F. DALE ROBERTSON, CHIEF OF THE FOREST SERVICE, ET AL., PETITIONERS V. METHOW VALLEY CITIZENS COUNCIL, ET AL. No. 87-1703 In the Supreme Court of the United States October Term, 1988 On Writ of Certiorari to the United States Court of Appeals for the Ninth Circuit Brief for the Petitioners PARTIES TO THE PROCEEDING The petitioners are F. Dale Robertson, Chief of the Forest Service; James Torrence, Regional Forester; William D. McLaughlin, Supervisor, Okanogan National Forest; and the Forest Service. The respondents are Methow Valley Citizens Council; Washington Environmental Council; Sierra Club; and Methow Recreation, Inc. TABLE OF CONTENTS Questions Presented Parties to the proceeding Opinions below Jurisdiction Statutes and regulations involved Statement Summary of argument Argument: I. NEPA does not require federal agencies to include in their environmental impact statements a complete plan to mitigate environmental damage or a "worst case" analysis of potential environmental harm A. NEPA's requirement that federal agencies prepare a detailed statement on the environmental consequences of major federal actions does not impose a substantive obligation to mitigate adverse environmental effects or a procedural obligation to develop a "complete mitigation plan" B. NEPA does not require federal agencies to prepare a "worst case" analysis of potential environmental harm if relevant information concerning significant environmental effects is unavailable or too costly to obtain II. The Forest Service may issue a special use permit for recreational use of national forest land in the absence of a "complete mitigation plan" Conclusion OPINIONS BELOW The decision of the court of appeals (Pet. App. 1a-19a) is reported at 833 F.2d 810. The decision of the district court (Pet. App. 20a-47a) is not yet reported. JURISDICTION The court of appeals entered its judgment on December 1, 1987. On February 18, 1988, Justice O'Connor extended the time for filing a petition for a writ of certiorari to and including March 30, 1988. On March 23, 1988, Justice O'Connor further extended the time for filing the petition to and including April 14, 1988, and the petition was filed on that date. This Court granted the petition for a writ of certiorari on June 27, 1988, consolidating this case with Marsh v. Oregon Natural Resources Council, No. 87-1704. /1/ The jurisdiction of this Court rests upon 28 U.S.C. 1254(1). STATUTES AND REGULATIONS INVOLVED Section 102 of the National Environmental Policy Act of 1969, 42 U.S.C. 4332, provides, in relevant part: The Congress authorizes and directs that, to the fullest extent possible: * * * (2) all agencies of the Federal Government shall -- * * * * * (C) include in every recommendation or report on proposals for legislation and other major Federal actions significantly affecting the quality of the human environment, a detailed statement by the responsible official on -- (i) the environmental impact of the proposed action, (ii) any adverse environmental effects which cannot be avoided should the proposal be implemented, (iii) alternatives to the proposed action, (iv) the relationship between local short-term uses of man's environment and the maintenance and enhancement of long-term productivity, and (v) any irreversible and irretrievable commitments of resources which would be involved in the proposed action should it be implemented. Pertinent excerpts from the federal regulations involved in this case are reproduced in the Addenda. QUESTIONS PRESENTED 1. Whether the National Environmental Policy Act requires federal agencies to include in each environmental impact statement: (a) a fully developed plan to mitigate environmental harm; and (b) a "worst case" analysis of potential environmental harm if relevant information concerning significant environmental effects is unavailable or too costly to obtain. 2. Whether the Forest Service may issue a special use permit for recreational use of national forest land in the absence of a fully developed plan to mitigate environmental harm. STATEMENT Petitioners seek reversal of a court of appeals decision overturning a magistrate's determination that the Forest Service had fully complied with the National Environmental Policy Act of 1969 (NEPA), 42 U.S.C. 4321 et seq., and the agency's regulations in deciding to issue a special use permit for the proposed Early Winters Ski Area in the Okanogan National Forest. 1. Beginning in the late nineteenth century, Congress took a series of legislative steps to provide for planned multiple use and development of the Nation's forests. See generally Wilkinson & Anderson, Land and Resource Planning in the National Forests, 64 Ore. L. Rev. 1, 15-90 (1985). Congress's actions have led to the creation of the National Forest System, managed by the Department of Agriculture's Forest Service. Congress has specifically directed the Forest Service to administer the national forests for a variety of sometimes conflicting uses, including "outdoor recreation, range, timber, watershed, and wildlife and fish purposes." Multiple-Use Sustained-Yield Act of 1960, 16 U.S.C. 528 et seq. See also National Forest Management Act of 1976, 16 U.S.C. 1600 et seq. As part of this multiple-use program, the Forest Service has permitted the development of 170 alpine ski areas within these federally reserved lands. See H.R. Rep. 99-709, 99th Cong., 2d Sess. Pt. 1, at 2 (1986). The ski areas, which occupy less than 1/20th of 1 percent of the national forest lands, account for more than 6 percent of recreational visitor use of the forests (ibid.). /2/ In 1968, Congress established the North Cascades National Park and directed the Secretaries of Agriculture and the Interior to designate portions of that enclave and adjacent national forests for public uses, including camping and ski areas. Act of Oct. 2, 1968, Sections 101, 504, 16 U.S.C. 90, 90d-3. Pursuant to this specific congressional directive, the Forest Service prepared a report, entitled the North Cascades Winter Sports Study (hereinafter North Cascades Study) to compare existing and potential ski areas in the national forests of the North Cascades and to recommend further ski development alternatives. The North Cascades Study, which was completed in 1970, concluded that existing ski areas could and should be expanded and identified a single site as suitable for development of a "major destination ski resort." /3/ That site, a 6,000-foot mountain known as Sandy Butte, is located in the Methow Valley region of the Okanogan National Forest. 2. In 1978, Methow Recreation, Inc. (MRI) applied to the Forest Service for a "special use" permit, pursuant to 36 C.F.R. 251.50, to build and operate an alpine ski resort at Sandy Butte that would be known as the Early Winters Ski Area. The Forest Service thereupon commenced the standard procedures that it normally employs for evaluating major development proposals. The Forest Service first conducts a thorough environmental and a preliminary financial analysis to determine whether the project concept is sound. If the Forest Service determines that the general scheme for development is acceptable, it may issue a special use permit, but the developer's construction and operation of the project will be conditioned upon the creation of an acceptable master plan for development. /4/ The Forest Service next reviews the developer's proposed master plan. Based on this proposed plan, and before the plan's approval, the Service also completes an additional environmental analysis of on-site impacts. Only after completion of the second environmental analysis and final approval of the completed master plan may the developer begin construction. All construction and operation of the facility must be in accordance with both the special use permit's requirements and the approved master plan. The Forest Service conducted its initial environmental analysis of the MRI proposal by preparing an environmental impact statement (EIS), known as the Early Winters Study, in accordance with Section 102 of NEPA, 42 U.S.C. 4332, and in cooperation with the state and local governments. /5/ The stated purpose of the Early Winters Study was to provide the Forest Service with "the information required to evaluate the potential for skiing at Early Winters, to assist in making a decision whether to issue a special use permit for downhill skiing on all or part of (Sandy Butte)" (Early Winters Study 1). The Study gave detailed consideration to five alternative levels of development, including a "no development" alternative (Alternative I), and identified the second highest level (Alternative IV) -- serving up to 8,200 skiers at one time -- as the preferred development alternative. /6/ The Early Winters Study made clear that a decision to go forward with a ski resort would not result immediately in development; rather, "(f)urther environmental analysis and review will be required prior to any decision by the Forest Service to allow a specific development at Early Winters, and by the responsible state and local government agencies, prior to any authorization to develop non-Forest Service lands" (Early Winters Study 1). Following issuance of a special use permit, the developer would have to submit a detailed mountain and base development plan for the Forest Service's approval, providing the precise ski area design (id. at xvi). At that stage, the Study explained, site-specific plans to mitigate environmental impacts would be required (id. at xvi, 69) ("All prescribed mitigation will be accomplished through the Ski Area Master Development Plan."). Although it was too early at this stage of the planning process to specify detailed mitigation measures, it was not too early to identify significant anticipated effects that major development might have on Sandy Butte and the surrounding communities. The Early Winters Study evaluated the potential impacts on air and water quality, vegetation, wildlife, fisheries, timber resources, socioeconomic conditions, land use, recreation, transportation, and public services (Early Winters Study 65-145). In each of these areas, the Study considered the impacts both within and without the Okanogan National Forest. It distinguished between "primary" (or "on-site") impacts, which would occur on the specific national forest lands occupied by a ski resort, and "secondary" (or "off-site") impacts, which would occur on other adjacent lands. This distinction is significant because neither the Forest Service nor the developer can control secondary effects resulting from third-party activities on non-federal lands. The Study recognized that the unpredictability of off-site development patterns limited its ability to project secondary impacts, stating (id. at 1-3): Since there are no pending proposals of plans to develop off-site lands, the evaluation of off-site impacts is not site-specific. It is general in nature, acknowledging to the extent practicable the impacts associated with the growth that is likely to be induced by development of Sandy Butte for skiing. The evaluation of off-site impacts (is) included to provide a more complete picture of the likely effects of ski development at Early Winters and alert other jurisdictions to decisions to (be) made. The Early Winters Study concluded that the proposed development would have various environmental effects -- including effects related to wildlife and air quality -- both on-site and off-site. The Study found that on-site and off-site development would affect Methow Valley's mule deer population. At Sandy Butte itself, ski runs and lifts, new roads, and other support facilities could damage the mule deer's fawning habitat (Early Winters Study 16, 75-76). /7/ The impacts on the mule deer resulting from off-site development of adjacent lands were expected to be more serious, ranging from an 8-15 percent reduction in the deer's winter habitat (id. at 76). /8/ Significantly, the Study recognized that these off-site effects would occur even if no ski area were built at Sandy Butte (ibid.) /9/ The Study further noted that off-site impacts not only were likely to be more