51.165(b)(2) in the section of its brief challenging 
the EPA�s methodology in setting SILs, and not in the section 
challenging the EPA�s authority to promulgate SILs. See 


Pet�r Br. at 32 n.12, 37 n.17. We are not now ruling on the 
methodology the EPA used to determine the SILs. Instead, 
we are vacating and remanding �� 51.166(k)(2) and 
52.21(k)(2) based on the EPA�s lack of authority to exempt 
sources from the requirements of the Act. Therefore, vacatur 
and remand of � 51.165(b)(2) is not necessary at this point. 

 

 Accordingly, we vacate and remand the portions of the 
EPA�s rule regarding SILs, with the exception of those 
portions codified in 40 C.F.R. � 51.165(b)(2). 

 

B. Significant Monitoring Concentrations 


 

As with the SILs, the Sierra Club argues that the EPA 
does not have de minimis authority to promulgate an SMC for 
PM2.5 that can be used to exempt an owner of a proposed 
source or modification from undertaking the year-long pre-
construction air quality monitoring requirement under 
� 165(e)(2) of the Act. As a threshold issue, however, the 
EPA argues that the Sierra Club�s challenge is time-barred 
under � 307(b)(1) of the Act because the EPA has used SMCs 
as a screening tool since 1980. See 42 U.S.C. � 7607(b)(1); 
45 Fed. Reg. 52,676, 52,710 (Aug. 7, 1980) (explaining that a 
source owner may be exempt from preconstruction 
monitoring if the source�s projected impact is de minimis). 
We disagree with the EPA that the Sierra Club�s petition is 
time-barred, and we agree with the Sierra Club that the EPA 
did not have de minimis authority to promulgate the SMC 
because we hold Congress was �extraordinarily rigid� in 
mandating preconstruction air quality monitoring. 

 

Section 307(b)(1) of the Act requires a petitioner seeking 
review of an EPA regulation to file its petition within sixty 
days from the date the challenged regulation was published in 
the Federal Register. 42 U.S.C. � 7607(b)(1). The EPA relies 


on our decision in Medical Waste Institute and Energy 
Recovery Council v. EPA, 645 F.3d 420 (D.C. Cir. 2011), to 
argue that � 307(b)(1) bars the Sierra Club�s challenge to the 
PM2.5 SMC. In that case, the petitioner challenged the EPA�s 
approach to setting the level of emissions control for 
pollutants emitted by medical waste incinerators. Id. at 422. 
The EPA had initially set these levels in 1997, but we 
remanded its regulations after granting an environmental 
organization�s petition for review. Id. at 423. The EPA 
issued a new rule in 2009 setting even more stringent levels 
for emissions control than it had in 1997, prompting another 
petition for review, this time by an industry organization. Id. 
at 424. In remaking the rule, the EPA used the same approach 
to setting the levels of emissions control for the same set of 
pollutants as it did in 1997, but used a different data set. Id. 
at 426�27. We held that because no one challenged the 
approach to setting levels of emissions control in 1997 � the 
same approach the EPA used in its 2009 regulation � the 
petitioners had failed to file a timely petition, and their 
challenge was thus barred by � 307(b)(1). Id. at 427. 

 

Our holding in Medical Waste Institute, however, does 
not apply in this case. The EPA has promulgated new 
regulations for a pollutant it did not regulate in 1980. See 45 
Fed. Reg. at 52,733�34 (listing SMCs for various pollutants 
that does not include PM2.5). By establishing a new 
monitoring exemption for a new pollutant, the EPA exposes 
its PM2.5 regulations, including whether it has authority to 
adopt the SMC exemption for PM2.5 and whether it used an 
appropriate method to determine the level of the SMC, to 
challenge by a timely filed petition. In Ohio v. EPA, 838 F.2d 
1325, 1328 (D.C. Cir. 1988), we opined that �the period for 
seeking judicial review may be made to run anew when the 
agency in question by some new promulgation creates the 
opportunity for renewed comment and objection.� Although 


not a parallel to this case in that the Ohio case concerned a 
reopening, we consider its reasoning instructive. 

 

This, of course, does not mean that a petitioner�s 
challenge to the EPA�s authority will always survive, as the 
EPA�s authority to promulgate certain regulations could be 
well-settled. The solution, however, is not to bar any 
challenges to that authority under � 307(b)(1) of the Act, but 
instead to consider the timely challenge and any relevant 
precedent demonstrating that the EPA has the authority in 
dispute. Because we have not yet decided whether the EPA�s 
de minimis authority allows it to establish SMCs as a 
screening tool to determine when to exempt sources from the 
Act�s preconstruction monitoring requirement, we will 
consider whether the EPA had authority to adopt an SMC for 
PM2.5. 

