Full opinion text
Opinion PER CURIAM. PER CURIAM: The Hazardous and Solid Waste Amendments of 1984 instituted a ban on the land disposal of classes of hazardous wastes unless certain conditions are met. Those amendments require the Environmental Protection Agency to follow a phased schedule for implementing the ban. In this case we consider various challenges to regulations implementing the final portion of this program, the so-called “third-third” rule, which largely covers the land disposal of wastes deemed hazardous because they possess certain defined characteristics. Various petitioners raise multi-faceted challenges. A group of industry trade associations and companies (collectively, “industry petitioners”) seek review of regulations mandating levels of treatment before land disposal that go beyond the removal of the attribute that led to the waste’s classification as hazardous. These petitioners claim that the EPA lacked authority under the statute to require treatment to such levels. The Fertilizer Institute raises procedural and substantive objections to provisions that bar dilution of certain wastes as a form of treatment prior to discharge into the waters of the United States from treatment facilities licensed under the Clean Water Act. Finally, three companies attack the imposition of new testing requirements at disposal facilities as arbitrary and insufficiently clear. We deny each of these petitions for review. Sections 3004(g)(5) and (m) of the Resource Conservation and Recovery Act (“RCRA”) (which are reprinted in Appendix A hereto) give the EPA the statutory authority to mandate the treatment of wastes to levels beyond those at which the wastes present the characteristics that caused them to be deemed hazardous. The EPA provided adequate notice of its intent to bar dilution of certain hazardous wastes at water treatment facilities that meet the standards of the Clean Water Act facilities. The regulations provide sufficient guidance as to how this part of the rule will work, and the distinction drawn between types of hazardous wastes appears reasonable. The challenge by the individual companies to testing protocols established in this rule is rejected. The procedures are both clear and reasonable. Several environmental organizations, as well as the Hazardous Waste Treatment Council, an association representing companies that treat hazardous waste (collectively, “NRDC petitioners”), present different objections. They assert that (1) the new rule’s “deactivation” treatment standard impermissibly allows the dilution, rather than treatment with specified technologies, of many characteristic wastes prior to land disposal; (2) the rule authorizes placement of untreated formerly characteristic wastes in surface impoundments within Clean Water Act treatment systems, or into underground injection wells, in violation of RCRA; (3) it arbitrarily created treatment standards for chromium and lead wastes; and (4) the rule provides an exception to treatment standards for wastes burned in industrial furnaces along with wastes exempted by the Bevill Amendment that violates that provision. In addition, the Council and Chemical Waste Management, Inc., a large waste disposal company, challenge certain testing procedures imposed by the regulations as impermissibly vague. The petitions brought by NRDC petitioners are granted in part and denied in part. Under the statute, dilution of characteristic hazardous wastes may constitute treatment, but only if no hazardous constituents are present following dilution that would endanger human health or the environment. The EPA concedes that dilution will not attain this result for certain characteristic wastes. For others, it has not made clear that dilution will meet the requirements for treatment. The standard is therefore vacated as to those wastes. The dilution of wastes in Clean Water Act facilities is acceptable so long as the toxicity of the waste discharged from the facility is minimized or eliminated consistent with RCRA. Similarly, disposal of wastes in underground injection wells may occur as long as the hazardous characteristics have been eliminated and any health and environmental dangers posed by hazardous constituents of the wastes are minimized. We remand the lead and chromium standards because the EPA appears ,to have relied on data that does not support its conclusions. We also remand the exemption from regulation under Subtitle C of RCRA of wastes burned with wastes exempted under the Bevill Amendment for consideration in an ongoing rulemaking addressing that question. Finally, Chemical Waste Management’s petition for review of test compliance procedures is denied. Testing procedures will be embodied in permits. Uncertainties over the standards can be resolved in the permit-writing process. TABLE OF CONTENTS I. Statutory and Regulatory Background. II. Treatment Standards for Characteristic Wastes. A. Proposed Rule. B. Final Rule. C. Standard of Review. D. Industry Petitioners’ Challenge to the Treatment Standards. E. NRDC Petitioners’ Challenge to Deactivation Treatment Standard_ 1. Ignitable Wastes. 2. Corrosive Wastes . 3. Reactive Wastes. III. The EPA’s Dilution Rules... A. Clean Water Act Treatment Systems.. 1. Background. 2. Analysis. B. Deep Injection Wells Regulated Under the Safe Drinking Water Act 1. Generally. 2. The Treatment Standard for Lead Wastewaters. C. The Fertilizer Institute’s Challenges to the Dilution Rules. 1. Notice and Opportunity to Comment. 2. Is the Rule Impermissibly Vague?. 3. Should Rule 268.3(b) Include Listed Wastes for which the EPA has Developed Concentration-Based Treatment Standards? IV. Miscellanea. A. Corroborative Testing. C. Exemption of Waste Burned in “Bevill” Units. B. Treatment Standards for Chromium Wastes. D. “Grab” Sampling. V. Conclusion. I. Statutory and Regulatory Background Subtitle C of the Resource Conservation and Recovery Act, 42 U.S.C. §§ 6921-6939b (1988), sets out a comprehensive regulatory system governing the treatment, storage, and disposal of hazardous wastes. Wastes are deemed hazardous in one of two ways: They possess one of the four hazardous characteristics identified by the EPA in 40 C.F.R. Part 261, Subpart C (“characteristic wastes”), see id. § 261.3(a)(2)(i) (1991), or have been found to be hazardous as a result of an EPA rulemaking. See id. Part 261, Subpart D (“listed wastes”). The four characteristics identified as hazardous are ignitability, corrosivity, reactivity, and extraction procedure (“EP”) toxicity. The hazards presented by ignitable, corrosive, and reactive (“ICR”) wastes are primarily, though not exclusively, the results of their physical properties. See 45 Fed.Reg. 33,066, 33,107-10 (1980). EP characteristic wastes contain toxic constituents. Id. at 33,107-12. These wastes remain hazardous until they cease to exhibit any of the characteristics identified in Sub-part C. See 40 C.F.R. § 261.3(d)(1). Characteristic wastes comprise over fifty percent of all the hazardous wastes generated in the United States each year. Although the EPA may list a waste if it possesses one of the four characteristics described above, in practice it will only list specific wastes that are either acutely hazardous or possess high levels of toxic constituents. See id.; 45 Fed.Reg. at 33,105-07. A listed waste loses its hazardous status only after a petition for its “delisting” is approved by the EPA in a notice-and-comment rulemaking. See 40 C.F.R. §§ 