Opinion ID: 4020089
Heading Depth: 1
Heading Rank: 5

Heading: 30-day rolling average

Text: As discussed, see supra § I.B.1.a, when the EPA sets a MACT floor, it begins by examining data generated by stack testing. Once the MACT standard is established, however, a source may (and in some cases, must) demonstrate compliance by implementing “continuous monitoring” instead 130 of conducting additional stack tests.39 See 2011 Proposed CISWI Rule on Reconsideration, 76 Fed. Reg. at 80,464-65. For a source using a continuous monitor, the EPA determines MACT-standard compliance based on the source’s thirty-day “rolling average.” Id. at 80,465. The calculation of a thirty-day rolling average is straightforward: the average of a source’s daily emissions for the immediately preceding thirty days. Each day produces a new rolling average and each “average is a separate compliance determination.” No. 11-1125 EPA Br. 88 n.17. In the EPA’s view, this “allow[s] operators sufficient flexibility for operational and control device adjustments should they be needed for short term fuel or waste characteristics variability.” 2011 Proposed CISWI Rule on Reconsideration, 76 Fed. Reg. at 80,465. The EPA also concluded that thirty-day rolling average violations will occur almost as frequently as violations of shorter rolling-average periods. Id. The CAA vests the EPA with authority to “prescribe procedures and methods for determining compliance and for monitoring and analysis of pollutants.” 42 U.S.C. § 7661c(b). We have emphasized that the EPA has “broad discretion in selecting a monitoring regime that ensures compliance, and as long as it reasonably articulate[s] the basis for its decision, [we] will defer to the informed discretion of the Agency, 39 As the name suggests, a continuous monitoring system measures the source’s emissions at all times and generally takes one of two forms: (1) a continuous parameter monitor, which measures, e.g., a source’s temperature, pressure or oxygen content; or (2) a continuous emissions monitor, which measures the pollutant concentration in the source’s emissions. 131 recognizing that analysis of this issue requires a high level of expertise.” White Stallion Energy Ctr., LLC v. EPA, 748 F.3d 1222, 1255 (D.C. Cir. 2014) (per curiam) (citation and internal quotation marks omitted), rev’d on other grounds by Michigan v. EPA, 135 S. Ct. 2699 (2015). Notwithstanding this deference, the Environmental Petitioners argue that allowing a source to demonstrate compliance by way of a thirty-day rolling average not only fails Chevron review but is also arbitrary. We disagree. First, they argue that the thirty-day rolling average fails at Chevron step 1 because it allows sources to emit HAPs continuously at the UPL-established MACT floor. Because they do not believe that the UPL represents the average emissions level achieved by the best performing sources, they argue that, ipso facto, allowing sources to continuously emit HAPs at the UPL level means that sources are permitted to emit at levels higher than the average levels achieved by the best performing sources. Because we have already concluded that the UPL is in fact a reasonable proxy for the average emissions level achieved by the best performing sources, see supra § IV.C, the Environmental Petitioners’ premise is inaccurate. And because the “total emissions from a unit complying with a rolling average must still be below the total emissions from a unit emitting continuously at the level of the standard,” No. 11-1125 EPA Br. 90, the Environmental Petitioners’ Chevron step 1 argument fails. The Environmental Petitioners’ Chevron step 2 argument fares no better. The EPA explained that (1) it expects to catch violations using a thirty-day rolling average “almost as much as for a shorter term average” and (2) it believes the longer average to be more effective in addressing “[c]oncerns of variability outside the operators[’] control such as fuel 132 content, seasonal factors, load cycling, and infrequent hours of needed operation.” 2011 Proposed CISWI Rule on Reconsideration, 76 Fed. Reg. at 80,465. Because the EPA “reasonably articulate[d] the basis for its decision,” we uphold it. White Stallion, 748 F.3d at 1255 (internal quotation marks omitted). Finally, we conclude that the EPA’s allowance of thirtyday rolling averaging does not reflect an arbitrary change in position. Although the Petitioners cite other rules that, in their view, manifest that the EPA once believed that longer averaging periods resulted in less stringent enforcement, most of the rules they cite have nothing to do with MACT-setting or MACT compliance40 and none evidences an unexplained or unjustified deviation. Similarly, the Petitioners point to the EPA’s explanation in the 2011 CISWI Rule that “24-hour block averages . . . would be inconsistent with the sampling time for the stack test data” to indicate an arbitrary change in position. See 76 Fed. Reg. at 15,728. But the EPA made this statement while discussing why stack-test data and continuous-monitoring data could not be used in tandem to set a MACT level, which says nothing about allowing emissions 40 The only exception is the EPA’s 1996 Medical-Waste Incinerators Rule, which provides that “[t]he period of time over which emissions are measured and then averaged to determine compliance with the regulation . . . must correspond to the period of time over which emission levels were measured and averaged in determining the emission limits included in the regulation.” Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Medical Waste Incinerators, 61 Fed. Reg. 31,736, 31,748 (June 20, 1996). This twenty-year-old statement, however, does not detract from the EPA’s well-reasoned defense of the thirty-day rolling average in the CISWI Rule. 133 averaging—long-term or otherwise—to gauge MACT-floor compliance. See id. And even if the Environmental Petitioners had directed us to a real about-face, the EPA’s justification for allowing the thirty-day rolling average convinces us that any change was not arbitrary. J. FUEL-COMBUSTION-BASED SUBCATEGORIES Section 7412 provides that the EPA may distinguish among “classes, types, and sizes” of sources when establishing emission standards. 42 U.S.C. § 7412(c), (d)(1). Under this authority, the EPA created subcategories of major source boilers based on the fuel the boiler was designed to burn. 2013 Major Boilers Rule, 78 Fed. Reg. at 7,144. The Environmental Petitioners challenge this decision on three grounds: First, they claim that the text of the statute forecloses the EPA from creating such subcategories. Next, they argue that the EPA’s subcategories are arbitrary because they permit a boiler to switch subcategories from year to year. Finally, they contend that the EPA’s action was arbitrary because the Agency failed to demonstrate with substantial evidence that burning a different fuel alters the boiler’s class, type, or size. These arguments fail. Section 7412(d) gives the EPA discretion to create subcategories based on boiler type, and nothing in the statute forecloses the Agency from doing so based on the type of fuel a boiler was designed to burn. Nor was the EPA’s decision to create such subcategories arbitrary and capricious. The Agency considered the relevant factors in coming to a reasoned decision that the type of fuel a boiler is designed to burn impacts the feasibility of emission standards. And, finally, the EPA based its technical judgment on sufficient record evidence. As a result, we deny the 134 Environmental Petitioners’ challenge to the EPA’s subcategorization of major source boilers based on the type of fuel the boiler is designed to burn. The Environmental Petitioners first claim that the text of the CAA forecloses the EPA from creating subcategories of “types” of boilers based on the fuel a boiler burns because a single boiler may use different fuels over the course of its lifetime. This may be true, but the Petitioners never explain what it is about the word “type” that bars the EPA from regulating a boiler that burns “x” differently from a boiler that burns “y.” According to its ordinary meaning, “type” is easily broad enough to accommodate changes in boiler characteristics from year to year. See OXFORD ENGLISH DICTIONARY (2013) (defining “type” as a “general form, structure, or character distinguishing a particular kind, group, or class of beings or objects”). There is no textual reason then to assume that a boiler’s type must be written in stone. Nor does our understanding of “type” write it out of the statute, as the Petitioners contend. The EPA has done what the term plainly encompasses: it has distinguished among boilers based on the kind of fuel the boiler burned over the last year. It is thus not surprising that we have interpreted a similar provision to permit distinctions based on fuel inputs. See Sierra Club v. Costle, 657 F.2d 298, 318-19 (D.C. Cir. 1981) (holding that the text of 42 U.S.C. § 7411, which allows the EPA to “distinguish among classes, types and sizes,” permits distinctions based on variations in the sulfur content of coal used by utility plants). Likewise, we conclude that section 7412’s undefined and unrestricted use of class, type, or size does not foreclose the EPA’s interpretation. 135 This court will, as a result, defer to the EPA’s interpretation so long as it is reasonable. See, e.g., Sierra Club I, 353 F.3d at 990. And here, it is. The Agency explained that boilers vary in their designs depending on the type of fuel they burn. 2010 Proposed Major Boilers Rule, 75 Fed. Reg. at 32,016-17. These differences, according to the Agency, affect boiler emissions and the feasibility of emission controls. Id. And, because design constraints also restrict a boiler’s ability to switch fuels, the Agency concluded that it could determine a boiler’s type by looking at the fuel it had burned over the previous 12-month period. Id. at 32,014. The Environmental Petitioners point to nothing in the record that calls into question either of these technical judgments, which receive great deference. See NRDC I, 489 F.3d at 1375. Nor do the Petitioners offer any additional reasons in support of their argument that the Agency has ventured beyond its authority under the statute. In fact, the EPA’s reasoning from the emissions data is consistent with the very existence of a subcategorization authority because the grant of this authority implicitly acknowledges that the EPA may need to set different emission standards within a category of major sources based on what is achievable for a subset of those sources. Because the statutory text readily encompasses the EPA’s interpretation for the reasons explained above, and because the Environmental Petitioners offer no additional argument as to why the EPA’s interpretation was unreasonable, we reject the Petitioners’ Chevron challenge to the EPA’s interpretation of its subcategorization authority. The Environmental Petitioners nevertheless claim that the EPA’s subcategories are arbitrary because a boiler is not of a different type when it can be a boiler “designed to burn coal” one year, and a boiler “designed to burn biomass” the next. But this argument fails for the same reasons as the Chevron 136 argument we just rejected. The fact that boilers may switch from one type to another over time does not, alone, render a subcategorization arbitrary. With no discernable basis to find the EPA’s choice here questionable, much less arbitrary, we reject this argument too. Finally, the Environmental Petitioners contend that the Agency failed to demonstrate with sufficient evidence, rather