Opinion for the court filed by Circuit Judge HENDERSON.
Concurring opinion filed by Circuit Judge RANDOLPH.
Opinion concurring in part and dissenting in part filed by Circuit Judge ROGERS.
KAREN LeCRAFT HENDERSON, Circuit Judge.
We address in this proceeding five petitions seeking review of two separate rules promulgated by the Environmental Protection Agency (EPA): (1) the National Emission Standards for Hazardous Air Pollutants for Industrial, Commercial, and Institutional Boilers and Process Heaters, 69 Fed.Reg. 55,218 (Sept. 13, 2004), as amended on recons., 70 Fed.Reg. 76,918 (Dec. 28, 2005), (Boilers Rule), promulgated pursuant to section 112 of the Clean Air Act (CAA), 42 U.S.C. § 7412; and (2) the Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Commercial and Industrial Solid Waste Incineration Units, 70 Fed.Reg. 55,568 (Sept. 22, 2005) (CISWI Definitions Rule), amending Standards of Performance for New Stationary Sources and Emissions Guidelines for Existing Sources: Commercial and Industrial Solid Waste Incineration Units, 65 Fed.Reg. 75,338 (Dec. 1, 2000) (CISWI Rule), promulgated pursuant to CAA section 129, 42 U.S.C. § 7429. Four environmental organizations — the Natural Resources Defense Council, the Sierra Club, the Environmental Integrity Project and the Louisiana Environmental Action Network (collectively, Environmental Petitioners)^ — challenge the CISWI Definitions Rule on the ground that its narrow definition of “commercial or industrial waste” contradicts the plain language of CAA section 129 and therefore impermissibly constricts the class of “solid waste incineration unit[s]” that are subject to the emission standards of the CISWI Rule. The Environmental Petitioners also challenge specific emission standards that EPA promulgated in the Boilers Rule and EPA’s methodology for setting them. A second set of petitioners — the American Municipal Power-Ohio, Inc. and six of its members, the cities of Dover, Hamilton, Orr-ville, Painesville, Shelby and St. Mary’s, (collectively, Municipal Petitioners) — challenges the Boilers Rule on the grounds that EPA failed to comply with the requirements of the Regulatory Flexibility [418]*418Act, 5 U.S.C. §§ 601 et seq., and that the standards as applied to small municipal utilities are unlawful. For the reasons set out below, we conclude that EPA’s definition of “commercial or industrial waste,” as incorporated in the definition of “commercial and industrial solid waste incineration unit” (CISWI unit), is inconsistent with the plain language of section 129 and that the CISWI Definitions Rule must therefore be vacated. We further conclude that, because the Boilers Rule must be substantially revised as a consequence of our vacatur and remand of the CISWI Definitions Rule, the Boilers Rule as well must be vacated.
I.
We first set out the statutory and regulatory background of the two challenged rules.
A. The Boilers Rule
CAA section 112 requires EPA to set a national emission standard for each category or subcategory of “major sources” of “hazardous air pollutant” (HAP) emissions, 42 U.S.C. § 7412(d)(1), that is, of stationary sources that emit (or have potential to emit) “10 tons per year or more of any [HAP] or 25 tons per year or more of any combination of [HAPs],” id. § 7412(a)(1).1 Section 112, as in effect until 1990, directed the EPA Administrator to “establish any such standard at the level which in his judgment provides an ample margin of safety to protect the public health from such hazardous air pollutant.” 42 U.S.C. § 7412(b)(1)(B) (1990). In 1990, the Congress amended section 112 to require technology-based standards in place of the previous risked-based standards. Clean Air Act Amendments, Pub.L. No. 101-549, 104 Stat. 2399 (1990). Under the 1990 CAA Amendments, EPA sets emission standards based on the “maximum achievable control technology” or “MACT” in a two-step process.
