52,710 (JAXX)). See 75 Fed. Reg. at 

64,866-67 (JAXX-XX) (40 C.F.R. § 51.166(i)(5)(i)(c); § 52.21(i)(5)(i)(c)). EPA 

proposed and evaluated three options for determining an appropriate SMC that 

would identify the degree of ambient impact on PM2.5 concentration that is truly de 

minimis. 72 Fed. Reg. at 54,141-42 (JAXX-XX). Ultimately, EPA selected the 

option that is based on the lowest detectable concentration, adjusted by a 

multiplication factor to account for errors that may arise from various activities 

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19

associated with air quality monitoring, such as sample collection, analytical 

measurement, calibration, and interferences. See 75 Fed. Reg. at 64,896 (JAXX). 

EPA followed the same practice it established in 1980, when it first 

promulgated the SMC provision. At that time, EPA determined the SMCs based 

on the then-current capability of obtaining a meaningful measure of ambient 

pollutant concentrations. Id. EPA promulgated values that represented five times 

the lowest detectable concentration in ambient air that could be measured by the 

instruments available. Id. (citing 45 Fed. Reg. at 52,710). This factor of five took 

into account the measurement errors associated with the monitoring of these low 

pollutant levels or small incremental changes in concentration. Id. 

In this Rule, EPA took another look at the minimum detection limit of 2 

μg/m3 used in 1980, and reaffirmed this value based on recent data. 75 Fed. Reg. 

at 64,896-97 (JAXX-XX). The minimum detection limit was “reaffirmed by 9 

years of field blank data collected by EPA through the PM2.5 Performance 

Evaluation Program.” Id. Then, based on information collected during this 

rulemaking, EPA used its assessment of the uncertainties introduced to the 

measurement of PM2.5 due to such factors as mechanical or operational variations 

in the sampling devices, and the possibility of human error associated with the 

performance of sampling device calibration and sample analysis. Id. at 64,896 

(JAXX). As a result of this new information, EPA reduced the uncertainty factor 

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20

from 5 to 2, which reduced the SMC value from 10 μg/m3 (that is, 5 times the 

detection limit of 2 μg/m3

) to the value established in this rule, 4 μg/m3. Id.8

STANDARD OF REVIEW

 EPA 

concluded that “there is little to be gained from preconstruction monitoring of 

PM2.5 concentrations that cannot be accurately measured.” Id. 

The CAA sets forth the appropriate standard of review, which is the same as 

the standard set forth in the Administrative Procedure Act (APA), 5 U.S.C. 

§ 706(2)(A). Catawba County, N.C. v. EPA, 571 F.3d 20, 41 (D.C. Cir. 2009)

(citations omitted). The Court considers whether EPA’s action was “arbitrary, 

capricious, an abuse of discretion, or otherwise not in accordance with law.” 42 

U.S.C. § 7607(d)(9)(A). The Court “must affirm the Rule if the record shows EPA 

considered all relevant factors and articulated a ‘rational connection between the 

facts found and the choice made.”’ Catawba, 571 F.3d at 41 (citing Burlington 

Truck Lines v. United States, 371 U.S. 156, 168 (1962)). Of particular note here, 

EPA is entitled to an “extreme degree of deference [] when it is evaluating 

scientific data within its technical expertise.” City of Waukesha v. EPA, 320 F.3d 

228, 247 (D.C. Cir. 2003) (internal quotation marks omitted). “Such deference is 

 

8

 As part of the grant of the State of Texas’s reconsideration petition, EPA has 

granted reconsideration of the SMC value to address Texas’s claim that the 

reduction of the uncertainty value from 5 to 2 was done without adequate notice 

and opportunity to comment.

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21

especially appropriate in [the court’s] review of EPA’s administration of the 

complicated provisions of the Clean Air Act.” Catawba, 571 F.3d at 41 (citation 

omitted). 

When reviewing EPA’s statutory interpretation, the Court first inquires 

whether Congress “has directly spoken to the precise question at issue,” in which 

case the Court “must give effect to the unambiguously expressed intent of 

Congress.” Chevron, U.S.A., Inc. v. NRDC, 467 U.S. 837, 842-43 (1984). If the 

statute is “silent or ambiguous with respect to the specific issue,” the Court moves 

to Chevron's second step and must defer to the agency's interpretation so long as it 

is "based on a permissible construction of the statute." Id. 

Under Chevron step two, considerable deference must be accorded to the 

interpretation of the agency assigned to administer that statute. In applying that 

deference, the agency’s interpretation must be upheld “if it is a reasonable 

interpretation of the statute – not necessarily the only possible interpretation, nor 

even the interpretation deemed most reasonable by the courts.” Entergy Corp. v. 

Riverkeeper, Inc., 556 U.S. 208, 218 (2009) (emphasis in original). Moreover, 

heightened deference is to be given to an agency’s interpretation of a statute that is 

complex and within the agency’s expertise. United States v. Mead, 533 U.S. 218, 

227-31 (2001). The CAA is precisely this type of statute. NRDC v. EPA, 571 F.3d 

1245, 1251 (D.C. Cir. 2009). See also Am. Electric Power Co. v. Connecticut, 131 

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22

S. Ct. 2527, 2533 n.2 (2011) (describing the “complicated issues related to carbondioxide emissions and climate change”). 

Finally, to the extent that EPA’s longstanding interpretation reflected in its 

PSD regulations authorizing the use of de minimis screening levels does not 

foreclose Petitioners’ arguments under 42 U.S.C. § 7607(b), see infra argument 

III.A, EPA’s interpretation must at the very least be accorded substantial 

deference. Envtl. Def. v. Duke Energy Corp., 549 U.S. 561, 575 (2007); Alaska 

Dep’t of Envtl. Conservation v. EPA, 540 U.S. 461, 487 (2004) (“We ‘normally 

accord particular deference to an agency interpretation of longstanding’ duration.”) 

(citations omitted). 

In reviewing EPA’s use of its de minimis authority recognized in Alabama 

Power Co. v. EPA, 636 F.2d 323, 360-61 (D.C. Cir. 1979), the Court should apply 

the same deference that is accorded the agency’s “reasonable interpretation of an 

ambiguous statute.” Envtl. Def. Fund, Inc. (“EDF”) v. EPA, 82 F.3d 451, 467

(D.C. Cir. 1996), amended by, 92 F.3d 1209 (D.C. Cir. 1996) (citing Chevron, 467 

U.S. at 843; Ohio v. EPA, 997 F.2d 1520, 1535 (D.C. Cir. 1993)); see also Ober v. 

Whitman, 243 F.3d 1190, 1195 (9th Cir. 2001) (“EPA, in discharging its duty to 

enforce the Act, is permitted under Chevron to exempt de minimis sources of PM10 from pollution controls.”). 

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SUMMARY OF ARGUMENT

 Petitioner Sierra Club attacks only those portions of the Rule promulgating 

the PM2.5 significant impact levels and significant monitoring concentration, 

challenging both EPA’s legal authority and its record-basis for adopting these 

provisions of the Rule. But, EPA’s use of SILs and SMC is consistent with EPA’s 

legal authority under the CAA, furthers the purposes of the statute, and is amply 

supported by the record.

