Opinion for the Court filed by Chief Judge WALD, Circuit Judge RUTH BADER GINSBURG, and Circuit Judge SILBERMAN.

1. INTRODUCTION ........................................................ 701

II. STANDING ............................................................ 703

A. The History of the Standing Issue in this Case .................. 703

B. A Brief Overview of Standing Doctrine ........................... 703

C. NWF's Standing on Particular Issues ............................. 706

1. Issues where the Secetary has Eliminated Minimum National

Environmental Standards (Four Issues) .................... 706

2. Issues where the Challenge to Standing Focuses on the

Adequacy of Affidavits (Fourteen Issues) ................. 709

a. Federal Lands ........................................... 711

b. Off-Site Facilities ..................................... 712

c. Host Soils .............................................. 713

d. Prime Farmland Lakes .................................... 713

e. Support Facilities on Prime Farmland .................... 714

f. Variances from Original Contours ........................ 714

g. Submerged Highwalls ..................................... 715

h. Actual Grazing on Land .................................. 715

D. Conclusion ...................................................... 716

III. MERITS .............................................................. 716

A. Prime Farmland and Pastureland Issues ........................... 716

1. Revegetation Success Standards for Prime Farmland ........... 716

2. Revegetation Success Standards for Grazing and Pastureland .. 718

3. Exemptions from Performance Standards for Prime Farmlands ... 719

a. Construction of Water Impoundments on Prime Farmland .... 719

b. Exemption for Prime Farmland Affected by Coal

Preparation Plants, Support Facilities,

and Roads ............................................ 722

B. Bonding to Assure Reclamation of Land Affected by Mine

Operations ..................................................... 723

1. Incremental and Phased Bonding .............................. 724

2. Bonding for Damage Caused by Subsidence of Land Overlying

Underground Mines ........................................ 726

C. Regulatory Guidance ............................................. 729

1. Alluvial Valley Floors ...................................... 729

2. Mine Waste .................................................. 731

3. Backfilling and Grading ..................................... 734

a. Contemporaneous Reclamation ............................. 735

b. Thin and Thick Overburden ............................... 736

c. Terraces ................................................ 737

D. Residual Issues ................................................. 739

1. Damage Caused by Subsidence of Land Overlying Underground

Mines .................................................... 739

2. Reshaping Cut and Fill Slopes (Roads and Underground Mines) . 741

3. Jurisdiction Over Processing and Support Facilities ......... 742

4. Alluvial Valley Floors Performance Standards ................ 746

5. Substantial Legal and Financial Commitment .................. 747

E. Residual Issues II .............................................. 748

1. Continually-Created Valid Existing Rights ................... 748

2. Values Incompatible with Surface Mining ..................... 751

3. Replacement of Damaged Water Supplies by Operators of

Underground Mines ...................................................... 753

a. The Unplain Meaning of Section 717(b) ................... 753

b. The "Puzzling Contradiction" of Section 508(a)(13)'s

Permitting Requirements .................................. 754

4. Exemption from Water Replacement Requirements for Holders of

Senior Water Rights ...................................... 756

5. Cumulative Hydrologic Assessment--What is "Anticipated

Mining"? ................................................ 757

6. Elimination of Underwater Highwalls ......................... 759

7. Temporary (but Long-Term) Storage of Top Soil ............... 760

8. Authority to Grant Variance from AOC Requirements ........... 761

9. Jurisdiction Over Non-Erosional Aspects of Air Quality ...... 764

10. Use of Proximity as a Factor in Determining Jurisdiction

Over Support Facilities .................................. 765

11. Delegability of Secretary's Authority Over Federal Land

Mining Permits ........................................... 766

IV. CONCLUSION .......................................................... 768WALD, Chief Judge, GINSBURG, RUTH BADER, Circuit Judge, and SILBERMAN, Circuit Judge:

The Surface Mining Control and Reclamation Act of 1977, Pub.L. No. 95-87, 91 Stat. 445 (codified as amended at 30 U.S.C. Secs. 1201 et seq.) ("the Surface Mining Act," "the Act," or "SMCRA"), emerged from prolonged deliberations that reach back to hearings and the introduction of legislation in the 90th Congress.1 The Act, as finally passed by the 95th Congress, established "a nationwide program to protect society and the environment from the adverse effects of surface coal mining operations." SMCRA Sec. 102(a). Environmental impacts from surface coal mining (and the surface impacts of underground coal mining operations) are regulated through two basic mechanisms: a permit system (Secs. 506-514) and a series of performance standards (Secs. 515-516). The Act's permit provisions require that before engaging in a surface coal mining operation, a mine operator must submit detailed information concerning the environmental consequences of the proposed mining operations and include a plan for reclaming affected lands as required by the Act. Once the mining operation has begun, the mine operator must adhere to the statutory environmental performance standards, many of which relate to the obligation to restore and reclaim affected lands. See SMCRA Secs. 515-516.

The Act can be enforced at either the state or federal level. After an interim period of direct federal regulation, states are authorized by the Act to assume a major regulatory role. A state wishing to take on that responsibility must submit a proposed regulatory program to the Secretary of the Interior ("Secretary"), who determines whether the state has the capability to implement SMCRA consistent with federal standards. With the Secretary's approval, the state then assumes primary responsibility for SMCRA enforcement and rulemaking.

The Act has been a fertile source of litigation since its inception. In 1977, numerous coal industry and environmental organizations filed suit in the District Court for the District of Columbia, challenging the interim program regulations that went into effect shortly after the Act's passage and continued until the permanent regulatory regime went into effect in 1979 and 1980. The district court consolidated those challenges and ruled on them in two separate opinions. In re Surface Mining Regulation Litigation, 452 F.Supp. 327 (D.D.C.1978); In re Surface Mining Regulation Litigation, 456 F.Supp. 1301 (D.D.C.1978). This court subsequently affirmed the district court's judgment in part, and reversed in part. In re Surface Mining Regulation Litigation, 627 F.2d 1346 (D.C.Cir.1980) ("SMRL ").

Buffeted by politics and the courts, the interpretation of SMCRA has been an epic in itself. In 1979 Secretary Andrus promulgated permanent program surface mining regulations which prompted a myriad of legal challenges. In a series of three opinions, the district court decided over 100 issues raised by the various parties. In re Permanent Surface Mining Regulation Litigation I, 13 E.R.C. 1586 (D.D.C.1979) (preliminary injunction); In re Permanent Surface Mining Regulation Litigation I, 14 E.R.C. 1083 (D.D.C.1979) ("PSMRL I (Round I )"); In re Permanent Surface Mining Regulation Litigation I, 19 E.R.C. 1477 (D.D.C.1980) ("PSMRL I (Round II )"). One aspect of those decisions, a challenge by the coal industry to the Secretary's rulemaking authority to require applicants for a permit to submit additional information not specifically enumerated in the Act, was eventually rejected on appeal by this court. In re Permanent Surface Mining Regulation Litigation, 653 F.2d 514 (D.C.Cir.) (en banc), cert. denied, 454 U.S. 822, 102 S.Ct. 106, 70 L.Ed.2d 93 (1981) ("PSMRL I "). Many other issues on appeal from the district court were overtaken by events. The presidential election of 1980 resulted in a change in administration mining policy. In 1981, while appeals relating to the 1979 regulations were pending, the new Secretary of the Interior, James Watt, announced his intention to repromulgate the permanent SMCRA program regulations. The entire case was accordingly remanded to the Secretary.

In his reconsideration of the 1979 regulations, Secretary Watt specifically asked commentators to focus on ways to increase the flexibility of federal supervision of state regulatory programs; and more generally, he requested suggestions on how to revise "excessive, burdensome, or counter-productive" regulations. States, citizen groups, and representatives of the coal industry responded with a range of proposals: increase the flexibility of regulations to permit case-by-case implementation, take into account the differences between coal producing regions, eliminate unreasonable difficulties and expense in complying with the regulations, and improve the enforcement program. In 1983, the Secretary announced revised regulations that, inter alia, granted both state regulators and coal mine operators greater discretion in complying with the general requirements of the statute. The Secretary also retained many of the 1979 regulations.

Many of the new "flexible" regulations were challenged by the National Wildlife Federation and other environmental groups (collectively referred to as "NWF").2 Several groups representing the coal industry ("Industry")3 mainly objected to regulations that had remained unchanged from the 1979 program. In four separate opinions, or "Rounds," the district court addressed the 113 issues presented by these various challenges.4 Over 30 of those issues are now before us on appeal.II. STANDING

At the outset, we confront the challenges posed by Industry to the standing of the National Wildlife Federation, appellants here. For reasons to follow, we conclude that district court Judge Flannery correctly found that NWF has standing to challenge each of the regulations in question. We proceed to discuss the merits of each challenge.