First, EPA identifies a MACT floor for each pollutant and source category. For “new sources” of HAP emissions, the MACT floor is “the emission control that is achieved in practice by the best controlled similar source, as determined by the [EPA] Administrator”; for “existing sources,” the MACT floor is “the average emission limitation achieved by the best performing 12 percent of the existing sources” or, if there are fewer than 30 sources, “the average emission limitation achieved by the best performing 5 sources.” 42 U.S.C. § 7412(d)(3). In the second step of the process, EPA selects as its technology-based standard either the applicable MACT floor identified in the first stage or a “beyond the floor” limitation more stringent than the MACT if such a standard is “achievable” in light of costs and other factors and methods listed in section 7412(d)(2). See generally Cement Kiln Recycling Coal. v. EPA, 255 F.3d 855, 857-58 (D.C.Cir.2001) (per curiam) (explaining two-step MACT process for hazardous waste combustors); Nat’l Lime Ass’n v. EPA, 233 F.3d 625, 628-29 (D.C.Cir.2000) (explaining two-step MACT process for portland cement manufacturing plants).
On September 13, 2004, EPA issued the Boilers Rule, which identified 18 subcategories of boilers emitting four different types of HAPs. See 69 Fed.Reg. at 55,223-24. EPA set out to establish the MACT floor for each subcategory emitting each [419]*419HAP according to the effectiveness of various add-on technologies. See 68 Fed.Reg. 1660, 1674 (Jan. 13, 2003) (proposed rule). Applying this methodology, EPA set 25 numerical emission standards. For the remaining 47 boiler subeategory/HAP emissions, EPA determined that the appropriate MACT floor was “no emissions reduction” because “the best-performing sources were not achieving emissions reductions through the use of an emission control system and there were no other appropriate methods by which boilers and process heaters could reduce HAP emissions.” 69 Fed.Reg. at 55,233. Accordingly, EPA adopted a “no control” standard, id., and, in addition, it set risk-based standards, also known as health-based standards, as alternatives to the MACT-based standards for hydrogen chloride and manganese. Id. at 55,227, 55,255.
On November 12, 2004, the Municipal Petitioners filed a petition for review of the Boilers Rule, challenging its Regulatory Flexibility Act certification and its treatment of small municipal utilities. The same day, the Environmental Petitioners filed both a petition for judicial review of the Boilers Rule and an administrative petition for reconsideration by EPA, challenging the no control standard and the risk-based alternatives. By notice published June 27, 2005, EPA granted reconsideration in part and solicited comments on the health-based compliance alternative for manganese in particular and, in general, the methodology for demonstrating eligibility for and compliance with health-based alternatives. 70 Fed.Reg. 36,907 (June 27, 2005). On July 29, 2005, the Environmental Petitioners filed a petition for review of the reconsideration notice insofar as it denied reconsideration in other respects. On December 28, 2005, EPA issued a reconsideration decision which modified the health-based alternative methodology. 70 Fed.Reg. 76,918 (Dec. 28, 2005). The Environmental Petitioners then filed another petition for review of the Boilers Rule on February 14, 2006.
B. The CISWI Definitions Rule
In addition to amending section 112, the 1990 CAA amendments also added section 129, which requires EPA to establish specific performance standards, including emission limitations, for “solid waste incineration units” generally, 42 U.S.C. § 7429(a)(1)(A), and, in particular, for “solid waste incineration units combusting commercial or industrial waste,” id. § 7429(a)(1)(D). Section 129 defines “solid waste incineration unit” as “a distinct operating unit of any facility which combusts any solid waste material from commercial or industrial establishments or the general public (including single and multiple residences, hotels, and motels).” Id. § 7429(g)(1) (emphases added). The statute includes four express exceptions to this definition for: (1) units requiring a permit under 42 U.S.C. § 6925, (2) “materials recovery facilities ... which combust waste for the primary purpose of recovering metals,” (3) qualifying “small power production facilities” and “cogeneration facilities” which combust “homogeneous waste” “for the production of electric energy or ... for the production of electric energy and steam or forms of useful energy (such as heat) which are used for industrial, commercial, heating or cooling purposes” and (4) qualifying “air curtain incinerators” that burn only “wood wastes, yard wastes and clean lumber.” Id. § 7429(g)(1).