260.20, 260.22; Shell Oil Co. v. EPA, 950 F.2d 741, 749 (D.C.Cir.1991). “Once a waste is listed or identified as hazardous, its subsequent management is regulated” under subtitle C of RCRA. American Petroleum Inst. v. EPA, 906 F.2d 729, 733 (D.C.Cir.1990) ("API”). The waste enters RCRA’s “cradle-to-grave” regulatory system; and “the waste’s treatment, storage, and disposal is usually regulated by permit.” American Mining Congress v. EPA, 907 F.2d 1179, 1182 (D.C.Cir.1990) (“AMC II”); see also RCRA §§ 3001-3004, 42 U.S.C. §§ 6921-6924. The management of a hazardous waste continues “until such time as it ceases to pose a hazard to the public.” Shell Oil, 950 F.2d at 754. Because “certain classes of land disposal facilities are not capable of assuring long-term containment of certain hazardous wastes,” RCRA § 1002(b)(7), 42 U.S.C. § 6901(b)(7), Congress amended subtitle C in 1984 to prohibit land disposal of many hazardous wastes. The Hazardous and Solid Waste Amendments of 1984, Pub.L. No. 98-616, 98 Stat. 3221 (1984) (“1984 Amendments”), gave the EPA significant authority to regulate land disposal. The statute expressed a general policy preference that “reliance on land disposal should be minimized or eliminated.” RCRA § 1002(b)(7), 42 U.S.C. § 6901(b)(7). A prohibition on disposal would apply unless the waste is treated so as to minimize the short-term and long-term threats to human health and the environment posed by toxic and hazardous constituents, RCRA § 3004(m), 42 U.S.C. § 6924(m), or unless the EPA finds that no migration of hazardous constituents from the facility will occur after disposal. Id. § 3004(g)(5), 42 U.S.C. § 6924(g)(5); see also Hazardous Waste Treatment Council v. EPA, 886 F.2d 355, 357 (D.C.Cir.1989), cert. denied, — U.S. -, 111 S.Ct. 139, 112 L.Ed.2d 106 (1990) (“HWTC III”). The 1984 Amendments specifically required the EPA to follow a phased schedule to implement the land disposal ban. They forbade the land disposal of hazardous wastes containing solvents and dioxins after November 8,1986. RCRA § 3004(e), 42 U.S.C. § 6924(e). A select list of other wastes were barred from land disposal after July 8, 1987 (“California list” wastes). Id. § 3004(d), 42 U.S.C. § 6924(d). Finally, the amendments ordered the Agency to rank all remaining hazardous wastes on the basis of their intrinsic hazard and the volume generated annually and to divide the list into three parts. Id. § 3004(g)(4), 42 U.S.C. § 6924(g)(4). The Administrator was then charged with the task of promulgating final regulations for each third of the list. See id. § 3004(g)(5), 42 U.S.C. § 6924(g)(5). Unless the Administrator promulgated regulations for wastes in the last third of the list by May 8, 1990, they could not be land disposed. Id. § 3004(g)(6)(C), 42 U.S.C. § 6924(g)(6)(C). Under the 1984 Amendments, the final regulations must prohibit[] one or more methods of land disposal of the hazardous wastes listed on such schedule' except for methods of land disposal which the Administrator determines will be protective of human health and the environment for as long as the waste remains hazardous.... For the purposes of this paragraph, a method of land disposal may not be determined to be protective of human health and the environment (except with respect to a hazardous waste which has complied with the pretreatment regulations promulgated under subsection (m) of this section) unless, upon application by an interested person, it has been demonstrated to the Administrator, to a reasonable degree of certainty, that there will be no migration of hazardous constituents from the disposal unit or injection zone for as long as the wastes remain hazardous. RCRA § 8004(g)(5), 42 U.S.C. § 6924(g)(5). The Administrator must also promulgate treatment standards, compliance with-which will authorize land disposal, at the same time he publishes the land ban. The treatment regulations shall specify[ ] those levels or methods of treatment, if any, which substantially diminish the toxicity of the waste or substantially reduce the likelihood of migration of hazardous constituents from the waste so that short-term and long-term threats to human health and the environment are minimized. Id. § 3004(m)(l), 42 U.S.C. § 6924(m)(l). The regulations under review implement the land-ban program for the last third of the ranked list of wastes, the “third-third.” They largely consist of treatment standards for characteristic wastes. See 55 Fed.Reg. 22,520-720 (1990). The final rule also modifies regulations governing characteristic wastes that are managed in treatment systems regulated through National Pollutant Discharge Elimination System permits issued under the Clean Water Act as well as regulations affecting those disposed of in underground injection wells regulated under the Safe Drinking Water Act. The rule establishes a variety of compliance requirements as well. Fourteen petitions for review were filed and consolidated into this proceeding. Petitioners divided the case into three groups of issues for purposes of briefing and argument. The first focuses on industry petitioners’ challenge to standards mandating treatment of characteristic wastes beyond the point at which they cease to display hazardous characteristics and on NRDC petitioners’ challenge to dilution as a method of treatment. The second centers on the Clean Water Act and underground injection well questions. The third consists of the remaining issues. This opinion adopts the same approach. II. Treatment Standards for Characteristic Wastes A. Proposed Rule As described above, at the outset of the RCRA program, the EPA identified four characteristics as hazardous: ignitability, corrosivity, reactivity, and EP toxicity. In its proposed rules, and in the final regulations, the Agency divided characteristic wastes into subcategories, suggesting treatment standards or levels for each subcategory. For some of these, the EPA proposed treatment to reduce the presence of the characteristic below the level at which the waste was defined as hazardous. For example, a waste is considered corrosive, and therefore hazardous, if it is aqueous and has a pH of less than two or greater than 12.5. The proposed rule required treatment that would result in a pH between six and nine. See 54 Fed.Reg. 48,372, 48,422 (1989). For other subcategories, however, the EPA suggested treatment to the characteristic level and no further. See id. at 48,420-26 (setting treatment levels and standards). The Agency stated that it possessed the authority to compel treatment below characteristic levels. See 54 Fed.Reg. at 48,-419. It took note of the argument that the characteristic levels represent the limit of subtitle C authority — that the Agency had no power to regulate a waste where the characteristic had been brought below the level deemed hazardous. Id. at 48,490. The Agency believed, however, that section 3004(m) extended its authority beyond that point. “[0]nce wastes become subject to section 3004(m), they remain subject to the requirements of that section until the section 3004(m) standard is satisfied.” . Id. The EPA concluded that it was directed by the statute to require a waste that is hazardous at the point of generation and is destined for land disposal to “be treated by methods which substantially reduce toxicity and minimize threats to human health and the environment.” Id. As to methods of treatment, the proposed rule largely followed the judgment made by the