serious than on-site impacts, they were also more difficult to predict with any precision because they depend on future actions by individuals, commercial interests, and local governments that are largely beyond the Forest Service's control. /10/ The Early Winters Study also addressed the proposed development's impact on air quality. It found that, while the ski resort itself "will not have a measurable effect on existing or future air quality" (Early Winters Study 65), the off-site effects would be substantial regardless of the size of the proposed ski resort. In particular, air quality studies showed that, even with no ski area development at Sandy Butte, increasing settlement of the Methow Valley -- and with it, an increase in automobile, fireplace, and wood stove use -- was destined to reduce air quality in the area below state standards (id. at 67). /11/ The secondary impacts from development of nearby private land would increase with successive levels of ski area development (id. at 65-67). For each area of impact, the Early Winters Study proposed measures to reduce or eliminate the adverse effects. The Study identified both "the mitigation measures the Forest Service will require as a condition of any special use permit issued for use of National Forest System lands" and "(m)itigation measures other agencies could use to deal with problems occurring on lands other than National Forest lands" (Early Winters Study 14). The Study further explained (id. at 14): These measures are conceptual and will be made more specific as part of the design and implementation stages of the planning process. If later steps of the approv(al) process identify other environmental problems associated with development on National Forest System lands, additional mitigations may be required. The Early Winters Study identified a number of methods for mitigating adverse impacts on wildlife. With respect to on-site impacts, the Study described how the ski area could be planned to locate runs, lifts, and roads away from water sources and fawning cover and recommended restrictions on travel and other activities in sensitive areas during the mule deer's fawning season (Early Winters Study 14-16). In addition, the Study noted that the Forest Service would further evaluate the impact of development on mule deer at the master plan review stage and propose additional mitigation measures at that time (ibid.) With respect to the more serious off-site impacts, the Study stressed the importance of zoning limitations to protect wildlife (id. at 77). /12/ In addition, the Study suggested that the local governments should acquire and manage some critical parcels and obtain conservation easements for others, incorporate special design features into the roads to protect wildlife, pass ordinances to protect wildlife from dogs, and discourage development near water sources (id. at 77-78). /13/ The Early Winters Study recognized that all of the major air quality impacts were expected to be generated by off-site combustion of wood for space heat and motor vehicle use during the ski season and therefore suggested that local governments institute off-site mitigation measures within their jurisdiction. The Study suggested that Okanogan County form an Air Quality Control Authority and create an airshed management plan, which would incorporate (1) building and zoning codes to restrict the number of wood stoves and fireplaces; (2) certification requirements to control emissions from woodstoves and fireplaces; and (3) monitoring and enforcement mechanisms (Early Winters Study 68-69). /14/ 3. The Regional Forester reviewed the Early Winters Study and concurred in its recommendation supporting a ski resort capable of serving 8,200 skiers. On July 5, 1984, he accordingly issued a decision to seek a qualified developer for Sandy Butte (Pet. App. 63a-71a). /15/ The Regional Forester explained that the highest development alternative (serving up to 10,200 skiers at one time) "would provide maximum utilization of the recreation resource opportunities and increased economic benefit to the area" (id. at 65a), and that the "no action" alternative "would cause the least disruption to the natural environment" (ibid.), but the selected alternative "provides a balance of concerns for the physical and biological components of the human environment in addition to concerns for social and economic welfare" (ibid.). He further observed that adverse environmental effects would result from all of the alternatives, including the "no action" option, that these adverse effects would result almost exclusively from off-site development, and that "(p)ractical measures to reduce the adverse impacts have been, or are in the process of being, implemented by Okanogan County" (id. at 67a). /16/ The Regional Forester also proposed to investigate ways to compensate for off-site destruction of mule deer winter range through the management of the Okanogan Forest as a whole (ibid.). 4. On October 1, 1984, respondents Methow Valley Citizens Council, et al. (MVCC), requested, pursuant to 36 C.F.R. 211.18, that the Chief of the Forest Service reverse the Regional Forester's decision. /17/ He denied that request, with an extensive discussion of the reasons supporting his decision, on December 16, 1985 (Pet. App. 49a-62a). Respondents then filed this action in the United States District Court for the District of Oregon. The complaint contended, among other claims, that the Early Winters Study did not conform to NEPA's requirements, that the Forest Service's decision to develop Sandy Butte was not in the public interest, and that the Forest Service had violated the National Forest Management Act of 1976, 16 U.S.C. 1600 et seq., and the Clean Air Act, 42 U.S.C. 7401 et seq. The parties agreed to submit the issues to a United States magistrate pursuant to 28 U.S.C. 636(c). The magistrate dismissed through summary judgment respondents' claims under the National Forest Management Act and the Clean Air Act, and after a four-day hearing to supplement the administrative record, he rejected all of respondents' remaining claims (Pet. App. 20a-48a). The magistrate concluded that the Forest Service's decision to go forward with the issuance of a special use permit was unreviewable under Ninth Circuit precedent (id. at 28a-30a); that even if it were reviewable, it was not arbitrary and capricious (id. at 30a n.4); and that it did not violate due process (id. at 31a). The magistrate next held that the Early Winters Study satisfied NEPA's requirements for an environmental impact statement (id. at 31a-47a. He rejected respondents' argument that the Study's discussion of alternative development sites was inadequate (id. at 34a-38a), observing that "the North Cascade Winter Sports Study, a work cited in the (Early Winters Study) and available to the public, had identified Sandy Butte as the only area in the Okanogan Forest having good potential as a major ski development" (id. at 37a), and that expansions of sites "a hundred or more miles away from the Okanogan National Forest are not reasonable alternatives" (ibid.). The magistrate further determined that the Early Winters Study adequately discussed the project's environmental impacts (id. at 38a-47a). He expressly approved the Study's discussion of impacts on mule deer (id. at 39a-40a) and on air quality (id. at 42a-45a) and specifically rejected respondents' contentions that the Forest Service was obligated to prepare a "worst case" analysis of the possible impacts (id. at 40a, 45a) and that the Study gave insufficient analysis to possible mitigation measures (id. at 41a-42a, 45a-46a). 5. Respondents appealed the magistrate's decision directly to the court of appeals (see 28 U.S.C. 636(c)(3)). The court reversed the magistrate's determination, holding that the Early Winters Study failed to satisfy NEPA's requirements and that the Forest Service's decision to issue a special use permit was arbitrary and capricious (Pet. App. 1a-19a). The court found the Early Winters Study to be flawed in three principal respects. First, the court held that the Study should have given detailed consideration to the possibility of expanding existing ski resorts as one of the alternative development proposals, rejecting the magistrate's determination that these were not reasonable alternatives (Pet. App. 8a-11a). Second, the court held that the statement did not provide a sufficiently detailed discussion of the environmental impacts of the proposed project on mule deer and air quality (id. at 11a-16a). The court specifically stated that if the government is unable to obtain adequate information on the effects of the project on mule deer, the government must conduct a "worst case" analysis of the environmental impacts (id. at 13a, 14a). /18/ Finally, the court held that Section 102 of NEPA (42 U.S.C. 4332) "requires that 'action be taken to mitigate the adverse effects of major federal actions'" (Pet. App. 17a). /19/ The court specifically ruled that an environmental impact statement must contain both a detailed plan to mitigate any adverse environmental effects and an analysis of the plan's effectiveness (ibid.). Having failed to include a "'complete mitigation plan'" (id. at 19a (citation omitted)), the Early Winters Study was "inadequate as a matter of law" (ibid.). With respect to the Forest Service's decision to issue a special use permit, the court acknowledged (Pet. App. 3a-4a) that its prior precedent had indicated that such decisions are not reviewable under the Administrative Procedure Act, 5 U.S.C. (& Supp. IV) 701-706. The court concluded, however, that subsequent Forest Service regulations had since created "'law' for this court to apply" and that the decisions were therefore now reviewable (Pet. App. 4a-5a). The court then held that the relevant Forest Service regulations (36 C.F.R. 251.54(e)(4) and 36 C.F.R. 251.56(a)(1)(ii) require "an adequate mitigation plan" (Pet. App. 5a n.3), and that the mitigation plan contained in the Early Winters Study was so inadequate that the "decision to grant the special use permit could be none other than arbitrary, capricious and an abuse of discretion" (ibid.). SUMMARY OF ARGUMENT The Forest Service has fully complied with NEPA and the agency's own regulations in deciding to issue a special use permit for the proposed Early Winters Ski Area. The court of appeals erred in holding that the Forest Service's environmental impact statement, the Early Winters Study, was deficient and that the Forest Service's regulations prohibit the issuance of a special use permit in the absence of a fully developed plan to mitigate environmental harm. 1. NEPA directs federal agencies proposing actions that significantly affect the quality of the human environment to prepare a detailed statement on the environmental consequences of the proposed action. NEPA Section 102(2), 42 U.S.C. 4332(2). See Baltimore Gas & Elec. Co. v. Natural Resources Defense Council, Inc., 462 U.S. 87, 97 (1983). NEPA's mandate to the agencies is "essentially procedural" (Vermont Yankee Nuclear Power Corp. v. Natural Resources Defense Council, Inc., 435 U.S. 519, 553 (1978)), and the only role for the courts is to ensure that the agency has taken a "hard look" at environmental consequences. Kleppe v. Sierra Club, 427 U.S. 390, 410 n.21 (1976). The court of appeals exceeded its proper role here. The court interpreted NEPA to create new substantive and procedural obligations, found nowhere in the statutory language or in the Council on Environmental Quality's (CEQ's) regulations implementing the Act. a. The court of appeals erred, first, in holding that NEPA imposes a substantive obligation on agencies "'to mitigate the adverse effects of major federal actions'" (Pet. App. 17a (citation omitted)). NEPA does not dictate what actions the agency should take in response to expected environmental consequences. As this Court has repeatedly stated, NEPA requires the agency to consider and inform the public of potential environmental impacts; it does not require the agency to "'elevate environmental concerns over other appropriate