Like the section 112 standards, section 129 standards are based on a MACT floor, which is substantially the same as under section 112: for new sources, it is “the emissions control that is achieved in practice by the best controlled similar unit”; for existing units, it is “the average emissions limitation achieved by the best [420]*420performing 12 percent of units in the category.” Id. § 7429(a)(2). Also, as with section 112 standards, EPA is to establish an above-the-floor standard if EPA determines it is “achievable” taking into account costs and other factors. Id.; see Ne. Md. Waste Disposal Auth. v. EPA, 358 F.3d 936, 944 (D.C.Cir.2004) (per curiam). Although section 129 “establishes emission requirements virtually identical to section [112’s],” Nat'l Lime Ass’n v. EPA, 233 F.3d at 631, the statutes nonetheless differ in two respects of particular significance here. First, as noted above, section 112’s MACT standards apply only to “major” sources of HAP emissions, while section 129’s MACT standards apply across the board to all solid waste incineration disposal units in a given category. Compare 42 U.S.C. § 7412(d)(1) (“The [EPA] 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 pursuant to subsection (c) of this section ....”) with id. § 7429(a)(1)(A) (“The [EPA] Administrator shall establish performance standards and other requirements pursuant to [42 U.S.C. § 7411] and this section for each category of solid waste incineration units.”). Second, section 129 requires that emission standards be set for certain pollutants that are not classified as section 112 HAPs (at least not in section 112’s “initial list,” see supra note 1) and therefore are not subject to section 112’s MACT standards, e.g. sulphur dioxide, nitrogen oxides and particulate matter. Compare id. § 7429(a)(4) with id. § 7412(b)(1). Finally, the Congress made section 129’s standards and section 112’s standards mutually exclusive by directing that “no solid waste incineration unit subject to performance standards under this section and [42 U.S.C. § 7411] shall be subject to standards under section 7412(d).” Id. § 7429(h)(2).
On December 1, 2000, EPA issued the CISWI Rule, setting emission standards for commercial and industrial solid waste incinerators pursuant to section 129. The Sierra Club filed a petition for review and the Louisiana Environmental Action Network and the National Wildlife Federation filed a petition for reconsideration by EPA, objecting that EPA had not subjected the rule’s definitions to comment. EPA granted the motion for reconsideration and filed a motion for voluntary remand, which the court granted on September 6, 2001.
On remand, EPA solicited comments on the CISWI Rule’s definitions of “solid waste,” “commercial and industrial waste” and “CISWI unit.” Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Commercial or Industrial Solid Waste Incineration Units, 69 Fed.Reg. 7390 (Feb. 17, 2004). On September 22, 2005, after receiving comments, EPA issued the CI-SWI Definitions Rule, which, as relevant here, contains definitions that are substantively the same as before reconsideration. The CISWI Definitions Rule defines a “commercial or industrial solid waste incineration unit,” in relevant part, as “any combustion unit that combusts commercial or industrial waste (as defined in this sub-part)” and then defines “commercial or industrial waste” to include only waste that is combusted at a facility that cannot or does not use a process that recovers thermal energy from the combustion for a useful purpose. 70 Fed.Reg. at 55,580-81 (codified at 40 C.F.R. § 60.2265).2 The [421]*421Environmental Petitioners filed a petition for review of the CISWI Definitions Rule on November 21, 2005.
II.
A. CISWI Definitions Rule
The Environmental Petitioners challenge EPA’s definition of “CISWI unit” insofar as it incorporates EPA’s definition of “commercial or industrial waste,” asserting that it is inconsistent with the plain language of section 129. We review the Environmental Petitioners’ challenge to EPA’s interpretation of section 129 under the two-step framework established in Chevron U.S.A. Inc. v. Natural Resources Defense Council, Inc., 467 U.S. 837, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984). See Ne. Md. Waste Disposal Auth., 358 F.3d at 944 (“Chevron ... governs our review of Industry Petitioners’ claim that the 2000 Rule conflicts with § 129(a)(2).”). Under Chevron:
We first ask “whether Congress has directly spoken to the precise question at issue,” in which case we “must give effect to the unambiguously expressed intent of Congress.” If the “statute is silent or ambiguous with respect to the specific issue,” however, we move to the second step and defer to the agency’s interpretation as long as it is “based on a permissible construction of the statute.”
Bluewater Network v. EPA, 372 F.3d 404, 410 (D.C.Cir.2004) (quoting Chevron, 467 U.S. at 842-43, 104 S.Ct. 2778). We agree with the Environmental Petitioners that EPA’s definition of “commercial or industrial waste,” as incorporated in the definition of CISWI units, stumbles on Chevron’s first step because it conflicts with the plain language of section 129.