A. The History of the Standing Issue in This Case

Standing has emerged as a prime issue in this appeal. Industry raised standing objections in the district court, but Judge Flannery initially made no fact findings on the subject. On appeal, however, Industry interposed a broad challenge to NWF's standing, reaching each of the 21 regulations contested by the environmental organizations. Specifically, Industry argued that NWF had failed to allege a constitutionally adequate injury with respect to each regulation. In the case of several regulations, Industry maintained that NWF had failed to demonstrate a sufficiently strong chain of causation between the challenged regulation and the alleged harm.5

After oral argument, this court remanded the record to Judge Flannery to make additional fact findings on standing. We instructed the district court to receive affidavits "demonstrating specific injury" to members of the plaintiff environmental organizations. NWF thereupon filed with the district court 70 affidavits, amounting to over 1,600 pages.

On August 10, 1987, Judge Flannery issued a memorandum opinion concluding that NWF's affidavits had alleged sufficiently specific injuries with regard to each regulation challenged by NWF to satisfy Article III of the Constitution. See In re Permanent Surface Mining Regulation Litigation, No. 79-1144, mem. op. (D.D.C. Aug. 10, 1987) (hereinafter "Findings on Standing").

In light of the vast expanse of issues before us in this appeal, we pause first to sort out which issues are, and are not, subject to standing challenges. NWF has not contested, nor could it seriously contest, the standing of Industry to challenge those regulations that Industry has assailed. Thus, as to issues on which Industry is pitted against the Secretary, no standing challenge is before this court.

Additionally, in the aftermath of Judge Flannery's memorandum opinion on standing, Industry concedes that NWF has standing to challenge three of the 21 regulations NWF has contested. These regulations involve: (1) the replacement of the water supply of property owners whose supply has been damaged by underground coal mining; (2) the measures coal operators must take to control "fugitive dust"; and (3) the requirement that regulatory authorities determine the probable cumulative impact of all anticipated mining prior to its inception. See Brief for Industry at 25, 27, 43 (conceding standing on these issues).6 After studying NWF's affidavits and reviewing Judge Flannery's treatment, see Findings on Standing, at 16-17, 19-20, 33-34, with regard to these three issues, we conclude along with Judge Flannery that NWF has satisfied the standing requirements of Article III of the Constitution. We are thus left with challenges to NWF's standing to contest the 18 remaining surface-mining regulations.

Standing jurisprudence is a highly case-specific endeavor, turning on the precise allegations of the parties seeking relief. Compare Sierra Club v. Morton, 405 U.S. 727, 92 S.Ct. 1361, 31 L.Ed.2d 636 (1972) (denying standing to an environmental organization challenging development of a ski resort in a national forest because it failed to identify "specific injury" to members) with United States v. SCRAP, 412 U.S. 669, 93 S.Ct. 2405, 37 L.Ed.2d 254 (1973) (finding pleadings alleged facts which, if true, would establish standing by environmental group to challenge Interstate Commerce Commission's allowance of rail freight increase which identified members whose recreational and aesthetic interests would be allegedly injured because rate increase would lead to heightened use of raw, instead of recycled, scrap metal). Thus, in this case, rather than passing a composite judgment on the standing of NWF with regard to the mass of regulations before us, we evaluate the nature of NWF's objection to each challenged regulation in order to determine whether NWF can contest these measures in court.

We begin our standing inquiry by recalling some principles of special relevance to this case. Standing involves both limitations imposed by the "case or controversy" requirement of Article III of the Constitution and "prudential limits on its exercise." Warth v. Seldin, 422 U.S. 490, 498, 95 S.Ct. 2197, 2205, 45 L.Ed.2d 343 (1974).7 The Supreme Court has construed the constitutional elements of the standing requirement as embracing three separate, yet necessarily intertwined components: The party invoking the court's authority must demonstrate (1) "some actual or threatened injury" that (2) "fairly can be traced to the challenged action" and (3) "is likely to be redressed by a favorable decision." Valley Forge Christian College v. Americans United for Separation of Church and State, 454 U.S. 464, 472, 102 S.Ct. 752, 758, 70 L.Ed.2d 700 (1982) (quoting Gladstone, Realtors v. Village of Bellwood, 441 U.S. 91, 99 S.Ct. 1601, 60 L.Ed.2d 66 (1979), and Simon v. Eastern Kentucky Welfare Rights Org., 426 U.S. 26, 38, 41, 96 S.Ct. 1917, 1924, 1925-26, 48 L.Ed.2d 450 (1976), respectively). See also Allen v. Wright, 468 U.S. 737, 751, 104 S.Ct. 3315, 3324, 82 L.Ed.2d 556 (1984).

The first of these elements, that a party "has been or will in fact be perceptibly harmed by the challenged agency action," see United States v. SCRAP, 412 U.S. at 688, 93 S.Ct. at 2416, is the core of standing. See Daughtrey v. Carter, 584 F.2d 1050, 1056 (D.C.Cir.1978) (characterizing injury requirement as "first and foremost element of standing"). The requisite injury cannot be to merely "abstract" interests, see Diamond v. Charles, 476 U.S. 54, 106 S.Ct. 1697, 90 L.Ed.2d 48 (1986); Simon, 426 U.S. at 40, 96 S.Ct. at 1925; Sierra Club, 405 U.S. at 739-40, 92 S.Ct. at 1368-69. Nevertheless, the "distinct and palpable injury," see Warth v. Seldin, 442 U.S. at 501, 95 S.Ct. at 2206, suffered by a party need not be tangible or great: an "identifiable trifle" will do. See United States v. SCRAP, 412 U.S. at 689 n. 14, 93 S.Ct. at 2417 n. 14.

Injury to aesthetic or recreational interests, as well as to more traditional economic interests, will support a claim of standing. See, e.g., Sierra Club, 405 U.S. at 734, 92 S.Ct. at 1366 ("Aesthetic and environmental well-being, like economic well-being, are important ingredients of the quality of life in our society, and the fact that particular environmental interests are shared by the many rather than the few does not make them less deserving of legal protection through the judicial process."); Montgomery Envtl. Coalition v. Costle, 646 F.2d 568, 576-78 (D.C.Cir.1980) ("concerned citizens" professing interest in the preservation of the environment held, under statutory provision incorporating the Sierra Club test, to have standing to challenge permits issued to sewage treatment plants); Committee for Auto Responsibility v. Solomon, 603 F.2d 992, 997-99 (D.C.Cir.1979), cert. denied sub. nom. Committee for Auto Responsibility v. Freeman, 445 U.S. 915, 100 S.Ct. 1274, 63 L.Ed.2d 599 (1980) (environmental organization has standing to challenge "[h]arm to health and conservational interests" stemming from failure of General Services Administration to prepare an environmental impact statement prior to leasing city land for use as a parking lot). Also significant here is the time-honored principle that harm can be actual or threatened, see Valley Forge, 454 U.S. at 472, 102 S.Ct. at 758, thus allowing those who plausibly anticipate future injury to bring suit. See Wilderness Soc'y v. Griles, 824 F.2d 4, 10-12 (D.C.Cir.1987) (discussing standards for determining when an allegation of threatened injury suffices for standing); see also National Wildlife Fed'n v. Burford, 835 F.2d 305, 313-14 (D.C.Cir.1987) (same).

The second prong of the standing inquiry is causation: the injury alleged must be "fairly traceable" to the action under attack. The Supreme Court's decisions on this point show that mere indirectness of causation is no barrier to standing, and thus, an injury worked on one party by another through a third party intermediary may suffice. See, e.g., Meese v. Keene, --- U.S. ----, 107 S.Ct. 1862, 95 L.Ed.2d 415 (1987) (would-be distributor has standing to challenge Justice Department's characterization of film as "political propaganda" under foreign agents' registration act because label could hurt his chances of reelection to state senate); United States v. SCRAP, 412 U.S. 669, 93 S.Ct. 2405. As we stated in Autolog Corp. v. Regan, 731 F.2d 25 (D.C.Cir.1984):

It is well settled that a plaintiff has standing to challenge conduct that indirectly results in injury.... 'We are concerned here not with the length of the chain of causation, but on [sic] the plausibility of each of the links that comprise the chain.'