than mere assertions, that burning a different fuel makes the boiler a different class, type, or size. The Petitioners largely fail to develop this argument and, regardless, the EPA easily met its burden. The EPA based its decision on documented emissions data, several reports provided by the National Energy Technology Laboratory on boiler operations, and operating manuals provided by boiler manufacturers. See, e.g., Summary of Public Comments and Responses for National Emission Standards for Hazardous Air Pollutants for Major Sources: Industrial, Commercial, and Institutional Boilers and Process Heaters, EPA-HQ-OAR-2002-00583511-A1 (Dec. 2012), at 558-63. These sources support the EPA’s decision to distinguish boilers based on the type of fuel they are designed to burn and the Agency’s conclusion that boilers designed for one fuel type are unlikely to use another fuel type. Id. The Petitioners present no contrary evidence, nor do they attack the validity or accuracy of the data that the EPA relied upon. We thus find no merit in the Petitioners’ various challenges to the EPA’s decision to subcategorize major boilers based on the fuel the boiler is designed to burn. K. “UNITS THAT BEGIN COMBUSTING SOLID WASTE” AS “EXISTING” SOURCES Section 7429(a)(2) distinguishes between “existing” and “new” CISWI units. The former must comply with floors set 137 at the “average emissions limitation achieved by the best performing 12 percent of units” and the latter must comply with stricter floors set at the level achieved by “the best controlled similar unit.” 42 U.S.C. § 7429(a)(2). “Modified” units, defined as units “at which modifications have occurred” that either experience changes that cost more than 50 per cent of the original construction price or result in increased emissions, see id. § 7429(g)(3), must be treated as “new,” see id. § 7429(g)(2). The preamble to the 2011 CISWI Rule states, “[u]nits that begin combusting solid waste are considered existing sources.” 76 Fed. Reg. at 15,714 (emphasis added). Commentators objected that this blanket statement contravened the Act’s plain terms, which mandate that the EPA treat such sources as “new,” not “existing,” if they meet the section 7429(g)(3) requirements. In its subsequent 2011 Proposed CISWI Rule on Reconsideration, the EPA refined its position: “An existing source will not be considered a new source solely due to a combustion material switch. Assuming new source applicability is not triggered, existing sources that change fuels or materials are considered existing sources . . . .” 76 Fed. Reg. at 80,459. The Environmental Petitioners argue that the EPA’s broad statement in the 2011 CISWI Rule indicates that it impermissibly changed its treatment of “modified sources” in contravention of the CAA. The EPA, however, agrees that any CISWI unit fitting the statutory criteria for a modified source must comply with new-unit MACT levels, not existing-unit MACT levels. See 42 U.S.C § 7429(g)(2). It also recognizes that its categorical statement in the 2011 CISWI Rule “may have been imprecise” and, in any event, it 138 argues that the Environmental Petitioners have taken its statement out of context. See No. 11-1125 EPA Br. 73. We agree with the Agency. The EPA’s later statement made clear that it intended to treat “sources that change fuels or materials” as “existing sources” unless “new source applicability,” as mandated by the Act, is “triggered.” See 2011 Proposed CISWI Rule on Reconsideration, 76 Fed. Reg. at 80,459. Moreover, the Agency provided its more precise statement while discussing specifically what constitutes a “modification” for the CISWI Rule. See id. (“An existing source will not be considered a new source solely due to a combustion material switch.”). It made its earlier, “imprecise” comment, in contrast, while describing when a fuel change could mean the difference between regulation under section 7412 or section 7429. See 2011 CISWI Rule, 76 Fed. Reg. at 15,714. Convinced that the EPA has not impermissibly changed the statutory definition of “modified” CISWI, we reject the Petitioners’ challenge. L. EXCLUSION OF “TEMPORARY” BOILERS FROM AREA BOILERS RULE In the final 2013 Area Boilers Rule, the EPA excluded “temporary boilers” from regulation under section 7412. See 78 Fed. Reg. at 7,491. The Rule defined “temporary boilers” as “any gaseous or liquid fuel boiler that is designed to, and is capable of, being carried or moved from one location to another by means of, for example, wheels, skids, carrying handles, dollies, trailers, or platforms.” Id. Moreover, a boiler is not a temporary boiler if any of the following apply: 139 (1) The equipment is attached to a foundation. (2) The boiler or a replacement remains at a location within the facility and performs the same or similar function for more than 12 consecutive months, unless the regulatory agency approves an extension. An extension may be granted by the regulatory agency upon petition by the owner or operator of a unit specifying the basis for such a request. Any temporary boiler that replaces a temporary boiler at a location within the facility and performs the same or similar function will be included in calculating the consecutive time period unless there is a gap in operation of 12 months or more. (3) The equipment is located at a seasonal facility and operates during the full annual operating period of the seasonal facility, remains at the facility for at least 2 years, and operates at that facility for at least 3 months of each year. (4) The equipment is moved from one location to another within the facility but continues to perform the same or similar function and serve the same electricity, steam, and/or hot water system in an attempt to circumvent the residence time requirements of this definition. 