Full opinion text
LEVIN H. CAMPBELL, Chief Judge. This is a petition to review the standards promulgated by the Environmental Protection Agency (“EPA”) for the long-term disposal of high level radioactive waste under the Nuclear Waste Policy Act of 1982, 42 U.S.C. §§ 10101-10226 (1982). The states of Maine and Vermont, and the Natural Resources Defense Council, Conservation Law Foundation of New England, and Environmental Policy Institute were the original petitioners. Later Minnesota and Texas also challenged the same standards in separate proceedings. All suits have been consolidated in this circuit. A coalition of nuclear power utilities has been permitted to intervene. I. STATUTORY BACKGROUND The challenged standards were written by the EPA to regulate harmful releases into the environment from radioactive waste stored in repositories planned for its disposal. (The standards also regulate releases occurring while the waste is being managed prior to its disposal.) The waste in question is derived from the fissioning of nuclear fuel in commercial nuclear power plants and in military reactors. Some of the material is first reprocessed so as to recover unfissioned uranium and plutonium. Reprocessing results in a transfer of most of the radioactivity into acidic liquids that are later converted into solid radioactive waste. Some spent nuclear fuel is not reprocessed and itself becomes a waste. Collectively this waste is called high level waste (“HLW”). It is extremely toxic and will maintain its toxicity for thousands of years. Recognizing the need for repositories within which to dispose safely of the growing amounts of HLW, Congress in 1982 enacted the Nuclear Waste Policy Act (“NWPA”), 42 U.S.C. §§ 10101 et seq. The Act provides for a coordinated effort within the federal government to design, construct and operate nationally at least two HLW disposal facilities. 42 U.S.C. § 10134(2)(A). Without foreclosing other disposal methods, Congress focused in the NWPA on the creation of repositories located deep underground. These will depend on the surrounding underground rock formations together with engineered barriers, to contain safely the radioactivity from these wastes. See H.R.Rep. No. 491, 97th Cong., 2d Sess. 29-34, reprinted in 1982 U.S.Code Cong. & Admin.News 3792, 3795-3800. The underground repositories are expected to be constructed using conventional mining techniques in geologic media such as granite, basalt (solidified lava), volcanic tuff (compacted volcanic ash) or salt. The solidified high level waste will be housed in canisters placed in boreholes drilled into the mine floor. When the repository is full, it will be backfilled and sealed. See Background Information Document for Final Rule at 4-1, 4-2. In the NWPA, Congress prescribed a complex process for selecting the sites of the high level waste repositories. We shall summarize the selection process since it is relevant to an overall understanding of the standards in question. The Department of Energy (“DOE”) begins the process by naming states containing “potentially acceptable sites.” 42 U.S.C. § 10136(a). Within 90 days of identification, DOE must tell the governors and legislatures of the identified states where these sites are. Simultaneously, DOE must adopt guidelines for the selection of sites in various geologic media. 42 U.S.C. § 10132(a). DOE is then to apply the guidelines to the potentially acceptable sites and nominate at least five sites as suitable for characterization as candidate sites for the first repository. 42 U.S.C. § 10132(a), (b)(1)(A). Under this format, DOE in February of 1983 identified nine potentially acceptable sites (a Nevada site in tuff; a Washington site in basalt; two Texas sites in bedded salt; two Utah sites in bedded salt; one Louisiana site in a salt dome; and two Mississippi sites in salt domes). See Background Information Document for Final Rule at 4-2. The Act required DOE to recommend to the President three of the nominated sites for detailed characterization studies. 42 U.S.C. § 10132(b)(1)(B). The President may then approve or disapprove a nominated site. 42 U.S.C. § 10132(c). In December 1984 DOE tentatively identified five sites for possible detailed site characterization. Three of these sites were formally recommended for detailed site characterization studies (Yucca Mountain site in Nevada; Deaf Smith County site in Texas; and the Hanford site in Washington). See Background Information Document at 4-5. Nominated sites recommended to and approved by the President are then to be characterized by DOE. 42 U.S.C. § 10133. After conducting the detailed site characterization studies, DOE must make a recommendation to the President concerning the final site approval. Before DOE recommends a site it must hold public hearings, must notify any affected state or Indian tribe, and must prepare an environmental impact statement for each site to be recommended to the President. The President must then submit to Congress an endorsement of one site from the three sites characterized and recommended by DOE. 42 U.S.C. § 10134(a)(2)(A). The site recommended by the President becomes the approved site for the first repository after 60 days, unless the affected state or Indian tribe submits to Congress a notice of disapproval. 42 U.S.C. § 10135(b). If such notice of disapproval is received, the site is disapproved unless, during the first 90 days after receipt of the notice, Congress passes a resolution of repository siting approval. 42 U.S.C. § 10135(c). The same site approval process is prescribed for the selection of a second federal repository site. Several federal agencies share responsibility for building, licensing and laying down standards for the HLW repositories. The Department of Energy is to design, build and operate each federally owned repository. 42 U.S.C. § 10134. However, the Nuclear Regulatory Commission (“NRC”) has responsibility to license the repositories. 42 U.S.C. § 10134(d). Under its licensure powers, the NRC regulates the construction of the repositories, licenses the receipt and possession of high level radioactive waste at the repositories, and authorizes the closure and decommissioning of repositories. See 42 U.S.C. § 10141(b). The EPA also has a major regulatory role. The Act provides that EPA, pursuant to authority under other provisions of law, shall, by rule, promulgate generally applicable standards for protection of the general environment from offsite releases from radioactive material in repositories. 42 U.S.C. § 10141(a) (emphasis added). The language, “pursuant to authority under other provisions of law," refers to the EPA’s responsibility and authority under the Atomic Energy Act of 1954, 42 U.S.C. § 2201(b). The Reorganization Plan No. 3 of 1970 (which was the vehicle used by the executive branch to organize the newly formed Environmental Protection Agency), transferred to the EPA certain functions of the Atomic Energy Commission to the extent that such functions of the Commission consist of establishing generally applicable environmental standards for the protection of the general environment from radioactive material. Reorganization Plan No. 3 of 1970, 3 C.F.R. § 1072 (1966-70 compilation). It is these generally applicable HLW environmental standards, recently promulgated by the EPA pursuant to the directive of the NWPA, which we are now called upon to review. DOE must follow these standards when siting, designing, constructing and operating the repositories. See 10 C.F.R. Part 960 (1987). The NRC must likewise obey them when licensing the repositories. See 10 C.F.R. Part 60 (1987). EPA’s standards will also apply to defense-related DOE facilities (not licensed by the NRC) which store and dispose of defense-related waste. II. THE HIGH LEVEL WASTE ENVIRONMENTAL STANDARDS The HLW environmental standards have two parts. Subpart A, 40 C.F.R. § 191.