731 F.2d at 31 (citations omitted) (quoting Public Citizen v. Lockheed Aircraft Corp., 565 F.2d 708, 717 (D.C.Cir.1977)). Other prominent cases in which the "fairly traceable" requirement was found satisfied despite a relatively attenuated chain of causation are Duke Power Co. v. Carolina Envtl. Study Group, 438 U.S. 59, 98 S.Ct. 2620, 57 L.Ed.2d 595 (1978), in which the Supreme Court held that an environmental group had standing to challenge Price-Anderson Act's limitation on utility liability in event of nuclear accident, and Japan Whaling Ass'n v. American Cetacean Soc'y, 478 U.S. 221, 106 S.Ct. 2860, 92 L.Ed.2d 166 (1986), in which the Court held that a whale-watching group had standing to challenge the failure of the Secretary of Commerce to cite Japan for violations of international limitations on harvesting of whales.

The final prong of current constitutional standing analysis is redressability. Redressability and causation analyses often replicate one another, particularly in cases where, as here, the relief requested is merely the cessation of illegal conduct. See Allen v. Wright, 468 U.S. at 753 n. 19, 104 S.Ct. at 3325-26 n. 19; see also Haitian Refugee Center v. Gracey, 809 F.2d 794, 801 (D.C.Cir.1987) (describing "traceability" and "redressability" requirements as "closely related"); cf. California Ass'n of the Physically Handicapped v. Federal Communications Comm'n, 778 F.2d 823, 825 n. 7 (D.C.Cir.1985) (explaining the distinction between the two requirements). We note, however, that a party seeking judicial relief need not show to a certainty that a favorable decision will redress his injury. A mere likelihood will do. Village of Arlington Heights v. Metropolitan Housing Corp., 429 U.S. 252, 261, 97 S.Ct. 555, 561, 50 L.Ed.2d 450 (1977); Regents of the Univ. of Cal. v. Bakke, 438 U.S. 265, 280-81, 98 S.Ct. 2733, 2743, 57 L.Ed.2d 750 (1978) (Powell, J.); International Ladies Garment Workers' Union v. Donovan, 722 F.2d 795, 811 n. 27 (D.C.Cir.1983), cert. denied, sub. nom. Breen v. International Ladies Garment Workers' Union, 469 U.S. 820, 105 S.Ct. 93, 83 L.Ed.2d 39 (1984). As we stated in Community Nutrition Inst. v. Block, 698 F.2d 1239, 1249 (D.C.Cir.1983), rev'd on other grounds, 467 U.S. 340, 104 S.Ct. 2450, 81 L.Ed.2d 270 (1984), a plaintiff need not "negate every 'speculative and hypothetical possibilit(y) ... in order to demonstrate the likely effectiveness of judicial relief.' "

With these guiding principles in mind, we turn to Industry's 18 remaining standing challenges to NWF's various claims. For the sake of coherence we have classified those challenges into two broad groups, each of which raises analytically similar issues.

1. Issues Where the Secretary Has Eliminated Minimum National Environmental Standards (Four Issues)

The first cluster of standing challenges includes four instances in which NWF has challenged Secretary Watt's elimination of minimum national standards governing various aspects of surface mining. These regulations involve (1) the contemporaneous reclamation of mined land; (2) the design of earth "terraces" on restored land; (3) the exemption from the "approximate original contour" requirement of lands featuring unusually thick or thin overburden; and (4) the information required from those seeking permits for activities that could unsettle alluvial valley floors.8 In each of these areas, the Secretary has eliminated regulations previously prescribed as minimum standards for implementing the broadly worded provisions of the Act. These regulatory floors were to guide federal enforcement or, in the event that states accepted the Act's invitation to assume regulatory authority, state enforcement.

The first NWF issue in this cluster stems from the requirement imposed by Sec. 515(b)(16) that mine operators reclaim land "as contemporaneously as practicable [to the] mining operations." In 1979, then-Secretary Andrus promulgated specific "time and distance" standards for such backfilling and grading, see 30 C.F.R. Sec. 816.101, but four years later, Secretary Watt repealed those standards, concluding that " 'contemporaneous reclamation' is a relative term which must be interpreted by each State on the basis of the mining conditions in its territory." 48 FED.REG. 23357-58 (1983).

The second issue relates to the requirement of Sec. 515(b)(3) that land be restored to its "approximate original contour." The regulations adopted in 1979 attached numerical benchmarks to this broad requirement, requiring terraces to be built with bench widths less than 20 feet and slopes between benches at less than a 50 degree angle. Secretary Watt's revisions, however, abandoned maximum bench widths and outslope angles, leaving to regulatory authorities the decision on a case-by-case basis whether to approve given terrace characteristics.

The third issue involves the exemption in Sec. 515(b)(3) from the requirement that lands be returned to their approximate original contour. The 1979 regulations provided numerical specifications for grants of a variance from the approximate original contour requirement; but in 1983, Secretary Watt eliminated the numerical standards, allowing variances whenever the mine operator asserts that spoil is either "insufficient" or "more than sufficient" to restore land to its approximate original contour. 30 C.F.R. Sec. 8XX-XXX-XXX (1986).

The fourth issue involves the information required of those seeking permits for operations that might affect alluvial valley floors. Section 515(b)(10)(F) requires surface coal mining operations to "preserve throughout the mining and reclamation process the essentially hydrologic functions of alluvial valley floors in the arid and semi-arid areas of the country." The original regulations contained precise specifications on the information needed in a permit application when a mine operator's proposed operations might affect an alluvial valley floor, but in 1983, Secretary Watt withdrew the enumeration of this "technical data, information and analysis." Instead, he required simply that "generally ... sufficient information be submitted to enable the regulatory authority to make the necessary determinations." 48 FED.REG. 29814 (1983).

With regard to each of these issues, NWF alleges that it suffers at the very least a threat of injury from the Secretary's deletion of the regulatory minimums. In response, Industry suggests that NWF has merely alleged a statutory violation without proffering a viable claim of specific injury. See Motion to Remand Certain Issues With Direction to Dismiss for Want of Jurisdiction and Ripeness (hereinafter "Brief for Industry"), at 12-15. Insofar as the first prong of the standing requirement, injury in fact, is concerned, we, however, are satisfied that NWF's affidavits now provide sufficient allegations of personalized injury to satisfy the Sierra Club and SCRAP standards for "injury in fact" in environmental cases. These affidavits provide sufficient details describing threatened injuries. Typically, NWF's affiants live in communities where surface mining operations have occurred. In addition to alleging past environmental degradation, these affiants describe in substantial detail the injuries they fear from ongoing and future mining operations. Those affiants addressing the contemporaneous reclamation, terracing and thick and thin overburden requirements allege that the new regulations permit greater deviance from the goal of approximating the original contour of the mined land, a major environmental goal of the Act. Those affiants addressing the deletion of specific information requirements regarding alluvial valley floors in permit applications allege that this policy will create an increased danger of degrading water supplies in the West.

Industry suggests that these affidavits are inadequate for failure to track the sometimes hypertechnical language of the statute, see, e.g., Brief for Industry at 23 ("Neither [affiant] so much as mentions ... the thick overburden exemption"), or for failure to describe with precision the harms they fear. See, e.g., id. at 21 ("[n]either points to any specific mine or terrace, and each offers only a general and irrelevant observation that their aesthetic enjoyment would be diminished...."). We disagree. Unyielding insistence on parroting the arcane technicalities of the law or regulations, however, would turn the standing requirement into a barrier impeding all but mining engineers from challenging this legislation. NWF's allegations of injury in these affidavits, far from being "an ingenious academic exercise in the conceivable," see SCRAP, 412 U.S. at 688, 93 S.Ct. at 2416, are the allegations of real people personally concerned about constitutionally-sufficient environmental, recreational, or aesthetic injuries. In view of the specificity of the numerous allegations affiants make concerning threatened deviations from reclaiming land to its original contour, those allegations are reasonably read to address the technical regulations which implement that important requirement. We therefore wholly concur in Judge Flannery's evaluation of the adequacy of these allegations to establish injury in fact with respect to each of these regulations. See Findings on Standing at 6-12, 25-26.

The more difficult issue regarding these four regulations is whether NWF has satisfactorily established that the injuries of which it complains are "fairly traceable" to the challenged action. Industry contends in each instance that the injuries cited in NWF's affidavits are merely speculative. Specifically, it makes three distinct arguments. First, Industry argues that because individual states may choose to adhere to the initial regulatory minimums set forth in 1979, any fear of laxer standards is premature. Second, it argues that the new, more nebulous regulations could still be interpreted so as to conform to, or even exceed, the previous minimum standards. Third, it maintains that threatened injury "can arise only after a government agency makes a future discretionary decision that may be either favorable or unfavorable to the plaintiff." See Brief for Industry at 10-11.