With regard to the significant impact levels, EPA reasonably interprets 

section 165(a)(3) of the CAA, 42 U.S.C. § 7475(a)(3), to allow the use of 

significance levels as a means to demonstrate that a source will not cause or 

contribute to any violation of the NAAQS or increment. The terms “cause, or 

contribute to” and “demonstrate” are ambiguous, and EPA reasonably interprets 

the statute to allow sources that do not contribute significantly to ambient air 

concentrations of PM2.5 to demonstrate compliance through modeling of the 

source’s impact measured against the SILs. 

However, EPA agrees with Petitioner that the statute should not be 

interpreted to allow the use of SILs to make the required compliance 

demonstration under section 165(a)(3) in circumstances where it can be shown that 

the source causes a NAAQS or increments violation that would not exist but for 

the emissions from that source. In the course of this litigation, EPA has come to 

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24

recognize that the regulatory text it adopted in 40 C.F.R. §§ 51.166(k)(2) and 

52.21(k)(2) does not accurately reflect EPA’s intent, because it does not afford 

permitting authorities sufficient discretion to deny sources use of the SILs where 

their use would lead to a new violation of the NAAQS or increment. Accordingly, 

EPA asks that the Court vacate and remand these provisions to EPA, so that EPA 

may initiate a rulemaking to revise them to reflect EPA’s intent.

Notwithstanding this error in the regulatory text, EPA submits that SILs 

generally are a valid exercise of EPA’s de minimis authority, and that the use of 

SILs generally should be upheld. Section 165(a)(3) requires sources to 

demonstrate they will not cause or contribute to any NAAQS or increments 

violation. EPA’s use of SILs as a means to demonstrate compliance with the 

NAAQS or increments thus implements the legislative design. Moreover, EPA 

rationally concluded that the SILs reflect the level at which a source’s impact is 

truly de minimis and thus requiring the source to perform a comprehensive 

cumulative impact analysis would yield only trivial gain.

Additionally, Petitioner fails to show that EPA’s adoption of a significant 

monitoring concentration for PM2.5 is inconsistent with the statute or EPA’s de 

minimis authority. First, Petitioner’s claim that EPA lacks the statutory authority 

to use a SMC to exempt a source from submitting a year’s worth of monitoring 

data is time-barred under section 307(b)(1) of the CAA, 42 U.S.C. § 7607(b)(1). 

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EPA promulgated the SMC provisions challenged here in 1980. EPA’s statutory 

interpretation to permit de minimis exemptions of the air quality monitoring 

requirement has not changed since EPA first adopted SMC for several pollutants in 

its 1980 PSD regulations. Accordingly, any challenges to that interpretation 

should have been raised long ago. Because EPA’s interpretation of its legal 

authority to adopt SMC has not changed since 1980, Petitioner cannot challenge it 

now. 

In any event, EPA’s use of SMC is firmly grounded in its inherent authority 

to adopt de minimis exemptions. EPA’s interpretation of CAA section 165(e)(2), 

42 U.S.C. § 7475(e)(2), to permit de minimis exemptions of the requirement for a 

year’s worth of preconstruction monitoring data when the source’s impact or the 

ambient air concentrations are below levels at which such concentrations can 

accurately be measured is reasonable. Further, EPA rationally concluded that the 

de minimis levels it selected as the SMC for PM2.5 reflect the levels below which 

concentrations cannot accurately be measured and thus the requirement to collect 

monitoring data would yield information of no more than trivial value.

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ARGUMENT

I. THE CAA AFFORDS EPA DISCRETION TO PROMULGATE SILs 

AS MEANS TO “DEMONSTRATE” THAT A SOURCE WILL NOT 

“CAUSE, OR CONTRIBUTE TO” A VIOLATION OF THE NAAQS 

OR INCREMENTS.

A. EPA Reasonably Interprets CAA Section 165(a)(3) to Allow the 

Use of SILs to “Demonstrate” that a Source Will Not “Cause, or 

Contribute to” a Violation of the NAAQS or Increments.

EPA reasonably interprets CAA section 165(a)(3), 42 U.S.C. § 7475(a)(3), 

to give it the discretion to adopt SILs for the purpose of demonstrating that a 

proposed new source or modification will have de minimis impacts on air quality 

and therefore will not cause or contribute to a violation of any NAAQS or 

increment. Petitioner’s primary argument to the contrary is that SILs are unlawful 

because they waive compliance with the NAAQS and increments. This argument 

misunderstands the purposes of the SILs and relies on an overly restrictive reading 

of the statute. The SILs are not intended to waive section 165(a)(3)’s requirement 

that a source demonstrate compliance with the NAAQS or increment. Rather, the 

purpose of SILs is to provide a means by which a source may make this 

demonstration. EPA’s interpretation of section 165(a)(3) to allow the use of SILs 

to make the required showing is a reasonable interpretation of a statute that is 

ambiguous as to this issue. Nothing in the CAA precludes EPA’s use of SILs in 

this manner.

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Section 165(a)(3) provides that “[n]o major emitting facility . . . may be 

constructed in any area to which [the PSD program] applies unless” . . . the facility 

“demonstrates” that its emissions “will not cause, or contribute to, air pollution in 

excess of any (A) [increment] for any pollutant . . . [or] (B) national ambient air 

quality standard for any pollutant.” 42 U.S.C. § 7475(a)(3) (emphasis added). 

While it is clear that such a demonstration must be made to obtain a PSD permit, 

the statute does not define the phrase “cause, or contribute to,” or specify how a 

facility is to “demonstrate” that it does not cause or contribute to a violation of the 

NAAQS or increments. Therefore, the statute is ambiguous with respect to the 

precise questions at issue here, and EPA’s permissible interpretation of these terms 

must be upheld. Chevron, 467 U.S. at 843. 

As this Court recently observed, dictionary definitions of “contribute” vary 

as to whether the word implicitly includes a level of significance or is defined 

without reference to any threshold level of significance. Catawba, 571 F.3d at 38-

39 (discussing meaning of “contribute” in 42 U.S.C. § 7407(d), and concluding 

that the provision “is ambiguous as to how EPA should measure contribution and 

what degree of contribution is sufficient”). In that case, petitioners had argued that 

EPA was required to interpret the word “contribute” in section 107(d) of the CAA 

to incorporate a significance threshold. Id. The Catawba court concluded that the 

fact that the term “contribute” may or may not connote a significance threshold 

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“alone suggests an ambiguity that fatally undermines petitioners’ Chevron step one 

argument” regarding the meaning of “contribute” in section 107(d). 571 F.3d at 

39. So it is here. Because Congress did not further define or quantify “contribute” 

in section 165(a)(3), it is “eminently reasonable to conclude that [Congress’s 

silence] is meant to convey nothing more than a refusal to tie the agency’s hands” 

as to the level of contribution necessary under section 165(a)(3). Entergy, 556 

U.S. at 222. 