-01-05 (1986), entitled “Environmental Standards for Management and Storage,” sets individual exposure limits from radiation releases during the management, interim storage, and preparation for disposal of the radioactive wastes. Subpart A requires that the management and storage of HLW during this phase be conducted in such a manner as to provide reasonable assurances that the total annual exposure to any individual member of the public shall not exceed a stated limit (25 millirems to the whole body, 75 millirems to the thyroid, and 25 millirems to any other critical organ), 40 C.F.R. § 191.03. Subpart A also allows the EPA to issue alternative standards for waste management and storage operations at DOE disposal facilities that are not regulated by the NRC (i.e., DOE defense-related facilities), 40 C.F.R. § 191.04. Subpart B, 40 C.F.R. § 191.11-.18 (1986), entitled “Environmental Standards for Disposal,” is intended to ensure long-term protection of public health and the environment from releases of radiation after the HLW has been stored in the chosen manner. Although this subpart was developed having in mind storage at underground repositories, the standards are said to apply also to any other disposal method that may be chosen. Subpart B comprises four different types of environmental standards. The first type is the general containment requirements, 40 C.F.R. § 191.13. These require that nuclear waste disposal systems be designed to provide a reasonable expectation, based on performance assessment, that the cumulative releases of radiation to anywhere in the “accessible environment,” for 10,000 years after disposal, shall not exceed certain designated levels. The term “accessible environment” is defined as the atmosphere; land surfaces; surface waters; oceans; and all of the “lithosphere” that is beyond the “controlled area.” 40 C.F.R. § 191.12(k). The “lithosphere,” as defined, includes the entire solid part of the earth below the surface, including any ground water contained within it. 40 C.F.R. § 191.12Q). The “controlled area” is the surface and underground area (and any ground water found therein) immediately surrounding the repository “that encompasses no more than 100 square kilometers and extends horizontally no more than 5 kilometers in any direction” from the disposed waste. 40 C.F.R. § 191.12(g). These definitions taken together show that the general containment requirements limit the total, cumulative releases of radiation, for 10,000 years, anywhere in the environment, outside the controlled area. Within the controlled area itself, the general containment requirements are inapplicable and, therefore, they place no limits on radiation releases. An example of how the general release limits apply is found in the limits for uranium. The repositories must be designed to give reasonable assurance that for the radionuclide uranium (and all its isotopes) the total radiation release, over a 10,000-year period, to the entire accessible environment (including any ground water) must be less than 100. curies (per 1,000 metric tons of heavy metal waste disposed of). Similar limits are established for other ra-dionuclides, e.g., Americium-241, -243; Plutonium-238, -239, -240, -242. See Table of Release Limits for Containment Requirements, 40 C.F.R. Part 191, Appendix A (1986). According to the EPA, the above general containment requirements constitute the principal protection mechanism of the HLW environmental standards. If cumulative releases are within these levels, overall adverse health effects upon the general population will be low. The EPA estimates that the general containment requirements limit population risks from the disposal of these wastes to “no more than the midpoint of the range of estimated risks that future generations would have been exposed to if the uranium ore used to create the wastes had never been mined.” 50 Fed.Reg. 38,-072, col. 1 (Sept. 19, 1985). The second type of environmental standard found in Subpart B is the assurance requirements, 40 C.F.R. § 191.14. These are a kind of practical backup to the cumulative release requirements just mentioned. The assurance requirements provide, among other things, that “active institutional controls” over disposal sites be maintained for as long a period of time as is practicable after disposal. 40 C.F.R. § 191.14(a). (Active institutional controls include actions like controlling public access to a site, performing maintenance operations and cleaning up releases.) Other facets of the assurance requirements are as follows: that disposal arrangements be monitored in the future to detect deviations from expected performance, 40 C.F.R. § 191.14(b); that there be permanent markers, records and archives (so-called “passive institutional controls”) to indicate to future generations the presence and location of the dangerous waste, 40 C.F.R. § 191.14(c); that disposal systems not rely on just one type of barrier to isolate waste, but rather employ both engineered and natural barriers, 40 C.F.R. § 191.14(d); that repository sites be selected that avoid areas where it is reasonable to expect future exploration for scarce or easily accessible resources, 40 C.F.R. § 191.14(e); that disposal systems be such that, for a reasonable time after disposal, most of the radioactive waste can be removed, 40 C.F.R. § 191.14(f). The assurance requirements are applicable only to disposal facilities that are not regulated by the NRC (i.e., certain DOE national defense-related facilities) because in its comments on the originally proposed rule, the NRC objected to inclusion of the assurance requirements, arguing that they transcended the EPA’s authority to set generally applicable environmental standards. The NRC felt that the assurance requirements were not environmental standards at all but rather were simply ways of ensuring compliance with environmental standards. Since it is the NRC’s responsibility to make sure that the repositories comply with the different regulations, the NRC saw the EPA’s assurance requirements as an intrusion upon the NRC’s jurisdiction. The agencies ultimately resolved the dispute by (1) making the EPA’s assurance requirements applicable only to facilities not licensed by the NRC, and (2) by having the NRC modify its regulations where necessary to incorporate the essence of the EPA’s assurance requirements. See 50 Fed.Reg. 38,072, col. 3. When the EPA published a first draft of its standards, Subpart B only included the two standards so far described (general containment requirements and assurance requirements). See Proposed Rule, 40 C.F.R. Part 191, 47 Fed.Reg. 58,196 (Dec. 29, 1982). The EPA at first believed that these two proposed standards — aimed to keep the total radiation release over a 10,-000-year period below specified safe limits — would suffice. Later, however, it was persuaded to add so-called individual protection requirements, to deal with the possibility that radioactivity might be concentrated in specific areas. Release limits designed to protect