Section 129 on its face applies to “solid waste incineration units” generally, 42 U.S.C. § 7429(a)(1)(A), and specifically to “solid waste incineration units combusting commercial or industrial waste,” id. § 7429(a)(1)(D). The statute further expressly defines “[t]he term ‘solid waste incineration unit’ ” plainly and broadly to include “a distinct operating unit of any facility which combusts any solid waste material from commercial or industrial establishments or the general public (including single and multiple residences, hotels, and motels).” Id. § 7429(g)(1) (emphases added). “The word ‘any’ is usually understood to be all inclusive.” Fin. Planning Ass’n v. SEC, 482 F.3d 481, 488 (D.C.Cir.2007); see New York v. EPA, 443 F.3d 880, 885 (D.C.Cir.2006) (“In a series of cases, the Supreme Court has drawn upon the word ‘any’ to give the word it modifies an ‘expansive meaning’ when there is ‘no reason to contravene the clause’s obvious meaning.’ ”) (quoting Norfolk S. Rwy. Co. v. Kirby, 543 U.S. 14, 31-32, 125 S.Ct. 385, 160 L.Ed.2d 283 (2004)) (citing HUD v. Rucker, 535 U.S. 125, 130-31, 122 S.Ct. 1230, 152 L.Ed.2d 258 (2002); United States v. Gonzales, 520 U.S. 1, 5, 117 S.Ct. 1032, 137 L.Ed.2d 132 (1997)). Applying the usual meaning here, we interpret section 129 under Chevron step 1 to unambiguously include among the incineration units subject to its standards any facility [422]*422that combusts any commercial or industrial solid waste material at all — subject to the four statutory exceptions identified above. See supra p. 1255. The definition EPA promulgated in the CISWI Definitions Rule, however, constricts the scope of this plain, broad language.
The CISWI Definitions Rule defines the term “CISWI unit” to include “any combustion unit that combusts commercial or industrial waste (as defined in this sub-part)” 70 Fed.Reg. at 55,580 (emphasis added). The same subpart, however, defines “commercial or industrial waste” narrowly to include only “solid waste ... that is combusted at any commercial or industrial facility using controlled flame combustion in an enclosed, distinct operating unit: (1) Whose design does not provide for energy recovery (as defined in this subpart); or (2) operated without energy recovery (as defined in this sub-part).” 70 Fed.Reg. at 55,572 (codified at 40 C.F.R. § 60.2265). EPA defines the term “energy recovery,” in turn, as “the process of recovering thermal energy from combustion for useful purposes such as steam generation or process heating.” Id. (codified at 40 C.F.R. § 60.2265). The effect of these definitions is to substantially reduce the number of commercial or industrial waste combustors subject to section 129’s standards by exempting from coverage any commercial or industrial incinerator combusting “solid waste” if the combustion unit’s design permits thermal recovery or the combustion process in fact recovers thermal energy — notwithstanding such a unit plainly fits the statutory definition of “solid waste incineration unit” as “any facility which combusts any solid waste material from commercial or industrial establishments,” 42 U.S.C. § 7429(g)(1) (emphases added). In the rulemaking, EPA asserted its definition simply resolves an ambiguity created by the Congress’s failure to provide a statutory definition of “commercial or industrial waste.” See CISWI Definitions Rule, 70 Fed.Reg. at 55,573 (“CAA section 129 is ambiguous because it does not contain definitions of certain terms.... [Sjection 129 does not define commercial or industrial waste. Inherent in EPA’s implementation of this statutory provision is the discretion to reasonably define what constitutes this undefined type of solid waste.”).3 We have previously rejected just such an argument, stating unequivocally: “There is no such rule of law.” Goldstein v. SEC, 451 F.3d 873, 878 (D.C.Cir.2006). As we there explained, “[t]he lack of a statutory definition of a word does not necessarily render the meaning of a word ambiguous, just as the presence of a definition does not necessarily make the meaning clear.” Id. Here, the statutory definition of “solid waste incineration unit” is clear and unambiguous as written — and EPA acknowledges as much when it objects to a “literal” reading of the definition’s language. See EPA Br. at 24 (asserting that “[a] literal interpretation of the definition of ‘solid waste incineration unit’ in section 129(g)(1), 42 U.S.C. § 7429(g)(1), would require EPA to treat as an incinerator any facility that combusts any amount of solid waste from a commercial or industrial source”). EPA offers three other arguments to support its definition of “commercial and industrial waste,” none of them any more persuasive.