EPA in previous land-ban program rulemakings. In those earlier rules, the EPA determined that treatment would be accomplished through the use of “best demonstrated available technologies.” See, e.g., 51 Fed.Reg. 40,572, 40,578 (1986) (solvents and dioxins); 53 Fed.Reg. 31,138, 31,-142 (1988) (first-third wastes). The proposed rule specified the particular technology to be used in the treatment of most ICR wastes. See 54 Fed.Reg. at 48,420-26. For a handful of others, the Agency offered a measure of flexibility by creating a “deactivation” category of treatment. According to the proposal, the EPA had “determined that within [several ICR subcategories] there appear to be a further variety of different waste groups, each with a certain degree of uniqueness with respect to hazard and handling requirements.” Id. at 48,419. Therefore, while the Agency recommended a number of methods, it proposed to allow generators or treaters of those wastes to select the appropriate method of treatment. Id. at 48,419-20. In implementing the land-ban program for solvents and wastes containing dioxins, the EPA barred dilution as an alternative for “adequate treatment.” See 51 Fed. Reg. at 40,639. As codified, the rule stated that no generator, transporter, handler, or owner or operator of a treatment, storage, or disposal facility shall in any way dilute a restricted waste ... as a substitute for adequate treatment to achieve compliance with subpart D of this part [setting forth treatment standards], ... or to circumvent a land disposal prohibition imposed by RCRA section 3004. 40 C.F.R. § 268.3(a) (1989). At several points in the proposed third-third rule, the EPA reaffirmed its decision that a generator or treater might not dilute wastes to escape the dictates of the land disposal program. In its discussion of ignitable wastes, the Agency stated that “a prohibited form of dilution that is used to remove a characteristic from a prohibited hazardous waste would be a violation of the dilution prohibition in [40 C.F.R.] section 268.3.” 54 Fed.Reg. at 48,422. Among the EPA’s concerns was the possibility that dilution of ignitable wastes would lead to dangerous emissions of volatile organic compounds, a problem that could be avoided by using other treatment methods. Id. “Accordingly, the Agency believes that dilution should not be a legitimate method for treating ignitable wastes.” Id. The EPA proposed a similar bar with regard to reactive wastes: “[Dilution of reactive wastes should not automatically be considered to be a légitimate form of treatment.” Id. at 48,426. It proposed that reactive cyanides and sulfides be treated like any toxic waste; “[w]ith respect to other reactive wastes, most cannot be diluted without violent reaction so that dilution is not a viable management alternative[.]” Id. Finally, the EPA suggested that corrosives be treated by neutralization, not dilution, to alter their pH. Id. at 48,422-23. According to the Agency, dilution would require the use of large amounts of water and would create a greater volume of waste; moreover, dilution “does not treat or remove hazardous constituents in the wastes.” Id. at 48,423. More broadly, the EPA expressed its concern, echoing Congress’ concern in indicating that dilution to avoid proper treatment was impermissible, [ ] that individual prohibited wastes [hazardous wastes destined for land disposal] not be mixed with larger volumes of other wastes (whether prohibited or not) to meet treatment standards without undergoing treatment that substantially reduces the prohibited wastes’ toxicity or mobility.... Consequently, it appears to the Agency that any dilution that fails to meet the standard in § 3004(m) of substantially reducing the prohibited waste’s toxicity or mobility is impermissible_ Further, with respect to organic constituents, ‘reduction of toxicity’ means actual removal of or chemical change to the constituent. Id. at 48,494 (citation omitted). But the Agency did seek comments on “whether dilution can be used as a means of supplanting a section 3004(m) treatment standard by being used to render a prohibited waste non-hazardous in lieu of actually treating the prohibited hazardous waste prior to land disposal.” Id. at 48,495. B. Final Rule In the final rule, the EPA revised many of its proposed treatment standards for ICR and toxic characteristic wastes. The EPA, however, did not back away from its basic position that it could require treatment below characteristic levels. Because “Congress has given apparently conflicting guidance on how the Agency should address land disposal prohibitions for characteristic wastes,” the EPA “believes it has authority to reconcile these potential conflicts and to harmonize statutory provisions to forge a coherent regulatory system.” 55 Fed.Reg. at 22,651. The EPA agreed with many participants in the comment period that “one permissible construction of the language in section 3004(g)” (which requires the promulgation of regulations “prohibiting ... methods of land disposal of the [listed] hazardous wastes”) is that subtitle C rules applied only to hazardous wastes, and therefore the applicability of the land disposal regulations must be judged at the moment of disposal. 55 Fed. Reg. at 22,652. Ultimately, the EPA concluded that Congress did not state when the status of the waste should be evaluated for purposes of the ban on land disposal; therefore, the EPA could choose to regulate the waste “at the point of generation or at the point of disposal (and possibly at some other point or combination of the two).” Id. While viewing its authority broadly, the EPA decided to exercise it sparingly: Today’s rule reflects a decision to take limited, but nonetheless significant, steps within the point of generation framework. As a general matter, the Agency believes that the goals of [the program] may require application of standards which go beyond the characteristic level ... in some future cases. Id. at 22,654. The final regulations call for treatment below characteristic levels for only a handful of wastes. Among ICR wastes, ignitable liquids with high total organic carbons (a subset of the subcategory of ignitable liquids for which the proposed rule required treatment to below characteristic levels by technology), see id. at 22,543-44, and reactive cyanides, see id. at 22,550-51, would be subject to enhanced treatment. The Agency backed away from its original plan to mandate enhanced treatment for corrosive characteristic wastes. The EPA determined that for most ICR wastes, treatment to characteristic levels would be sufficient. The Agency found upon review that [t]he environmental concerns from the properties of ignitability, corrosivity, and reactivity are different from the environmental concern from EP toxic wastes. Toxic constituents can pose a cumulative impact on land disposal even where waste is below the characteristic level. Where wastes pose an ascertainable toxicity concern ... the Agency has developed treatment standards that address the toxicity concern and (in effect) require treatment below the characteristic level_ Otherwise, treatment that removes the properties of ignitability, cor-rosivity, and reactivity, fully addresses the environmental concern from the properties themselves. Id. at 22,655. The EPA also retreated from its emphasis on technology-based treatment in the final regulations, altering its position on the use of dilution as a method of treatment: In