individuals were thought necessary because, while overall releases to the environment as a whole would be within tolerable limits, particular individuals might end up being exposed to excessively large doses of radiation: for example, radiation from waste eventually released into, and concentrated in, ground water that is in the immediate vicinity of a repository. The EPA explained that Since ground water generally provides relatively little dilution, anyone using such contaminated ground water in the future may receive a substantial radiation exposure (e.g., several rems per year or more). This possibility is inherent in collecting a very large amount of radioactivity in a small area. See 50 Fed.Reg. 38,077, col. 3. Therefore, after the notice and comment period, two additional provisions, the individual protection requirements, and the ground water protection requirements, were added to Subpart B of the final rule. These were mainly intended to protect individuals located near a repository who might be exposed to contamination emanating from the site. The individual protection requirements, 40 C.F.R. § 191.15, require that disposal systems be designed to provide a reasonable expectation that, for 1,000 years after disposal, the annual radiation exposure to any member of the public in the accessible environment shall not exceed 25 millirems to the whole body or 75 millirems to any organ. The standard requires that in assessing the anticipated performance of a repository, all potential so-called “pathways” of radiation releases from the repository must be considered. The term “potential pathway” represents the expected scenario of how the released radioactivity will travel from the repository to the accessible environment and ultimately to individuals. There are various possible pathways which could result in exposures to individuals. These possible pathways include, for example, direct releases via seepage to the land surface and then to food crops ingested by man; or similar releases travel-ling to a river or to an ocean and then to fish which man would ingest; or releases to ground water that is used for drinking. See Background Information Document for Final Rule at Chapter 7. As discussed above, the Agency was concerned about individual exposures especially because of the possibility that radiation might be released to and become concentrated in ground water, some of which might permeate even the rock surrounding a repository and might find its way, in time, to supplies of ground water beyond the site. Since ground water contaminated by seepage from the site might be used for drinking water, the individual protection requirements expressly require that in determining whether a repository will comply with the annual exposure limits, the assessments must assume that individuals consume all their drinking water (two liters per day) from any “significant source” of ground water outside of the controlled area. This express requirement places an indirect limit on releases to ground water outside of the controlled area (the “controlled area” being, as already described, the area occupied by the repository and a specified surface and below-ground area surrounding the repository, see definition supra). The fourth section of Subpárt B is the special source ground water protection requirements, 40 C.F.R. § 191.16. The term “ground water protection requirements” is somewhat misleading. The provision does not protect ground water generally but only ground water of a very special type within or very near “controlled areas.” Thus these requirements apply only to Class I ground waters, as defined by the EPA’s Ground-Water Protection Strategy, that also meet the following three conditions: (1) They are within the controlled area or near (less than five kilometers beyond) the controlled area; (2) they are supplying drinking water for thousands of persons as of the date that the Department [of Energy] selects the site for extensive exploration as a potential location of a disposal system; and (3) they are irreplaceable in that no reasonable alternative source of drinking water is available to that population. See 40 C.F.R. § 191.12(n). The radiation concentration limits set by this rule are similar to the maximum radiation concentration limits established under the Safe Drinking Water Act, 42 U.S.C. §§ 300f-j, for community water systems. See 40 C.F.R. Part 141. As with the individual protection requirements, the ground water protection requirements will apply only for the first 1,000 years after disposal. Class I ground waters are defined as ground waters that are highly vulnerable to contamination because of local hydrological characteristics and that are also either irreplaceable (ie., there is no reasonable alternative source of drinking water) or vital to a particularly sensitive ecological system. Environmental Protection Agency, Ground-Water Protection Strategy at 5-6 (August 1984). The ground water protection requirements thus apply to an extremely narrow category of ground water found within, or within five kilometers of, the repository site. The Agency explained that the ground water protection requirements provision is necessary and adequate to avoid any significant degradation of this important ground water resource. See 50 Fed. Reg. 38,074 (Sept. 19, 1985). The practical effect of these requirements seems less to provide ongoing regulation than simply to deter the choosing of a site containing ground water of this especially valuable kind upon which “thousands of persons” already depend. If this were the real purpose, however, the EPA did not say so in so many words. III. OUR STANDARD OF REVIEW In reviewing the above described standards, which were promulgated pursuant to notice and comment rulemaking, see 5 U.S.C. § 553(c) (1982), we must make sure that the Agency followed proper procedures in developing the final standards and that the Agency acted within its statutory authority. South Terminal Corp. v. EPA, 504 F.2d 646, 655 (1st Cir.1974). If so, we will invalidate the standards only if they are “arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law.” 5 U.S.C. § 706(2)(A) (1982). In reviewing administrative actions, courts will look to see whether the agency has adequately explained the facts and policies upon which it relied. BASF Wyandotte Corp. v. Costle, 598 F.2d 637, 652 (1st Cir.1979), cert. denied, 444 U.S. 1096, 100 S.Ct. 1063, 62 L.Ed.2d 784 (1980); National Nutritional Foods Association v. Weinberger, 512 F.2d 688, 701 (2d Cir.) (agency obliged to publish statement of reasons for conclusions that will be sufficiently detailed to permit judicial review), cert. denied, 423 U.S. 827, 96 S.Ct. 44, 46 L.Ed.2d 44 (1975). Reviewing courts also require that the facts relied upon have some supporting basis in the administrative record. BASF Wyandotte Corp., 598 F.2d at 652. If these requirements are satisfied, we will not substitute our judgment for that of the agency. Objections to the merits of the standards are outside our province unless it is shown that the agency’s decision was not based on relevant factors or was a clear error of judgment. South Terminal Corp., 504 F.2d at 655. We will delve into the soundness of the agency’s reasoning only to ascertain that the conclusions reached are rationally supported. Id. at 655 n. 5. In their challenge to the HLW standards, petitioners raise numerous and varied objections. The Natural Resources