2013 Area Boilers Rule, 78 Fed. Reg. at 7,491-92. 140 Environmental Petitioners challenge this exclusion as a violation of the EPA’s obligations under the CAA to regulate all boilers listed under section 7412. By its own terms, the 2011 Area Boilers Rule “applies to all existing and new industrial boilers, institutional boilers, and commercial boilers located at area sources. Boiler means an enclosed combustion device having the primary purpose of recovering thermal energy in the form of steam or hot water.” 76 Fed. Reg. at 15,557; see also 76 Fed. Reg. at 15,554 (“EPA is promulgating national emission standards for control of hazardous air pollutants from two area source categories: Industrial boilers and commercial and institutional boilers.”). Environmental Petitioners claim the general term “boiler” necessarily encompasses temporary boilers: “[T]he category of ‘boilers’ plainly includes temporary boilers, just as the category of ‘courts’ includes federal courts, or the category of ‘dogs’ includes brown dogs.” No. 11-1141, Envtl. Pet’rs’ Reply Br. 7. According to Petitioners, then, sections 7412(c) and 7412(d) of the CAA require the EPA to issue emission standards for temporary boilers as well as “permanent” boilers. See 42 U.S.C. § 7412(c)(2) (“For the categories and subcategories the Administrator lists, the Administrator shall establish emission standards . . . .”); id. § 7412(d)(1) (“The Administrator shall promulgate regulations establishing emission standards for each category or subcategory of major sources and area sources of hazardous air pollutants listed for regulation . . . .”). To the extent Environmental Petitioners challenge as unreasonable the EPA’s justifications for declining to set emission standards for temporary boilers, they cannot prevail. “Under arbitrary-and-capricious review, EPA’s determinations are presumptively valid provided [they] meet[] a minimum rationality standard.” Nat’l Ass’n for Surface 141 Finishing, 795 F.3d at 7 (internal quotation marks omitted). So the question is whether the EPA offered a sufficiently rational explanation for its exclusion of temporary boilers. The EPA has done so here. First, contrary to Petitioners’ claims, temporary boilers were never considered an inexorable part of the “industrial boiler” category section 7412 requires the EPA to regulate. While the EPA only listed generic area source categories—“industrial boilers” and “institutional/commercial boilers”—in its 1999 rulemaking, it has since refined these broad categories pursuant to its statutory authority. See National Air Toxics Program: The Integrated Urban Strategy, 64 Fed. Reg. 38,706, 38,721 tbl.2 (July 19, 1999). In doing so, the EPA excluded several other subgroups of boilers that might otherwise be read as falling under one of the general boiler categories. See, e.g., 2013 Area Boilers Rule, 78 Fed. Reg. at 7,492 (excluding boilers already regulated by other MACT standards); 2011 Proposed Area Boilers Rule on Reconsideration, 76 Fed. Reg. at 80,539 (excluding electric and residential boilers as not part of either source category). The EPA’s clarification that temporary boilers were never considered part of the “industrial boilers” category was simply another refinement, as contemplated by the statute. See 42 U.S.C § 7412(e)(4) (precluding judicial review until the EPA has issued its final emission standards for a category or subcategory). Second, as both the EPA and Industry Intervenors note, the parallel rule for major source boilers has always explicitly excluded temporary boilers from its “industrial boiler” categorization. See 40 C.F.R. § 63.7491(j). The EPA thus considered commenters’ requests to add a similar clarification to the 2013 Area Boilers Rule and reasonably decided to do so. See, e.g., American Forest & Paper Association, Comments on Proposed Area Source Rule (AF&PA 142 Comments), EPA-HQ-OAR-2006-0790-1939 (Aug. 23, 2010), at 58 (No. 11-1141 J.A. 389). EPA explained this choice in its proposed rule: Owners and operators of regulated sources have pointed out that temporary boilers are small (less than 10 MMBtu/hr heat input) and are generally owned and operated by contractors, rather than the facility. As a result, they are not included in the facility’s operating permits because state and federal CAA operating permit programs have historically classified such units as insignificant sources. The owners and operators also noted that compliance with the work practice requirements applicable to these small boilers would be complicated because they are typically located on site for less than a year, but would be subject to biennial management practice requirements. We agree that the source category identified in subpart JJJJJJ should specifically exclude these temporary boilers because they have been considered insignificant sources, and were not included in the EPA’s analysis of the source category. 2011 Proposed Area Boilers Rule on Reconsideration, 76 Fed. Reg. at 80,535. The unique nature of temporary boilers favors their exclusion. These boilers tend to be rented for use on a temporary basis and come in “shop-fabricated package designs.” AF&PA Comments, at 58 (No. 11-1141 J.A. 389). 