We disagree with each of these arguments. At the outset, we note that Industry's contentions as to the speculative nature of NWF's challenge relate as much to ripeness as they do to causation; we therefore address each of Industry's contentions in turn with an eye to ripeness as well as to standing doctrine.

Industry's first argument--that it is conceivable that individual states will continue to apply the older, 1979 regulations with their precise minimum standards--does not stand up. With regard to each regulation, NWF has identified at least one plaintiff living in a state directly governed by Secretary Watt's deletion of the 1979 standards. Specifically, NWF has identified at least one of its members who lives in a state in which the federal government enforces surface-mining standards because the lands in question are federal ones, or because the state has not accepted the federal invitation to assume responsibility for enforcement. Although NWF's 70 affidavits offer a number of examples upon which standing might be found on these four issues, we need only note that several plaintiffs identified by NWF live in Tennessee, a state in which the federal government enforces surface-mining standards. Theses affiants allege threatened injuries stemming from the relaxation of the federal government's approximate original contour standards. See, e.g., Hollis Aff.; Little Aff.; Miller Aff.; Smiddy Aff.; S. Williams Aff. Similarly, Neil McBride, also a Tennessee resident, alleges injuries from the diminution of permit information required by the federal government for activities that could harm alluvial valley floors. See McBride Aff.

Thus, the first argument put forth by Industry--that some cooperating states may choose to retain or even exceed the 1979 standards--is irrelevant, for NWF has identified plaintiffs directly governed by the Secretary's new regulations.9

As its second causation/ripeness argument, Industry repeatedly asserts that the newer regulations remain susceptible to interpretive constructions in which they would be every bit as stringent as the more specific 1979 standards, see, e.g., Brief for Industry at 18-20, 21, 22, 33. It strains credulity, however, to suggest that the Secretary, in abandoning minimum standards, sought to encourage mining concerns to exceed the previous regulatory floors. Mining concerns were, after all, free to undertake extra precautions under the 1979 regulations; the paramount impact of the 1983 deletions is to position Industry to do less rather than more to restore mined land.

Although we do not read the Act to require that every statutory prescription be fleshed out by numerical standards, see, e.g., infra section III-C-3, we do regard Congress' admonitions--notably those expressed in the House Report--regarding the need for specific regulations as supporting the inference that a causal connection exists between deletion of regulatory specifics and adverse environmental effects. And while Congress cannot create standing on its own, it can provide legislative assessments which courts can credit in making standing determinations. See Autolog Corp. v. Regan, 731 F.2d 25, 31 (D.C.Cir.1984) ("we must give great weight to this congressional finding [of causation] in our standing inquiry"); see also Animal Welfare Inst. v. Kreps, 561 F.2d 1002, 1010 (D.C.Cir.1977), cert. denied sub nom. Fouke Co. v. Animal Welfare Inst., 434 U.S. 1013, 98 S.Ct. 726, 54 L.Ed.2d 756 (1978) (deferring to congressional determination that causation existed "as a matter of law"). Congress' suggestion here that the deletion of minimum standards might lead to lessened protection is just such a legislative assessment.

Industry's third contention is that NWF cannot challenge the Secretary's relaxed regulations until a decision unfavorable to plaintiffs is actually made under them. In support of this contention, Industry cites a string of cases from the Supreme Court and this circuit purportedly saying that the existence of an intervening discretionary authority blocks standing and/or ripeness. See Brief for Industry at 11 n. 11. Industry's cases, however, arise in a very different context. They all involve parties seeking to overturn rules or enactments before such enactments have been enforced against them personally. See, e.g., Brown v. Hotel Employees, 468 U.S. 491, 104 S.Ct. 3179, 82 L.Ed.2d 373 (1984); Pacific Gas & Elec. v. Energy Resources Conservation & Dev. Comm'n, 461 U.S. 190, 103 S.Ct. 1713, 75 L.Ed.2d 752 (1983); International Longshoremen's & Warehousemen's Union v. Boyd, 347 U.S. 222, 74 S.Ct. 447, 98 L.Ed. 650 (1954); Cabais v. Egger, 690 F.2d 234 (D.C.Cir.1982). By contrast, NWF here challenges currently operative rules that require no act of administrative discretion to affect environmentalist plaintiffs. Cf. Japan Whaling Ass'n, 478 U.S. 221, 106 S.Ct. 2860, 92 L.Ed.2d 166 (standing found where harm to whalewatchers from failure to sanction Japan for whale-harvesting could ensue without any further governmental action).

In any event, Industry's argument overlooks fundamental principles of ripeness analysis. Insofar as the constitutional dimensions of the ripeness requirement are concerned, a clear case or controversy exists here, given the significant likelihood of injury to NWF's members in states, such as Tennessee, where the federal government is the direct regulatory authority. See, e.g., Babbitt v. United Farm Workers National Union, 442 U.S. 289, 298, 99 S.Ct. 2301, 2308, 60 L.Ed.2d 895 (1979) ("[a] plaintiff who challenges a statute must demonstrate a realistic danger of sustaining a direct injury as a result of the statute's operation or enforcement"). Nor do the prudential components of the ripeness requirement impede NWF's claim, in light of Congress' express intent that those suits challenging the surface mining regulations be judged under "the broadest standing requirements enunciated by the U.S. Supreme Court." See H.R.REP. NO. 218, 95th Cong., 1st Sess. 90 (1977), reprinted in 1977 U.S.CODE CONG. & ADMIN.NEWS 593, 622.10

For the foregoing reasons, we regard the threat to NWF's members as "sufficiently real and immediate to show an existing controversy," see Blum v. Yaretsky, 457 U.S. 991, 1000, 102 S.Ct. 2777, 2784, 73 L.Ed.2d 534 (1982), and we therefore find that NWF has standing to challenge these four regulations.11

2. Issues Where the Challenge to Standing Focuses on the Adequacy of Affidavits (Fourteen Issues)

The primary focus of Industry's remaining 14 challenges to standing is on the adequacy of NWF's affidavits in alleging an injury in fact.

We quickly dispose of six of these challenges; these involve (1) the Secretary's determination of the proper amount of the bond that underground mining operations must post; (2) the Secretary's endorsement of "incremental" and "phased" bonding, both of which NWF alleges allow initial bonds posted by mining operations to fall below the figure established by the statute; (3) the Secretary's interpretation of the scope of the "valid existing rights" exception to the general SMCRA prohibition of surface mining on certain federal lands; (4) the Secretary's determination that the exception allowing surface mining on federal lands which have "no significant recreational, timber, economic or other values which may be incompatible with surface mining operations," see SMCRA Sec. 522(e)(2), allows surface mining in all circumstances except where incompatibility is permanent and reclamation is impossible; (5) the Secretary's decision to eliminate two specific design criteria for dry waste piles, which had been set forth pursuant to the statutory requirement in SMCRA Sec. 515(f) that he establish standards and criteria for waste piles; and (6) the Secretary's creation of what amounts to a first-in-time, first-in-right exception to the general requirement that surface mine operators replace the water supply of property owners whose supply was contaminated or interrupted as a result of the mining operation.12

Industry's objections to standing on these issues, as we have noted, generally challenge NWF's allegations of injury in fact. These assertions are without merit. As with the three issues discussed earlier on which Industry conceded standing, see supra, NWF's affidavits here allege injury and make out highly plausible lines of causation leading from the Secretary's acts to the injury.