considerations.'" Baltimore Gas & Elec. Co., 462 U.S. at 97-98 (citation omitted). The court of appeals' conclusion, which respondents themselves have declined to defend (Br. in Opp. 9), is accordingly incorrect. The court of appeals' misperception of NEPA's function led the court to misconstrue the statute's procedural requirements. The court's erroneous premise that NEPA requires federal agencies to mitigate adverse environmental effects prompted it to require that agencies include in every environmental impact statement a "complete mitigation plan" for dealing with environmental harm. No one disputes that a federal agency can and should consider mitigation opportunities when assessing the environmental consequences of a proposed action. Indeed, the CEQ's implementing regulations direct that mitigation opportunities be considered and discussed during the preparation of an environmental impact statement. But the court's inflexible requirement that an agency must prepare a "complete mitigation plan" is foreign to NEPA and would impede the goal of sound agency decisionmaking. "NEPA does not require agencies to adopt any particular internal decisionmaking structure." Baltimore Gas & Elec. Co., 462 U.S. at 100. The agency has broad discretion to determine the form and scope of the mitigation discussion in light of the particular circumstances, provided only that the environmental review as a whole satisfies NEPA's specific requirements and that the resulting decision is not arbitrary or capricious. See id. at 97-98, 105-106. This case aptly illustrates why there is neither need nor warrant for courts to impose additional obligations. The Forest Service prepared the Early Winters Study to assist its determination whether to authorize construction of a proposed ski area whose on-the-ground dimensions and form could not be determined until later stages in the planning process. The Early Winters Study accordingly discussed mitigation measures at a conceptual level appropriate for that stage of decisionmaking. The Forest Service reasonably concluded, in accordance with the concept of tiered decisionmaking, that a general discussion of possible mitigation measures would sufficiently inform its inquiry whether to go forward with the project. The court of appeals' decision would forbid this manifestly sensible approach to project planning and development. b. The court of appeals also erred in requiring the Forest Service to prepare a "worst case analysis" of environmental harm if, on remand, relevant scientific information on environmental effects is unavailable or too costly to obtain. As we explain in somewhat greater detail in the companion case, Marsh v. Oregon Natural Resources Council, No. 87-1704, NEPA itself prescribes no particular method for dealing with uncertainty; the CEQ introduced worst case analysis as its prescribed method for addressing this problem. The CEQ's experience with worst case analysis revealed, however, that the method did not fulfill NEPA's objectives, and the agency therefore has replaced it with a more manageable methodology that identifies "reasonably foreseeable" environmental impacts. See 40 C.F.R. 1502.22. The court of appeals' conclusion that "NEPA caselaw" (Pet. App. 13a n.11) requires that agencies continue to employ worst case analysis is based upon a misreading of those cases, which merely interpreted the worst case regulation. The court of appeals clearly overstepped its authority in overruling the CEQ regulatory revision. 2. The court of appeals not only miscontrued NEPA, it also imported its incorrect view of NEPA's mitigation requirements into Forest Service regulations governing the issuance of special use permits. The regulations require that special use permits contain terms and conditions to minimize environmental damage (36 C.F.R. 251.56(a)(1)(ii), but they do not require the sort of "complete mitigation plan" that the court of appeals contemplates. Congress placed the authority to specify conditions for ski resort special use permits in the Forest Service (16 U.S.C. 497), and that agency has never interpeted its resulting regulation to require a "complete mitigation plan." The Forest Service's interpretation of its regulation is reasonable and entitled to deference. E.g., Lyng v. Payne, 476 U.S. 926, 939 (1986). ARGUMENT I. NEPS DOES NOT REQUIRE FEDERAL AGENCIES TO INCLUDE IN THEIR ENVIRONMENTAL IMPACT STATEMENTS A COMPLETE PLAN TO MITIGATE ENVIRONMENTAL DAMAGE OR A "WORST CASE" ANALYSIS OF POTENTIAL ENVIRONMENTAL HARM The National Environmental Policy Act of 1969 directs federal agencies proposing actions that significantly affect the quality of the human environment to prepare a detailed statement on the environmental consequences of the proposed action. NEPA Section 102(2), 42 U.S.C. 4332(2). This procedural requirement serves two purposes: First, it obligates the agency to consider the environmental effects of the proposal; and second, it assures the public that the agency has considered environmental concerns in the decisionmaking process. Baltimore Gas & Elec. Co. v. Natural Resources Defense Council, Inc., 462 U.S. 87, 97 (1983). The federal agencies are well versed in NEPA's requirements, they commonly utilize environmental impact statements as a central element of their planning processes, and they have prepared thousands of such statements over the past 18 years. The court of appeals' decision in this case departs from precedent and established practice to put forward a novel interpretation of NEPA's requirements that would profoundly alter the federal agencies' compliance obligations. The court's decision would require all environmental impact statements to contain detailed and demonstrably effective plans for mitigating environmental harm and, whenever the agency lacks information or adequate scientific methodology to determine precisely a potential environmental effect, to include a "worst case" analysis. Neither NEPA, the Council on Environmental Quality's implementing regulations, nor this Court's precedents provide a basis for imposing those requirements. As we demonstrate below and in our brief in the companion case, Marsh v. Oregon Natural Resources Defense Council, No. 87-1704, the court's rigid directives are not only contrary to federal law, they would actually impede the goal of informed agency decisionmaking by preventing federal agencies from carrying out their resource management responsibilities through systematic project development. /20/ A. NEPA's Requirement That Federal Agencies Prepare A Detailed Statement on the Environmental Consequences of Major Federal Actions Does Not Impose A Substantive Obligation To Mitigate Adverse Environmental Effects Or A Procedural Obligation To Develop A "Complete Mitigation Plan" 1. This Court has clearly articulated the role that NEPA assigns to the federal agencies and the courts. Section 102(2)(C) of NEPA (42 U.S.C. 4332(2)(C)) requires federal agencies to prepare an environmental impact statement that describes "'every significant aspect of the environmental impact of a proposed action'" and that "inform(s) the public that it has indeed considered environmental concerns in its decisionmaking process." Baltimore Gas & Elec. Co., 462 U.S. at 97 (quoting Vermont Yankee Nuclear Power Corp. v. Natural Resources Defense Council, Inc., 435 U.S. 519, 553 (1978)). While "NEPA does set forth significant substantive goals for the Nation, * * * its mandate to the agencies is essentially procedural." Vermont Yankee Nuclear Power Corp., 435 U.S. at 558. Furthermore, "the only procedural requirements imposed by NEPA are those stated in the plain language of the Act" (id. at 548). "The procedural duty imposed upon agencies (by Section 102(2)(C)) is quite precise, and the role of the courts in enforcing that duty is similarly precise." Kleppe v. Sierra Club, 427 U.S. 390, 406 (1976). "The only role for a court is to insure that the agency has taken a 'hard look' at environmental consequences; it cannot 'interject itself within the area of discretion of the executive as to the choice of the action to be taken'" (id. at 410 n.21 (citation omitted)). Furthermore, the courts should defer to the judgment of the Council on Environmental Quality (CEQ) -- the agency responsible for assuring proper implementation of NEPA (42 U.S.C. 4344) -- which has promulgated regulations for preparing environmental impact statements. See 40 C.F.R. 1501.1 et seq. "CEQ's interpretation of NEPA is entitled to substantial deference." Andrus v. Sierra Club, 442 U.S. 347, 358 (1979). The court of appeals seriously departed from these principles. Relying solely on lower court precedent, the court of appeals concluded that NEPA requires federal agencies to assume significant new substantive and procedural obligations with respect to mitigation of environmental harm. The court based its mitigation requirement on the fundamentally mistaken premise that Section 102 of NEPA "requires that 'action be taken to mitigate the adverse effects of major federal actions'" (Pet. App. 17a, citing Stop H-3 Ass'n. v. Brinegar, 389 F. Supp. 1102 (D. Haw. 1974)). Neither Section 102, nor any decision of this Court interpreting that provision, imposes any such requirement. /21/ The court's reliance on Stop H-3 Ass'n (which was reversed on other grounds, 533 F.2d 434 (9th Cir.), cert. denied, 429 U.S. 999 (1976)) is obviously misplaced. /22/ Section 102 of NEPA, by its express terms, requires federal agencies to prepare a "detailed statement" of a proposed project's environmental consequences, including "adverse environmental effects which cannot be avoided," "alternatives to the proposed action," the relationship between "local short-term uses" and "long-term productivity," and "any irreversible and irretrievable commitments of resources" (42 U.S.C. 4332). Section 102 thus assures that all federal agencies will take environmental concerns into account in their decisionmaking processes. See Weinberger v. Catholic Action, 454 U.S. 139, 143 (1981); Strycker's Bay Neighborhood Council, Inc. v. Karlen, 444 U.S. 223, 227 (1980); Andrus v. Sierra Club, 442 U.S. 347, 350-351 (1979). See also 40 C.F.R. 1501.1. But Section 102 does not dictate what actions the agency should take in response to expected environmental consequences; indeed, "the Act mandates no particular substantive outcomes" (City of New York v. United States Dep't of Transportation, 715 F.2d 732, 748 (2d Cir. (1983), cert. denied, 465 U.S. 1055 (1984)). Instead, NEPA leaves substantive decisions to the agency. As this Court has repeatedly emphasized, NEPA requires the agency to consider and inform the public of potential environmental impacts; it does not require the agency to "'elevate environmental concerns over other appropriate considerations.'" Baltimore Gas & Elec. Co., 462 U.S. at 97-98 (quoting Strycker's Bay Neighborhood Council, Inc., 444 U.S. at 227). Accord Vermont Yankee Nuclear Power Corp., 435 U.S. at 558; Kleppe v. Sierra Club, 427 U.S. at 410 n.21. The court of appeals' conclusion that NEPA "requires that 'action be taken to mitigate the adverse effects of major federal actions'" is thus patently incorrect. Indeed, even respondents decline to defend the court's proposition; they contend that they "never have asserted that NEPA imposes a substantive duty to mitigate" (Br. in Opp. 9). /23/ 2. The court of appeals' misperception of NEPA's function has led the court to misconstrue the statute's formal requirements. The court's erroneous premise that NEPA requires federal agencies to mitigate adverse environmental effects prompted it to construct a rigid and unwarranted procedural regime for developing mitigation measures. The court concluded that whenever a federal agency prepares an environmental impact statement, it must include "a thorough discussion of measures to mitigate the adverse environmental impacts of a proposed action" and "'must analyze the mitigation measures in detail and explain the effectiveness of the measures'" (Pet. App. 17a (quoting Oregon Natural Resources Council v. Marsh, 820 F.2d at 1055)). The court