Defense Council (“NRDC”), among others, charges that the individual and ground water protection requirements are not in accordance with law since the EPA has violated a duty under the Safe Drinking Water Act to prevent the endangerment of drinking water by underground injection. The state of Texas claims that in enacting the ground water protection requirements, the EPA has failed to provide legally adequate notice and comment procedures. In addition to these two broad attacks on the standards, all the petitioners raise numerous other claims. They contend, inter alia, that certain aspects of the standards are either irrational or arbitrary; are not supported in the record; or are not adequately explained by the agency. Because of the nature and complexity of these standards, many of these complaints are interrelated and overlap. We shall now consider the various claims, turning first to the contention that EPA has violated the Safe Drinking Water Act. IV. DO EPA’S REGULATIONS VIOLATE THE SAFE DRINKING WATER ACT? Part C of the Safe Drinking Water Act, 42 U.S.C. § 300h (1982) (“SDWA”), indicates that the EPA has a duty to assure that underground sources of drinking water will not be endangered by any underground injection. Petitioners argue here that endangerment of such drinking water is bound to result if HLW is disposed of, underground, under standards no more stringent than the EPA’s current HLW regulations. Since violations of the SDWA are inevitable, so petitioners argue, the present regulations are “not in accordance with law” and hence invalid. To understand this argument we must first look at the SDWA, an Act which preceded the NWPA. The SDWA was enacted in 1974 to assure safe drinking water supplies, protect especially valuable aquifers, and protect drinking water from contamination by the underground injection of waste. The SDWA required the EPA to promulgate standards to protect public health, by setting either (1) maximum contaminant levels for pollutants in a public water supply, or (2) a treatment technique to reduce the pollutants to an acceptable level if the maximum contaminant level is not economically or technologically attainable. Maximum contaminant levels are to be established at a level having no known or adverse human health effect, with an adequate margin for safety. 42 U.S.C. § 300g-l(b)(l)(B). The EPA has established maximum contaminant levels for man-made radionuclides, see 40 C.F.R. § 141.16, as well as a maximum contaminant level for naturally occurring radium, see 40 C.F.R. § 141.15. These standards apply to “public water systems” which regularly supply water to 15 or more connections or to 25 or more individuals at least 60 days per year. 42 U.S.C. § 300f(4); 40 C.F.R. § 141.1(e). The public water system has the responsibility to make sure the water it supplies meets these limits. In effect, the community water system must either clean up existing water if below standard, or find a new water supply which meets the maximum contaminant levels. The EPA is given certain powers to enforce its standards. 42 U.S.C. § 300g-3(b). The SDWA also authorizes EPA to designate, on its own initiative or upon petition, an area as having an aquifer which is the sole source of the area’s water supply and which would create a significant hazard to public health if contaminated. Once an area is so designated, no federal assistance may be provided for any project in the area which EPA determines may contaminate the aquifer. See 42 U.S.C. § 300h-3(e). The SDWA’s only provision for directly regulating pollution-causing activities is found in Part C, 42 U.S.C. § 300h. There Congress sought to protect underground sources of drinking water from what are termed “underground injections.” Underground injection is the subsurface emplacement of contaminating fluids by well injection. 42 U.S.C. § 300h(d)(l). Part C requires the EPA to promulgate regulations governing underground injection control programs. The EPA is directed to publish a list of each state for which an underground injection control program would be necesary to assure that underground injection would not endanger drinking water sources. 42 U.S.C. § 300h-l(a). The EPA has listed all states as needing underground injection control programs. 40 C.F.R. § 144.1(e). The EPA is also required to promulgate regulations governing state underground injection control programs to ensure that the state programs prevent underground injection which could endanger drinking water sources. 42 U.S.C. § 300h(a)(l), (b)(1). If a state program does not comply with the EPA’s regulations, the EPA itself is to promulgate a regulatory program for that state and enforce compliance. 42 U.S.C. § 300h-l(c). To be approved by EPA, a state control program has to meet certain standards. It must prevent underground injection unless authorized by permit or rule; it may authorize underground injection only where it is demonstrated that the injection will not endanger drinking water sources; and it shall include inspection, monitoring, recordkeeping and reporting requirements. 42 U.S.C. § 300h(b)(l)(A)-(C). State regulatory programs (as well as any EPA regulations for non-complying states) apply to underground injections by federal agencies as well as all others. 42 U.S.C. § 300h(b)(l)(D). In requiring EPA to regulate state underground injection control programs, Congress restrained the EPA’s authority in several ways in order to accommodate existing state programs and avoid disrupting oil and gas production. EPA's regulations may not interfere with or impede the production or recovery of oil or natural gas, unless such requirements are essential to assure that underground sources of drinking water will not be endangered by such injection. 42 U.S.C. § 300h(b)(2). EPA’s regulations are to reflect the variations in geologic, hydrological or historical conditions between the states. 42 U.S.C. § 300h(b)(3)(A). To the extent feasible, EPA is not to promulgate rules which unnecessarily disrupt state underground injection control programs that were earlier in effect. 42 U.S.C. § 300h(b)(3)(B). Congress made it clear, however, that, despite the deference the EPA was to afford the states, the goal of protecting underground drinking water was to be preeminent. The SDWA states, Nothing in this section shall be construed to alter or affect the duty to assure that underground sources of drinking water will not be endangered by any underground injection. 42 U.S.C. § 300h(b)(3)(C). This language in particular, petitioners say, establishes that the EPA has an overriding statutory mandate, unaffected by the NWPA, to protect underground drinking water against endangerment. The SDWA defines what is meant by the term “endanger”: Underground injection endangers drinking water sources if such injection may result in the presence in underground water which supplies or can reasonably be expected to supply any public water system of any contaminant, and if the presence of such contaminant may result in such system’s not complying with any national primary drinking water regulation or may otherwise adversely affect the health of persons. 