 

Subsection (e) of � 165 of the Act requires that before a 
PSD permit application can be reviewed, either the State or 
the permit applicant must conduct an analysis of the ambient 
air quality at the proposed site and in areas which the 
applicant�s facility may affect. 42 U.S.C. � 7475(e)(1). 
Under subsection (e)(2), this analysis 

 

shall include continuous air quality monitoring data 
gathered for purposes of determining whether 
emissions from such facility will exceed the 
[increment] or the maximum allowable concentration 
permitted under [the NAAQS]. Such data shall be 
gathered over a period of one calendar year preceding 
the date of application for a permit under this part 
unless the State, in accordance with regulations 
promulgated by the [EPA], determines that a complete 
and adequate analysis for such purposes may be 
accomplished in a shorter period. The results of such 


analysis shall be available at the time of the public 
hearing on the application for such permit. 

 

Id. � 7475(e)(2). 

 

 We read � 165(e)(2) of the Act as an �extraordinarily 
rigid� mandate that a PSD permit applicant undertake 
preconstruction monitoring. Indeed, we recognized the 
rigidity of this subsection in Alabama Power when we held 
that �[t]his is a plain requirement for inclusion of monitoring 
data.� Alabama Power, 636 F.2d at 372 (holding that the 
EPA did not have authority to dispense with monitoring 
where Congress mandated the use of that technique, even 
though monitoring technology at the time was limited). 
Congress�s use of the word �shall� in each sentence of the Act 
evidences a clear legislative mandate that the preconstruction 
monitoring requirement applies to PSD permit applicants. 
That Congress provided only one exception to this monitoring 
requirement � a shorter monitoring period � suggests that 
Congress did not intend any other exceptions. See Sierra 
Club v. EPA, 294 F.3d 155, 160 (D.C. Cir. 2002). If Congress 
sought to give the EPA discretion to eliminate the monitoring 
requirement it could have used less rigid language to achieve 
that result, as it has in other subsections of � 165. For 
example, in 42 U.S.C. � 7475(e)(2), Congress provided that 
�[air quality] data shall be gathered over a period of one 
calendar year preceding the date of application for a permit 
under this part unless the State, in accordance with regulations 
promulgated by the [EPA], determines that a complete and 
adequate analysis for such purposes may be accomplished in a 
shorter period.� (emphasis added). In contrast, � 7475(a)(7) 
requires as a condition for obtaining a PSD permit, that an 
owner or operator of a proposed source or modification agree 
to post-construction monitoring as �may be necessary to 
determine the effect which emissions� from the facility may 


have on air quality. (emphasis added). Moreover, the 
exception for a shorter monitoring period only applies when 
the permitting authority determines that a complete and 
adequate analysis may be accomplished in a shorter period. 
EPA has not explained how a �complete and adequate� 
analysis may be accomplished without any of the monitoring 
data required by � 165(e)(2). 

 

 Given how extraordinarily rigidly Congress stated its 
monitoring mandate in � 165(e)(2), we are not persuaded by 
the EPA�s arguments that it has de minimis authority to 
exempt the preconstruction monitoring requirement. The 
EPA argues that the Sierra Club fails to show that the statute 
is so rigid that it precludes the exercise of the EPA�s de 
minimis authority. The EPA, however, does not explain how 
the statute is ambiguous, but instead asserts that there is a 
�virtual presumption� of inherent agency authority. Resp�t 
Br. at 46; see Public Citizen v. Young, 831 F.2d 1108, 1113 
(D.C. Cir. 1987). This argument is circular. Even if a 
�virtual presumption� exists, that presumption can be rebutted 
by an �extraordinarily rigid� statutory mandate. See Public 
Citizen, 831 F.2d at 1113. Whether we call preconstruction 
monitoring a �plain requirement� or a requirement mandated 
by an �extraordinarily rigid� statute, the result is the same: the 
EPA has no de minimis authority to exempt the requirement. 