specifically stated: The importance of the mitigation plan cannot be overestimated. It is a determinative factor in evaluating the adequacy of an environmental impact statement. Without a complete mitigation plan, the decisionmaker is unable to make an informed judgment as to the environmental impact of the project -- one of the main purposes of an environmental impact statement. Pet. App. 19a (quoting Oregon Natural Resources Council v. Marsh, 820 F.2d at 1055). The court of appeals' inflexible new procedural requirements are foreign to NEPA and would ultimately impede the goal of sound agency decisionmaking. No one questions that a federal agency can and should consider mitigation opportunities when assessing the environmental consequences of a proposed action. The crucial issue here is the role that mitigation considerations play in the agency's environmental review. The court of appeals concluded that NEPA requires mitigation and that the government must therefore develop a "complete mitigation plan" as an essential element of an environmental impact statement (Pet. App. 17a, 19a). The government urges a fundamentally different proposition: NEPA requires environmental analysis and disclosure, and the government must therefore discuss mitigation in a manner that aids reasoned decisionmaking. See 40 C.F.R. 1502.1. "As Vermont Yankee made clear, NEPA does not require agencies to adopt any particular internal decisionmaking structure." Baltimore Gas & Elec. Co., 462 U.S. at 100. The agency has broad discretion to determine the form and scope of the mitigation discussion in light of the particular circumstances, subject only to the requirements that the environmental review as a whole satisfies NEPA's specific requirements and that the resulting decision is not arbitrary or capricious. See Baltimore Gas & Elec. Co., 462 U.S. at 97-98, 105-106. The need for this flexibility becomes obvious when one considers the broad variety of contexts in which mitigation considerations may become relevant. The federal agencies must prepare an environmental impact statement (or explain why a statement is not necessary) for the full gamut of government activities, ranging from proposals for legislation, to physical construction and improvements, to the issuance of permits. /24/ In addition, federal agencies frequently find it necessary or desirable to provide a series of such statements at various stages of a single project's development. /25/ The relevance of and opportunities for mitigation vary considerably depending on the nature and complexity of the activity and the stage at which the environmental impact statement is being prepared. It would not be feasible, and often would be counterproductive, to develop a "complete mitigation plan" in every circumstance. For example, a federal agency considering whether to initiate an extensive new resource development program -- such as a coal leasing program -- will generally prepare a programmatic environmental impact statement at the conceptual stage of consideration. See 40 C.F.R. 1501.4, 1502.4(b). See, e.g., Kleppe v. Sierra Club, 427 U.S. at 400. The agency cannot be expected, however, to prepare a "complete mitigation plan" at that preliminary point of the decisionmaking process. As a contrasting example, an agency considering whether to undertake a discrete project that has particular features designed to eliminate environmental harm need not prepare an environmental impact statement if it determines, as a result of an environmental assessment, that there will be no significant environmental impact. See 40 C.F.R. 1501.4, 1508.9, 1508.13. See, e.g., Friends of Endangered Species, Inc. v. Jantzen, 760 F.2d 976, 987 (9th Cir. 1985). An agency making that determination can reasonably be expected to have a detailed statement of the mitigation measures in hand if it relies on those measures in reaching its decision. /26/ Obviously, the agency's obligation to discuss mitigation measures will depend on the nature of the proposed agency action. The CEQ's implementing regulations, which are binding on all federal agencies (Exec. Order No. 11,991, 3 C.F.R. 123, 124 (1978)), therefore provide a flexible approach to the consideration and discussion of such measures. The regulations, which broadly define the term "mitigation" to include virtually any technique that avoids, elminates, ameliorates, or compensates for environmental harm (40 C.F.R. 1508.2), /27/ require a federal agency to consider mitigation opportunities at three stages of the NEPA review process. First, the CEQ regulations direct that when a federal agency takes the initial step of defining the "scope" of an environmental impact statement, it should consider the adoption of mitigation measures, not already included in the proposed action, as one type of alternative to the proposed action. See 40 C.F.R. 1508.25. /28/ This provision thus assures that when an agency determines the relevant range of alternatives, it will consider, in addition to the "(n)o action alternative" and "(o)ther reasonable courses of actions" (40 C.F.R. 1508.25(b)), the possibility of modifying the proposal to reduce or eliminate environmental harm. Second, the CEQ regulations direct that once the agency has defined the scope of its environmental review, it should address mitigation in the body of the environmental impact statement when discussing proposal alternatives and environmental consequences. See 40 C.F.R. 1502.14, 1502.16. These provisions, which instruct the agency to consider "appropriate mitigation measures not already included in the proposed action or alternatives" (40 C.F.R. 1502.14(f)) thus encourage the agency to consider mitigation opportunities that were not identified in the scoping process. Third, the CEQ regulations state that if, upon completion of the environmental analysis, the agency chooses to go forward with the proposal, it must indicate in its record of decision "whether all practicable means to avoid or minimize environmental harm from the alternative selected have been adopted, and if not, why they were not." 40 C.F.R. 1505.2(c). The record of decision must also summarize a monitoring and enforcement program "where applicable for any mitigation" (40 C.F.R. 1505.2(c)), and the agency must confirm that the mitigation measures are ultimately implemented (40 C.F.R. 1505.3). These provisions ensure that the agency will consider mitigation opportunities in making its decision and will institute any measures that are chosen. The CEQ's regulations are "designed to make the environmental impact statement process more useful to decisionmakers and the public; and to reduce paperwork and the accumulation of extraneous background data, in order to emphasize the need to focus on real environmental issues and alternatives" (Exec. Order No. 11,991, 3 C.F.R. 123 (1978)). They permit a federal agency to consider mitigation opportunities in a systematic fashion and in accordance with NEPA's statutory framework. The regulations neither broaden nor restrict the scope of the inquiry that NEPA mandates; instead, they provide a blueprint for compliance. /29/ Furthermore, they preserve the agency's basic discretion under NEPA to determine in any particular case how far-ranging, thorough, or detailed the mitigation discussion should be. /30/ The CEQ regulations, which have the characteristic NEPA hallmark of adaptability, can be employed throughout the entire spectrum of agency decisionmaking. Furthermore, they ensure that an agency can target its discussion of mitigation to the particular decision at hand. Given NEPA's "quite precise" procedural instructions (Kleppe, 427 U.S. at 406) and the CEQ's carefully crafted implementing regulations, there is no need or warrant for courts to impose additional compliance procedures. The court of appeals' rigid new requirement that all environmental impact statements must contain a "complete mitigation plan" not only exceeds the court's proper role (see, e.g., id. at 410 n.21), it is both unworkable and unnecessary. As this case aptly demonstrates, that judicially coined requirement seriously impedes the NEPA review process with no corresponding benefits. 3. The Forest Service conscientiously complied with NEPA and the CEQ regulations in preparing the Early Winters Study and, specifically, in discussing mitigation measures. As a result of preliminary scoping, the Forest Service elected to employ a "tiered" environmental analysis in this case. See note 25, supra. Thus, as its preface explains, the Study's inquiry was directed solely to the general question "whether National Forest System lands should be used for (a ski resort at Sandy Butte) and, if so, at what level" (Early Winters Study xvi). The Early Winters proposal, at this stage, was a concept whose on-the-ground dimensions and form had not yet been determined. The Study discussed mitigation measures at a conceptual level appropriate for that stage of decisionmaking. The Forest Service chose a manifestly prudent approach. It would be impractical (if not impossible) to develop detailed mitigation plans prior to the determination of the ski area master plan; furthermore, it would be a potentially wasteful expenditure of time and money to develop detailed mitigation plans before the Forest Service determined whether any project would be allowed. The Forest Service reasonably concluded, in accordance with the concept of tiered decisionmaking, that the detailed mitigation measures were not yet ripe for specification, and a general discussion of possible mitigation measures would sufficiently inform its inquiry whether to go forward with the project. Again, NEPA and the implementing regulations require only that opportunities for mitigation be discussed. /31/ The Early Winters Study's discussion of mitigation measures was general in content, but it was extensive in scope and did fully discuss opportunities for mitigation at this stage of the decisionmaking process. The Study identified a broad range of mitigation measures and divided them into two categories: on-site measures, which the Forest Service would make either a condition of the special use permit or a condition of approval of the master plan; and off-site measures, which the Forest Service proposed but which would require the cooperation of state and local government. /32/ The Study explained that specific measures to mitigate wildlife impacts on-site would have to await review of the detailed master plan (Early Winters Study 16, 77), but some of the measures that would be considered included: (1) locating runs, lifts, roads, and other facilities to minimize disturbance of wildlife wintering areas. (2) leaving dead and defective trees standing in timbered areas where skier safety can be protected. (3) restricting activity on selected roads during mule deer fawning season (June). (4) locating new service roads away from water sources and fawning cover. (5) evaluating impact to mule deer migration routes in review of the master plan. (6) designing nearby and off-site timber sales to retain adequate travel corridors, foraging, roosting, and nesting sites for spotted owls. (7) protecting other likely migration routes between summer and winter habitats for spotted owls and restricting other activities within the spotted owls' home range. (8) protecting springs and riparian areas within the permit zone. See Early Winters Study 16-17. Off-site measures could include: (1) limiting development on deer winter range and along migration routes through rezoning options, tax incentives, and other means. In this regard, the Study emphasized that protection of vital portions would be assured prior ski hill development. (2) encouraging conservation easements between private individuals and trust agencies through use of tax incentives. (3) acquiring essential tracts for migrating deer, to be administered by a wildlife management agency (e.g., Washington Department of Game). (4) minimizing road kills of deer and other wildlife through use of warning signs, speed limits, and roadway design. (5) enacting dog control ordinances. (6) zoning to discourage