42 U.S.C. § 300h(d)(2). Petitioners assert that the EPA, in promulgating the HLW standards, has violated this so-called “no endangerment mandate” because its rules will allow underground injections that result in radiation contamination of underground drinking water supplies. Analysis of petitioners’ argument requires us to address several questions: (1) whether storage of HLW in underground repositories will constitute an “underground injection” as that term is used in the SDWA; (2) whether the EPA’s HLW standards sanction activities that will “endanger drinking water,” as that phrase is used in the SDWA; and (3) whether, if the two previous questions are answered in the affirmative, EPA’s HLW regulations are contrary to law or, if not, are nonetheless arbitrary and capricious. We shall deal with each of these questions in turn. (1) Does Storage Of HLW In Underground Repositories Constitute Underground Injection? What petitioners call the no endangerment provision of the SDWA, 42 U.S.C. § 300h(b)(3)(C), indicates that the EPA has a duty “to assure that underground sources of drinking water will not be endangered by any underground injection.” For the Agency to have violated that duty by adopting the present HLW regulations, it is necessary that the proposed placing of HLW in underground repositories constitute an “underground injection.” The SDWA defines underground injection as the “subsurface emplacement of fluids by well injection.” 42 U.S.C. § 300h(d)(l) (emphasis added). The EPA, in its regulations enacted pursuant to the SDWA, has defined the terms “fluids” and “well injection.” Well injection is the “subsurface emplacement of fluids through a bored, drilled or driven well; or through a dug well, where the depth of the dug well is greater than the largest surface dimension.” 40 C.F.R. § 146.3. The Department of Energy, in its Mission Plan, has described how the HLW will be disposed of underground. The HLW will be removed from transportation casks, packaged and then transferred underground through the waste-handling shaft. “Once underground, the wastes will be em-placed in boreholes_” Mission Plan at 33. Thus it seems that waste will be “em-placed underground through a bored, drilled or driven shaft.” The EPA has defined the term “fluids” broadly as including a “material or substance which flows or moves whether in a semi-solid, liquid, sludge, gas or any other form or state.” 40 C.F.R. § 146.3. This definition was taken directly from the legislative history which made it clear that “[t]he definition of ‘underground injection’ is intended to be broad enough to cover any contaminant which may be put below ground level and which flows or moves, whether the contaminant is in semi-solid, liquid, sludge, or any other form or state.” H.R.Rep. No. 1185, 93d Cong., 2d Sess., reprinted in 1974 U.S.Code Cong. & Admin.News 6454, 6483. The definition of high level waste in the NWPA shows that at least some of the waste material to be disposed of originates in a liquid form. The term “high-level radioactive waste” means— (A) the highly radioactive material resulting from the reprocessing of spent nuclear fuel, including liquid waste produced directly in reprocessing and any solid material derived from such liquid waste that contains fission products in sufficient concentrations.... 42 U.S.C. § 10101(12). According to the EPA, the waste to be stored underground will be converted, before storage underground, into a solid. See Background Information Document at 3-4. This does not mean that the contemplated waste disposal system is not an underground injection, since the definition of fluids (following the directive in the legislative history, see supra ) is very broad and includes waste “in any other form or state” if it flows or moves. 40 C.F.R. § 146.3. The dangerous component of this waste, i.e., the radiation, regardless of whatever “form or state” it is emitted from, will flow or move, thus having the capacity to do harm to drinking water sources far distant from the original site as more conventional injected fluids would do. The HLW waste rules “apply to radionuclides that are projected to move into the ‘accessible environment’ during the first 10,000 years.” See Preamble, 50 Fed. Reg. 38,071, col. 2. The definition of “barrier” in the regulations includes a structure which prevents or substantially “delays movement” of water or radionuclides toward the accessible environment. 40 C.F.R. § 191.12(d). The Arizona Nuclear Power Project, et al., intervenors in this case, argue that disposal of this radioactive waste underground is not the “type” of underground disposal that Congress was concerned with when it enacted Part C of the SDWA. In-tervenors claim that the type of underground injection which disturbed Congress was a method whereby contaminants were injected into the subsurface and allowed to disperse freely into the general environment. Intervenors assert that the type of disposal contemplated by the HLW rules is different because the waste will be packaged in containers, and will be surrounded by barriers that are designed to isolate this waste from the environment. Thus, they conclude, Part C does not apply to this disposal system. While Congress may have been especially concerned with a different type of underground disposal when it passed Part C of the SDWA, this does not negate its overall intent to protect future supplies of drinking water against contamination. Unusable ground water is unusable ground water no matter whether the original source of the pollution arrived in a loose, free form manner, or in containers injected into the ground. We find no language in the SDWA showing that Congress meant to regulate only certain forms of underground pollution, while overlooking other forms of contamination of ground water via underground injection. Indeed, the legislative history indicates that the phrase “underground injection which endangers drinking water sources” was to have the broadest applicability: It is the Committee’s intent that the definition be liberally construed so as to effectuate the preventative and public health protective purposes of the bill. The Committee seeks to protect not only currently-used sources of drinking water, but also potential drinking water sources for the future.... The Committee was concerned that its definition of “endangering drinking water sources” also be construed liberally. Injection which causes or increases contamination of such sources may fall within this definition even if the amount of contaminant which may enter the water source would not by itself cause the maximum allowable levels to be exceeded. The definition would be met if injected material were not completely contained in the well, and if it may enter either a present or potential drinking water source, and if it (or some form into which it might be converted) may pose a threat to human health or render the water source unfit for human consumption. H.R.Rep. No. 1185, 93d Cong., 2d Sess., reprinted in 1974 U.S.Code Cong. & Admin.News at 6484. We believe that the narrow and constrained reading of Part C of the SDWA advocated by intervenors would do violence to the intent of Congress. We decline that reading. We conclude that the primary disposal method being considered, underground repositories, would likely constitute an “underground injection” under the SDWA. (2) Do The Regulations Under Review Sanction Activities That Will “Endanger Drinking Water”? Part C of the SDWA, 42 U.S.C. § 300h(b)(3)(C), speaks of the EPA’s duty “to assure that underground sources of drinking water will not be endangered by any underground injection.” (Emphasis supplied.) Assuming, as discussed above, that the planned disposal of HLW in underground repositories amounts to “underground injection,” will such injection, if carried out under the EPA’s current HLW standards, “endanger” underground sources of drinking water? We believe the answer is “yes.” As noted, the term “endanger” is defined in the SDWA to include any injection which may result in the presence “in underground water which supplies or can reasonably be expected to supply any public water system of any contaminant ... if the presence of such contaminant may result in such system’s not complying with any national primary drinking water regulation.” 