143 Temporary boilers also “typically only fire gas or liquid fossil fuels (natural gas or distillate oil) which may be cleaner than the boiler(s) they are temporarily replacing. In addition, these units often do not have exhaust stacks that meet EPA Method 1 requirements for application of test methods.” Id. Regardless, during the rulemaking, Environmental Petitioners argued the EPA had “not explained why this is a distinction that justifies differential treatment, let alone an exemption.” See Area Boilers Rule—Responses to Comments, at 65. The EPA responded by explaining that rather than having “created a category or subcategory of ‘temporary boilers’ and then exempted them from the standards,” the Agency never “intend[ed] to regulate temporary boilers under the area source standards” in the first place. See id. The EPA further noted that, “[b]y their nature of being temporary, these boilers operate in place of another non-temporary boiler while that boiler is being constructed, replaced or repaired, in which case we counted the non-temporary boiler as the one being regulated.” Id. Finally, the Agency concluded regulation of temporary boilers was not necessary to meet its statutory emission requirements under sections 7412(c)(6) and 7412(c)(3) of the CAA. Id. In its final rule, the EPA reiterated this explanation: “Similar to residential boilers, we did not intend to regulate temporary boilers under the area source standards because they are not part of either the industrial boiler source category or the commercial/institutional boiler source category.” 2013 Area Boilers Rule, 78 Fed. Reg. at 7,491. The final regulation also included a detailed explanation of how EPA decided on its limited definition of “temporary boilers.” See id. at 7,499. The evidence before the Agency supported its decision to exclude temporary boilers. Indeed, the EPA “cogently explain[ed]” why it exercised its discretion in this manner, 144 such that this court concludes the Agency’s choice “was the product of reasoned decision making.” U.S. Telecom Ass’n v. FCC, 227 F.3d 450, 460 (D.C. Cir. 2000). We therefore uphold the EPA’s exclusion of temporary boilers from regulation of area source boilers. M. WORK-PRACTICE STANDARDS FOR COAL-FIRED BOILERS When setting emission limits for area sources, the EPA enjoys greater discretion than when setting limits for major sources. With respect to major sources, the EPA has to promulgate MACT standards, see 42 U.S.C. § 7412(d)(2), whereas for area sources the EPA can generally promulgate more lenient GACT standards, see id. § 7412(d)(5). The CAA, however, singles out seven particularly hazardous pollutants that require stricter regulatory standards, even for area sources.41 Under section 7412(c)(6), the EPA must “list categories and subcategories of sources assuring that sources accounting for not less than 90 per centum of the aggregate emissions of each such pollutant” are regulated. The EPA listed a variety of area sources under section 7412(c)(6) in its 1998 rulemaking based on their Hg and POM emissions. See Proposed 2010 Area Boilers Rule, 75 Fed. Reg. at 31,898; Source Category Listing for Section 112(d)(2) Rulemaking Pursuant to Section 112(c)(6) Requirements, 63 Fed. Reg. 17,838, 17,849-50 (Apr. 10, 1998). But the Agency subsequently refined that list and ultimately concluded only 41 These seven pollutants are: (i) alkylated lead compounds, (ii) polycyclic organic matter (POM), (iii) hexachlorobenzene, (iv) mercury (Hg), (v) polychlorinated biphenyls, (vi) 2,3,7,8- tetrachlorodibenzofurans, and (vii) 2,3,7,8-tetrachlorodibenzo-p- dioxin. See 42 U.S.C. § 7412(c)(6). 145 coal-fired area boilers needed to be listed to meet the statute’s 90 per cent emissions threshold. See 2010 Proposed Area Boilers Rule, 75 Fed. Reg. at 31,898; see also No. 11-1141 EPA Br. 14 (“[T]he coal-fired subcategory is responsible for over 82 percent of the mercury emissions from the [area source] category in the inventory, even though it represents only 2 percent of the boilers in the category.”). Under section 7412(c)(6), the EPA was therefore required to set either a MACT limit under section 7412(d)(2), a health threshold under section 7412(d)(4), or a workpractice standard under section 7412(h) for all coal-fired boilers. The Agency chose to set MACT numerical emission limits for Hg and CO42 at new and existing large coal-fired boilers. 2013 Area Boilers Rule, 78 Fed. Reg. at 7,488. However, the EPA found it “technologically and economically impracticable to apply [its] measurement methodology to . . . small sources,” and so it chose to institute a work-practice standard43 for all new and existing small coalfired boilers. Id. at 7,488-89. This work-practice standard requires small coal-fired units to be periodically tuned up but does not impose any numeric emission limit. See id. The EPA similarly decided that, for large coal-fired boilers undergoing a startup or a shutdown, a work-practice standard—rather than a numeric emission standard—was 42 Because the EPA chose to regulate POM emissions indirectly—by using CO emissions as a surrogate—the standards it set under section 7412(c)(6) are for CO rather than POM. See 2013 Area Boilers Rule, 78 Fed. Reg. at 7,488, 7,503. 43 In their brief, Environmental Petitioners alternate between the terms “operational standards” and “work-practice standards,” both of which fall under section 7412(d)(2)(D). This opinion will use “work-practice standards” for simplicity. 146 most practicable. See id. at 7,518 tbl.2 (requiring owners of large “[e]xisting or new coal-fired” boilers to “[m]inimize the boiler’s startup and shutdown periods and conduct startups and shutdowns according to the manufacturer’s recommended procedures”). Environmental Petitioners challenge the EPA’s decision to employ work-practice standards as a violation of 7412(d)(2)’s mandate to achieve the “maximum degree of reduction in emissions.” We examine Petitioner’s statutory argument step-by-step, as it hinges on the interplay between several statutory provisions. First, section 7412(c)(6)—which governs regulation of Hg and POM emissions—requires the Administrator to regulate sources of these pollutants under either section 7412(d)(2) or (d)(4). Section 7412(d)(4) allows the Administrator to establish health-based emission standards; it is not implicated here. Instead, the EPA decided to regulate coal-fired boilers under section 7412(d)(2). Section 7412(d)(2) instructs the Administrator to achieve “the maximum degree of reduction in emissions of the hazardous air pollutants . . . that the Administrator, taking into consideration the cost of achieving such emissions reduction, and any non-air quality health and environmental impacts and energy requirements, determines is achievable for new or existing sources.” The Administrator is authorized to use several means to achieve this reduction including implementing “design, equipment, work practice, or operational standards . . . as provided in [section 7412(h)].” 