development in riparian areas. See Early Winters Study 77-78. Both on-site and off-site measures would be formulated in conjunction with the Washington Department of Game. The Early Winters Study's proposed measures for mitigating the relatively minor on-site air quality impacts included prompt revegetation of disturbed areas, mandatory application of dust control measures, and compliance with established federal and state smoke management practices (Early Winters Study 69). Proposals to mitigate the more serious off-site air quality impacts included: (1) forming an Air Quality Control Authority or similar administrative structure pursuant to Washington law; (2) developing an airshed management plan resulting in air quality standards stricter than existing state standards. As part of the plan's development, the following measures would be considered: -- developing land use codes addressing site development and project design directed at energy efficiency and air pollution control. -- requiring all new construction to be fully weatherized to reduce the need for supplemental heating sources (especially wood) beyond the central facility's heating needs. -- restricting the number of fireplaces and wood stoves. In particular, few fireplaces should be allowed in tourist accommodations. -- encouraging the use of alternative, nonpolluting energy sources. -- establishing certification mechanisms for wood stoves and fireplace inserts. -- developing air pollution monitoring to alert local residents to imminent pollution episodes and to record long term changes in air quality levels. The long term data would be used to evaluate the success or failure of the mitigation measures and to impose more stringent measures if standards are violated. -- developing enforcement measures to assure compliance with standards. See Early Winters Study 68-69. The Study also suggested other mitigation measures addressed to construction and operation, water quality, soils, fisheries, cultural and visual resources, and other effects (id. at 14-17, 69-78, 101-136). Thus, it is unquestionable that significant portions of the Early Winters Study were devoted to discussing mitigation measures. This compendious discussion was sufficiently thorough for the decision at hand: namely, whether to allow a prescribed level of ski area development at Sandy Butte. The Chief of the Forest Service and the magistrate, who served as the factfinder in this dispute, both agreed that the Study's mitigation discussion satisfied NEPA's requirements (Pet. App. 41a-42a, 45a-46a, 58a-59a). The Study placed primary emphasis on identification of unmitigated environmental impacts because those impacts defined the potential seriousness of the environmental harm that could be encountered and thus were highly relevant to the decision whether any development should be allowed. The Forest Service reasonably determined that an in-depth discussion of mitigation measures (which could only diminish the seriousness of the unattenuated environmental impacts) played a less significant role at this stage of the decisionmaking process, particularly since the details of those measures could not be specified in the absence of state and local government cooperation and the formulation of a master development plan (Early Winters Study 14; Pet. App. 58a-59a; see also id. at 41a-42a, 45a-46a). /33/ The Forest Service's decision to provide a general, rather than a detailed, discussion of mitigation measures simply puts into practice the incontestible principle, recognized in Vermont Yankee Nuclear Power Corp., that the level of detail an agency employs in its environmental discussions must be determined in light of "feasibility" and "(c)ommon sense" (435 U.S. at 551). Indeed, the lower courts have specifically held that where mitigation details are contingent on presently unknown factors, it is appropriate for an agency to limit its discussion accordingly. See, e.g., Concerned Citizens on I-190 v. Secretary of Transportation, 641 F.2d 1, 5-6 (1st Cir. 1981). Even if there were any doubt on that score, the Forest Service's expert judgment, which is based on extensive project planning experience, would be entitled to substantial deference. /34/ The court of appeals, therefore, erred in concluding that the Early Winters Study failed to address mitigation adequately. Moreover, the court's blanket requirement that agencies prepare a "complete mitigation plan" is both unworkable and unwise. The court's requirement pervasively conflicts with CEQ regulations /35/ and would expunge from NEPA the flexibility that allows vastly different federal agencies to perform meaningful environmental analyses tailored to their functions and needs. Agencies would no longer be able to plan and implement their activities through staged project development (see note 25, supra). As this case demonstrates, an agency cannot develop a "complete mitigation plan" at the preliminary stages of the decisionmaking process. The court's requirement would accordingly have the perverse effects of (1) encouraging agencies either to invest large sums of money and time before making even preliminary decisions or to defer environmental analysis until far along in the planning process; and (2) discouraging agencies from identifying mitigation measures that may be possible but cannot be guaranteed. /36/ As a result, the court's decision would reduce, rather than enhance, the agency's ability to conduct informed and well-reasoned decisionmaking. And the courts themselves would be forced to expend considerable energy adjudicating the ultimately discretion-laden question whether a "complete mitigation plan" is sufficiently detailed to qualify as "complete." This Court has repeatedly emphasized that the courts have a limited role to play under NEPA. E.g., Baltimore Gas & Elec. Co., 462 U.S. at 97-98. The court of appeals here has not only overturned the magistrate's manifestly correct decision, it has rewritten NEPA to suit its own vision of environmental policy. The court has clearly overstepped its proper bounds. B. NEPA Does Not Require Federal Agencies To Prepare A "Worst Case" Analysis Of Potential Environmental Harm If Relevant Information Concerning Significant Environmental Effects is Unavailable Or Too Costly To Obtain 1. The court of appeals also erred in concluding (Pet. App. 13a-14a) that NEPA requires the Forest Service to conduct a "worst case" analysis on remand if relevant scientific information on environmental effects is unavailable or too costly to obtain. As we explain below, and in somewhat greater detail in our brief in Marsh v. Oregon Natural Resources Council, supra, NEPA itself prescribes no particular method for dealing with the problem of scientific uncertainty; instead, the CEQ introduced worst case analysis as a method for addressing that problem. The CEQ's experience with worst case analysis ultimately revealed that the method did not effectively fulfill NEPA's objectives, and the agency therefore has replaced it with a more manageable methodology that identifies "reasonably foreseeable" environmental impacts. The court of appeals nevertheless insisted that "NEPA caselaw" (Pet. App. 13a n.11) requires that agencies continue to employ worst case analysis. That conclusion is fatally infirm; worst case analysis is a product of the CEQ regulations only, and the case law on that subject merely interprets those regulations. Accord Note, Federal Agency Treatment of Uncertainty in Environmental Impact Statements Under the CEQ's Amended NEPA Regulation Section 1502.22: Worst Case Analysis or Risk Threshold?, 86 Mich. L. Rev. 777, 819-820 (1988). The CEQ originated the concept of worst case analysis in its 1978 implementing regulations. See 43 Fed. Reg. 55,978, 55,997. Those regulations, which were promulgated pursuant to presidential order, represented the CEQ's first attempt to provide an authoritative blueprint for NEPA compliance that would be binding on every federal agency. See id. at 55,978. Section 1502.22, which came to be known as the worst case requirement, described the government's obligation to obtain information relevant to a proposed action's significant adverse environmental effects. See 40 C.F.R. 1502.22 (1985). /37/ Under that section, the agency was required, if possible, to obtain the information and to include it in the environmental impact statement (40 C.F.R. 1502.22(a) (1985)). If the information were unavailable or too costly to obtain, the agency was required to "weigh the need for the action against the risk and severity of possible adverse impacts" and to provide a "worst case analysis and an indication of the probability or improbability of its occurrence" (40 C.F.R. 1502.22(b) (1985)). The CEQ did not explain why it chose worst case analysis over other methods for dealing with uncertainty (see 43 Fed. Reg. 55,984 (1978)), and the regulation itself did not explain how an agency was to go about conducting a worst case analysis. As a result, federal agencies encountered substantial difficulties in implementing the worst case requirement. See, e.g., Note, supra, 86 Mich. L. Rev. at 798-799 n.106. Meanwhile, the courts' interpretation of the worst case regulation, accompanied by judicial second-guessing of the agencies' scientific determinations, rendered the method largely unworkable. The courts repeatedly overturned agency worst case analyses and instructed the agency to evaluate rigorously a broad spectrum of highly remote possibilities, declaring "the specific worst case to be examined by the agency on remand, including the particular scientific models and studies to be applied and the research to be performed" (id. at 808). See, e.g., Save Our Ecosystems v. Clark, 747 F.2d 1240, 1244-1246 (9th Cir. 1984); Southern Oregon Citizens Against Toxic Sprays, Inc. v. Clark (SOCATS), 720 F.2d 1475, 1479 (9th Cir. 1983), cert. denied, 469 U.S. 1028 (1984) (White and O'Connor, JJ., dissenting); Sierra Club v. Sigler, 695 F.2d 957 (5th Cir. (1983). See generally Note, supra, 86 Mich. L. Rev. at 798-804. In 1986, following this Court's denial of the government's petition for a writ of certiorari in SOCATS, the CEQ replaced the worst case regulation with a new regulation that, in that agency's judgment, provides "a wiser and more manageable approach to the evaluation of reasonably foreseeable significant adverse impacts in the face of incomplete or unavailable information in an EIS." 51 Fed. Reg. 15,620 (1986). /38/ The new regulation states that if "incomplete information relevant to reasonably foreseeable significant adverse impacts is essential to a reasoned choice among alternatives and the overall costs of obtaining it are not exorbitant, the agency shall include the information in the environmental impact statement" (40 C.F.R. 1502.22(a)). If information relevant to reasonably foreseeable significant adverse impacts cannot be obtained, the agency must include four items in the environmental impact statement: (1) a statement that the information is incomplete or unavailable; (2) a statement of the relevance of the incomplete or unavailable information to evaluating impacts; (3) a summary of existing credible scientific evidence relevant to evaluating impacts; and (4) the agencies' evaluation of the impacts based upon theoretical approaches or research methods generally accepted in the scientific community (40 C.F.R. 1502.22(b)). /39/ The revised regulation accordingly requires "federal agencies to evaluate the reasonably foreseeable significant adverse impacts of an action, even in the face of unavailable or incomplete information" (51 Fed. Reg. 15,621 (1986)). It "specifies that the evaluation must be carefully conducted, based upon credible scientific evidence, and must consider those reasonably foreseeable significant adverse impacts which are based on scientific evidence" (ibid.). In short, the amended regulation "retains the duty to describe the consequences of a remote, but potentially severe impact, but grounds the duty in evaluation of scientific opinion rather than in the framework of a 'conjectural "worst case analysis."'" 