Industry attempts to impugn NWF's affidavits, mostly by disaggregating each allegation so as to make it appear to hinge on the chance occurrence of multiple unlikely contingencies. See, e.g., Brief for Industry at 24 (contending that absence of a subsidence bond could produce damage only if five events coincided, and therefore describing the alleged injury as "remote and speculative"); see also id. at 41-44 (deploying same form of argumentation with regard to validly existing rights, significant values in national forests, and junior water rights). Industry's attack falters on Autolog Corp., like this a case involving a motion for summary judgment for want of standing; in Autolog, we emphasized that it is not the length of the chain of causation, but rather its plausibility, that is dispositive in standing analysis. Industry's attempt to blend its substantive defense of the merits of the Secretary's actions into its standing argument, see, e.g., Brief for Industry at 24 (suggesting that the incremental bonding regulations are unobjectionable because they mirror a "similarly flexible provision" in the 1979 regulations), likewise cannot overcome NWF's allegations of injuries sufficient to satisfy the standing requirement.13

Industry's arguments with reference to NWF's challenges to the remaining eight issues make more colorable contentions, and we therefore treat them individually.

a. Federal Lands

NWF's challenge here is to the Secretary's delegation to a state agency of his duty to approve "mine plans" on federal lands. Under the Act, as the district court noted, a state may agree to regulate mining operations on federal land, but the Act also provides that "[n]othing in this subsection shall be construed as authorizing the Secretary to delegate to the States his duty to approve mining plans on Federal lands." SMCRA Sec. 523(c).14

The district court concluded that NWF had standing to challenge this delegation. See Findings on Standing, at 18-19. On appeal, Industry focuses its challenge to standing entirely upon the affidavit of Colorado residents Timothy and Susan Brater, upon which the district court had heavily relied. The Braters had alleged injury on the ground that they had sued to challenge the Secretary's decision to issue a permit to a nearby mine, but that the Secretary had moved to dismiss on the ground that he no longer has authority with respect to the mine, having delegated it to the state of Colorado under a cooperative agreement. Industry now alleges that because the Braters' petition has already been heard twice by the Secretary in previous chapters of the dispute, the Braters lose no substantive or procedural rights as a result of the delegation, and thus NWF, to which the Braters belong, has no standing. See Brief for Industry at 26.

We disagree. Setting aside the issue of whether the Braters have lost a procedural right, Industry wholly fails to counter NWF's separate contention that its affiants lose a distinctive federal substantive right by dint of the delegation to the states: the right to have an environmental impact statement (EIS) prepared. Affiant Arthur Hayes fears that his ability to evaluate and oppose future mining will be impaired in the absence of an EIS, see Hayes Aff., and affiants Edward Dobson, Patty Kluver, and Wallace McRae voice similar concerns. See Dobson Aff., Kluver Aff., McRae Aff. We conclude that, for affiants voicing environmental concerns like those in the aforementioned affidavits, the elimination of the opportunity to see and use an EIS prepared under federal law does constitute a constitutionally sufficient injury on which to ground standing. See Action Alliance of Senior Citizens v. Heckler, 789 F.2d 931, 937-39 (D.C.Cir.1986) (denial of access to government-provided information regarding services available to the elderly held a sufficient injury on which to ground standing); Cady v. Morton, 527 F.2d 786, 790 (9th Cir.1975) (absence of an EIS constitutes injury on the basis of which plaintiffs could sue for violation of National Environmental Policy Act of 1969 (NEPA)); Scientists' Inst. for Pub. Information, Inc. v. Atomic Energy Comm'n, 481 F.2d 1079, 1087 n. 29 (D.C.Cir.1973) (agency's decision not to draft a NEPA statement caused injury in fact satisfying Sierra Club test); National Org. for the Reform of Marijuana Laws (NORML) v. United States Dep't of State, 452 F.Supp. 1226, 1230 (D.D.C.1978) (citing Scientists' Inst. and concluding that NORML had alleged a sufficient "informational interest" under NEPA in challenging agencies' failure to prepare and consider an EIS with respect to United States participation in herbicide spraying of marijuana plants); Natural Resources Defense Council v. Securities and Exch. Comm'n, 389 F.Supp. 689, 698 (D.D.C.1974) (failure of SEC to make public disclosure of certain information held sufficient injury to support plaintiffs' standing to sue).

b. Off-Site Facilities

Under this heading, NWF challenges the Secretary's interpretation of the jurisdictional scope of the Act. The Act, in Sec. 701(28), states that it covers "surface coal mining operations." In 1983, however, the Secretary excluded from his definition of that term facilities that process coal but do not separate coal from its impurities. Additionally, the Secretary defined that statutory term to exclude off-site facilities beyond a certain distance from a mining operation.15

The district court concluded that the affidavits produced by NWF adequately alleged standing. See Findings on Standing, at 20-21 (citing McBride Aff.; Fretwell Aff.). Industry challenges this determination, arguing that the affiants in question did not spell out the types of off-site operations they fear with sufficient specificity to cover all the contingencies NWF now raises. See Brief for Industry at 27. We disagree. Contrary to Industry's assertions, the McBride affidavit, for example, does voice concern about off-site injuries, citing "coal crushing tipples and rail loadout facilities" alongside two Tennessee highways. See McBride Aff. at 5.

More generally, as in its arguments about NWF's standing to challenge the regulations imposing minimum environmental standards, Industry adopts too parsimonious a reading of the standing requirement, one too hypertechnical to be supportable. Both the above-named affiants, as well as others, see, e.g., Combs Aff., allege ongoing harms stemming from the failure to restrict certain off-site operations. Standing on this issue does not require meticulous specificity, or the affiants' intimate familiarity with operations on neighboring land. The core issue here is the scope of jurisdiction over offsite facilities, an issue the affiants identified by the district court surely have standing to raise. In attempting to disaggregate this issue so as to require NWF to name plaintiffs suffering from every conceivable side-effect of the Secretary's narrower conception of the Act's jurisdiction, Industry would turn the standing requirement from a means of identifying genuine controversies into a barrier blocking challenges by all but the most greviously afflicted plaintiffs.

c. Host Soils

NWF here challenges the Secretary's interpretation of Sec. 515(b)(5) of the Act, which provides that coal operators must carefully remove and replace topsoil displaced by their activities. The Secretary in 1983 issued a regulation allowing the storage on host soil of topsoil salvaged from adjacent mining activities, an interpretation NWF contends will damage the topsoil.16

The district court concluded that NWF had standing to bring this challenge, see Findings on Standing, at 22-23 (citing Smith Aff.). Industry now argues before us that the district court overlooked the existence of other regulations that impose "protective conditions," thereby limiting possible harm stemming from the newer regulations. This argument, however, goes not to standing, but to the substantive validity of the new regulations.

Industry also challenges as speculative the Smith affidavit upon which the district court relied. See, e.g., Brief for Industry at 29 (concluding that Ms. Smith would be injured only upon the chance occurrence of eight events, one of which it deems to have only a 0.8% chance of occurring). We disagree; Ms. Smith alleged injury with sufficient plausibility and specificity when she asserted:

I am concerned that since our farmland contains prime farmland soils located over [a lessee coal company's] mineral holdings that our farming productivity will suffer as a result of [the company's] future mine. I am especially concerned with the surface impacts and disturbances that the future mine may produce, particularly related to the redistribution and spreading of additional soils from the disturbed area over non-disturbed topsoil.

See Smith Aff. at p 4 (emphasis added). We again recall this court's caution in Autolog Corp., 731 F.2d at 31, that "we are concerned ... not with the length of the chain of causation, but with the plausibility of each of the links that comprise the chain." The Smith affidavit evinces an altogether reasonable fear of threatened harm. Accordingly, we conclude that NWF has standing to challenge this regulation.

d. Prime Farmland Lakes

Under the SMCRA, prime farmland, after a mining operation, generally must be restored to crop-producing land at 100% of the land's pre-mining productivity. NWF here challenges a regulation promulgated by Secretary Watt that creates an exception to this rule; the regulation permits as an acceptable post-mining use of prime farmland "last-cut lakes," which are permanent impoundments of water.17

The district court, observing that NWF had named individuals alleging both aesthetic injury and economic harm, concluded that NWF had standing to challenge this regulation. See Findings on Standing, at 23-24. Industry's response is two-fold: it argues, first, that impoundments were permitted under the original regulations under some circumstances, and second, that presuming specific injury to an individual is unduly speculative.