42 U.S.C. § 300h(d)(2). Measured against this definition, the HLW standards permit contamination of most categories of underground water within the so-called controlled area without restriction of any type. More fundamentally, they permit water supplies outside the controlled area to be contaminated by radiation up to individual exposure levels that exceed the levels allowed in national primary drinking water regulations. It follows that the HLW regulations under review not only do not “assure” the non-endangerment of underground sources of drinking water, but sanction disposal facilities allowing certain levels of endangerment as that term is used in the SDWA. We shall now discuss our conclusions in greater detail. A. Endangerment In Controlled Area The two major components of the HLW rules, the general containment requirements and the individual protection requirements, supra, set limits on radiation releases to every part of the earth, including ground water, beyond the area under direct control of those in charge of disposing of this waste (referred to as the controlled area). These requirements have various release limits (depending on which rule is involved, i.e., the limits of the general containment requirements are of a different type from those of the individual protection requirements) which apply outside the controlled area, but neither sets limits on contamination of ground water within the controlled area. A further component, the special source ground water protection requirements, sets limits on releases to certain ground water supplies found within the controlled area, or within five kilometers of the controlled area. However, this rule applies to only a very special class of ground water. Thus, while the ground water outside the controlled area is covered by both the general containment requirements and the individual protection requirements (the sufficiency of which we shall later address), there is essentially no protection of ground water within the controlled area (other than the specific ground water rule, infra, with its highly limited applicability). This is because the general containment and individual protection requirements apply only to releases to the accessible environment. The accessible environment is defined as “(1) the atmosphere; (2) land surfaces; (3) surface waters; (4) oceans; and (5) all of the lithosphere that is beyond the controlled area.” 40 C.F.R. § 191.12(k). Lithosphere is defined as the solid part of the earth below the surface, including any ground water contained within it. 40 C.F.R. § 191.12(j). Controlled area is defined as: (1) A surface location, to be identified by passive institutional controls, that encompasses no more than 100 square kilometers and extends horizontally no more than five kilometers in any direction from the outer boundary of the original location of the radioactive wastes in a disposal system; and (2) the subsurface underlying such a surface location. 40 C.F.R. § 191.-12(g). Thus the two broadly applicable rules (general containment and the individual protection requirements) set some limits on radiation releases to every part of the earth, including the ground water, except within the controlled area, i.e., the part of the earth immediately surrounding the repository. This means that any ground water found within the controlled area (except the special water protected under the ground water protection requirements) may be contaminated without limit. The administrator has explained that the definition of “accessible environment,” was intended to reflect the concept that the geologic media surrounding a mined repository are part of the long-term containment system, with disposal sites being selected so that the surrounding media prevent or retard transport of radion-uclides through ground water. Such surrounding media would be dedicated for this purpose, with the intention to prohibit incompatible activities (either those that might disrupt the disposal system or those that could cause significant radiation exposures) in perpetuity. Applying standards to the ground water contained within these geologic media surrounding a repository would ignore the role of this natural barrier, and it could reduce the incentive to search for sites with characteristics that would enhance long-term containment of these wastes. 50 Fed.Reg. 38,077, col. 1. The administrator further explained that the accessible environment does not include the lithosphere (and the ground water within it) that is below the “controlled area” surrounding a disposal system. The standards are formulated this way because the properties of the geologic media around a mined repository are expected to provide much of the disposal system’s capability to isolate these wastes over these long time periods. Thus, a certain area of the natural environment is envisioned to be dedicated to keeping these dangerous materials away from future generations and may not be suitable for certain other uses. 50 Fed.Reg. 38,071, col. 2. Hence the regulations under review deliberately expose the ground water in the controlled area to contamination in the belief that the controlled area may appropriately be used in this manner to keep the dangerous high level wastes “away from future generations.” There can be little doubt, therefore, that the current HLW standard allows “endangerment,” as the term is used in the SDWA, of most kinds of drinking water sources in the controlled area. However, as we later discuss, the EPA’s choice to sacrifice the purity of water at repository sites as part of the control strategy was impliedly sanctioned by Congress when, subsequent to passage of the SDWA, it enacted the Nuclear Waste Policy Act. We accordingly find no illegality. (Our conclusion in this regard is discussed in a later part of this opinion.) While unlimited “endangerment” of most waters is thus allowed (albeit permissibly) within the controlled area, there is within the controlled area one special category of ground water which, as we have seen, receives special protection. The special source ground water protection requirements afford protection to Class I ground water of certain types in and close to (within five kilometers of) the controlled area. The ground water requirements limit the radionuclide concentrations in these Class I waters for 1,000 years to no more than concentration limits similar to those established for community water systems under the SDWA. That is, this standard sets limits that are compatible with the maximum contaminant level for man-made radiation set under the SDWA. Thus, when applicable, the special source ground water protection requirements comply with the no endangerment policy expressed in Part C of the SDWA since they exactly parallel the limits set by the EPA under the SDWA. However, the ground water protection requirements apply only to so-called “Class I” ground water (as defined in the EPA’s