50 Fed. Reg. 32,237 (1985). 2. The court of appeals refused to give effect to the CEQ's carefully deliberated regulatory revision, holding here and in Marsh that NEPA requires worst case analysis irrespective of the CEQ regulations. See Pet. App. 12a-13a & n.11. The court incorrectly reasoned that the CEQ's "rescission * * * does not nullify the (worst case) requirement, Marsh, 820 F.2d at 1058 n.8, since the regulation was merely a codification of prior NEPA caselaw" (Pet. App. 13a n.11). In support of that assertion, the court of appeals summarily cited its previous decisions in Save Our Ecosystems and SOCATS. But Save Our Ecosystems simply cites SOCATS for that proposition. See 747 F.2d at 1244. SOCATS, in turn, simply cites Sierra Club v. Sigler, 695 F.2d at 971. There the trail ends. Neither Sigler nor any previous case holds that NEPA requires the federal agencies to conduct a worst case analysis. The question in Sigler was whether the Army Corps of Engineers was required to comply with the CEQ's worst case analysis regulation under the particular facts of that case. The Fifth Circuit first observed that while there "is some language in NEPA which may be said to endorse generally the concept of a worst case analysis" the statute's "literal language does not require a worst case analysis" (695 F.2d at 969). The court next noted that NEPA does contemplate that agencies would engage in "'(r)easonable forecasting and speculation'" concerning future environmental effects, including the "probabilities of the occurrence" and the "'cost of uncertainty -- i.e., the costs of proceeding without more and better information'" (id. at 970). /40/ The court then stated that the "CEQ's worst case analysis merely codifies these judicially created principles" (id. at 971). Thus, the Fifth Circuit concluded that the worst case regulation was the CEQ's mechanism for implementing certain judicially recognized NEPA objectives. The court did not hold that the worst case methodology was the only allowable mechanism for effecting those general goals. Accord Note, supra, 86 Mich. L. Rev. at 797-798; see also id. at 798 n.105, 801-802 & nn. 120-121, 812-814, 819-820. Indeed, the court of appeals'conclusion here that NEPA requires a worst case analysis is inconsistent with that court's own prior case law, which recognizes that "(a) reasonably thorough discussion of the significant aspects of the probable environmental consequences is all that is required by an EIS." Trout Unlimited v. Morton, 509 F.2d 1276, 1283 (9th Cir. 1974). /41/ The CEQ has adhered to the objectives identified in Sigler, but has determined that "the 'worst case analysis' requirement is an unproductive and ineffective method of achieving those goals" (51 Fed. Reg. 15,618, 15,620 (1986)). The CEQ has therefore adopted "a wiser and more manageable approach to the evaluation of reasonably foreseeable significant adverse impacts in the face of incomplete or unavailable information" (id. at 15,620). The court of appeals' decision in this case effectively rescinds the CEQ's new regulation and, contrary to that court's own decision in Trout Unlimited, installs worst case analysis as a permanent feature of NEPA compliance. This aspect of the court of appeals' decision is obviously contrary to this Court's holding that the CEQ's judgment is entitled to substantial deference, even when the agency alters its procedures for NEPA compliance. Andrus v. Sierra Club, 442 U.S. 347, 358 (1979). See also, e.g., American Trucking Ass'ns v. Atchison, T. & S.F. Ry., 387 U.S. 397, 416 (1967); Sierra Club v. Sigler, 695 F.2d 957, 967, 972 (5th Cir. 1983) (recognizing that NEPA requires adherence to CEQ regulations, even when CEQ changes its interpretation, and that CEQ regulations are entitled to substantial deference). /42/ And, as is true of its novel mitigation requirements, the court of appeals' holding here would have severe consequences. As the CEQ has explained, requiring a worst case analysis forces federal agencies to conduct wasteful and time-consuming inquiries into speculative impacts that lack "a firm connection between credible science and the hypothetical consequences of an agency's proposed action" (50 Fed. Reg. 32,236 (1985)). This sort of "pure conjecture * * * lacking a credible scientific basis is not useful to either the decisionmaker or the public" (ibid., emphasis in original). The CEQ, after careful deliberation, properly elected to eliminate its worst case analysis requirement. The court of appeals improperly relied on a "contrived 'common law' rationale for overruling the CEQ" (Note, supra, 86 Mich. L. Rev. at 820). II. THE FOREST SERVICE MAY ISSUE A SPECIAL USE PERMIT FOR RECREATIONAL USE OF NATIONAL FOREST LAND IN THE ABSENCE OF A "COMPLETE MITIGATION PLAN" The court of appeals not only misconstrued NEPA, it also imported its incorrect vision of NEPA into Forest Service regulations governing the issuance of special use permits. The Forest Service regulations at issue here require the applicant to include in its application "measures and plans for the protection and rehabilitation of the environment during construction, operation, maintenance, and termination of the project" (36 C.F.R. 251.54(e)(4)). The regulations further provide that a special use permit "shall contain: (1) Terms and conditions which will * * * (ii) minimize damage to scenic and esthetic values and fish and wildlife habitat and othe(r)wise protect the environment" (36 C.F.R. 251.56(a)(1)(ii)). /43/ The court of appeals interpreted these provisions to require the Forest Service to prepare "an adequate mitigation plan" prior to issuing a permit (Pet. App. 5a n.3). The court specifically stated (ibid.): Since the mitigation "plan" here at issue is so vague and undeveloped as to be wholly inadequate (citing the court's discussion of NEPA mitigation requirements), the Regional Forester's decision to grant the special use permit could be none other than arbitrary, capricious and an abuse of discretion. The court thus invalidated the Forest Service's decision to issue a special use permit on the ground that the Forest Service, by failing to satisfy the court's newly fashioned NEPA requirement that agencies prepare a "complete mitigation plan," failed to satisfy the agency's own regulations. The court's reasoning does not withstand scrutiny. As a preliminary matter, the Forest Service regulations provide that a special use permit must "contain" various terms and conditions (36 C.F.R. 251.56(a)(1)(ii)); the regulations in no way expressly require the agency to prepare a mitigation plan as a procedural prerequisite in deciding whether to issue a permit. /44/ And specifically, while the pertinent regulation states that a special use permit shall contain terms and conditions protecting the environment, it preserves the Forest Service's discretion to determine the appropriate terms and conditions. The Forest Service did not abuse its discretion here. In accordance with its standard practices, the Forest Service issued a special use permit that included a series of provisions conditioning all construction on the Forest Service's prior approval of a fully developed master plan (which was to contain detailed mitigation measures) and requiring the developer to protect scenic and aesthetic values, prevent soil erosion and degradation of water, soil, and air quality, and immediately to cease construction upon discovery of archaeologically or historically significant material. See U.S. Dep't of Agriculture Forest Service Special Use Authorization, Region 06, User No. 4171 (Methow Recreation Inc.), paras. 41, 44, 48, 49, 50, 54, 62, 76. /45/ The court of appeals exceeded its authority -- here as well as under its interpretation of NEPA (see pages 21-38, supra) -- in requiring the Forest Service to develop a judicially dictated "complete mitigation plan." The Forest Service's authority to issue the special use permit rested upon the Act of March 4, 1915, ch. 144, 38 stat. 1101, which provides in pertinent part (16 U.S.C. 497 (emphasis added)): The Secretary of Agriculture is authorized, under such regulations as he may make and upon such terms and conditions as he may deem proper, (a) to permit the use and occupancy of suitable areas of land within the national forests, not exceeding eighty acres and for periods not exceeding thirty years, for the purpose of constructing and maintaining hotels resorts, and any other structures or facilities necessary or desirable for recreation, public convenience, and safety * * *. See H.R. Rep. 99-709, supra, Pt. 1, at 2-3 (describing the permitting procedures). /46/ Thus, Congress plainly gave the Secretary of Agriculture (and, through delegation, the Forest Service) broad authority to determine appropriate terms and conditions. /47/ Pursuant to that grant of authority, the Forest Service has consistently issued special use permits imposing terms and conditions similar to those employed here. The Forest Service originally instructed its personnel, through guidelines issued prior to NEPA's passage, that when authorizing special uses they should impose conditions to minimize harm to resources. /48/ The agency promulgated its present regulations addressing permit terms and conditions in 1980. See 45 Fed. Reg. 38,324. Those regulations were intended to preserve the agency's "flexibility in tailoring authorizations to fit the actual situation" (id. at 38,325) and were not intended to change in any significant way the past practices for issuing ski resort special use permits. /49/ The Forest Service regulations, by their terms, do not specify what mitigation measures must be incorporated into special use permits. There is no indication that they were ever intended to require the kind of "complete mitigation plan" that the court itself created -- without statutory authority -- in Oregon Natural Resources Council v. Marsh, supra, and reaffirmed in this case. /50/ The Forest Service, instead, has routinely imposed terms and conditions similar to those ultimately imposed here. The court of appeals' holding "runs roughshod over the established proposition that an agency's construction of its own regulations is entitled to substantial deference." Lyng v. Payne, 476 U.S. 926, 939 (1986). "In construing administrative regulations, 'the ultimate criterion is the administrative interpretation, which becomes of controlling weight unless it is plainly erroneous or inconsistent with the regulation.'" United States v. Larionoff, 431 U.S. 864, 872 (1977) (quoting Bowles v. Seminole Rock & Sand Co., 325 U.S. 410, 414 (1945)). The Forest Service's interpretation and application of its regulation here is plainly reasonable and deserves deference. By contrast, the court's decision, which would require every special use permit henceforth issued to contain a detailed plan to mitigate on- and off-site effects, is without basis in either the pertinent regulations or the governing statutes. CONCLUSION The judgment of the court of appeals should be reversed with instructions to remand the case to the agency for further proceedings. /51/ Respectfully submitted. CHARLES FRIED Solicitor General ROGER J. MARZULLA Assistant Attorney General LAWRENCE G. WALLACE Deputy Solicitor General JEFFREY P. MINEAR Assistant to the Solicitor General PETER R. STEENLAND, JR. VICKI L. PLAUT Attorneys SEPTEMBER 1988 /1/ We have simultaneously submitted a separate brief in Marsh. /2/ In 1986, Congress explicitly recognized that national forests often embrace terrain uniquely suitable for skiing and created a special permitting process for developing ski areas. National Forest Ski Area Permit Act of 1986, 16 U.S.C. (Supp. IV) 497b. Prior to 1986, a ski area operating within a national forest required two Forest Service permits: one permit, covering up to 80 acres, was issued for a total of 30 years; a second permit, encompassing the remainder of the ski area, was issued subject to annual renewals. See 16 U.S.C. 497, 551. The second permit, which posed an annual prospect of non-renewal or changed permit conditions, impeded a developer's ability to obtain financing for