First, EPA asserts the legislative history of section 129 supports its position [423]*423that “any,” as used in the statutory definition of CISWI to modify “solid waste,” was intended to bear “a narrower meaning in context than it has in common usage,” EPA Br. at 31, thereby allowing thermal energy recovery facilities to be exempted from the definition of “solid waste incineration unit.” Cf. Bell Atl. Tel. Cos. v. FCC, 131 F.3d 1044, 1047-48 (D.C.Cir.1997) (stating “Supreme Court has specifically held that in context the word ‘any’ may be construed in a non-expansive fashion”) (citing O'Connor v. United States, 479 U.S. 27, 31, 107 S.Ct. 347, 93 L.Ed.2d 206 (1986)). In particular, EPA points to remarks made by three senators during debate which acknowledged a “solid waste disposal crisis” and supported recycling and recovering resources in the solid waste disposal process — most notably, the remarks of one senator in support of the express statutory exemptions for “secondary materials recovery facilities from these requirements because their specific purpose is to recover valuable materials” and for “facilities regulated under the Public Utilities Regulatory Policy Act,” 16 U.S.C. § 824a-3. See EPA Brief at 32-34 (citing 1 A Legislative History of the Clean Air Act Amendments of 1990 1131 (Comm. Print 1993) (Sen.Dole); 4 id. 7049 (Sen.Dole); id. at 7051 (Sen.Durenberger); id. at 7054 (Sen.Baucus)). “It is true ... that we ‘may examine the statute’s legislative history in order to “shed new light on congressional intent, notwithstanding statutory language that appears superficially clear.” ’ ” Consumer Elecs. Ass’n v. FCC, 347 F.3d 291, 298 (D.C.Cir.2003) (quoting Nat’l Rifle Ass’n v. Reno, 216 F.3d 122, 127 (D.C.Cir.2000)) (quoting Natural Res. Def. Council, Inc. v. Browner, 57 F.3d 1122, 1127 (D.C.Cir.1995)). But “ ‘the bar is high,’ ” id. (quoting Williams Cos. v. FERC, 345 F.3d 910, 914 (D.C.Cir.2003)), and “only rarely have we relied on legislative history to constrict the otherwise broad application of a statute indicated by its text,” id. Here, EPA cannot clear the high bar relying solely on the isolated remarks of a few senators. Cf. Davis County Solid Waste Mgmt. v. EPA, 101 F.3d 1395, 1407 (D.C.Cir.1996) (finding contradictory comments of individual senators during section 129 debates “too ‘meager [a] record’ ” to rely on “ ‘given the clear statutory language’ to the contrary”) (quoting Engine Mfrs. Ass’n v. EPA, 88 F.3d 1075, 1091 (D.C.Cir.1996)). In any event, the remarks that EPA cites, when viewed in the context of the express and unambiguous provisions in the statute, show only that when the Congress wanted to exempt a particular kind of solid waste combustor from section 129’s coverage— based on the desirability of resource recovery or any other interest — -it knew how to accomplish this through an express statutory exception and in fact did so for four specific classes of combustion units. See 42 U.S.C. § 7429(g)(1). Had the Congress intended to exempt all units that combust waste for the purpose of recovering thermal energy, it could likewise have expressly provided for their exemption in the statute. See Sierra Club v. EPA, 294 F.3d 155, 160 (D.C.Cir.2002) (if statute “details the conditions in which EPA may extend the attainment deadline,” “[w]e cannot but infer from the presence of these specific exemptions that the absence of any other exemption for the transport of ozone was deliberate, and that the Agency’s attempt to grant such a dispensation is contrary to the intent of the Congress”); TRW Inc. v. Andrews, 534 U.S. 19, 28, 122 S.Ct. 441, 151 L.Ed.2d 339 (2001) (“ ‘Where Congress explicitly enumerates certain exceptions to a general prohibition, additional exceptions are not to be implied, in the absence of evidence of a contrary legislative intent.’ ”) (quoting Andrus v. Glover Constr. Co., 446 U.S. 608, 616-17, 100 S.Ct. 1905, 64 L.Ed.2d 548 (1980)). But the Congress [424]*424did not — and EPA may not, consistent with Chevron, create an additional exception on its own. In sum, “[i]n this context, there is no reason the usual tools of statutory construction should not apply and hence no reason why ‘any should not mean ‘any.’ ” New York v. EPA, 443 F.3d 880, 886 (D.C.Cir.2006). In New York v. EPA, the court rejected EPA’s narrow construction of the statutory definition of “modification,” contained in CAA section 111, as “any physical change in, or change in the method of operation of, a stationary source which increases the amount of any air pollutant emitted by such source or which results in the emission of any air pollutant not previously emitted,” 42 U.S.C. § 7411(a)(4) (emphasis added). The court accorded “an expansive meaning” to the term “any,” 443 F.3d at 885-86, thereby expanding the class of new sources subject to new source emission standards. See 42 U.S.C. § 7411(a)(2) (defining “new source” as “any stationary source, the construction or modification of which is commenced after the publication of regulations ... prescribing a standard of performance under this section which will be applicable to such source” (emphasis added)); id. § 7411(b) (requiring EPA to establish emission standards for “new sources”). The court explained that “the context of the Clean Air Act warrants no departure from the word’s customary effect.” New York v. EPA, 443 F.3d at 885-86. We likewise give an expansive reading to “any” to increase the number of CISWI units subject to section 129’s emission standards, reading sections 111 and 129 in pari materia. Cf. Bluewater Network, 372 F.3d at 411 (reading CAA § 213(a)(3) in pari materia with CAA § 202(i)(2) as “technology-forcing”).
Second, EPA contends that “[b]y specifying that the classification of a source turns on its primary function, the [CISWI] Definitions Rule reasonably distinguishes between incinerators, which are ‘designed to discard materials by burning them at high temperatures and leaving as little residue as possible,’ and boilers, which are ‘designed to recover the maximum amount of heat from a material’s combustion.’ ” EPA Br. at 36 (quoting Summary of Public Comments and Responses, OAR-2003-0119-0038, at 15 (JA 1271)). The distinction EPA draws may well be reasonable but it is not the line drawn by the Congress in section 129 to separate a CISWI unit from a boiler when it unambiguously defined the former term as “any facility which combusts any solid waste material,” 42 U.S.C. § 7429(g) (emphasis added). This plain statutory language governs— and halts our review at Chevron’s step 1.
Finally, EPA asserts that section 129(h)(2), which makes section 112’s and section 129’s standards mutually exclusive (by directing that “no solid waste incineration unit subject to performance standards under [section 129] and [42 U.S.C. § 7411] shall be subject to standards under section [42 U.S.C. § ] 7412(d)”), “implicitly gave EPA the discretion to implement the requirements of section 129 in a way that avoids results inconsistent with the statutory purpose.” EPA Br. at 41. EPA reasons that section 129’s exclusivity language “directs EPA to make the MACT standards mutually exclusive but does not tell EPA how to accomplish this task, instead leaving the line-drawing details to EPA’s considered judgment.” Id. We perceive no such gap in the statute, which simply directs EPA in plain terms to subject a solid waste combustion facility exclusively to section 129’s standards, and not to section 112’s, if the facility fits section 129’s clear definition of “solid waste incineration unit.” The provision gives EPA a straightforward directive to draw the distinction based solely on the applicability vel non of section 129’s definition. It confers no discre[425]*425tion in this respect, either express or implied.
B. Boilers Rule
Having determined that EPA’s definition of “solid waste incineration unit” conflicts with the plain meaning of section 129 and must therefore be vacated, we next address the Environmental Petitioners’ and the Municipal Petitioners’ challenges to the Boilers Rule and conclude they are premature as the Boilers Rule cannot survive as currently promulgated.