EPA has long interpreted the phrase “cause or contribute” to refer to 

significant or non-de minimis emission contributions. 72 Fed. Reg. at 54,139

(JAXX); In re Prairie State Generating Co., 13 E.A.D. at 105-08; see, e.g., NSR 

Workshop Manual at C.52 (JAXX) (“The source will not be considered to cause or 

contribute to the violation if its own impact is not significant at any violating 

receptor at the time of each predicted violation.”). EPA’s New Source Review 

regulations, at 40 C.F.R. § 51.165(b)(2), promulgated in 1987, 52 Fed. Reg. at 

24,713, provide that a new source or modification proposing to locate in an 

attainment area will be considered to “cause or contribute to” a violation of the 

NAAQS in a nonattainment area if its emissions would exceed specific 

“significance levels” identified in the regulations. If the emissions from the 

proposed source or modification would have an ambient impact in a nonattainment 

area that exceeds the SILs, i.e., a significant impact, the source is considered to 

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“cause, or contribute to” the NAAQS violation and may not receive a PSD permit 

unless it obtains emissions reductions to compensate for its impact. 40 C.F.R. 

§ 51.165(b)(2)-(3). 

Additionally, section 165(a)(3) does not specify the method a source must 

use to “demonstrate” that it will not “cause, or contribute to” a NAAQS or 

increment violation. See 42 U.S.C. § 7475(a)(3). By its silence, Congress left it to 

EPA to determine how best to implement Congress’s intent that new or modified 

sources “demonstrate” compliance with the increment and NAAQS before 

obtaining a PSD permit. Nothing in the statute precludes EPA from using a 

modeling analysis that relies on significance levels as a means to demonstrate 

whether a source will “cause, or contribute” to a violation of the NAAQS or 

increments. 

In fact, Congress expressed in explicit terms its intent that EPA determine 

precisely how section 165(a)(3)’s core requirements should be implemented. CAA 

section 165(e)(3), 42 U.S.C. § 7475(e)(3), expressly directs EPA to promulgate 

regulations regarding the appropriate ambient air quality analyses to be performed 

in implementing section 165. Additionally, section 165(e)(3)(D), 42 U.S.C. 

§ 7475(e)(3)(D), directs EPA to specify each model to be used under specified sets 

of conditions. Thus, while the statute clearly gives EPA the discretion to require a 

cumulative impact analysis, it does not preclude EPA generally from promulgating 

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regulations that allow a source to “demonstrate” that its emissions alone are de 

minimis and therefore do not “cause or contribute to” a NAAQS or increment 

violation. Because the SILs are a reasonable method for demonstrating 

compliance with the NAAQS and increments, Petitioner’s argument that EPA’s 

use of SILs waives section 165(a)(3)’s core requirement is unavailing. 

Although EPA has not previously incorporated every application of the SILs 

into the PSD regulations at issue here, 40 C.F.R. §§ 51.166 and 52.21, EPA 

historically has supported using SILs to determine whether a new or modified 

source wishing to locate in an attainment area must conduct a more extensive 

cumulative impact analysis to demonstrate that it will not “cause or contribute to” a 

violation of the NAAQS or PSD increment. See 72 Fed. Reg. at 54,139 (JAXX). 

Thus, EPA stated in its NSR Workshop Manual, drafted in 1990, that “EPA does 

not require a full impact analysis for a particular pollutant when emissions of that 

pollutant from a proposed source or modification would not increase ambient 

concentrations by more than prescribed significant ambient impact levels.” NSR 

Workshop Manual at C.24 (JAXX). 

Numerous other guidance documents also recognize the use of SILs as an 

appropriate screening tool to determine whether a proposed source’s ambient 

impact is significant “so as to warrant a comprehensive, cumulative air quality 

analysis to demonstrate compliance with the NAAQS.” E.g., Memorandum, from 

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Stephen D. Page, Director, Office of Air Quality Planning and Standards, to 

Regional Air Division Directors, “Guidance Concerning the Implementation of the 

1-hour SO2 NAAQS for the Prevention of Significant Deterioration Program at 4, 

Aug. 23, 2010 (JAXX). 9

Indeed, in Sur Contra La Contaminacion (“SURCCO”) v. EPA, 202 F.3d 

443, 448 (1st Cir. 2000), the First Circuit upheld EPA’s use of SILs to grant a PSD 

permit. In that case, SURCCO had argued that it was improper for EPA to issue 

the permit without requiring a full impact analysis of the proposed source’s sulfur 

 EPA’s longstanding policy and practice of interpreting 

the “cause or contribute” demonstration in section 165(a)(3) to include a 

significance inquiry “tends to show that the EPA’s current practice is a reasonable 

and hence legitimate exercise of its discretion.” Entergy Corp., 556 U.S. at 224. 

 

9

 See also Memorandum from Stephen D. Page, Director, Office of Air 

Quality Planning and Standards, to Regional Air Division Directors, “Guidance 

Concerning the Implementation of the 1-hour NO2 NAAQS for the Prevention of 

Significant Deterioration Program at 11, June 29, 2010 (JAXX); Memorandum 

from Gerald A. Emison, Director, EPA Office of Air Quality Planning and 

Standards, to Thomas J. Maslany, Director, Air Management Division, “Air 

Quality Analysis for Prevention of Significant Deterioration (PSD)” at 1 (July 5, 

1988) (JAXX) (“Historically, the [EPA’s] position has been that a PSD source will 

not be considered to cause or contribute to a predicted NAAQS or increment 

violation if the source’s estimated air quality impact is insignificant (i.e., at or 

below defined de minimis levels.”); Memorandum from Richard G. Rhodes, 

Director, Control Programs Development Division, EPA, to Alexandra Smith, 

Director, Air and Hazardous Materials Division, EPA Region 10, “Interpretation of 

‘Significant Contribution,’” (Dec. 16, 1980) (JAXX-XX) (a source will not be 

viewed as causing or contributing to a violation if the source’s impact is lower than 

the SILs at the time and location of the violation).

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dioxide emissions. Id. The Court held that “[i]t was rational for the Agency to 

prefer its own model, to reject SURCCO’s proposed alternative modeling that 

allegedly showed sulfur dioxide emissions above the threshold levels, and to 

accept, instead, [the applicant’s] modeling.” Id. The Court thus found that EPA 

was “within its discretion, under the regulations, to exempt [the applicant] from 

conducting a full impact analysis.” Id. The First Circuit’s acceptance of EPA’s 

reliance on a SIL in the context of a specific permit challenge as a sufficient 

demonstration of compliance with the NAAQS and increments further shows the 

reasonableness of EPA’s interpretation of the statute.

B. EPA Agrees that SILs Should Not Be Used to Exempt a Source 

Whose Emissions are Shown to Cause a Violation of the NAAQS 

or Increment.

EPA does not dispute Petitioner’s contention that section 165(a)(3) 

unambiguously requires all permit applicants to demonstrate that proposed 

construction will not cause or contribute to a violation of air quality standards. 

Likewise, EPA agrees that SILs should not be used to justify issuing permits to 

sources whose emissions will in fact cause violations of the NAAQS. Thus, EPA 

acknowledged in the preamble to the Rule that there may be circumstances in 

which an impact from an individual source could cause a NAAQS or increment 

violation even if the impact falls below the applicable SILs. For example, EPA 

specifically cautioned against the use of SILs in circumstances where the ambient 

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air quality in an area is close to the NAAQS or close to consuming the increment. 