Ground-Water Protection Strategy published in August 1984). In addition, they apply only to those “Class I” waters which also meet the following conditions: (1) They are within the controlled area or near (less than five kilometers beyond) the controlled area; (2) they are supplying drinking water for thousands of persons as of the date that the Department [of Energy] selects the site for extensive exploration as a potential location of a disposal system; and (3) they are irreplaceable in that no reasonable alternative source of drinking water is available to that population. Clearly, the applicability of the special source ground water protection requirements is very much restricted. Petitioners, indeed, make much of this. They assert that this rule violates the SDWA’s no endangerment policy since it protects so limited a class of water within so small an area, omitting the great bulk of the nation’s usable ground water. But while petitioners are doubtless right concerning the narrow scope of this provision, their criticism fails to take account of the EPA’s strategy of dedicating the geologic media within the controlled area (including any ground water found within such geologic media) to serve as a part of the containment mechanism. The EPA obviously intended the special source ground water rule to provide protection only to a small category of ground water deemed to be so valuable that it should not be used for containment purposes. As the Agency assumed that ground water within the controlled area will be part of the containment mechanism, and that therefore a direct limit on releases to ground water within the controlled area is an exception to the general approach, it is understandable that any ground water requirements within the controlled area would have a very limited applicability. These ground water requirements will likely serve more as a deterrent to siting repositories at places containing valuable ground water resources of this description than as a protective mechanism at actual repositories (where the special ground water covered by the ground water rule is unlikely to be present). Moreover, the ground water requirements have no effect more than five kilometers beyond the controlled area. It follows that there will likely be no protection to ground water within an actual controlled area site. B. Endangerment Beyond Controlled Area We turn next to the larger issue of whether the HLW regulations permit “endangerment” as defined in the SDWA of underground drinking water sources beyond the controlled areas. As just discussed, the special source ground water requirements do not apply at all outside the repository site and five kilometers beyond. The individual protection requirements, however, while not a ground water rule as such, give a considerable measure of protection to ground water outside the controlled area. The individual protection requirements are designed to protect individuals in the vicinity of a disposal system by setting annual individual exposure limits effective for 1,000 years. (This contrasts with the general containment release limits which are designed to reduce risks to the general population through standards which limit the cumulative release of radiation for 10,-000 years anywhere in the accessible environment.) The Agency added the individual protection requirements because, although it felt that the general containment requirements would ensure that the overall population risks to future generations would be acceptably small, it also felt that individuals near the repositories might receive substantially greater exposure to radiation than the average person. While overall releases from a repository could be within the total cumulative release limits of the general containment requirements, there might be nearby localities where the radiation would be concentrated, and thus pose a substantial risk to some individuals. As the Agency explained in the preamble to the HLW rules: Even with good engineering controls, some waste may eventually (i.e., several hundreds or thousands of years after disposal) be released into any ground water that might be in the immediate vicinity of a geologic repository. Since ground water generally provides relatively little dilution, anyone using such contaminated ground water in the future may receive a substantial radiation exposure (e.g., several rems per year or more). This possibility is inherent in collecting a very large amount of radioactivity in a small area. 50 Fed.Reg. 38,077, col. 3. To avoid this problem the Agency added the individual protection requirements. The individual protection requirements limit the annual exposure from the disposal system to any individual member of the public for the first 1,000 years to no more than 25 millirems to the whole body, or 75 millirems to any organ. This limit applies outside the controlled area. Inherent in the individual protection requirements is an indirect protection of ground water because in assessing compliance with this requirement, all potential pathways of radiation from the repository to individuals must be considered, and the assumption must be made that an individual drinks two liters per day from any significant source of ground water outside the controlled area. A significant source of ground water is defined as any aquifer currently providing the primary source of water for a community water system, or any aquifers that satisfy five technical criteria. These criteria, according to the EPA, identify underground water formations that could meet the needs of community water systems in the future. See 50 Fed.Reg. 38,078, col. 3. While the individual protection requirements thus provide a level of protection, they also tolerate levels of contamination of drinking water sources well in excess of primary drinking water standards established by EPA under the SDWA, thus permitting “endangerment” of such sources as defined in the SDWA. Pursuant to the SDWA, the EPA has established the maximum contaminant level for man-made ra-dipnuclides in drinking water. 42 U.S.C. § 300g-l. Accordingly, “drinking water shall not produce an annual dose equivalent to the total body or any internal organ greater than 4 millirem/year.” 40 C.F.R. § 141.16(a). With the exception of two specific radionuclides (Tritium and Strontium-90), the concentration of man-made radion-uclides causing 4 millirems total body (or organ dose equivalents) is to be calculated on the basis of assuming that the individual will consume two liters of drinking water per day. 40 C.F.R. § 141.16(b). As set out, supra, drinking water supplies are to be considered endangered under the SDWA if the underground injection “may result in the presence in underground water which supplies or can reasonably be expected to supply any public water system of any contaminant, and if the presence of such contaminant may result in such system’s not complying with any national primary drinking water regulation.” 