all cases, the Agency has determined that for non-toxic hazardous characteristic wastes, it should not matter how the characteristic property is removed so long as it is removed. Thus, dilution is an acceptable treatment method for such wastes. Id. at 22,532. The Agency included dilution within the ambit of the “deactivation” treatment standard. The final rule defined the standard as “Reactivation to remove the hazardous characteristics of a waste due to its ignitability, corrosivity, and/or reactivity.” Id. at 22,693. As long as these characteristics are removed, any method can be employed under the final regulations. The EPA allowed full discretion among specified technological methods of treatment (such as neutralization or incineration) as well as dilution with water or other wastes. For toxic wastes, the prohibition on dilution remained. See id. at 22,-656. The Agency admitted that it believes the mixing of waste streams to eliminate certain characteristics] is appropriate treatment for most wastes which are purely corrosive, or in some cases, reactive or ignitable. As a general matter, these are properties which can effectively be removed by mixing. Id. (emphasis added). It further conceded that this approach does not fully address the potential problem of toxic constituents that may be present in such wastes, nor encourages minimization or recovery of non-toxic characteristic hazardous wastes. EPA has determined that these potential problems should be addressed, if at all, in other rulemakings ... and are too difficult to resolve in this proceeding, given the extraordinary pressures and limited review time imposed by the May 8 [1990] statutory deadline. Id. at 22,665-66. Only in three subcategories of ICR wastes did the EPA mandate the use of technological treatment: reactive sulfides, 57 Fed.Reg. 8,086, 8,089 (1992) (technical correction to third-third rule); reactive cyanides, 55 Fed.Reg. at 22,551; and ignitable liquid nonwastewater wastes containing more than ten percent total organic compounds, id. at 22,544. For all corrosive wastes, other ignitable liquid wastes (nonwastewaters with low total organic compounds and ignitable waste-waters), ignitable compressed gases, ignitable reactive wastes, explosive wastes, water reactives, and other reactives dilution would be acceptable. Id. at 22,543-53. C. Standard of Review Industry and NRDC petitioners challenge the third-third rule’s treatment standards as incompatible with RCRA. We typically analyze such claims under the familiar standard of Chevron U.S.A. Inc. v. NRDC, 467 U.S. 837, 104 S.Ct. 2778, 81 L.Ed.2d 694 (1984). Under Chevron, unless Congress has spoken directly to these questions, the EPA’s determinations are entitled to deference, if reasonable. Id. at 842-43, 104 S.Ct. at 2781-82. D. Industry Petitioners’ Challenge to the Treatment Standards Industry petitioners contend that RCRA does not provide authority for the EPA to mandate treatment of characteristic wastes after their ignitability, corrosiveness, reactivity, or EP toxicity has been addressed. They make a straightforward argument: Subtitle C regulations attach to a waste only when it is hazardous. The moment a waste ceases to meet the regulatory definition of a hazardous waste, the EPA loses its authority to regulate further. Thus, in industry petitioners’ view, RCRA’s cradle-to-grave system covers waste only if it remains hazardous throughout its life and at the moment of its burial. Industry petitioners point to a welter of provisions in RCRA where the words “hazardous waste” are used as proof that the statute applies only to waste defined as hazardous. Subtitle C, they explain, is entitled “Hazardous Waste Management,” and the entire subtitle addresses that problem — the management of hazardous waste. They add that some statements by the EPA have suggested the same reading of the statute. See, e.g., 54 Fed.Reg. 1,056, 1,093 (1989) (a waste that no longer exhibits a hazardous characteristic “is no longer subject to the requirements of Subtitle C of RCRA”). In their view, the 1984 Amendments did not change this boundary. They point out that land disposal is defined in part as “any placement of such hazardous waste in a landfill, [or] surface impoundment,” RCRA § 3004(k), 42 U.S.C. § 6924(k); that section 3004(g) similarly “prohibit[s] one or more methods of land disposal of [] hazardous wastes,” id. § 6924(g)(5); and, finally, that section 3004(m) authorizes land disposal of hazardous waste that has been treated, suggesting to industry petitioners that the provision specifically authorizes only the disposal of wastes that remain hazardous after treatment. Thus, they conclude, the disposal restrictions can apply only to wastes that are hazardous at the moment of disposal. In its brief, the EPA reiterates the rationales stated in its final rule: The key provisions of the land-ban program, sections 3004(g)(5) and (m), can be read as allowing the Agency to apply land disposal restrictions at any time it wishes; those provisions at a minimum contemplate activity that occurs before land disposal; section 3004(m)(l) requires treatment to avoid the prohibition on land disposal; and treatment must take place, by definition, before dis- ' posal occurs. This reading, the EPA adds, dovetails with the concern expressed in the report accompanying the Senate version of the 1984 Amendments, that hazardous waste not be diluted and then disposed of in landfills. See S.Rep. No. 284, 98th Cong., 1st Sess. 17 (1983) (“Senate Report”). The Agency reasons that the subtitle C program can attach at the point of generation, and the broad language of section 3004(m)(l) allows additional treatment to remove risks posed by wastes beyond those inherent in the characteristic. To succeed in their Chevron step one argument, industry petitioners must show that Congress “has directly spoken to the precise question at issue” and has “unambiguously expressed [its] intent.” 467 U.S. at 842-43, 104 S.Ct. at 2781-82. We find little support in the statute or our prior decisions for the notion that Congress mandated the line industry petitioners draw. These petitioners believe that the definition of a hazardous waste acts as a revolving regulatory door, allowing continual entrance and egress from RCRA’s requirements. The key provisions of the statute support a contrary view — that hazardous waste becomes subject to the land disposal program as soon as it is generated. RCRA directs the Administrator to “promulgate regulations identifying the characteristics of hazardous waste ... which shall be subject to the provisions of this subchapter.” RCRA § 3001(b)(1), 42 U.S.C. § 6921(b)(1). This appears to bring a waste within the statutory scheme once it is identified as hazardous. Under the dictates of the 1984 Amendments, the Administrator “shall promulgate regulations ... [banning land disposal for] any hazardous waste identified or listed ‘ under section 6921 of this title.” RCRA § 3004(g)(4), 42 U.S.C. § 6924(g)(4). Again, the focus is on the identification of a waste as hazardous. This reading of the statute is consistent with our prior interpretations. In API, we explained that “[o]nce a waste is listed or identified as hazardous, its subsequent management is regulated.” API, 906 F.2d at 733. After the 1984 Amendments, we added, regulation of the waste included the prohibitions of section 3004. Id. In Shell Oil, we noted that the power to manage waste is created “[a]t [the] point” a