We disagree with each of these contentions. First, while the original regulations may not have categorically proscribed any impoundments of water, Secretary Watt's regulation indisputably made such impoundments more likely than previously, and the permissibility of that policy change is an issue we address on the merits, not in the context of standing. We also disagree with Industry's dismissive treatment of NWF's specific allegations. Affiant Janis King, for example, lives on, rents and farms land classified as prime farmland; her property is adjacent to a strip of land mined by a nearby company. The company has left last-cut impoundments on the neighboring land and failed to return it to prime farmland. Ms. King describes at some length the interference posed by such impoundments to the operation of her seed corn business and to her aesthetic interests, which she has standing to raise under Sierra Club. See King Aff. Accordingly, we conclude on this issue that NWF has standing.

e. Support Facilities on Prime Farmland

NWF here challenges an exception authorized by Secretary Watt to the rule that prime farmland be completely restored, one that would exempt support facilities associated with surface mining operations and underground mining operations. The district court concluded that NWF had standing. See Findings on Standing, at 24-25.18

Industry's argument on appeal is that the affidavit on which the district court relied, that of Eleanor Smith, is inapposite to the challenge lodged by NWF. Industry contends that although Ms. Smith refers only to support facilities associated with underground mining, NWF's challenge is specifically addressed to support facilities associated with surface mines. See Brief of NWF as Appellees and Appellee-Intervenors at 43-44 & n.*. NWF replies that although Ms. Smith refers to underground mining, her affidavit leaves open the possibility that surface as well as underground mining may be covered by the lease on her property. See Opposition of NWF to Industry's Motion to Remand at 32 & n. 34. We agree. The Smith affidavit states a broad concern with the effects of surface mining in her area, see Smith Aff. at paragraphs 3, 8. In light of this fact, we cannot conclude that her lease permits only underground mining. We therefore conclude that her affidavit is sufficient to establish NWF's standing with respect to this issue.

f. Variances From Original Contours

Under the SMCRA, mining operators are expected generally to restore their land to its approximate original contour. The Act, however, grants a limited variance for lands whose slope exceeds 20 degrees. In his 1983 regulations, however, Secretary Watt broadened this variance to include lands whose slope was below 20 degrees, a step NWF has challenged as inconsistent with Congress' intent that mined lands be returned to a state that "closely resemble[s]" its pre-mining condition. See SMCRA Sec. 701(2).19

The district court concluded that NWF had standing to challenge this variance, see Findings on Standing, at 26-28, a finding Industry protests. It focuses upon the affidavit of Granville Burchard, heavily relied on by the district court. According to Industry, this affidavit misinterprets what the regulations allow and complains more about past than threatened harm. Whatever the inadequacies in Mr. Burchard's affidavit, however, other NWF affidavits satisfactorily plead injury. See, e.g., Ford Aff. (expressing concern over "granting [of] any variances to allow leaving highwalls on non-steep slopes" on land near her home because "[s]uch a variance would adversely impact my enjoyment of the natural vistas of these hills"). Accordingly, we find NWF has standing to challenge the Secretary's regulation.

g. Submerged Highwalls

NWF here challenges a regulation that it alleges falls short of requiring mining operations to backfill highwalls created by mining when those highwalls are part of a pit that will be filled with water and thus become a last-cut lake. See Findings on Standing, at 28. The regulations, as the district court observed, "merely contain[ ] a general proviso that vertical highwalls be placed sufficiently below the waterline 'to provide adequate safety and access for the proposed water users.' " Id. (quoting 30 C.F.R. Sec. 816.49(a)(9)).20

The district court concluded that NWF had standing, observing that NWF had alleged injuries including dangers to recreational users of lakes and fishermen. Id. at 28-29 (citing Smith Aff.; Nelson Aff.). Industry's argument on appeal is that (1) the new regulations provide adequate safety for prospective swimmers, (2) the district court exaggerated the concerns of affiant Nelson, and (3) finding injury sufficient to support standing would require a chain of events altogether too speculative. See Brief for Industry at 37-39. We disagree. Again we emphasize that the protections built into the new regulations bear on the merits of the Secretary's interpretation, not on standing. Moreover, although affiant Nelson did not precisely mention the elimination of fishing species, as the district court implied he did, he does state: "I also favor backfilling and regrading of those highwalls because it provides certain species of fish with a shallow habitat necessary for spawning or as habitat." Id. Industry's attempt to denigrate Mr. Nelson's claim of injury to his interest in observing fishing species is unpersuasive. Finally, we reject Industry's by-now familiar refrain that NWF's injury is unduly speculative with our by-now familiar observation that no amount of linguistic disaggregation dissipates the plausibility of the affiants' claim, here, that inadequate reparation of mining damage in the form of highwalls can harm local fish. Accordingly, we find NWF to have standing.

h. Actual Grazing on Land

NWF here challenges a regulation for failing to require that when grazing is the designated post-mining use of land, the mine operator must use the land for grazing for two years before his bond on that land is released.21

The district court concluded that NWF had standing to challenge this regulation, citing affidavits of two sportsmen who alleged that their ability to hunt wildlife had been impaired by the failure to restore wildlife habitats to pre-mining conditions. In response, Industry argues that hunting is not grazing, and thus that the two hunters have no standing to challenge a regulation for want of better encouragement of grazing.

We disagree. Industry's argument is premised on the assumption that enhanced grazing itself is NWF's goal. That assumption is incorrect. NWF's argument is rather that grazing is the best measure of successful revegetation, and thus that NWF members harmed by incomplete reclamation of grazing and pasturelands have standing to challenge the Secretary's regulation as inadequate. Sportsmen who claim that the resulting failure to restore wildlife habitats has impaired their ability to hunt are surely among those harmed by incomplete regulation. Accordingly, we conclude that the district court correctly held that NWF has standing.

For the reasons stated above, we conclude that the district court correctly found that NWF has standing to challenge each of the regulations at issue, and accordingly we proceed to discuss their merits.

We consider under this heading two Industry challenges to the district court's dispositions, and one advanced by NWF. In each instance, we affirm the district court's rulings, essentially for the reasons stated by the district judge.

1. Revegetation Success Standards for Prime Farmland

In order to show effective reclamation of prime farmland,22 the Secretary requires, as the measure of soil productivity, and prior to the release of the mine operator's performance bond, the actual growth of crops for at least a three-year period. 30 C.F.R. Sec. 823.15(b).23 Industry complains that the Secretary and, on review, the district court failed to consider adequately whether a careful use of soil survey techniques would measure soil productivity in the manner (a) required by the statute, or (b) if not required by the Act, then at least preferable under the relevant section.

The Secretary's regulation calls for a comparison of the reclaimed land's actual crop productivity with the productivity of neighboring, nonmined prime farmland of the same soil type. To promote a valid comparison, similar management techniques must be employed and similar crops must be grown; measurement adjustments may be made, with the concurrence of the U.S. Soil Conservation Service, to account for disease, pest, and weather conditions, or specific management practice variations. Before revegetation will be accepted as successful, resulting in release of all or part of a performance bond or deposit, see SMCRA Sec. 519(c)(2),24 average yield of the restored soil over a period of three or more crop years must equal or exceed the average yield of the comparison area.

Industry urges initially that the Sec. 519(c)(2) words "until soil productivity for prime farm lands has returned to equivalent levels of yield" are qualified by the further words of the section, "as determined from the soil survey performed pursuant to section 507(b)(16)." Under Industry's reading, a post-mining soil survey, not actual cropping, is the statutory requirement. The district court, however, concluded that the Secretary was entitled to require actual farming and we agree.

As the district court observed, "[t]he survey required by [Sec. 507(b)(16) ] must be performed before mining takes place, to determine the exact location of the prime farmland. Thus, Congress could not have envisioned that [such a] survey could ... reveal the success of the reclamation operation." PSMRL II (Round II), 21 E.R.C. at 1732-33 (emphasis added). Section 519(c)(2), as we read it, relies on the pre-mining soil survey only to ensure that the comparison area is of the "same soil type" as the mined land in its pre-mined state. Furthermore, the words "equivalent levels of yield," as they appear in the section, are most naturally and plausibly read to anticipate comparison of production yields between the reclaimed land and the nonmined reference area.25 See FTC v. Manager Retail Credit Co., Miami Br. Office, 515 F.2d 988, 995 (D.C.Cir.1975) (courts should avoid reading statutes in a manner that renders passages functionless). We therefore reject the contention that the statute commands the use of soil survey techniques to measure soil productivity.

As to the preferable measurement method, the Secretary stated in the preamble to Sec. 823.15 of the regulation: "OSM [the Office of Surface Mining] has determined that cropping is the only method currently available to test the restoration of the productivity of prime farmland soils because insufficient research has been published that demonstrates the reliability of any other method." 48 FED.REG. 21458 (1983). Industry concedes "an even division of opinion as to whether the necessary techniques in a soil survey dealing with reclaimed cropland have yet been developed," but urges that a soil survey nonetheless "provides a more accurate and much easier measure of soil productivity than does actual crop growth." Brief for Appellants NCA at 52. The Secretary, however, was alert to factors detracting from the reliability of actual crop growth (i.e., the impossibility of ensuring identical management practices between sample and reference areas, yield variations due to weather, disease or pest circumstances, see Brief for Appellants NCA at 51 & nn. 52-56). He endeavored to provide for reliability-enhancing adjustments, see 30 C.F.R. Sec. 823.15(b)(8), and considered this course sounder than adopting a standard as to which, even its proponents concede, "there seems to be respectable opinion that further refinement is necessary." Brief for Appellants NCA at 53.26

In sum, we do not hold that actual crop growth is required by the Act, although the statute at least arguably suggests such a requirement. Having rejected as unfounded Industry's contention that a soil survey is required, we have no cause to disturb the Secretary's reasoned and expert judgment that actual crop growth is the appropriate means to measure achievement of the statutory objective of restoration of prime farmland. See Motor Vehicle Mfrs. Ass'n v. State Farm Mut. Auto. Ins. Co., 463 U.S. 29, 43, 103 S.Ct. 2856, 2866-67, 77 L.Ed.2d 443 (1983).