42 U.S.C. § 300h(d)(2) (emphasis supplied). Since the maximum contaminant level of four millirems was promulgated as a national primary drinking water regulation under the SDWA, and since the individual protection requirements (promulgated under the NWPA) allow an individual dose of 25 millirems, it follows that the individual protection requirements allow HLW to be disposed of under circumstances that, in time, may result in endangering underground sources of drinking water. It can be argued that the individual protection requirements do not necessarily endanger ground water resources because the allowable exposure (25 millirems) might result through a pathway that does not include contamination of ground water supplies. There are several possible pathways that the EPA considers when assessing individual exposure. These possible pathways include direct releases to the land surface, releases through a river, releases to an ocean (then to ocean fish which man would ingest). See Background Information Document at Chapter 7. It is conceivable that an individual could receive only 2 millirem/year from underground drinking water sources and the remaining 23 milli-rems from a different pathway. This, theoretically, would not result in ground water contamination in violation of the no endangerment mandate, ie., ground water would still be under four millirems. However, this scenario is highly unlikely. In the preface to the HLW rules the EPA concedes that “the geological and geochemical characteristics of appropriate sites tend to concentrate eventual releases of wastes in any ground water that is close to the site.” Preamble, 50 Fed.Reg. 38,078. Moreover, the Agency admitted that even with very good engineered controls, radiation may eventually be released in ground water in the immediate vicinity of a repository. 50 Fed.Reg. 38,077, col. 2. The Agency states that “anyone using such contaminated ground water in the future may receive a substantial radiation exposure (e.g., several rems per year or more).” 50 Fed.Reg. 38,077, col. 3 (emphasis supplied). Since a rem is equal to 1,000 millirems (a millirem equals one thousandth of a rem), a possible exposure level of several rems per year will equate to several thousand millirems. In view of the EPA’s own references to substantial exposure through sources of drinking water, it seems clear that a large proportion of the allowable 25 millirems would reach the individual through the drinking water pathway. We note in this regard that the definition of endangerment, found in the SDWA, see 42 U.S.C. § 300h(d)(2), does not require actual violations of primary drinking water standards but rather merely that underground injection may result in contamination in excess of the maximum contamination levels set forth pursuant to the Safe Drinking Water Act. Nor is a violation of the no endangerment provision prevented by EPA’s assertion, in the preamble to these rules, that the individual protection requirement “in no way limits the future applicability of the Agency’s drinking water standards (40 C.F.R. Part 141) — which protect community water supply systems through institutional controls.” 50 Fed.Reg. 38,073, col. 2. Once HLW is placed in a repository, the situation may well be irreversible: there may be no feasible way, years later, to arrest ongoing contamination of surrounding water supplies. To be sure, if a community’s water supply is contaminated above levels set in the SDWA, authorities may require that it be abandoned and a new source of supply used. But the EPA’s duty under the SDWA is to ensure non-endangerment of underground sources of drinking water. 42 U.S.C. § 300h(b)(3)(C). This cannot be done after the fact. The individual protection requirements may allow endangerment of drinking water supplies in another way. The individual protections apply for 1,000 years, as compared to the general containment requirements, which apply for 10,000 years. Thus, after 1,000 years, exposures to individuals near the repositories are not regulated (other than to the extent that the generally applicable 10,000 year cumulative release limits regulate any releases near the repositories). Apparently the rule allows for virtually unlimited degradation of underground water supplies near the control area after 1,000 years. Thus, after 1,000 years, the no endangerment provision would be violated. Whether this is a permissible deviation is discussed below. We mention it in this section merely as a further way that the current rules may be said to permit endangerment. We conclude that the individual protection requirements will permit repositories to be built and used for the disposal of HLW which will, judged by the stricter standard of the SDWA, “endanger” drinking water supplies. (3) Does Noncompliance With SDWA Make The Regulations Contrary To Law Or Arbitrary And Capricious? We have determined in sections (1) and (2) above that the challenged HLW regulations pertain to underground injection, and that the standards they provide will allow underground sources of drinking water to be “endangered” within the meaning of the SDWA. We must now ask whether the foregoing conclusions cause the current regulations to be contrary to law or arbitrary and capricious. The EPA asserts that the no endangerment provision of the SDWA applies to the EPA only in its role as administrator under the SDWA. In its different role as regulator of the disposal of high level waste under the NWPA, the Agency argues that it is free to adopt standards different from the ground water standards established under SDWA. EPA also makes other arguments supporting the proposition that the SDWA is irrelevant to our review of the HLW standards. See infra. In analyzing the relation between the SDWA’s no endangerment provision and the HLW standards, we divide our discussion into two parts: (A) Non-compliance with the SDWA in the controlled area, and (B) Non-compliance outside the controlled area. Briefly summarized, our conclusion in respect to (A) is that when enacting the Nuclear Waste Policy Act of 1982, 42 U.S.C. §§ 10101-10226 (1982), Congress was aware that the area in immediate proximity to the buried HLW would likely be dedicated as a natural protective barrier, and hence could become contaminated. We read the NWPA as containing, by implication, authority for the EPA to depart from SDWA standards in any “controlled area.” It follows that insofar as the regulations under review permit radiation contamination of ground water located within the controlled area itself, they are not contrary to law nor do we find them to be arbitrary and capricious. In respect to (B) our conclusion is different. We find no evidence that Congress expected the HLW standards to permit underground sources of drinking water outside the controlled area to be degraded to levels beneath the standards EPA had established under the SDWA. At very least, such permitted degradation, without any accompanying explanation showing a clear need or justification for a different and lower standard than the SDWA prescribes, is arbitrary and capricious. We now discuss these matters in detail. (A) Non-compliance With The SDWA In The Controlled Area As we have pointed out above, the only protection for ground water within the controlled area comes from the special source ground water requirements. These requirements, however, only apply to specially defined Class I ground waters supplying drinking water “for thousands of persons.” It is quite likely that the ground water found in the controlled areas of actually selected repositories will not be of this type. Hence in the controlled area there will probably, as a practical matter, be no limits on the radioactive contamination of such ground water as is present. It follows that any ground water within the controlled area which is a source or potential so'urce of drinking water will be subject to “endangerment” within the SDWA. However, based on