waste is defined as hazardous and discarded. Shell Oil, 950 F.2d at 754. Once in the system, we found that the power to manage hazardous waste provided by RCRA gave the EPA the authority to regulate waste until “it ceases to pose a hazard to the public.” Id.; see also RCRA § 1004(7), 42 U.S.C. § 6903(7) (defining “hazardous waste management”). We therefore deferred to the EPA's determination that resource recovery from hazardous waste came within the Agency’s subtitle C authority. Industry petitioners nevertheless contend that we adopted the exact position they now advocate in American Mining Congress v. EPA, 824 F.2d 1177 (D.C.Cir.1987) (“AMC I”). To be sure, in AMC I, we stated that the EPA’s authority, in the first instance, extends only to waste that is identified as hazardous, id. at 1179, and that Congress took care in drafting the definition of solid waste to reflect its concern over the reach of the EPA’s authority, id. at 1188-89 and n. 17. But, as we emphasized in Shell Oil, the definitions of solid and hazardous wastes provide the keys to entrance into the RCRA system; “[o]nly materials that meet both definitions will come within the [RCRA] ‘cradle-to-grave’ regulatory scheme,” Shell Oil, 950 F.2d at 754 (emphasis added); and we also stated that once within the system, the waste will remain there so long as it poses a threat to the public health and safety. Id. AMC I turned on the question of whether secondary materials immediately reused within an industrial process had been “discarded” under the terms of RCRA. We concluded that they had not. AMC I, 824 F.2d at 1185-87. Our decision in that case stands for no more. See Shell Oil, 950 F.2d at 755-56. The 1984 Amendments also provide the EPA with the authority to mandate treatment past the point at which a characteristic is removed. Section 3004(g)(5) requires the Administrator to promulgate regulations prohibiting land disposal of hazardous wastes “except with respect to a hazardous waste which has complied with the pretreatment regulations promulgated under subsection (m) of this section.” 42 U.S.C. § 6924(g)(5). Subsection (m)(l), in turn, calls on the Administrator to specifyf ] those levels or methods of treatment, if any, which substantially diminish the toxicity of the waste or substantially reduce the likelihood of migration of hazardous constituents from the waste so that short-term and long-term threats to human health and the environment are minimized. RCRA § 3004(m)(1), 42 U.S.C. § 6924(m)(l). The requirement that treatment “substantially diminish the toxicity” or substantially reduce the likelihood of migration of hazardous constituents suggests concerns that go beyond the characteristics identified in 40 C.F.R. Part 261, subpart C. Similarly, in concluding that the EPA had the authority to require technologies that go beyond the elimination of hazardous characteristics, we have noted that “minimize” offers a broad mandate: “To ‘minimize’ something is, to quote the Oxford English Dictionary, to ‘reduce [it] to the smallest possible amount, extent, or degree.’ ” HWTC III, 886 F.2d at 361. In HWTC III, the Chemical Manufacturer’s Association (“CMA”) attacked treatment standards for solvents under the land disposal program because the EPA required treatment of all solvents, not simply those deemed unsafe. See id. at 361. The CMA argued that this regime could result in treatment “below established levels of hazard,” and therefore was an unreasonable interpretation of the Act. Id. at 362. We disagreed, noting that section 3004(m) demands that treatment minimize risks to health and the environment. Treatment might be unreasonable, we added, if the EPA required treatment of wastes that “posed no threat to human health or the environment.” Id. at 363. That was not the case in HWTC III, nor is it true here. We conclude that, in combination, sections 3004(g)(5) and (m) provide the EPA with authority to bar land disposal of certain wastes unless they have been treated to reduce risks beyond those presented by the characteristics themselves. We also find the Agency’s assertion of regulatory authority over the wastes from the moment they are generated to be “based on a permissible construction of the statute.” Chevron, 467 U.S. at 843, 104 S.Ct. at 2782. E. NRDC Petitioners’ Challenge to Deactivation Treatment Standard NRDC petitioners ask this court to vacate the deactivation treatment standard as applied to ICR wastes because it authorizes the dilution of these wastes to eliminate their ignitability, corrosiveness, or reactivity rather than mandating use of technological treatment. NRDC petitioners rely on the language of section 3004(m)(l), statements in the legislative history of the 1984 Amendments, and the overall structure of the RCRA program as support for their position that treatment does not include dilution. They claim that some form of technology must be used to treat wastes in all instances. They also contend that dilution fails to satisfy the statutory requirement that treatment minimize short-term and long-term threats to human health and the environment, or to substantially diminish the toxicity of the waste. In their view, the removal of these characteristics through dilution only affects the short-term risk that the waste will manifest that property; it does not address the threats posed by the hazardous organic and inorganic constituents of those wastes. NRDC petitioners also assert that the Agency’s interpretation of RCRA fails Chevron’s second step because the statute does not permit a plea of time pressures as a reason for failing to require treatment at the levels mandated by section 3004(m). See 55 Fed.Reg. at 22,665-66. We believe that dilution can, in principle, constitute an acceptable form of treatment for ICR wastes. We do not read the 1984 Amendments as mandating the. use of the best demonstrated available technologies (“BDAT”) in all situations. To reiterate, section 3004(m)(l) directs the Administrator to specify[ ] those levels or methods of treatment, if any, which substantially diminish the toxicity of the waste or substantially reduce the likelihood of migration of hazardous constituents from the waste so that short-term and long-term threats to human health and the environment are minimized. 42 U.S.C. § 6924(m)(l). NRDC petitioners insist that under the plain terms of this provision, the deactivation standard fails because dilution is not a “method of treatment.” Although they acknowledge that the statutory definition of “treatment” is broad enough to encompass dilution, see RCRA § 1004(34), 42 U.S.C. § 6903(34), they maintain that Congress had a more exacting criterion in mind when it enacted section 3004(m). We agree that the section imposes an exacting standard: It requires that treatment prior to land disposal “substantially diminish the toxicity of the waste or substantially reduce the likelihood of migration of hazardous constituents from the waste so that short-term and long-term threats to human health and the environment are minimized.” RCRA 3004(m)(l), 42 U.S.C. § 6924(m)(l). But this provision does not bar dilution as a means of treating ICR wastes; instead, it defines the purposes that a method of treatment must achieve. Any treatment that meets those objectives is permissible. When read against RCRA’s broad definition of treatment, we cannot say Congress clearly barred dilution as an acceptable methodology. See Chevron, 467 U.S. at 842-43, 104 