As the Environmental Petitioners noted at oral argument, if the court requires EPA to revise the CISWI Definitions Rule, as we do in this opinion, the Boilers Rule will need to be revised as well because the universe of boilers subject to its standards will be far smaller and more homogenous after all CISWI units, as the statute unambiguously defines them, are removed from its coverage. See Natural Res. Def. Council v. EPA, Nos 04-1385 et al., 2/23/07 Oral Argument Tr. at 37-38. Given the likelihood (if not certainty) that the Boilers Rule will change substantially as a result of our vacatur of the challenged “solid waste” definition, we believe the Boilers Rule should be vacated in its entirety and remanded for EPA to repromulgate after revising the CISWI Definitions Rule. Cf. Friends of the Earth, Inc. v. EPA, 446 F.3d 140 (D.C.Cir.2006) (remanding to district court with instruction to vacate “daily load” limits on effluent discharges as inconsistent with statutory language).4 It is therefore premature to consider the Environmental Petitioners’ or the Municipal Petitioners’ challenges to the current rule. Cf. Ala. Power Co. v. EPA, 40 F.3d 450, 456 (D.C.Cir.1994) (vacating rule and declining to resolve issue rendered moot thereby).
In choosing to vacate rather than simply remand the CISWI Definitions Rule and the Boilers Rule, we disagree with our dissenting colleague who would not vacate either of the Rules because “the court has traditionally not vacated the rule if doing so would have adverse implications for public health and the environment.” Dissent at 1265 (citing Sierra Club v. EPA, 167 F.3d 658, 664 (D.C.Cir.1999); Nat’l Lime Ass’n v. EPA, 233 F.3d at 635). We find the cited cases distinguishable from the situation here.
As a result of our decision today, neither of the two Rules survives remand in anything approaching recognizable form. As the Environmental Petitioners point out, our rejection of EPA’s definition of “commercial or industrial waste,” as incorporated in the definition of CISWI, will “shift thousands of units that are currently regulated under the section 112 Boilers Rule into the CISWI category, subject to regulation under section 129” and “[a]s a result, the populations of units subject to EPA’s boilers and CISWI rules will change substantially,” requiring that EPA “recalculate the stringency of the emissions standards for the newly expanded CISWI category and the newly shrunk boilers category.” Envtl. Pet’rs Br. at 29. By contrast, in declining to vacate the standard successfully challenged in Sierra Club, the court expressly noted it was “possible that EPA may be able to explain it” on remand, 167 F.3d at 664. In National Lime Association, we remanded because EPA “failed to consider non-air quality health and environmental impacts of potential beyond-the-floor standards for HAP metals, and because it relied on a factually incorrect assertion in rejecting such standards.” 233 F.3d at 635. In [426]*426neither case did our decision foreclose EPA from promulgating the same standards on remand.
Moreover, we find this case much like Cement Kiln Recycling Coal. v. EPA, 255 F.3d 855 (D.C.Cir.2001) (per curiam), in which we vacated the challenged emission standards, notwithstanding the environmental petitioners’ request to leave them intact, because we had “chosen not to reach the bulk of industry petitioners claims, and leaving the regulations in place during remand would ignore petitioners’ potentially meritorious challenges.” 255 F.3d at 872. Similarly here, we elect not to address potentially meritorious challenges to the Boilers Rule raised by the Municipal Petitioners — that EPA violated the CAA by failing to create a separate subcategory for small municipal utilities.
In light of the need for wholesale revision on remand of both the CISWI Definitions Rule and the Boilers Rule and the effect that leaving the Boilers Rule in place would have on the Municipal Petitioners, we believe the appropriate course is to vacate the Rules in their entirety. To remedy the resulting lack of standards, any party “may file a motion to delay issuance of the mandate to request either that the current standards remain in place or that EPA be allowed reasonable time to develop interim standards.” Cement Kiln, 255 F.3d at 872 (citing Columbia Falls Aluminum Co. v. EPA, 139 F.3d 914, 924 (D.C.Cir.1998)).
For the foregoing reasons, we grant the Environmental Petitioners’ petitions for review of the CISWI Definitions Rule (No. 05-1434) and consequently vacate and remand both the CISWI Definitions Rule and the Boilers Rule. We further dismiss as moot both the Environmental Petitioners’ and the Municipal Petitioners’ petitions for review of the vacated Boilers Rule (Nos. 04-1385, 04-1386, 05-1302 and 06-1065).
So ordered.