2. Revegetation Success Standards for Grazing and Pastureland

Rejecting NWF's challenge, repeated here, the district court upheld the Secretary's revegetation regulation for land with a post-mining grazing or pastureland use, 30 C.F.R. Sec. 816.116(b)(1).27 That regulation aims to ensure reclamation success by requiring, at a minimum, that "the ground cover and production of living plants on the revegetated area shall be at least equal to that of a reference area or such other success standards approved by the regulatory authority." Id.

NWF argues first that soil surveys alone are inadequate to demonstrate the success of grazing land reclamation, and second that actual grazing must be required because it is the only reliable measure of range land revegetation success. The district court agreed that "the use of a soil survey alone is insufficient," but found that the Secretary so recognized. PSMRL II (Round III), 620 F.Supp. at 1563. In this court too, the Secretary of the Interior has represented that the regulation does not contemplate reliance on a soil survey "or any other method not based on actual production to establish vegetative success." Brief for the Secretary of the Interior as Appellee at 23-24; see also 49 FED.REG. 40148 (1983) (preamble to final rule). Thus, there appears to be no contest over the insufficiency of a soil survey. The genuine issue concerns the actual production method necessary or proper to determine vegetation success.

For its second point, NWF relies most heavily on a National Academy of Science Report on mined land reclamation, National Research Council, Surface Mining: Soil, Coal, and Society 124-26 (1981). We comprehend that study, as did the Secretary and the district court, to conclude that evaluation of the productivity of soil reclaimed for grazing must be based on measurements of actual production. But we do not find in the study, any more than the Secretary or the district court did, insistence that grazing is the only acceptable method of establishing range land revegetation success.28 In sum, we cannot say that the Secretary acted unreasonably in declining to require grazing to test reclamation success on sites designated as post-mining range or pastureland; it was sufficient, we hold, for the Secretary to require the use of a reference area comparison or other approved success standard that measures actual vegetation production.

3. Exemptions from Performance Standards for Prime Farmlands

The Secretary's regulations specify performance standards--measures mine operators must take--to secure eventual restoration of prime farmland to its original state and use following mining. See 30 C.F.R. Secs. 823.12 et seq. These prime farmland protective regulations govern soil removal, storage, replacement, and restoration. An anterior regulation, 30 C.F.R. Sec. 823.11,29 describes instances in which a mine operator can obtain exemption from the prime farmlands performance standards. NWF successfully challenged in the district court two of the Sec. 823.11 exemptions; one relates to water bodies or impoundments, 30 C.F.R. Sec. 823.11(b), the other, to coal preparation plants, support facilities, and roads, 30 C.F.R. Sec. 823.11(a). Industry has appealed these twin rulings. We affirm both.

a. Construction of Water Impoundments on Prime Farmland

Section 823.11(b) of the regulations condones reclaiming land that had been prime farmland prior to mining by constructing a permanent water impoundment, if the mine operator satisfies the general conditions for altering the use of affected land and if the water body is designed to minimize the loss of prime farmland. The Secretary had proffered a construction of the water impoundment exception that would limit the allowance to those found beneficial or necessary to agricultural activity, i.e., water bodies necessary for irrigation of prime farmland would be allowed. But the district court, in agreement with Industry, found no such limitation in the provision; purposes for impoundments allowed by the regulation, the court enumerated, "include[d] recreational, municipal water supply, replacement of wetlands, livestock consumption, and esthetic improvement." PSMRL II (Round II), 21 E.R.C. at 1734. The court concluded that, desirable as such uses may be, the Actspecifically, Sec. 510(d)(1)--does not countenance them. Accordingly, the court struck down the provision because it sanctioned "a broad and impermissible variance from the post-mining use of prime farmland." Id.30

Industry locates in Sec. 515(b)(8) of the Act "unequivocal[ ]" authorization for "the creation ... of permanent impoundments when reclaiming mined land," and maintains that "the statute at no point commands that all prime farmland be reclaimed to crop farming." Brief for Appellants NCA at 54-55.31 We find Industry's argument unpersuasive and hold that the Act and its legislative history impel the district court's ruling.

Taking one step back from the subsection Industry advances, we come upon the instruction, in Sec. 515(b)(7), that "for all prime farm lands ... to be mined and reclaimed ... operator[s] shall" follow specified soil removal, storage, and replacement procedures deemed necessary by Congress to restore the productivity of mined prime farmland. See also H.R.REP. NO. 218, 95th Cong., 1st Sess. 67 (1977), reprinted in 1977 U.S.CODE CONG. & ADMIN.NEWS 593, 605 (standards designed to assure full reclamation).32 We emphasize the words "all" and "shall" in the Sec. 515(b)(7) prescription. Beyond question, Congress did not intend to allow any mined prime farmland to be left altogether unreclaimed, and the subsection appears to instruct, inclusively, that all prime farmland reclamation shall, "as a minimum," be conducted pursuant to the statutorily enumerated requirements. The listed requirements entail precise and arduous specifications that are altogether unnecessary, indeed counterproductive, to the construction of a water impoundment. We leave open the question whether, without defying congressional intent, the Secretary might plausibly urge a narrow exception allowing water impoundments necessary or beneficial to prime farmland activity. See supra note 30. Section 515(b)(7), it suffices to point out here, plainly supports the district court's conclusion that a general exception for water impoundments authorizes impermissible post-mining uses of prime farmland.

Section 519(c)(2) of the Act also accords with the district court's ruling and is dissonant with Industry's position. See supra note 24. This section permits release of the bond or deposit placed by a mine operator to guarantee satisfactory reclamation only when the soil productivity of the affected prime farmland has been returned to levels of yield equivalent to those of neighboring, nonmined prime farmland. While the provision does not say in so many words that "mine operators shall restore prime farmland to its pre-mined use," bond release is impermissible until such restoration is achieved.

We reproduce in the margin a significant excerpt from the legislative history. The item is a statement by Senator Culver, sponsor of an amendment to the Act; as proposed by Senator Culver, the amendment expressly denied a mining permit to any operator unable to demonstrate the ability fully to restore prime farmland, if the mine area at stake included more than ten percent prime farmland.33 The Culver statement strongly maintained that alternate uses of prime farmland, even uses perceived by a regulator as "higher" or "better," are inappropriate, and therefore must be disallowed by those who administer the Act. We find in the legislative history no reference to any objection to the amendment on the ground that alternate post-mining uses for prime farmland should be permitted; dissenters merely urged that the Act already protected prime farmland so that the amendment was superfluous. 123 CONG.REC. 15712 (1977) (statement of Senator Hansen); 123 CONG.REC. 15718 (1977) (statement of Senator Melcher). Senator Culver's amendment was incorporated into the Senate bill, and it emerged from the Conference Committee and full Congress without even the ten percent threshold limitation proposed by its sponsor. See SMCRA Sec. 510(d)(1). The subsection containing Senator Culver's amendment is the very one featured by the district court in holding that the regulation's water impoundment exception is at odds with the Act.