S.Ct. at 2781-82. NRDC petitioners advert to a number of statements in the legislative history that they believe make clear Congress’s unexpressed intent to prohibit dilution as a form of treatment in all cases. They cite, for example, the committee report accompanying the Senate version of the 1984 Amendments, which notes that hazardous waste should be “transformed to a less hazardous chemical form through treatment.” Senate Report at 17. More directly, the report states: The dilution of wastes by the addition of other hazardous wastes or any other materials during waste handling, transportation, treatment, or storage is not an acceptable method of treatment to reduce the concentration of hazardous constituents. Only dilution which occurs as a normal part of the process that results in the waste can be taken into account in establishing concentration levels. Id. These petitioners also quote from Senator Moynihan’s statement explaining the floor amendment that became section 3004(m): “The requisite levels o[r] methods of treatment established by the Agency should be the best that has been demonstrated to be achievable.” 130 Cong.Rec. 20,803 (1984) (statement of Sen. Moynihan). They infer from this that only treatment with technology will meet the standard of section 3004(m). We are unpersuaded. The Senate committee version of the 1984 Amendments, which the committee report addresses, mandated the treatment of EP toxic wastes among the many others specified in the legislation. It did not require the treatment of ICR wastes. See Senate Report at 17-18. The strong statements cautioning against dilution as a means of treatment must be read in that context. Similarly, Senator Moynihan’s statement referred to the particular problem of highly mobile, highly toxic wastes. See 130 Cong.Rec. S9,178. These citations to legislative history do not show that Congress spoke directly to the dilution of ICR wastes. See Chevron, 467 U.S. at 842-43, 104 S.Ct. at 2781-82. We are more troubled by the question whether the dilution of certain ICR wastes will satisfy section 3004(m). Treatment must meet the standards established by that section, and its requirements are clear: It must remove the characteristic and reduce the presence of hazardous constituents when those constituents are present in sufficient concentrations to pose a threat to human health or the environment. The EPA’s regulations “must be fully consistent with” those requirements. NLRB v. United Food & Commercial Workers Union, Local 23, AFL-CIO, 484 U.S. 112, 123, 108 S.Ct. 413, 416, 98 L.Ed.2d 429 (1987). We find it unclear whether dilution is fully consistent with section 3004(m)’s treatment standards for all of the subcategories of ICR wastes for which the EPA has proscribed deactivation. As we have explained, the proposed rule pointed to significant problems that could arise if dilution was accepted as a means of treating ICR wastes. In the final regulations, the Agency found that deactivation “addresses the environmental concern from the properties themselves.” 55 Fed.Reg. at 22,655. The EPA admitted, however, that “the characteristic level is only one indicator of hazard and, thus, removal of the specific characteristic is not the same as assuring that the waste is safe.” Id. at 22,651. It then acknowledged “that this approach does not fully address the potential problem of toxic constituents that may be present in [ICR] wastes, nor encourage[ ] minimization ... of non-toxic characteristic hazardous wastes.” Id. at 22,665. The Agency’s brief contains a similar admission. Brief for Respondent at 96-97. Unfortunately, these confessions are not a substitute for a rule conforming to the statute’s command. We conclude that the deactivation standard, in its present form, is permissible only in the case of corrosive wastes; and then only so long as they do not contain hazardous constituents that, following dilution, would themselves present a continuing danger to human health or the environment. 1. Ignitable Wastes At oral argument, counsel for the EPA conceded that some ignitable wastes subject to the deactivation standard include hazardous or toxic constituents that will remain after dilution, perhaps at sufficient levels to pose a risk to human health and the environment. See also Reply Brief for NRDC petitioners at 12-14 (ignitable wastes have significant hazardous constituents); EPA, Final BDAT Background Document (May 1990), at 2-2 and 2-3, reprinted in Joint Appendix (“J.A.”) at 456-57 (same). Further, in the proposed rule, the EPA barred dilution of all ignitable wastes because of the risk of emissions of volatile organic compounds during dilution and the possibility that the waste would regain its ignitability after dilution. See also BDAT Background Document at 2-10, reprinted in J.A. at 464 (“If the ignitable wastes are diluted, [volatile organic compounds] will ordinarily be emitted in concentrations far exceeding those emitted by treatment processes in which these volatiles are destroyed.”). The final regulations suggested a number of technology-based treatment methods that might be used for ignitable wastes, but in the end authorized dilution if it would remove the characteristic alone, except for ignitable wastes including more than ten percent total organic compounds. In its brief, the Agency stated that the problem of emissions and the possibility that the waste would regain its ignitability were not significant, that some dilution pri- or to treatment would be beneficial, and that the problem of VOC emissions, if any occur, would be “best addressed by establishing air emission limitations in the future.” Brief for Respondent at 93. In view of the EPA’s position that treatment pursuant to section 3004(m) requires the removal of a waste’s hazardous characteristic and the reduction of other hazardous constituents, and the Agency’s concessions that constituents are present in some ignitable wastes subject to the deactivation standard, we vacate this part of the rule. To conform with its own reading of section 3004(m), the Agency must identify the ignitable wastes that include, after dilution, sufficiently high levels of hazardous constituents to pose a risk to human health or the environment, and propose a method of treatment that will deal with these threats. In addition, the Agency must address the problem of VOC emissions from ignitable wastes during dilution. The EPA’s statement that it believes that VOC emissions can be controlled by changes in operating parameters is inadequate. It must state, with evidentiary support, that the risk of VOC emissions during dilution is minimal for ignitable wastes now subject to the deactivation standard, or it must require actions to minimize that risk. 2. Corrosive Wastes The EPA asserts in its brief that the sole problem posed by corrosive wastes is their corrosiveness: “[Tjhere are no hazardous constituents in the waste.” Brief for Respondent at 94. Counsel for the EPA made essentially the same representation at oral argument. But NRDC petitioners come to a different conclusion. They point to the proposed rule, see 54 Fed.Reg. at 48,423 (“The Agency prefers neutralization of corrosive wastes over simple dilution because dilution simply creates a larger volume of wastes but does not treat or remove . hazardous constituents in the wastes.”), and a statement from the EPA’s BDAT Background Document stating that some corrosive wastes do in fact possess hazardous constituents beyond their potential for corrosion. See BDAT Background Document at 3-2, reprinted in J.A at 485 (“Typically, corrosive wastes that are disposed of by deep well injection are likely to contain toxic organics, whereas landfilled wastes are likely (38 percent) to contain heavy metals.”); see also id. at 3-7, reprinted in J.A. at 490 (residue from neutralized corrosive wastes can exhibit the characteristic of EP toxicity). NRDC petitioners acknowledge that corrosive wastes can be treated effectively by mixing acid and alkaline wastes; but they object to dilution with water because it will not treat the toxic constituents they claim are present in corrosive wastes. Reply Brief for NRDC petitioners at 15. The final regulations themselves are somewhat ambiguous on the question of the presence of hazardous constituents. In discussing the deactivation standard applied to acids and alkalines, the EPA states that “many [corrosive] wastes also are hazardous for other reasons, and may require that additional treatment processes be employed besides neutralization, incineration or recovery.” 