42 U.S.C. § 7412(d)(2)(D). Section 7412(h)(1) states: “[I]f it is not feasible in the judgment of the Administrator to prescribe or enforce an emission standard for control of a [pollutant], the Administrator may, in lieu thereof, promulgate a . . . work-practice standard . . . , which in the Administrator’s judgment is consistent with the provisions of 147 subsection (d) or (f) of this section.” Petitioners do not dispute the EPA’s ability to set work-practice standards here; they instead focus on section 7412(h)’s requirement that any such standards be “consistent with” subsection (d)—which requires the “maximum degree of reduction in emissions.” According to Petitioners, the EPA’s decision to set these particular work-practice standards fails at both Chevron steps. With respect to Chevron step 1, Petitioners argue the “EPA does not claim the operational standards [for coal-fired boilers] are ‘consistent with the provisions of subsection (d) or (f)’ of § 7412.” No. 11-1141 Envtl. Pet’rs’ Br. 33. In other words, because these work-practice standards “do not even purport” to be consistent with section 7412(d)’s mandate to maximize reduction of emissions, “they are unlawful under Chevron step one.” Id. Petitioners point to the EPA’s specific findings to support this claim: for large coal-fired boilers, the EPA found that mercury emissions could be reduced by 75 to 82 per cent through the use of a fabric filter. Id. But, according to Petitioners, the “EPA admits the tuneup program [for small coal-fired boilers] will reduce emissions by only one percent.” Id. And, with respect to large coal-fired boilers undergoing startup or shutdown, Petitioners argue the “EPA does not claim that ‘following the manufacturer’s recommended procedures’ during startup and shutdown will reduce emissions at all.” Id. At the familiar Chevron step 1, the court must “first examine the statute de novo, employing traditional tools of statutory construction.” Nat’l Ass’n of Clean Air Agencies, 489 F.3d at 1228 (internal quotation marks omitted). If the Congress’s intent is clear, then the Agency’s interpretation is afforded no deference, and the court “must give effect to the unambiguously expressed intent of Congress.” Id. 148 In this case, Environmental Petitioners place too much emphasis on certain snippets of the statute without examining the larger context. For one, Petitioners seem to argue that the EPA must adopt work-practice standards that result in the maximum possible reduction of emissions, without taking into account any other considerations. But section 7412(d)(2) itself belies this claim: it says the EPA must promulgate standards that require “the maximum degree of reduction in emissions . . . that the Administrator, taking into consideration the cost of achieving such emission reduction, and any non-air quality health and environmental impacts and energy requirements, determines is achievable.” 42 U.S.C. § 7412(d)(2) (emphasis added). This portion of the statute explicitly defers to the Administrator’s judgment regarding a standard’s “achievability,” even though it directs him to consider particular factors in making that assessment. Section 7412(h) similarly requires the Administrator to adopt a work-practice standard that in his judgment is consistent with section 7412(d)(2)’s mandate. We therefore cannot accept Petitioners’ suggestion that Congress unambiguously required the EPA to adopt standards that result in the maximum reduction of emissions that is technologically feasible. Environmental Petitioners’ challenge to these workpractice standards as unreasonable under Chevron step 2 and arbitrary under State Farm presents a closer call. With respect to Chevron step 2, the court must “uphold an agency’s interpretation if it is reasonable.” Ariz. Pub. Serv. Co. v. EPA, 211 F.3d 1280, 1287 (D.C. Cir. 2000). And, “even where EPA’s construction satisfies Chevron, [the court] still must ensure that its action is not otherwise arbitrary and capricious. The arbitrary and capricious standard is ‘[h]ighly deferential,’ and it ‘presumes the validity of agency action.’” Nat’l Ass’n 149 of Clean Air Agencies, 489 F.3d at 1228 (citations omitted). As long as an agency has “considered the relevant factors and articulated ‘a rational connection between the facts found and the choice made,’” then its decision must be upheld. Allied Local & Reg’l Mfrs. Caucus, 215 F.3d at 68. Petitioners mount both a “facial” and a substantive challenge to the EPA’s rationale for adopting work-practice standards. First, Petitioners claim the EPA’s decision is arbitrary because it fails “to reconcile its approach with the statutory requirement [of section 7412(d)(2)].” No. 11-1141 Envtl. Pet’rs’ Br. 34. Specifically, Petitioners insist the EPA must explicitly state somewhere that these particular workpractice standards are “consistent” with section 7412(d)(2). See id. at 33-34. Otherwise, Petitioners contend, the Court must simply “assume that the Agency heeded § 7412(h)’s ‘consistent with’ requirement, notwithstanding the EPA’s failure to acknowledge and apply that requirement in the record.” No. 11-1141 Envtl. Pet’rs’ Reply Br. 10. The Agency responds that, “by identifying the tune-up and startup/shutdown