See 75 Fed. Reg. at 64,894 (JAXX) (“[W]e have historically cautioned states that 

the use of a SIL may not be appropriate when a substantial portion of any NAAQS 

or increment is known to be consumed.”). Similarly, EPA stated that SILs should 

not be used where a number of de minimis impacts could collectively cause a 

violation. See RTC at 62 (JAXX) (“If, for example, the cumulative effect of a 

number of de minimis impacts in an area can be shown to cause air quality 

problems that are not being addressed simply because no source’s impact is 

“significant” then the permitting authority must address the air quality problems, 

whether by using lower de minimis levels or temporarily cease using the de 

minimis concept altogether where it is known to allow the adverse conditions to 

worsen without remedy, or taking some other step to address the problems.”).

In short, EPA did not and does not intend for SILs “to be used as a means 

for allowing known adverse air quality situations to be ignored just because they 

are small.” RTC at 62 (JAXX). Thus, in the preamble to the final Rule, EPA 

stated: “[N]otwithstanding the existence of a SIL, permitting authorities should 

determine when it may be appropriate to conclude that even a de minimis impact 

will ‘cause or contribute’ to an air quality problem and to seek remedial action 

from the proposed new source or modification.” 75 Fed. Reg. at 64,892 (JAXX). 

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In the course of this litigation, however, EPA has come to the conclusion 

that the regulatory text it promulgated in 40 C.F.R. §§ 51.166(k)(2) and 

52.21(k)(2) does not correctly implement EPA’s intent in this regard. In particular, 

where information exists demonstrating that a proposed source’s impact would 

cause a NAAQS or increments violation, which violation would not exist but for

the source’s impact at any particular location, then EPA agrees it would not be 

appropriate to use the SILs. EPA believes that the regulatory text it adopted does 

not allow permitting authorities the discretion to require a cumulative impact 

analysis, notwithstanding that the source’s impact is below the SIL, where there is 

information that shows the proposed source would lead to a violation of the 

NAAQS or increments. This was not EPA’s intent in promulgating this rule. 

Therefore, EPA seeks vacatur and remand of the regulatory text promulgated in 

this Rule at 40 C.F.R. § 51.166(k)(2) and 52.21(k)(2) so that the Agency may 

consider how to revise those provisions to ensure that SILs are not used in 

circumstances where a source’s impact may lead to a NAAQS or increment 

violation.10

 

10 EPA plans to issue guidance in the near future on how the PM2.5 SIL values 

that remain in 40 C.F.R. § 51.165(b) may be properly applied as part of a 

demonstration to show that a source’s impact will not cause or contribute to a 

violation of the NAAQS or increments. This guidance would apply until revised 

regulations can be finalized.

 

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Vacating and remanding these discrete provisions (40 C.F.R. 

§§ 51.166(k)(2) and 52.21(k)(2)) does not require that the Court vacate the entire 

Rule. The test for assessing whether portions of a challenged regulation are 

severable is to determine whether or not the agency would have adopted the 

severed portion on its own. See Davis County Solid Waste Mgmt. v. EPA, 108 F.3d 

1454, 1458-59 (D.C. Cir. 1997). The record here demonstrates that EPA intended 

the other portions of the Rule to operate with or without the SIL provisions that 

EPA now concedes are improperly written. As EPA explained in the final Rule 

preamble, SILs are not mandatory or required elements of an approvable PSD state 

implementation plan, even though they are considered to be useful components for 

implementing the PSD program. 75 Fed. Reg. at 64,899-901 (JAXX-XX. In other 

words, the absence of the SILs in the regulation would not have any meaningful 

effect on the implementation of the PSD increments and SMC for PM2.5 that EPA 

adopted in this Rule. Thus, even though EPA is conceding that the Court should 

invalidate the SIL provisions of the Rule, the Court need not invalidate the portions 

of the Rule establishing PM2.5 increments or SMC. 

Additionally, we note that the regulatory text in 40 C.F.R. § 51.165(b)

(which established SILs as a tool for showing that a source will cause or contribute 

to a NAAQS violation) and 40 C.F.R. Pt. 51, App. S (which uses SILs as a 

threshold for the applicability of certain Appendix S requirements) do not contain 

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the same language as EPA promulgated in this Rule in 40 C.F.R. §§ 51.166(k)(2)

and 52.21(k)(2) that leads EPA to seek the remand of those provisions. We also 

note that Petitioner does not in this petition challenge the SILs contained in 40 

C.F.R. § 51.165(b) on the grounds that they are outside of EPA’s statutory 

authority under the CAA (see Pet. Br. 20 n.8 and 32 n.12). Although Petitioner 

does challenge the reasonableness of the PM2.5 SIL values incorporated into EPA’s 

existing regulation at 40 C.F.R. § 51.165(b)(2) (Pet. Br. 37 n.17), for the reasons 

discussed below, EPA submits that these values are fully supported by the 

administrative record and therefore should be upheld.

II. EPA’s ADOPTION OF SILs IS SUPPORTED BY ITS INHERENT 

AUTHORITY UNDER ALABAMA POWER TO CREATE DE 

MINIMIS EXEMPTIONS.

 In Alabama Power, the D.C. Circuit recognized that EPA has the inherent 

authority under the CAA to exempt emissions increases from new or modified 

sources from some or all of the PSD requirements where such emissions would be 

de minimis and thus their regulation would yield only trivial or no value. Ala. 

Power Co., 636 F.2d at 360-61. The authority to exempt de minimis activity from 

regulation where such regulation would result in trivial or no benefit is part of an 

agency’s usual responsibility to carry out a statutory scheme, like the CAA. In 

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fact, there is “virtually a presumption in its favor.” Public Citizen v. Young, 831 

F.2d 1108, 1113 (D.C. Cir. 1987). 

As applied here, EPA is using SILs to identify a level of impact on ambient 

air quality that EPA regards as truly de minimis, in that requiring more detailed air 

quality analysis would have virtually no benefit. A source that demonstrates its 

impact does not exceed a SIL is not required to conduct more extensive air quality 

analysis or modeling to demonstrate that those emissions “will not cause, or 

contribute to” a violation of the NAAQS or increment. 42 U.S.C. § 7475(a)(3). 

Because in such circumstances the source’s impacts alone are de miminis, i.e., 

insignificant, a cumulative impact analysis and modeling by that source would 

yield information of trivial value. It thus makes little economic or environmental 

sense to require that work to be done.

As discussed more fully below, EPA’s interpretation of section 165(a)(3) to 

allow sources with de minimis impacts to demonstrate compliance with NAAQs 

and increments without a comprehensive cumulative impact analysis is firmly 

grounded in EPA’s de minimis authority under Alabama Power and reflects a 

permissible construction of the statute under Chevron. Petitioner’s arguments 

against EPA’s use of its de minimis authority should be rejected. The statute is not 

so rigid as to foreclose EPA’s use of SILs as a means for making the demonstration 

required by section 165(a)(3) of compliance with the NAAQS and increments. 

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Contrary to Petitioner’s argument, SILs are not intended to waive the central 

requirements of section 165(a)(3) but, rather, are a tool to implement Congress’s 

intent. Moreover, the SILs in the Rule are based on EPA’s reasonable assessment 

of the level at which a source’s impact is truly de minimis. 

A. EPA Reasonably Interprets Section 165(a)(3) to Allow the Use of 

SILs as De Minimis Thresholds. 