55 Fed.Reg. at 22,549. The Agency also explains that [c]orrosivity is not defined in the same way EP Toxic wastes are defined. Cor-rosivity is not based on a toxic constituent, where the environmental concern is mass-loading in the environment. With respect to the issue of toxics present in these corrosive wastes,. EPA notes that if a corrosive waste also exhibits the toxicity characteristic, it must be treated to meet the treatment standard for the toxic constituent as well.... Id. This ■ explanation begs the question of what is required if the toxic constituent is present in insufficient quantities to cause the waste to be classified as EP toxic as well as corrosive, but in sufficient quantities to engage section 3004(m)’s concerns over residual effects. We agree with the EPA that dilution can be an acceptable form of treatment of corrosive wastes. But in the face of this record, we cannot rely on the assertions made in the EPA's brief and oral argument that corrosive wastes pose no hazards other than those presented by this characteristic. If, however, the facts will support these assurances, the EPA may cure this defect and meet the requirements of section 3004(m) with a statement, backed by evidence, that the corrosive wastes subject to the deactivation standard do not contain hazardous constituents that pose a threat to human health and the environment. If such a statement may be made, the Agency should be able to revise its rulemaking prior to the issuance of the mandate in this case. 3. Reactive Wastes With regard to reactive wastes, we have a problem of a different kind. Although, in the final regulations and in its brief, the EPA spoke of ICR wastes generally when it confessed that hazardous constituents might remain in some wastes following deactivation, see 55 Fed.Reg. at 22,-655-56; Brief for Respondent at 96-97, we find nothing in the proposed or final regulations to suggest that reactive wastes contain such constituents, other than reactive cyanides and sulfides for which the EPA ordered technological treatment. Nor have NRDC petitioners identified any. Therefore, we have no basis for vacating the use of the deactivation standard for the remaining subcategories of reactive wastes because of the threat of migration of hazardous constituents. The EPA, however, has only partially addressed the problem, raised in the proposed rule, of the effect of dilution on reactive wastes — that those wastes could display their reactive characteristic in the process of dilution. See 54 Fed.Reg. at 48,426. See also BDAT Background Document at 4-3, reprinted in J.A. at 503 (water reactives “(1) react violently with water; (2) form potentially explosive mixtures with water; or (3) when mixed with water, generate toxic gases, vapors, or fumes in a quantity sufficient to present a danger to human health or the environment.”). In the final regulations, based on comments received, the EPA suggested that dilution with “certain organic liquids” prior to dilution with water would remove the risk of a violent reaction in the three subcategories of reactive wastes for which the deactivation treatment standard is permitted, allowing subsequent incineration or chemical treatment. 55 Fed.Reg. at 22,553. The Agency noted that it was “not restricting the use of this practice” for any reactive waste. Id. The final regulations thus offer no assurance that dilution of explosive, water reactive, or other reactive wastes will not create a risk of violent reaction. The final regulations state that the Agency will not prohibit the practice of diluting wastes with other materials to reduce the risk of reaction, and suggest that this might be a useful step to take prior to technological treatment. This ignores the reality of the EPA’s deactivation standard: Dilution of these wastes by any method is permissible if it removes the characteristic. We grant, on narrow grounds, the petition for review as to reactive wastes. The Agency must limit dilution to methods that will curb the risk of violent reactions, mandate preliminary steps to prevent such reactions, require a technological treatment, or find, with the backing of evidence, that there is no significant risk of reaction present for any of the three subcategories of reactive wastes for which deactivation is a permissible form of treatment. Finally, contrary to what the EPA suggests, it will not suffice that the Agency promises to fully address certain unresolved problems of hazardous constituents in future rulemakings. In enacting the 1984 Amendments, Congress imposed very strict deadlines. Moreover, it has chosen to enforce them by decreeing that any hazardous waste that is not covered by a valid regulation within the date specified will be denied land disposal. We understand the enormous difficulties that the Agency has undoubtedly faced, given competing obligations and the complexity of the task. Nevertheless, we cannot treat the final rule as other than that — the EPA’s final response to the task entrusted to it by Congress. Cf. State of Colorado v. Dep’t of Interior, 880 F.2d 481, 485 (D.C.Cir.1989) (regulations promulgated by the deadline “constitute the [Agency’s] complete response in compliance with the statutory requirements.”). III. The EPA’s Dilution Rules The issues that we next face focus on challenges to the EPA’s new dilution permissions, formulated to integrate RCRA requirements with Clean Water Act (“CWA”) treatment systems and deep injection wells regulated pursuant to the Safe Drinking Water Act (“SDWA”). Contemporaneously with the promulgation of the third-third rule, the EPA amended a rule that had prohibited dilution of wastes in lieu of treatment. Pursuant to the amended rule, centralized CWA treatment systems may aggregate certain characteristic waste streams; the aggregation results in dilution that purportedly removes the hazardous characteristic without treatment. Under this new rule, dilution is allowed where the EPA has not specified a particular treatment method and where the CWA system includes a treatment protocol addressed to the types of characteristic wastes being aggregated. As a consequence of this rule, CWA treatment facilities may continue to use unlined surface impoundments as part of their treatment trains. The EPA also promulgated a new rule that permits the operators of deep injection wells to dilute all