 

 Without pointing out any ambiguity in Congress�s 
mandate, the EPA asserts that the purpose of the statute�s 
preconstruction monitoring requirement �is to provide data 
for purposes of performing an air quality analysis,� and that it 
can reasonably conclude �the statute permits an exemption for 
collection of data that is not useful to carrying out the 
purposes of the statute.� Resp�t Br. at 49. The EPA confuses 
the purpose of � 165(e)(2)�s monitoring requirement. The 
statute explicitly states that one purpose of the monitoring 


requirement is to determine whether emissions from a 
proposed source or modification will exceed the increments or 
NAAQS. 42 U.S.C. � 7475(e)(2). We logically infer from 
this statement that Congress intended the monitoring 
requirement to establish the baseline air quality in an area 
before the owner of a proposed source or modification even 
applies for a PSD permit. If an area�s pre-existing ambient 
PM2.5 concentration is so high that a violation of the NAAQS 
or increment is imminent, a source below the SMC may 
nevertheless cause a violation if built or modified. This is 
true even if the source�s projected ambient impact on PM2.5 is 
so low that the difference in air quality before and after 
construction would be impossible to measure with accuracy. 
But a permitting authority cannot know how close an area is 
to violating the NAAQS or increment unless it knows the 
existing ambient concentrations of PM2.5 before a source is 
constructed or modified. 

 

 The EPA�s argument also fails to address Congress�s 
mandate that the results of the air quality analysis required by 
� 165(e) be made available to the public at the time of a 
hearing for a PSD permit. Id. � 7475(e)(2). Indeed, one of 
Congress�s stated purposes in enacting the PSD provisions 
was �to assure that any decision to permit increased air 
pollution in any area to which� the PSD provisions apply be 
made only after careful evaluation by the permitting authority 
and �after adequate procedural opportunities for informed 
public participation in the decisionmaking process.� 42 
U.S.C. � 7470(5) (emphasis added). Congress�s express 
statement that the public shall have air quality data to allow 
for informed participation in PSD application hearings 
bolsters our conclusion that the EPA has no authority to 
exempt the monitoring requirement. 

 


 In addition to arguing that � 165(e)(2) was 
extraordinarily rigid, the Sierra Club contends that the EPA 
has no de minimis authority because the PM2.5 SMC thwarts 
the legislative design of the Act. The EPA addresses this 
argument by making two arguments. First, the EPA states 
that it has advised permitting authorities not to apply the 
monitoring exemption when an area�s ambient concentration 
is close to the NAAQS or the consumption of the increment. 
Second, the EPA asserts that exempting preconstruction 
monitoring in areas where the ambient concentration itself is 
below the SMC (and thus not capable of accurate 
measurement, regardless of a proposed source�s projected 
impact) furthers legislative design by avoiding pointless 
expenditures of effort. 

 

Both these points ignore the rigidity of the statute. 
Because the statute leaves no room for exemptions, such as 
those at issue, granting the permitting authorities discretion to 
apply the exemption is beyond the EPA�s statutory authority. 
As to the EPA�s second point, we agree with the Sierra Club 
that the estimation that an area is below the SMC does not 
render monitoring superfluous because monitoring could 
reveal that the estimate was incorrect. More importantly, 
Congress provided a clear mandate that the EPA does not 
have authority to disregard, even if the mandated 
requirements appear to it to be superfluous. 

 

To authorize the EPA to exempt the plain requirement of 
preconstruction monitoring and to retain (and delegate) 
discretion on when such an exemption should apply would 
allow the EPA to engage in an impermissible cost-benefit 
analysis. As we explained in Alabama Power, �implied 
authority is not available for a situation where the 
regulatory function does provide benefits, in the sense of 
furthering the regulatory objectives, but the agency concludes 


that the acknowledged benefits are exceeded by the costs.� 
Alabama Power, 636 F.2d at 361. To engage in cost-benefit 
decisions, the EPA�s implied authority �must be based not on 
a general doctrine but on a fair reading of the specific statute, 
its aims and legislative history.� Id. The monitoring 
requirement is a regulatory function that provides benefits, 
and the statute precludes the EPA from exempting that 
requirement. Although the year-long preconstruction 
monitoring requirement may be onerous and, in some cases, 
EPA deems it more costly than beneficial, the EPA may not 
substitute its policy for that of Congress. 

 

III. CONCLUSION 


 

For the foregoing reasons, we vacate and remand to the 
agency for further consideration the portions of the EPA�s 
rule addressing SILs, except for the parts of its rule codifying 
PM2.5 SILs in 40 C.F.R. � 51.165(b)(2). We grant the Sierra 
Club�s petition as to the parts of the EPA�s rule establishing a 
PM2.5 SMC, and vacate them because these parts of the rule 
exceed the EPA�s statutory authority. See 42 U.S.C. 
� 7607(d)(9)(3). 

 

So ordered.