As discussed above, section 165(a)(3), 42 U.S.C. § 7475(a)(3), does not 

specify how the required demonstration of whether a source will “cause, or 

contribute to” a NAAQS or increment violation is to be made, and EPA’s 

interpretation of that provision to allow the use of SILs as a means to demonstrate 

compliance is reasonable. Petitioner’s argument that the statute is extraordinarily 

rigid, foreclosing the use of SILs, is based on its misunderstanding of how SILs 

operate. The use of SILs does not waive the mandatory requirement in section 

165(a)(3) that a source “demonstrate” that it “will not cause, or contribute to,” a 

violation of the NAAQS or increments. Rather, SILs are a means of demonstrating 

through modeling that the source’s impact will be sufficiently low relative to the 

NAAQS or increments that such impact will not cause or contribute to a NAAQS 

or increments violation. 

Petitioner’s contention that Congress’s use of the terms “no” and “any” in 

section 165(a)(3) reflects the sort of rigid language that forecloses EPA’s de 

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minimis authority (Pet. Br. 21) ignores that this Court has approved de minimis

exemptions from similarly broad and sweeping language. In EDF v. EPA, 82 F.3d 

at 465, for instance, the Court considered EPA’s use of its de minimis authority in 

the context of section 176(c) of the CAA, which provides that “[n]o department, 

agency, or instrumentality of the Federal Government shall . . . support in any way

. . . any activity which does not conform to an implementation plan.” 42 U.S.C. 

§ 7506(c) (emphasis added). The Court in EDF concluded this language was not 

so rigid as to foreclose de minimis exceptions, notwithstanding the words “no” and 

“any.” EDF, 82 F.3d at 466. The language in section 165(a)(3) is no more rigid 

than the language in section 176(c). If the Court found the language of the 

conformity provision in EDF to admit of de minimis exceptions, so too should this 

Court conclude that section 165(a)(3) authorizes EPA to use SILs as de minimis

thresholds for demonstrating that a source does not cause or contribute to NAAQS 

or increments violations. 

This Court’s decision in New York v. EPA, 443 F.3d 880, 888 (D.C. Cir. 

2006), also is instructive. In that case, the Court vacated an EPA rule that 

interpreted “any physical change” in the definition of “modification” in 42 U.S.C. 

§ 7411(a)(4) to exempt physical changes that do not exceed 20% of the 

replacement value and do not change the source’s basic design parameters. The 

Court reasoned that the plain language of the statute said “any” and there is “no 

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reason why ‘any’ should not mean ‘any.’” Id. However, the court in that case 

discussed the de minimis principle as a separate question, noting that the Alabama 

Power court acknowledged that EPA could apply the de minimis principle in 

applying the statutory definition of “modification.” Id. at 888. 

The one de minimis case Petitioners cite, Public Citizen v. Young, 831 F.2d 

at 1111-13, involves statutory language that does not parallel the usage of the 

terms “no” or “any” in section 165(a)(3). Compare 21 U.S.C. § 376e(b)(5)(B) (“a 

color additive . . . shall be deemed unsafe . . . if . . . [it] is found . . . to induce 

cancer” in man or animal), with 42 U.S.C. § 7475(a)(3) (“no major emitting facility 

. . . may be constructed in any area to which [the PSD program] applies unless,” 

inter alia, the facility “demonstrates . . . that [its] emissions . . . will not cause, or 

contribute to” any violation of the NAAQS or increment). Accordingly, Public 

Citizen does not support Petitioner’s reading of the statute as “extraordinarily 

rigid.”

Petitioner’s argument that the absence of the word “significant” from section 

165(a)(3) forecloses EPA from applying a de minimis exemption also is 

unavailing. As discussed above, the term “contribute to” may or may not connote 

a significance threshold and therefore is ambiguous. Catawba, 571 F.3d at 39. 

Thus, nothing in the statute precludes EPA from interpreting the phrase to mean a 

contribution that is significant. Indeed, “it is eminently reasonable to conclude that 

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41

[Congress’s silence] is meant to convey nothing more than a refusal to tie the 

agency’s hands” as to the level of contribution necessary under section 165(a)(3). 

Entergy, 556 U.S. at 222. EPA’s interpretation of “contribute” in section 165(a)(3) 

to mean “significantly contribute” furthers the legislative intent that EPA ensure 

that economic growth occur consistent with preserving air quality, as provided in 

42 U.S.C. § 7470(3). 

Finally, that section 165 provides several express waivers from the 

requirement in section 165(a)(3) does not show that Congress intended to foreclose 

EPA’s use of its de minimis authority in this Rule. See Pet. Br. at 21-22. EPA is 

not waiving the requirement in section 165(a)(3); EPA is establishing de minimis

levels that allow a source to demonstrate through modeling that its impact will not 

cause or contribute to a NAAQS or increments violation. In any event, Petitioner’s 

reliance on Kokechick Fishermen’s Ass’n v. Sec’y of Commerce, 839 F.2d 795, 

801-02 (D.C. Cir. 1988), is misplaced, as that case is clearly distinguishable. In 

that case, the court’s analysis of the relevant statute turned on its conclusion that 

the text does not allow balancing of marine mammal protection against fishing 

interests. Id. at 801-02. In contrast, in CAA section 160, 42 U.S.C. § 7470, 

Congress has identified various purposes of the PSD program, seemingly at some 

tension with one another, including encouraging economic growth and preventing 

significant deterioration of air quality, and it has required EPA to balance these 

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competing interests. EPA’s use of SILs as a means of demonstrating compliance 

with NAAQS and increments is one reasonable approach to balancing these 

competing purposes of the statute. 

B. EPA’s Interpretation of Section 165(a)(3) to Allow the Use of SILs 

to Demonstrate Compliance with NAAQS and Increments 

Furthers the Legislative Design. 

 Because SILs are a means of demonstrating compliance with the NAAQS 

and increments, they also implement the legislative design. Petitioner’s argument 

that SILs thwart the legislative design is based on their assumption that SILs waive 

the requirement in section 165(a)(3) that permit applicants “demonstrate” that they 

will not “cause, or contribute to” a violation of the NAAQS and or the increments. 

Pet. Br. 29. As discussed in argument I.B., supra, EPA agrees with Petitioner that 

SILs should not be used to justify permitting a source without a cumulative 

analysis in circumstances where there is information to suggest that use of the SIL 

in this manner would lead to a violation of the NAAQS or increment. Because 

EPA recognizes that the regulatory language it adopted in 40 C.F.R. 

§§ 51.166(k)(2) and 52.21(k)(2) does not provide permitting authorities discretion 

not to apply SILs for the particular purpose covered by these provisions, EPA 

agrees that §§ 51.166(k)(2) and 52.21(k)(2) should be vacated and remanded. 

With appropriate safeguards addressing circumstances when SILs should not be 

used, however, SILs remain a reasonable mechanism to meet section 165(a)(3)’s 

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43

requirements that sources demonstrate compliance with the NAAQS and 

increments.

C. The SILs Identify Levels below which a Source’s Impact is Truly 

De minimis, and thus Requiring a Cumulative Impact Analysis 

Would Yield Information of Only Trivial Value.