characteristic wastes, in lieu of treatment, prior to underground injection. NRDC petitioners contend that aggregation and dilution of characteristic wastes in CWA facilities, in lieu of treatment, is inconsistent with the requirements for hazardous waste management under RCRA. According to the NRDC, under RCRA subtitle C, solid waste is subject to RCRA’s treatment requirements at the moment it exhibits a hazardous characteristic; and the waste may leave the RCRA system only when treated pursuant to RCRA section 3004(m)(l) or when disposed in a facility meeting the no migration requirement of RCRA section 3004(g). Because surface impoundments are technically “land disposal” facilities, NRDC petitioners argue that placement of “decharacterized” wastes in these CWA impoundments before treatment pursuant to section 3004(m) violates RCRA’s land ban. Similarly, NRDC petitioners assert that the rule permitting dilution in lieu of treatment prior to deep well injection violates RCRA because it allows land disposal of untreated hazardous wastes. The Fertilizer Institute argues that the EPA’s new interpretive guidance for the dilution prohibitions should be struck down because they were promulgated without adequate notice and comment and that the new dilution prohibition is overly restrictive. For reasons that will follow, we grant in part and deny in part the challenges of NRDC petitioners; and we deny in toto the claims raised by the Fertilizer Institute. We hold that the new CWA dilution permission is valid where the waste is decharac-terized prior to placement in a CWA surface impoundment and subsequently treated in full conformity with section 3004(m)(l) standards. Aggregation prior to treatment is not per se unacceptable. Aggregation itself occurs in tanks and is, therefore, not “land disposal”; and RCRA does not require treatment before aggregation. To the extent that aggregation in tanks and dilution results in the removal of the waste’s characteristic and the minimization of the toxicity of the constituents as required under section 3004(m), all that RCRA commands has been achieved. However, where aggregation and dilution does not eliminate the characteristic or (more likely) does not minimize the toxicity of the constituents, then RCRA requires further treatment. In those instances where aggregation and dilution result in the elimination of the characteristic, but the toxicity of the constituents has not been minimized, the required further treatment of the constituents may occur after the waste leaves the CWA tank and enters the surface impoundment. Although a surface impoundment is technically a form of “land disposal,” and treatment therein normally would be dt odds with the commands of RCRA, this approach is nonetheless acceptable because RCRA requires some accommodation with CWA. However, in all other respects, treatment of solid wastes in a CWA surface impoundment must meet RCRA requirements prior to ultimate discharge into waters of the United States or publicly owned treatment works (“POTWs”). If the treatment in the CWA surface im-poundment succeeds in removing the toxicity to the extent 3004(m)(l) would have required, then RCRA does not require a separate treatment regimen. In other words, what leaves a CWA treatment facility can be no more toxic than if the waste streams were individually treated pursuant to the RCRA treatment standards. Applying the same principles to the deep injection well rule, we hold that dilution is permissible prior to injection only where dilution itself fully meets the section 3004(m)(l) standards. A. Clean Water Act Treatment Systems 1. Background The Federal Water Pollution Control Act, popularly known as the Clean Water Act, establishes a comprehensive treatment regime to eliminate “the discharge of pollutants into the navigable waters” of the United States. CWA § 101(a)(1), 33 U.S.C. § 1251 (1988). In general, the CWA prohibits the discharge of any pollutant into the waters of the United States.- CWA § 301(a), 33 U.S.C. § 1311(a) (1988). “This basic rule admits of a critical exception— the discharge of pollutants is permitted if the source obtains and complies with a permit that limits the amounts and kinds of pollutants which can lawfully be discharged.” NRDC v. EPA, 822 F.2d 104, 108 (D.C.Cir.1987). Regulations for permits are established through the Clean Water Act effluent guidelines and pretreatment standards and are applied through the National Pollutant Discharge Elimination System (“NPDES”); permits are issued thereunder to qualifying owners and operators of facilities that discharge into waters of the United States or POTWs. See CWA §§ 401, 402, 33 U.S.C. §§ 1341, 1342 (1988). Treatment facilities operating pursuant to the CWA often receive waste streams from many sources, and generally these streams are combined for centralized treatment. Following aggregation, the facilities sometimes place the combined stream in unlined surface impoundments as part of the CWA treatment train. These impound-ments do not meet RCRA subtitle C standards and they are regulated solely under RCRA subtitle D (solid wastes). However, as the EPA noted in the final rule, the use of surface impoundments for solid wastes clearly implicates the land ban under RCRA. See 55 Fed.Reg. at 22,657. The CWA treatment facilities at issue here do not handle listed hazardous wastes; thus, prior to the third-third proceeding, which classified and identified the characteristic hazardous wastes, the use of an unlined surface impoundment did not implicate RCRA at all. In addition, under RCRA rules prior to the third-third proceeding, the EPA prohibited dilution of any hazardous waste. Thus, once a waste was determined to be hazardous, it had to be “treated” under RCRA; dilution was not a form of treatment, nor could it be used to avoid RCRA’s treatment rules: No generator, transporter, handler, or owner or operator of a treatment, storage, or disposal facility shall in any way dilute a restricted waste or the residual from treatment of a restricted waste as a substitute for adequate treatment to achieve compliance with Subpart D of this part, to circumvent the effective date of a prohibition in subpart C of this part, to otherwise avoid a prohibition in subpart C of this part, or to circumvent a land disposal prohibition imposed by RCRA section 3004. 40 C.F.R. § 268.3 (1989); see also, e.g., Land Disposal Restrictions for Certain “California List” Hazardous Wastes, 52 Fed.Reg. 25,760, 25,778 (1987) (“EPA [is] amending] the § 268.3 dilution prohibition ... to include dilution to avoid a prohibition in Subpart C of Part 268 {e.g., a dilution to below the restrictions levels for the California list wastes) and dilution to circumvent the effective date of a Subpart C prohibition on land disposal.”). The EPA specifically noted, however, that it did not intend to prohibit “legitimate aggregation of waste streams {e.g., wastewaters) to facilitate centralized treatment.” Id. Although CWA treatment facilities handled characteristic wastes before the adoption of the third-third rule, there were no land-ban requirements under RCRA directed at these wastes. Thus, as to these wastes, CWA facilities faced no restrictions under RCRA prior to the third-third rule. After promulgation of the third-third rule, however, CWA facilities handling characteristic wastes became subject to potential regulation under RCRA’s subtitle C im-poundment and land-ban requirements. For li