requirements as ‘work practices,’ [it] is stating that those standards are issued under section 7412(h) and are consistent with the requirements of section 7412(d) (i.e., MACT).” No. 11-1141, EPA Br. 71. The EPA did acknowledge it has an obligation to maximize emission reductions under section 7412(d)(2) when promulgating work-practice standards. See 2011 Area Boilers Rule, 76 Fed. Reg. at 15,568 (“CAA section 112(h) authorizes the Administrator to promulgate [a work-practice standard] consistent with the provisions of CAA sections 112(d) or (f) . . . .”). However, Petitioners are correct that the Agency did not make a finding on the record that these work-practice 150 standards would achieve the highest emissions reduction possible. But the lack of an explicit statement does not automatically condemn this portion of the rule. See Bowman, 419 U.S. at 286 (“[W]e will uphold a decision of less than ideal clarity if the agency’s path may reasonably be discerned.”). The Petitioners offer no support for their contention that the EPA must make an express finding that its standards are “consistent” with section 7412(d)(2). Nor does our conclusion requires us to merely “assume” that the Agency’s actions comport with section 7412(d)(2). Instead, as we usually do when presented with such arguments, we review the rulemaking record to determine whether the justifications the EPA offered for adopting these work practices standards were permissible. 1. Small Coal-Fired Boilers First, with respect to small coal-fired boilers, the EPA determined that a biennial tune-up requirement would best comply with section 7412(h)’s requirements. As a starting point, the EPA surveyed a sample of state regulations mandating various work-practice standards for small coalfired boilers; the Agency found that ten states required tuneups, two required periodic inspections, one required operator training, and one required operation in accordance with manufacturer specifications. 2011 Area Boilers Rule, 76 Fed. Reg. at 15,573-74. The EPA thus concluded that tune-ups were the most typical work-practice standard employed for this type of boiler. Id. The Agency also found that regular tune-ups could lower HAP emissions by increasing the efficiency of small coal-fired boilers. See id. at 15,575 (“A tune-up performed to the manufacturer’s specifications would 151 ensure the highest energy efficiency and reduce fuel usage, which will ultimately reduce HAP emissions.”); see also 2010 Proposed Area Boilers Rule, 75 Fed. Reg. at 31,908 (“A boiler tune-up provides potential savings from energy efficiency improvements and pollution prevention. . . . In addition, the cost of a boiler tune-up appears minimal compared to the cost for testing and monitoring to demonstrate compliance with an emission limit.”).44 The EPA elected to implement a work-practice standard because the typical method used to measure emissions of Hg and CO could not be used to sample emissions from stacks with small diameters (less than 12 inches). See 2011 Area Boilers Rule, 76 Fed. Reg. at 15,568. Because many small coal-fired boilers have stacks with diameters below 12 inches—and because many of these boilers “do not currently have sampling ports or a platform for accessing the exhaust stack”—the Agency concluded the cost of testing and monitoring these small boilers would “present an excessive burden for smaller sources.” Id. The Agency’s consideration of cost effectiveness is particularly appropriate in this context because the “vast majority” of area source boilers are “generally owned and operated by small entities,” which would be disproportionately burdened by a numeric emissions limit. See Fact Sheet: Final Adjustments to the Air Toxics Standards for Industrial, Commercial, and Institutional Boilers at Area Source Facilities, 1, 2 (No. 11-1141 J.A. 68444 The EPA’s discussion of boiler tune-up advantages occurs mainly in the context of its decision to select a GACT standard rather than any numeric emission standards for certain boilers. Environmental Petitioners challenge this decision on similar grounds, see supra § IV.H. But the benefits of periodic tune-ups also apply to the coal-fired boilers at issue here. 152 85); see also 2010 Proposed Area Boilers Rule, 75 Fed. Reg. at 31,906 (“The results of the analysis indicate that total compliance costs exceed 3 percent (and can reach as high as 19 percent) of the average firm revenues for 79 percent of the facilities.”). Environmental Petitioners counter that while tune-ups may minimally reduce HAP emissions, they do not maximize this reduction per section 7412(d)(2)’s mandate.45 But Petitioners view section 7412(d) too myopically; under that section, the Administrator is empowered to adopt standards that “tak[e] into consideration the cost of achieving such emission reduction.” 42 U.S.C. § 7412(d)(2). The EPA here examined the costs of imposing a numeric emission standard on small coal-fired boilers and found that option “not feasible” due to high costs and monitoring difficulties, considerations equally permissible under section 7412(d)(2). Petitioners argue that requiring the use of a fabric filter would have resulted in greater reductions, but they are unable to point to any small coal-fired boiler that currently uses such a filter. See 2010 Proposed Area Boilers Rule, 75 Fed. Reg. at 31,906 (“For existing [small] area source boilers, the only work practice being used that potentially controls mercury 45 Petitioners also point to a comment they made in the record arguing that a tune-up standard “would not achieve emission reductions that are consistent with the definition of MACT,” and urge that the EPA never addressed these concerns. See National Association of Clean Air Agencies, Comments on EPA Proposals for Regulation of Hazardous Air Pollutants (HAPS), EPA-HQOAR-2006-0790, EPA-HQ-OAR-2002-0058, EPA-HQ-OAR2003-0119 (Aug. 23, 2010), at 21-22 (No. 11-1141 J.A. 417-18). But this comment was specifically addressed to gas-fired boilers, and it is inapposite to the EPA’s consideration of standards for coal-fired boilers. 