EPA has provided a reasoned explanation that shows air quality impacts 

below the SILs are truly de minimis. Petitioner’s arguments do not so much 

challenge the particular values EPA determined are appropriate de minimis levels 

as they rehash their arguments, addressed above, that the use of SILs is foreclosed 

by the statute and thus that EPA could identify no appropriate de minimis level. 

The most direct attack Petitioner makes on the numeric values of the SILs is to 

argue that EPA did not provide any evidence to support the SILs it set. See Pet. 

Br. 38-39. Contrary to Petitioner’s assertions, the rationale for the SILs adopted is 

fully explained and supported by evidence in the record. 

EPA calculated the SILs by multiplying the ratio of the PM2.5 NAAQS to the 

PM10 NAAQS by the existing PM10 SILs, which are set forth in 40 C.F.R. 

51.165(b)(2). 75 Fed. Reg. at 64,893 (JAXX). To determine that these levels 

reflect truly de minimis impacts, EPA analyzed them in comparison to the impact 

EPA deems insignificant for purposes of determining whether a source is a major 

emitting facility. Id. EPA determined that the ambient impact resulting from the 

application of the SIL is comparable to the range of ambient concentrations 

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deemed de minimis under EPA’s 1980 regulations establishing significance rates 

for purposes of the major source determination. Id.; see supra background section 

II.C.1. (comparing these SILs as a percentage of the PM2.5 NAAQs and increments 

to the significance levels for PM10). EPA reasonably relied on significance levels 

established in analogous contexts as a basis for its determination that the SILs here 

reflect the levels below which any further regulation would yield, at most, only 

trivial benefits. See EDF, 82 F.3d at 467 (upholding EPA’s finding of de minimis

impacts based on previously adopted de minimis levels); Ober, 243 F.3d at 1196

(same). 

III. EPA PROPERLY USED ITS DE MINIMIS AUTHORITY TO ADOPT 

SIGNIFICANT MONITORING CONCENTRATIONS.

As part of the required PSD review of new or modified sources of air 

pollution, CAA section 165, 42 U.S.C. § 7475, and EPA’s implementing 

regulations require a source to collect preconstruction monitoring data. 

Specifically, section 165(a)(7), 42 U.S.C. § 7475(a)(7), requires “such monitoring 

as may be necessary to determine the effect which emissions from any [covered] 

facility may have, or is having, on air quality in any areas which may be affected 

by emissions from such source.” Additionally, section 165(e)(2), 42 U.S.C. 

§ 7475(e)(2), calls for collecting one year’s worth of preconstruction monitoring 

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data, unless the permitting authority determines a complete and adequate analysis 

may be accomplished in a shorter period. 

Under EPA’s longstanding interpretation of the Act, as reflected in 

regulations first adopted in 1980, EPA may use its de minimis authority to exempt 

sources from providing such monitoring data if the source can demonstrate that 

either its ambient impact or the ambient concentration with regard to a pollutant is 

less than a value known as the significant monitoring concentration, or SMC. See

72 Fed. Reg. at 54,141 (JAXX); 45 Fed. Reg. 52,676, 52,707 (JAXX, XX); 40 

C.F.R. §§ 51.166(m), 52.21(m). EPA first adopted this interpretation in its 1980 

PSD implementation regulations, 45 Fed. Reg. at 52,705-710 (JAXX-XX), when it 

promulgated a number of SMCs to be used as screening tools for sources to use to 

determine whether they should conduct site-specific preconstruction monitoring. 

In the present Rule, EPA amended its PSD implementing regulations by 

adopting an SMC for PM2.5. 75 Fed. Reg. at 64,895 (JAXX) (40 C.F.R. 

§§ 51.166(i)(5)(i)(c), 52.21(i)(5)(i)(c)). As it did in the 1980 Rule, EPA based the 

SMC on its de minimis authority recognized in Alabama Power. 75 Fed. Reg. at 

64,895-96 (JAXX-XX). Like the other pollutants for which EPA has promulgated 

SMCs, EPA concluded that there is little to be gained from requiring the collection 

of preconstruction monitoring data for PM2.5 concentrations that are at levels so 

low that they cannot be accurately measured. Id. 

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Petitioner’s arguments against the SMC must be rejected. As an initial 

matter, this Court does not have jurisdiction to consider Petitioner’s claim that 

EPA lacks the authority to implement SMCs. EPA adopted the provisions of the 

PSD regulations at issue here, 40 C.F.R. §§ 51.166(i)(5) and 52.21(i)(5), in 1980. 

At that time, EPA set forth its interpretation of the CAA to allow the use of de 

minimis thresholds for determining whether a source must collect a year’s worth of 

monitoring data. If Petitioner wished to challenge that interpretation, it was 

required to do so within 60 days of publication of the regulation in the Federal 

Register. Section 307(b), 42 U.S.C. § 7607(b), precludes Petitioner from raising 

the issue now. 

To the extent the Court reaches Petitioner’s argument that the statute does 

not authorize SMCs, Petitioner fails to show that the statute is so rigid as to rebut 

the “virtual presumption” of inherent agency authority to create de minimis

exemptions from regulatory burdens that will have little or no benefit. Second, 

Petitioner misconstrues the basis for the exemption to be that all monitoring is 

“pointless.” Pet. Br. 43. To the contrary, EPA reasonably determined that 

monitoring that would not provide accurate data would not serve the purposes of 

the Act. Third, Petitioner’s argument that the SMC is arbitrary ignores EPA’s 

explanation in the record, which shows that the SMC reflects a narrowly tailored 

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exemption applicable only where the value of the monitoring data is likely to be 

trivial.

A. Petitioner’s Challenge to EPA’s Authority to Adopt SMCs is 

Time-Barred. 

CAA section 307(b)(1), 42 U.S.C. § 7607(b)(1), directs that any petition for 

review must be filed within sixty days from the date that notice of the challenged 

action appears in the Federal Register. The filing period in the Clean Air Act “is 

jurisdictional in nature.” Motor & Equip. Mfrs. Ass’n v. Nichols, 142 F.3d 449, 

460 (D.C. Cir. 1998) (citation and internal quotation marks omitted). Thus, if the 

petitioner has failed to comply with it, the Court is “powerless to address their 

claim.” Medical Waste Inst. & Energy Recovery Council v. EPA, 645 F.3d 420, 

427 (D.C. Cir. 2011). Here, Petitioner failed to comply with this requirement with 

regard to its claim that EPA lacks the authority to adopt SMCs.

As noted, EPA first promulgated SMCs in its 1980 regulations 

implementing the PSD provisions of the CAA. 45 Fed. Reg. at 52,733-34 (JAXXXX). At that time, EPA asserted its interpretation of section 165(e)(2) of the CAA 

to permit a permitting authority to exempt a source from submitting a year’s worth 

of preconstruction monitoring data if the source could show either that the source’s 

proposed impact or the ambient air quality concentrations were below de minimis

levels promulgated as “significant monitoring concentrations.” 45 Fed. Reg. at 

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48

52,708-710 (JAXX-XX). EPA relied on the same interpretation of the Act in 

promulgating the PM2.5 SMC here. Indeed, EPA did not substantively modify the 

regulatory text Petitioner challenges, except to add a new SMC for PM2.5.