Industry's reliance on Sec. 515(b)(8)'s recognition that permanent water impoundments may be created on mined land does not aid the more focused inquiry we must make. That provision instructs that any water impoundment constructed on mined land must meet certain performance standards, but it neither requires mine operators to build impoundments, nor says they may do so regardless of the prior use of the land. The Act anticipates that mine operators will be able "to comply with each of the requirements set out in section 515." SMCRA Sec. 508(a)(5) (emphasis added); see also SMCRA Sec. 515(b) (listed performance standards shall be required "as a minimum"). The district court thus most plausibly comprehended Congress to have ordered that permanent water impoundments unconnected to prime farmland use not be constructed on prime farmland. Compare SMCRA Sec. 515(b)(7) (obligation to follow specified restoration procedures) with SMCRA Sec. 515(b)(8) (permission to construct permanent water impoundments). We have no warrant to disturb the district court's solidly-supported disposition.

b. Exemption for Prime Farmland Affected by Coal Preparation

The exemption contained in Sec. 823.11(a) of the Secretary's regulation, see supra note 29, applies to surface and underground mines alike, and concerns "[c]oal preparation plants, support facilities, and roads" that "affect a minimal amount of land." 30 C.F.R. Sec. 823.11(a). To fall within the exemption, these facilities must be "actively used over extended periods of time." Id. On NWF's challenge, the district court remanded this exemption for two distinct reasons. First, the court held that despite adequate reasons for exempting land underlying surface facilities of underground mines, the Secretary had too swiftly equated surface mining with underground mining for the purpose at hand. The district judge instructed the Secretary to reconsider, taking account of "basic differences" between the two operations. Second, the district court found the exemption imprecise because the Secretary had not further defined the terms "extended periods of time" and "minimal amount of land." PSMRL II (Round II), 21 E.R.C. at 1734-35. This second ruling is not contested on appeal. The challenge here is limited to Industry's objection to the district court's first basis for the remand.

We note, initially, that Industry misdescribes what the district court held. The ruling we review does not command application of Sec. 515(b)(7) of the Act to the soil under support facilities for surface mines. But see Brief for Appellants NCA at 59, 63. Rather, the remand called for a more cogent explanation of the Secretary's action, so that the court could intelligently rule on the consistency of that action with the statute.

The regulatory preamble to Sec. 823.11, 48 FED.REG. 21452-55 (1983), offers two reasons for ranking surface mining operations with underground operations in the context at issue. First, the Secretary referred to the district court's 1980 ruling that it would be unreasonable not to exempt underground mine operators' surface support facilities that are actively used over extended periods of time but affect a minimal amount of land. See PSMRL I (Round II), 19 E.R.C. at 1480-81. The Secretary thought that the same rationale, i.e., the arbitrariness of "command[ing] operators to segregate [and store] the topsoil and the underlying horizons for 20-40 years in situations where reclamation will affect a small area," id., "appl[ies] equally well to such facilities associated with surface mines. Surface mines often use the same types of facilities as underground mines and for comparable periods of time." 48 FED.REG. 21453 (1983).

Second, the Secretary relied upon his own finding that, for restoring prime farmland affected by surface support facilities, the prime farmlands standards provide procedures less suitable than those contained in the general performance standards.34 A "reasonable construction of the prime farmland sections of the Act," the Secretary commented, "does not require that they be applied to 'areas' where their special protections would be to no avail." 48 FED.REG. 21453 (1983).

The Secretary's first justification, as the district court observed, did not adequately explain why the court's 1980 opinion, written with underground mine facilities in mind, should apply to surface facilities for surface mining operations. During the comment period on Sec. 823.11, two commenters noted that surface mine operations, unlike underground mine operations, constantly disturb and reclaim the surface in the process of removing coal. 48 FED.REG. 21453 (1983); see SMCRA Sec. 515(b)(16) (reclamation is to proceed as contemporaneously as possible to the land disturbance). Soil affected by surface mine facilities, these comments suggested, need not be stored for 20-40 years until the facilities are dismantled, but could be used in the reclamation of the earliest mine cuts. Similarly, the prime farmland area affected by facilities for the life of the mine might be reclaimed using soil removed from the final mine cut.

Industry stresses that neither the district court nor this court is qualified to settle questions of mining techniques, i.e., to say "how surface mines deal with the soil under support facilities." Brief for Appellants NCA at 62. We do not pretend to mining technique expertise, nor did the district court. We do insist, however, that the Secretary tell us comprehensibly, based on his expertise, why--despite "basic differences between surface and underground mining operations," PSMRL II (Round II), 21 E.R.C. at 1735--a decision focused on facilities serving underground mines applies "equally well" to facilities supporting surface mines.

The Secretary's second prop for Sec. 823.11(a) is unstable at two critical joints. First, the proffered explanation addresses only, and thus could justify only, exemption from the special soil removal, storage, and replacement standards; the explanation does not tell us why the special soil restoration requirements of 30 C.F.R. Sec. 823.15 need not be observed. And second, the explanation loses some of the force it might otherwise have when, three sentences after the Secretary concludes that the special performance standards "would be to no avail" for land affected by support facilities, he stresses that "only [facilities] which affect a minimal amount of land are exempted [from prime farmland performance standards]." 48 FED.REG. 21453 (1983). We do not comprehend why the effectiveness of the reclamation scheme the Secretary appraises as superior when support facilities are involved, see supra note 34 and accompanying text, should vary according to the amount of land to be reclaimed.35 The Secretary's position on this matter, in short, is in need of clearer statement.

The district court, we reiterate, remanded Sec. 823.11(a) because "the Secretary's reasoning [was] flawed." PSMRL II (Round II), 21 E.R.C. at 1735. We agree. The district court did not rule that the requirements of Sec. 515(b)(7) of the Act are nonwaivable even as to soil under support facilities for surface mines, nor do we.36

B. Bonding to Assure Reclamation of Land Affected by Mine Operations

In this part we address three challenges to district court rulings relating to the Secretary's bonding regulations. We reverse the district court's rulings, challenged by Industry, regarding incremental and phased bonding; the Secretary's regulations on these bonding arrangements, we hold, are compatible with the Act. We uphold the district court's ruling, challenged by NWF, that the initial bond for an underground operation need not be set at an amount sufficient to cover the cost of restoring land damaged by subsidence.

To facilitate bonding arrangements by mine operators, the Secretary has authorized the states (as regulatory authority) to implement plans allowing both incremental and phased bonding. Under the incremental bonding prescription, 30 C.F.R. Sec. 800.11(b),37 an operator is not required to bond all at once the entire area to be mined in a given permit term.38 Instead, the state plan may permit the operator to bond, and then commence operations on, smaller units, specifically, "[i]ndependent increments ... of sufficient size and configuration to provide for efficient reclamation operations." 30 C.F.R. Sec. 800.11(b)(4).

Under the Secretary's authorization for phased bonding, 30 C.F.R. Sec. 800.13(a)(2),39 an operator need not post one bond covering all phases of reclamation. Instead, the regulatory authority may allow the operator to obtain separate bonds for each of the three phases of reclamation (backfilling, regrading and drainage control; revegetation; all remaining reclamation), provided that all phase bonds are posted at the outset, that each bond is sufficient to cover reclamation work in the phase for which it is written, and that the sum of the bonds posted equals or exceeds the total amount needed to complete the reclamation plan for the entire area covered. 30 C.F.R. Sec. 800.13(a)(2); see 48 FED.REG. 32936, 32938, 32941 (1983).40 As each reclamation phase is completed, the bond for that phase, subject to limitations,41 will be released. If the mine operator defaults, "[f]orfeiture of phase bonds ... will involve forfeiture of the total of the phase bonds remaining for the area or increment." 48 FED.REG. 32956 (1983). The Secretary has repeated his assurance that later phase bonds could be forfeited in the event that an earlier bond was released before the need for additional work was discovered. Supplemental Brief for the Secretary of the Interior at 2, 4-5; Correction to Supplemental Brief for the Secretary of the Interior at 2.

The district court found the incremental bonding allowance impermissible under Sec. 509(a) of the Act;42 the court read that provision to require each bond to cover no less than "the entire area to be mined in a given permit term." PSMRL II (Round II), 21 E.R.C. at 1743. Phased bonding, the district court held, was inconsistent with Sec. 509(b) of the Act;43 the court read that provision to prohibit "break[ing] the bond into specific phases of reclamation." Id. at 1744. Rejecting the Secretary's argument that Sec. 509(c) of the Act allows both bonding forms as "alternative system[s],"44 the district court ruled that Sec. 509(c) countenances only "alternatives to bonding," id. at 1743, not alternative bonding schemes.

We pretermit the question whether incremental and/or phased bonding can be accommodated within the terms of Secs. 509(a) and (b) of the Act. Section 509(c), we hold, reasonably could be read by the Secretary to permit his approval of alternative bonding methods that will fulfill the purposes of the Act. While Sec. 509(c) is not a model of the drafter's art, and the district court's reading of the provision is a plausible one, we defer to the reasonable interpretation ultimately proffered by the Secretary. Chevron U.S.A. Inc. v. NRDC, 467 U.S. 837, 844-45, 104 S.Ct. 2778, 2782-83, 81 L.Ed.2d 694 (1984); Chemical Mfrs. Ass'n v. NRDC, 470 U.S. 116, 125, 105 S.Ct. 1102, 1107, 84 L.Ed.2d 90 (1985).