its capital-intensive facilities, which often involve "thousands of acres on which construction, operation and maintenance may take place" (H.R. Rep. 99-709, supra, Pt. 1, at 2). The new law encourages ski area development by replacing the dual permits with single 40-year permits (id. at 3). /3/ A "major destination ski resort" is a large, multiple-season ski area with sufficient ski runs, adequate vertical rise, sufficiently varied activities and high-quality base facilities to entice vacationers to travel long distances and to stay several days at the site. /4/ This conditional special use permit typically establishes the basic financial terms of the permit, includes general restrictions on future operation, and entitles the developer to conduct on-site exploration in order to generate a master plan for the project, which -- in the case of a ski resort -- generally requires a substantial investment and consumes three to five years. As noted above, the permit, by itself, does not allow the developer to engage in any construction activities on forest land. It does, however, provide the developer with an assurance -- before continuing a lengthy and expensive planning process -- that the Forest Service will not authorize another developer to undertake the proposed project. /5/ The final environmental impact statement -- formally entitled the Early Winters Alpine Winter Sports Study and sometimes referred to as an "FEIS" -- was released on August 31, 1984 (49 Fed. Reg. 34,575). The Forest Service completed and circulated a draft of the Early Winters Study in 1982, but delayed release of the final version while Congress considered including Sandy Butte in a proposed wilderness area. On July 3, 1984, Congress passed the Washington State Wilderness Act of 1984, Pub. L. No. 98-339, 98 Stat. 299, designating as wilderness certain portions of the National Forest System in Washington -- not including Sandy Butte -- and directing that "other National Forest System lands in the State of Washington be available for nonwilderness multiple uses" (Section 2(b), 98 Stat. 299). The Senate Report accompanying the Act spoke directly to the issue of further development at Sandy Butte: That area of the Okanogan National Forest known as Sandy Butte has been excluded from wilderness designation in S. 837. * * * The designation by Congress in S. 837 makes it unnecessary to further withhold the Sandy Butte/Early Win(t)ers Alpine Winter Sports Study FEIS pending completion of the Okanogan Forest Plan. The Forest Service and the Department of Agriculture are directed to allow the evaluation process for the Sandy Butte development to proceed without additional delay * * *. S. Rep. 98-461, 98th Cong., 2d Sess. 11 (1984). For the Court's convenience, we have lodged copies of the Early Winters Study with the Clerk of the Court. /6/ The alternatives ranged from denying the request to build a ski resort (Alternative I) to allowing development of a ski area capable of serving 10,500 skiers at one time (Alternative V). The Early Winters Study did not give detailed consideration to the expansion of existing ski areas or the development of new ski areas at other locations. The North Cascades Study had considered these options and had concluded that -- of 23 existing and potential sites -- Sandy Butte was the only site in the State of Washington suitable for new development as a major ski area. See Early Winters Study 6-7; see also Pet. App. 37a, 51a-52a. /7/ Sandy Butte also is a major source of summer range for the mule deer. The Study predicted, however, that while the ski area would decrease the summer range by between 5 and 10 percent, the remaining summer range would be sufficient for the existing herd, even with maximum development (Early Winters Study 75). /8/ The Washington Department of Game estimated that the mule deer could face a 50 percent reduction in winter range (Early Winters Study 76). However, the state agency's representative was unable to explain how the agency had reached that assessment. See Tr. 388-390 (May 8, 1986). /9/ The Early Winters Study stated (at 76) that "expected winter range encroachment would noticeably reduce numbers of deer in the Methow (Valley) with any alternative." The "no action" alternative was expected to have serious impacts on the mule deer because the area was projected to sustain a significant increase in human population even if no ski development occurred at Sandy Butte (id. at vii, 65, 76, 104). /10/ "Off-site effects are more difficult to estimate, due to the uncertainty of where other public and private lands may become developed. In general, wildlife habitats and populations would suffer with the increased habitat loss, human activity, game harvesting, predation harassment by dogs and cats, and other encroachment" (Early Winters Study 76). /11/ "Without mitigation, modeled values for total suspended particulates (TSP) indicate nearly all areas of the Upper Methow Valley will experience concentrations in excess of the State standard, even with Alternative I (the no action alternative)" (Early Winters Study 67). /12/ "Since loss of winter range and disruption of migration routes are primary concerns which will cause declines in deer numbers, protection of vital portions (of winter range) will be assured prior to ski hill development. Rezoning is essential and will occur * * *" (Early Winters Study 77). /13/ In July 1985, Okanogan County entered into a memorandum of understanding with the Forest Service agreeing to institute these actions (Pet. App. 42a). The County has since passed a new zoning ordinance and a dog control ordinance. /14/ The Forest Service, the United States Environmental Protection Agency, the State Department of Ecology, and Okanogan County subsequently entered into a memorandum of understanding committing the county to develop and enforce an air quality ordinance and other mitigation measures necessary to maintain air quality within the standards of the state air quality implementation plan (Pet. App. 45a-46a). The Forest Service agreed, in turn, to ensure that measures sufficient to maintain air quality were in place before allowing any construction of permitted facilities at Sandy Butte (Supplemental Excerpts of Record 47-48). By September 1986, Okanogan County had adopted a strict new air quality ordinance. /15/ This decision did not identify either the developer or the exact configuration of a ski development at Sandy Butte. Instead, it established that the Forest Service would seek a qualified applicant to develop a ski area of a certain size in compliance with certain financial and environmental requirements (Pet. App 63a-71a). /16/ As we have noted, see notes 13-14, supra, these efforts included the development of various local restrictions to protect wildlife and air quality (see Pet. App. 66a-70a). The Forest Service also agreed to ensure that measures sufficient to maintain air quality were in place before allowing any construction of permitted facilities at Sandy Butte. See Supplemental Excerpts of Record 47-48. /17/ For convenience, we refer to these parties as the respondents. When referring to the developer, which is also a respondent to our petition, we shall use the abbreviation MRI. /18/ The court based this requirement on its recent decision in Oregon Natural Resources Council v. Marsh, 820 F.2d 1051, 1058-1059 (1987), cert. granted, No. 87-1704 (June 27, 1988). /19/ The court quoted Stop H-3 Ass'n v. Brinegar, 389 F. Supp. 1102, 1111 (D. Haw. 1984), rev'd on other grounds, 533 F.2d 434 (9th Cir.), cert. denied, 429 U.S. 999 (1976). /20/ The court of appeals erred in two other respects, but we have not sought this Court's review of those errors. First, the court incorrectly concluded that the Early Winters Study's discussion of development alternatives was inadequate (Pet. App. 8a-11a). The significance of that ruling, however, is limited to the case at hand. The court appears to have agreed that the reasonableness of the alternatives depends essentially upon the scope of the proposed action as defined by the agency (Pet. App. 9a); it simply ignored the agency's own description of the scope of its action (see pages 5-6, supra). The court also erred in summarily overruling the Study's scientific determination, affirmed by the magistrate (Pet. App. 44a-45a), that the ski area would not have a significant impact on air quality in the Pasayten Wilderness Area. See, e.g., Anderson v. City of Bessemer City, 470 U.S. 564, 573-575 (1985) (appellate court is obligated to give deference to the original factfinder); Baltimore Gas & Elec. Co., 462 U.S. at 103 (reviewing court "must generally be at its most deferential" when reviewing scientific determinations). That narrow factual question is, however, peculiar to this case; moreover, the government is seeking reiteration of this Court's deference principles in the companion case, Marsh v. Oregon Natural Resources Council, No. 87-1704. Finally, we note that respondent is mistaken in suggesting (Br. in Opp. 22 n.16) that the government does not seek review of the court's determination that the Study inadequately discussed impacts on mule deer and upper Methow Valley air quality. The court's sole basis for finding those discussions inadequate was the absence of a detailed mitigation plan and a worst case analysis. See Pet. App. 12a-15a, 16a-19a. Those issues are both addressed in this brief. /21/ The court of appeals first suggested that proposition in Oregon Natural Resources Council v. Marsh, supra, based on a misconstruction of one of its prior precedents. The Marsh court stated that environmental impact statements must include a discussion of measures to mitigate adverse environmental consequences, adding that "(a)s long as significant measures are undertaken to mitigate the project's effects, the measures need not compensate completely for adverse environmental impacts" (820 F.2d at 1055). The court obtained the quoted language from Friends of Endangered Species, Inc. v. Jantzen, 760 F.2d 976, 987 (9th Cir. 1985). As we explain (note 26, infra), the Jantzen passage does not support the court of appeals' suggestion that environmental impact statements must always provide for some mitigation; read in context, the passage states that if an agency substantially mitigates the environmental effects of its actions, it may not need to prepare any environmental impact statement at all. See 760 F.2d at 987. /22/ The 1974 district court decision in Stop H-3 states, without any citation of authority, that "NEPA implies a requirement that action be taken to mitigate the adverse effects of major federal actions" (389 F. Supp. at 1111 (emphasis added)). That statement was dubious authority when written; this Court's subsequent decisions /23/ When Congress has wished to impose substantive environmental protection obligations on federal agencies, it has done so explicitly. For example, Congress specified in the Endangered Species Act of 1973 (ESA), Pub. L. No. 93-205, 87 Stat. 884, that federal agencies shall "insure that any action authorized, funded, or carried out * * * is not likely to jeopardize the continued existence of any endangered species" (16 U.S.C. 1536(a)(2)). See Roosevelt Campobello Int'l Park v. EPA, 684 F.2d 1041, 1049 (1st Cir. 1982). Similarly, Congress specified in Section 4(f) of the Department of Transportation Act of 1966, Pub. L. No. 89-670, 80 Stat. 934, that the Secretary of Transportation may approve a transportation project requiring use of a public park, recreation area, wildlife refuge, or historic site only if "there is no prudent and feasible alternative to using that land; and * * * the program or project includes all possible planning to minimize harm to the (land)" (49 U.S.C. 303). These statutes, which were enacted in the same general time frame as NEPA, demonstrate that when Congress wishes to impose substantive mitigation obligations, it does so expressly. The court of appeals' effort to write such a duty into NEPA would usurp Congress's deliberate contrary choice. /24/ See, e.g., Scientists' Inst. for Pub. Information, Inc. v. AEC, 