11

 Pursuant to section 307(b)(1), challenges to EPA’s interpretation of the 

CAA as reflected in the SMC were required to have been raised within 60 days of 

when the regulation was first published in the Federal Register. 42 U.S.C. 

§ 7607(b)(1). As the Court recently held in the context of another CAA regulation: 

“The sixty-day window provided by statute has long since closed, and we may not 

reopen it and entertain a belated challenge to the EPA’s [SMC] approach now.” 

Medical Waste Inst., 645 F.3d at 427. This is true even though Petitioner lodged 

objections to EPA’s SMC approach during the rulemaking. See id. Petitioner’s 

objection to EPA’s authority to adopt SMCs is time-barred.

 

12

 

11 In this Rule, EPA made minor technical corrections to the language in 40 

C.F.R. §§ 51.166(i)(5) and 52.21(i)(5) to address an erroneous cross-reference to a 

subparagraph (i)(8), which EPA inadvertently failed to change when the 

paragraphs were renumbered in an earlier rulemaking. 75 Fed. Reg. at 64,897 

(JAXX).

12 Notably, Petitioner recognizes that they cannot challenge here EPA’s 

authority to adopt the SILs at 40 C.F.R. § 51.165(b) (compare Pet. Br. 20 n.8 and 

32 n.12, with Pet. Br. 37 n.17), which were first promulgated in 1987. Petitioner 

fails to explain, however, why the same does not hold true for Petitioner’s belated 

attempt to challenge EPA’s longstanding regulations adopting SMC. 

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B. EPA’s Interpretation of Section 165 (e)(2) is a Permissible 

Construction of the Statute.

To the extent the Court reaches Petitioner’s statutory challenge to the SMC, 

EPA reasonably interprets the statute to allow an exemption from the 

preconstruction monitoring requirement based on de minimis levels reflecting 

current capabilities to accurately measure ambient air concentrations. The purpose 

of the statute’s monitoring requirement is to provide data for purposes of 

performing an air quality analysis. It is reasonable for EPA to conclude that the 

statute permits an exemption for collection of data that is not useful to carrying out 

the purposes of the statute. 

Petitioner’s argument that CAA section 165(e)(2) forecloses any de minimis

exemptions because it sets forth a plain requirement for monitoring data (Pet. Br. at 

41(citing Alabama Power)), proves too much. By definition, an agency’s authority 

to adopt de minimis exemptions as recognized in Alabama Power is inherent—that 

is, not express in the statute. 636 F.2d at 360 (“Courts should be reluctant to apply 

the literal terms of a statute to mandate pointless expenditures of effort.”). Thus, 

while it is true that the court in Alabama Power, 636 F.2d at 372, interpreted 

section 165(e)(2) as a “plain requirement” for monitoring data that could not be 

categorically waived on the ground of technological infeasibility, that does not 

mean EPA is foreclosed from exercising its de minimis authority to craft a more 

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narrowly tailored exemption, as it did here. Further, this Court has recognized that 

an agency’s inherent authority to adopt de minimis exemptions is “virtually a 

presumption.” Public Citizen, 831 F.2d at 1113. To argue, as Petitioner does, that 

the statute sets forth a plain requirement is not sufficient to rebut that presumption. 

Petitioner must show that the statute is “extraordinarily rigid” before an agency 

will be precluded from adopting a de minimis exemption. Alabama Power, 636 

F.2d at 360-61. 

Moreover, Petitioner cannot buttress its interpretation of the statute as 

“extraordinarily rigid” by arguing that Congress’s inclusion of an express 

exemption in section 165(e)(2), forecloses EPA from adopting de minimis

exemptions. Alabama Power recognizes an agency’s inherent authority to adopt 

exemptions for de minimis exemptions that are not otherwise explicitly authorized 

by the statute. Whether a statute may be read to implicitly authorize non-de 

minimis exceptions in the face of exemptions expressly authorized by Congress is a 

separate question. See, e.g., New York, 443 F.3d at 887-88 (distinguishing the 

issue in that case, i.e., whether the agency may create implicit exemptions in the 

face of explicit exemptions, from an agency’s inherent Alabama Power authority 

to create de minimis exemptions). Thus, the principle of statutory construction 

Petitioner relies upon is inapposite in the context of an agency’s implied authority 

to create de minimis exemptions. 

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To the extent the exemption in section 165(e)(2) is relevant at all, the 

language of the exemption supports EPA’s interpretation of the statute. Section 

165(e)(2) authorizes EPA to establish regulations allowing a permitting authority 

to require less than one year’s data if “a complete and adequate analysis for such 

purposes may be accomplished in a shorter period.” 42 U.S.C. § 7475(e)(2)

(emphasis added). This language further demonstrates that the purpose of the 

preconstruction monitoring requirement is to provide data that is sufficient to 

conduct a “complete and adequate analysis.” If the monitoring data is inaccurate 

or could lead to uncertainty, then requiring its collection does not serve the 

purposes of the statute. EPA’s decision to create a de minimis exemption based on 

the levels below which ambient pollutant concentrations can accurately be 

measured furthers Congress’s intent and therefore is an appropriate exercise of 

EPA’s de minimis authority.

C. The SMC Implements the Legislative Design By Exempting Data 

that Is Not Accurate Enough to Serve any Useful Purpose.

The purpose of de minimis exemptions is to inject a limited degree of 

flexibility into the statute, where an otherwise rigid application would thwart the 

legislative purposes. See Alabama Power, 636 F.2d at 360. The SMC for a 

pollutant reflects levels below which concentrations of that pollutant in ambient air 

cannot accurately be measured. There is no purpose in requiring collection of data 

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that cannot be relied upon in an analysis of ambient air quality under the statute. 

EPA’s decision to create a de minimis exemption based on the levels below which 

pollutant concentrations can accurately be measured furthers Congress’s intent and 

therefore is an appropriate exercise of EPA’s de minimis authority. 

Petitioner’s assertion that the SMC thwarts the legislative purposes (because 

it allows NAAQS violations) ignores that EPA has long stated that permitting 

authorities should not apply the exemption in circumstances where an area’s 

ambient concentration is close to the NAAQS or the consumption of the increment. 

45 Fed. Reg. at 52,710 (JAXX) (SMCs “should not be used when (1) there is an 

apparent threat to an applicable PSD increment or NAAQS based on modeling 

alone or (2) when there is a question of adverse impact on a Class I area.”). 

Moreover, Petitioner fails to explain how the collection of possibly inaccurate data 

or uncertain data would enable permitting authorities to determine whether a 

proposed new source will violate the NAAQS or increments. In fact, EPA 

concluded the opposite. EPA found that preconstruction monitoring of ambient 

concentrations that are below the SMC “could not be used for any quantitative 

purposes because [the results] would not provide the desired confidence of 

accuracy and precision.” RTC at 92 (JAXX). EPA reasonably concluded that, in 

these circumstances, “the time and expense of a year of preconstruction monitoring 

data would be wasted.” Id. EPA’s use of its de minimis authority to avoid such 

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“pointless expenditures of effort” furthers the legislative design and should be 

upheld. Alabama Power, 636 F.2d at 360. 

D. The SMC Reflects the Level at Which Regulatory Benefits are 

Truly De minimis. 