153 and POM emissions is a boiler tune-up.”). Evidence before the agency in fact indicated that the best performing small coal boilers for POM emission use no add-on controls. See Memorandum from Amanda Singleton & Brandon Long, Eastern Research Group, to Jim Eddinger, EPA (MACT/GACT Mem.), App. E-2a (No. 11-1141 J.A. 540). It was therefore reasonable for the EPA, when considering costs, to conclude that biennial tune-ups would allow for the maximum “achievable” reduction in emissions. Petitioners’ most compelling argument involves the EPA’s lack of data on small coal-fired boilers. As they point out, the EPA’s summary of its 2008 combustion survey makes no mention of any small coal-fired boilers. See MACT/GACT Mem., App. D-3, tbl.1 (No. 11-1141 J.A. 523). And the EPA never directly addressed whether control technologies, such as fabric filters, were useable by small boilers; “[t]he only claim EPA made in the record is that tuneups are the most effective option that [small] coal-fired boilers . . . are currently using, not that tune-ups yield the maximum reduction ‘achievable.’” No. 11-1141 Envtl. Pet’rs’ Reply Br. 11. In Sierra Club II, this court agreed with Sierra Club’s challenge to the EPA’s use of a work-practice standard instead of an emission floor because the “EPA never determined that measuring emissions from ceramics kilns was impracticable; it determined only that it lacked emissions data from ceramics kilns. EPA thus had no basis under section 7412(h) for using work practice standards.” 479 F.3d at 884. That context is somewhat distinguishable, given that the statute there explicitly required the EPA to make a “feasibility” finding (as discussed above), but it could be argued that the EPA here lacked the data to determine whether tune-ups were “consistent with” section 7412(d)(2). 154 Ultimately, though, the high level of deference afforded the EPA counsels in favor of upholding this work-practice standard. Although the EPA did not explicitly state that tuneups were the best option to reduce emissions while still “considering costs,” this finding can be inferred from the record as a whole. For instance, the EPA found that “[n]one of the States for which we have an inventory have an applicable emissions limit” for small coal-fired boilers, except New Jersey, which actually has tune-ups as its work-practice standard. 2010 Proposed Area Boilers Rule, 75 Fed. Reg. at 31,909. Based on these findings, it can reasonably be inferred that—given the prevalence of these small boilers—at least a few would be using a control technology if that were technologically or economically feasible. Because numeric emissions cannot easily be measured from these smaller sources and the costs of outfitting them with such technology would be cost prohibitive, the EPA’s choice of tune-ups as the work-practice standard is sufficiently reasonable to uphold under both Chevron step 2 and State Farm. The Agency’s choice is consistent with section 7412(h)’s “feasibility” requirement and with section 7412(d)(2)’s instruction to maximize emission reductions while also considering costs. 2. Large Coal-Fired Boilers Undergoing Startup or Shutdown The record for large coal-fired boilers undergoing startup or shutdown is less extensive but again the EPA’s determination is reasonable. While large coal-fired boilers are required to meet numeric emission standards during “normal” operations, the EPA adopted a work-practice standard for the temporary periods of startup and shutdown. See 40 C.F.R. § 63.11214 (“[M]inimize the boiler’s startup and shutdown periods following the manufacturer’s 155 recommended procedures, if available. If manufacturer’s recommended procedures are not available, you must follow recommended procedures for a unit of similar design for which manufacturer’s recommended procedures are available.”). Environmental Petitioners contend that the EPA never stated this practice would reduce emissions at all, and therefore it has not met its burden under section 7412(d)(2). But we have already explained that no express finding of consistency with section 7412(d)(2) need be made. Here, the record suggests that the work-practice standard the Agency chose would reduce emissions, and we therefore can “reasonably [] discern[]” the Agency’s path. Bowman, 419 U.S. at 286. Specifically, the EPA explained that requiring boilers to operate in startup and shutdown mode for “sufficient time to conduct the required test runs [to impose numeric standards] could result in higher emissions than would otherwise occur.” 2011 Major Boilers Rule, 76 Fed. Reg. at 15,642. Industry stakeholders also pointed out that “it is very common . . . for certain control devices to be out of operation during periods of start-up due to the nature of the equipment.” See American Chemistry Council, Comments on EPA’s Proposed Rule for National Emission Standards for Hazardous Air Pollutants for Area Sources, EPA-HQ-OAR2006-0790 (Aug. 23, 2010), at 31 (No. 11-1141 J.A. 386). Because the control technology is temporarily offline, “it is likely that emissions will exceed the standards proposed [during that time period].” Id. A work-practice standard that requires facilities to minimize the time their boilers spend in startup or shutdown thus seems calculated to maximally reduce emissions during those periods—and Petitioners fail to provide any viable alternative. We therefore conclude the EPA’s decision to adopt these work-practice standards for large coal-fired boilers during startup and shutdown was reasonable. 156