Petitioner’s argument that EPA cannot show monitoring benefits are trivial 

(Pet. Br. 47-54) misunderstands or mischaracterizes the purpose and scope of the 

SMC exemption and ignores the analysis in the record supporting the values EPA 

selected as the SMC for PM2.5. As already discussed, the purpose of the exemption 

is to exempt permit applicants from having to collect monitoring data when the 

source’s impact or the ambient concentrations are below the level at which the 

concentrations may accurately be measured. EPA does not deem all monitoring to 

be trivial, as Petitioner suggests. Pet. Br. 47. Rather, EPA believes there is little 

value to requiring additional monitoring data to be collected when the source’s 

impact or the ambient concentrations in the area are below the levels at which the 

concentrations can accurately be measured. 75 Fed. Reg. at 64,896 (JAXX). As 

noted above, representative data may already be available. Thus, the exemption is 

narrowly targeted to exempt only those instances where the collection of 

monitoring data is not likely to be useful in any ambient air quality analysis. Id. 

See RTC at 91-92 (JAXX-XX). As such, it is an appropriate de minimis exemption 

under Alabama Power. 636 F.2d at 361 (valid de minimis exemption is one that is 

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54

“narrow in reach and tightly bounded by the need to show that the situation is 

genuinely de minimis”). 

Further, EPA fully explained its choice of the SMC value in the record. 

EPA proposed and evaluated three options for determining an appropriate SMC 

that would identify the degree of ambient impact on PM2.5 concentration that is 

truly de minimis. 72 Fed. Reg. at 54,141-42 (JAXX-XX). EPA selected the option 

that is based on the lowest detectable concentration—or minimum detection 

limit—adjusted by a multiplication factor to account for errors that may arise in 

monitoring from various sources, such as sample collection, analytical 

measurement, calibration, and interferences. See 75 Fed. Reg. at 64,896 (JAXX). 

EPA’s reasoning reflects a rational connection between the SMC values selected 

and EPA’s goal of exempting monitoring that would be of little value. 

Accordingly, EPA’s judgment is entitled to deference. 

Moreover, EPA in this rulemaking took another look at the detection limit 

originally used in 1980, and reaffirmed this value based on recent data. 75 Fed. 

Reg. at 64,896-97 (JAXX-XX) (minimum detection limit was “reaffirmed by 9 

years of field blank data collected by EPA through the PM2.5 Performance 

Evaluation Program.”) Then, based on information collected during this 

rulemaking, EPA used its assessment of the uncertainties introduced to the 

measurement of PM2.5 due to mechanical or operational variations of the sampling 

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55

devices, and human error associated with the performance of sampling device 

calibration and sample analyses. Id. As a result of this new information, EPA 

reduced the uncertainty factor from 5 to 2, which reduced the SMC value from 10 

μg/m3 (that is, 5 times the detection limit of 2 μg/m3

) to the value established in 

this rule, 4 μg/m3

. Id. EPA’s thorough examination of these technical issues 

further supports the reasonableness of its decision. 

However, that EPA gave permitting authorities the discretion to consider 

whether monitoring might provide more than trivial benefits, notwithstanding the 

SMC, shows that EPA properly limited the exemption to those situations that are 

truly de minimis.

13

Finally, EPA considered and rejected Petitioner’s argument that there is no 

rational relationship between basing the SMC on monitoring accuracy and 

applying it based on a measurement of a source’s predicted increase in emissions 

based on modeling. In that argument, Petitioner does not dispute that the predicted 

 Thus, contrary to Petitioner’s argument, EPA’s limitation of 

the use of the SMC supports rather than undermines its use of its de minimis

authority.

 

13 In contrast to the language in §§ 51.166(k)(2) and 52.21(k)(2) that EPA 

concedes is erroneous, the language in §§ 51.166(i)(5) and 52.21(i)(5) of EPA’s 

regulations leaves more room for permitting authority discretion. See e.g., 40 

C.F.R. § 51.166(i)(5) (“may exempt ... from the requirements of paragraph (m) of 

this section, with respect to monitoring”). 

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impact of a source might be below levels that could be accurately measured, but 

argued that there was still value to preconstruction monitoring. Pet. Br. 51. As 

EPA explained in response to comments, “any difference in the ambient 

concentration due to such a source [with impacts below the SMC] would be too 

small to be measured accurately, so any attempt to quantify the impact of a source 

based on preconstruction and post-construction monitoring in the area would be 

inconclusive.” RTC at 92 (JAXX). Similarly, EPA concluded that a source trying 

to measure ambient concentrations below the SMC “would be trying to measure 

concentrations that are in the range where uncertainties exist, and the results of the 

monitoring could not be used for any quantitative purposes.” RTC at 92 (JAXX). 

In such circumstances, there would be no benefit to be gained from the time and 

expense of collecting a year’s worth of data and a de minimis exception is 

appropriate. Id. 

CONCLUSION

For all of the foregoing reasons, the Court should uphold EPA’s use of its de 

minimis authority to promulgate SILs and SMC in general, but vacate and remand 

to EPA those portions of the SIL regulations codified at 40 C.F.R. §§ 51.166(k)(2)

and 52.21(k)(2), so that EPA may revise the text to properly reflect EPA’s intent 

that the SILs not be used in circumstances where their use may lead to a new 

violation of the NAAQS or increments. Further, the Court should find that 

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Petitioner’s challenge to EPA’s authority to adopt the SMC is time-barred and 

dismiss that portion of their challenge for lack of jurisdiction. The Court should 

otherwise deny the remainder of the issues raised by the petition. 

Dated: April 6, 2012 Respectfully submitted,

 IGNACIA S. MORENO

 Assistant Attorney General

 /s/ Jessica O’Donnell 

 JESSICA O’DONNELL

 United States Department of Justice

 Environment & Natural Resources Division

 Environmental Defense Section

P.O. Box 7611

 Washington, D.C. 20024

 Tel: 202-305-0851

 Jessica.O’Donnell@usdoj.gov

Of Counsel:

BRIAN DOSTER

SCOTT JORDAN

United States Environmental Protection Agency

Office of General Counsel

1200 Pennsylvania Avenue, N.W. 

Washington, D.C. 20460

 

 Counsel for Respondents

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CERTIFICATE OF SERVICE

I hereby certify that a copy of the foregoing proof Brief for Respondent was 

served, this 6th day of April, 2012, on all registered counsel, through the Court’s 

CM/ECF system.

 /s/ Jessica O’Donnell 

Jessica O’Donnell

 United States Department of Justice

 Environment & Natural Resources Div.

 Counsel for Respondent EPA

USCA Case #10-1413 Document #1367679 Filed: 04/06/2012 Page 72 of 73
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CERTIFICATE OF COMPLIANCE WITH WORD LIMITATION

Pursuant to Federal Rule of Appellate Procedure 32(a)(7)(C), I hereby 

certify that the foregoing proof Brief of Respondent EPA contains 12,636 words as 

counted by the Microsoft Office Word 2007 word processing system, and thus 

complies with the applicable word limitation.

 /s/ Jessica O’Donnell 

Jessica O’Donnell

 United States Department of Justice

 Environment & Natural Resources Div.

 Counsel for Respondent EPA

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