481 F.2d 1079, 1092 (D.C. Cir. 1973) ("NEPA statements can and do vary, from relatively short and simple analyses of the environmental effects of smaller projects to complex multi-volume works for projects of multi-billion-dollar dimensions."). /25/ The CEQ has encouraged agencies to utilize the practice of "tiering" environmental impact statements. See 40 C.F.R. 1502.20, 1508.28. Tiering is simply a method of implementing the familiar and sensible concept of staged project development. See, e.g., D. Dannenbring & M. Starr, Management Science: An Introduction 548 (1981) ("A project is itself a combination of many varied and complex tasks or activities. These tasks are interdependent in that most cannot begin until some other task has been completed."). Tiering "is appropriate when it helps the lead agency to focus on the issues which are ripe for decision and exclude from consideration issues already decided or not yet ripe" (40 C.F.R. 1508.28). /26/ Prior to the Ninth Circuit's decisions here and in Marsh, legal challenges involving an agency's discussion of mitigation measures typically arose out of the agency's determination that mitigation measures obviated the need for an environmental impact statement. In response, the courts consistently recognized that a "Finding of No Significant Impact" (40 C.F.R. 1508.13), is appropriate if otherwise significant environmental effects will be remedied by mitigation measures built into the project. See Friends of Endangered Species, Inc. v. Jantzen, 760 F.2d at 987; Louisiana v. Lee, 758 F.2d 1081, 1083 (5th Cir. 1985), cert. denied, 475 U.S. 1044 (1986); Cabinet Mountains Wilderness/Scotchman's Peak Grizzly Bears v. Peterson, 685 F.2d 678, 681-684 (D.C. Cir. 1982); Preservation Coalition, Inc. v. Pierce, 667 F.2d 851, 860-861 (9th Cir. 1982); City & County of San Francisco v. United States, 615 F.2d 498, 501 (9th Cir. 1980); Maryland-National Capital Park & Planning Comm'n v. U.S. Postal Service, 487 F.2d 1029, 1039 (D.C. Cir. 1973). See also 46 Fed. Reg. 18,026 (1981). The Ninth Circuit specifically stated in this context that "so long as significant measures are undertaken to 'mitigate the project's effects,' they need not completely compensate for adverse environmental impacts." Friends of Endangered Species, Inc. v. Jantzen, 760 F.2d at 987 (emphasis in original; citation omitted). The court of appeals' Marsh decision mistakenly cited Jantzen for the radically different proposition that an environmental impact statement must always provide for some mitigation of environmental harm. See Oregon Natural Resources Council v. Marsh, 820 F.2d at 1055. See note 21, supra. /27/ The CEQ regulations state that mitigation includes (40 C.F.R. 1508.20): (a) Avoiding the impact altogether by not taking a certain action or parts of an action. (b) Minimizing impacts by limiting the degree or magnitude of the action and its implementation. (c) Rectifying the impact by repairing, rehabilitating, or restoring the affected environment. (d) Reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action. (e) Compensating for the impact by replacing or providing substitute resources or environments. /28/ Once an agency decides that it will prepare an environmental impact statement, it commences "an early and open process for determining the scope of issues to be addressed and for identifying the significant issues related to a proposed action" (40 C.F.R. 1501.7). The "scope" of an environmental impact statement "consists of the range of actions, alternatives, and impacts to be considered" in the document (40 C.F.R. 1508.25). /29/ Thus, the CEQ regulations require the agency to consider mitigation measures with reference to NEPA's specific criteria, including the environmental impact of the proposed action; the adverse environmental impacts that cannot be avoided; and alternatives to the proposed actions. See 42 U.S.C. 4332(2)(C). /30/ NEPA requires a "detailed statement" of environmental consequences, but it does not require that every subsidiary matter (such as mitigation) be discussed comprehensively, nor does it require -- explicitly or implicitly -- a detailed discussion of mitigation. Obviously, an agency's discussion of the five subjects identified in NEPA can be "detailed" even if the discussion of their subsidiary components, viewed individually, contains varying levels of detail. /31/ The CEQ regulations expressly sanction the Forest Service's approach. The pertinent regulation states in part (40 C.F.R. 1508.28): Tiering is appropriate when the sequence of statements or analyses is: * * * (b) From an environmental impact statement on a specific action at an early stage (such as need and site selection) to a supplement (which is preferred) or a subsequent statement or analysis at a later stage (such as environmental mitigation). /32/ The Forest Service also made clear that further on-site mitigation measures would be imposed later in the planning process, if the need for additional measures became apparent (Early Winters Study 14). As to off-site mitigation, the Forest Service was aware that development and enforcement would be largely outside its control (id. at 1-3). /33/ That judgment is consistent with the view, expressed by the Ninth Circuit as well as other courts, that the planning process is an ongoing endeavor and that agencies should be encouraged to develop and institute mitigation measures as the project develops, even after the environmental analysis is complete. See Village of False Pass v. Clark, 733 F.2d 605, 616 (9th Cir. 1984); Township of Springfield v. Lewis, 702 F.2d 426, 437-438 (3d Cir. 1983); National Indian Youth Council v. Watt, 664 F.2d 220, 225 (10th Cir. 1981); Concerned Citizens on I-190 v. Secretary of Transportation, 641 F.2d 1, 6 (1st Cir. 1981). See also County of Suffolk v. Secretary of the Interior, 562 F.2d 1368, 1378 (2d Cir. 1977), cert. denied, 434 U.S. 1064 (1978). In Township of Springfield, for example, the court of appeals determined that mitigation measures added to a project after circulation of the final environmental impact statement do not trigger a requirement to supplement the statement, in part because the measures were a specification of general measures spelled out in that statement. In fact, the Third Circuit noted that "'the responsiveness to environmental concerns demonstrated by these changes reflects a commendable effort to comply with the spirit of NEPA.'" 702 F.2d at 438 (citations omitted). /34/ This obviously is not a case, like Jantzen (see note 26, supra), where the planned implementation of mitigation measures eliminated the need for an environmental impact statement. And contrary to respondents' suggestion (Br. in Opp. 3, 18, 19), the Early Winters Study did not "rely upon" or "assume" mitigation in discussing adverse environmental effects. Rather, the Study provided a detailed discussion of the project's significant environmental effects without mitigation and then identified mitigation measures that, by definition, could be expected to reduce those impacts. See Early Winters Study 65-144. The Study's qualitative statements that implementation of mitigation measures would reduce adverse impacts (see Early Winters Study 67, 76, 77, 78, 145) are adequately supported and are certainly reasonable. Furthermore, the Forest Service did not "rel(y) upon potential mitigation measures to conclude that a project's ultimate impacts are acceptable" (Br. in Opp. 18). The Forest Service's record of decision recognized that adverse effects would occur with any of the proposed alternatives and specified that mitigation measures would be implemented to reduce those impacts (Pet. App. 67a; see also id. at 58a-59a). Thus, the Forest Service imposed mitigation measures as part of its decision, but it did not conclude that absent the success of those measures, the project would be environmentally unacceptable. Nor would any policy reflected in NEPA be served by inhibiting an agency from adopting mitigation measures designed to enhance the environment beyond the level that the agency would find minimally acceptable. /35/ See, e.g., 40 C.F.R. 1501.2, 1502.5(b) (mandating early application of NEPA); 40 C.F.R. 1502.2(a)-(c) (requiring that environmental impact statements be analytic rather than encyclopedic, that impacts be discussed in proportion to their significance, and that statements be concise and "no longer than absolutely necessary to comply with NEPA and with these regulations"); 40 C.F.R. 1502.2(f) (forbidding agencies from committing resources in a manner that will bias the agency's ultimate decision); 40 C.F.R. 1502.20 (encouraging tiered environmental analysis). /36/ Notably, if environmental analyses were deferred to satisfy the requirements of this decision, the agencies would run the serious risk of having projects enjoined on the ground that irretrievable commitments have been made without the requisite environmental analysis. /37/ This regulation, which remained unchanged from 1978 to 1985, is reproduced in full in Addendum A, pages 2a-3a, infra. /38/ Our brief in Marsh (87-1704 Gov't Br. 27-31) describes in detail the genesis of CEQ's decision to revise the regulation. The regulation itself is reproduced in Addendum A, pages 1a-2a, infra. /39/ "Reasonably foreseeable impacts" are expressly defined to include "impacts which have catastrophic consequences, even if their probability of occurrence is low, provided that the analysis of the impacts is supported by credible scientific evidence, is not based on pure conjecture, and is within the rule of reason" (40 C.F.R. 1502.22(b)). /40/ The court specifically cited Scientists' Inst. for Pub. Information, Inc. v. AEC, 481 F.2d 1079, 1092 (D.C. Cir. 1973); Carolina Envtl. Study Group v. United States, 510 F.2d 796, 799 (D.C. Cir. 1975); and Alaska v. Andrus, 580 F.2d 465, 473-474 (D.C. Cir. 1978), vacated on other grounds, 439 U.S. 922 (1978). /41/ The CEQ was well aware of the case law concerning the "worst case" requirement when it promulgated the new regulation. The CEQ specifically considered whether those cases mandated worst case analysis and concluded that they did not (51 Fed. Reg. 15,625 (1986)): Comment: Case law required worst case analysis prior to adoption of (the worse case regulation). Response: This assertion is incorrect. Case law prior to the adoption of 40 CFR 1502.22 did require agencies to make a "good faith effort * * * to describe the reasonably foreseeable environmental impact(s)" of the proposal and alternatives to the proposal in the face of incomplete or unavailable information, consistent with the "rule of reason" (citation omitted). The "worst case analysis" requirement was a technique adopted by CEQ as a means of achieving the goals enunciated in such case law. The "worst case" requirement itself, however, was clearly a "major innovation." * * * The U.S. Court of Appeals for the Fifth Circuit, interpreting the "worst case analysis" requirement for the first time in a litigation context, recognized that it was an innovation of CEQ. Sierra Club v. Sigler, 695 F.2d 957, 972 (5th Cir. 1983). CEQ has since observed difficulties with the technique of "worst case analysis" and is replacing it with a better approach to the problem of incomplete or unavailable information. A number of commenters requested CEQ to state that the new regulation is "intended to repudiate and overrule the Ninth Circuit decisions on worst case analysis" (51 Fed. Reg. 15,625 (1986)). The CEQ recognized that its new regulation did not "overrule" judicial interpretations of the worst case requirement; instead, it simply rendered them irrelevant. The agency accordingly responded that "(t)he Ninth Circuit opinions are based on the requirements of former Section 1502.22, or agency reflections thereof, and are inapplicable to this revision" (ibid.). /42/ Even the respondents in Marsh v. Oregon Natural Resources Council have conceded (Br. in Opp. 11) that the CEQ's judgment is entitled to "substantial deference." /43/ The Forest Service regulations are reproduced in relevant part in Addendum B, pages 4a-5a, infra. /44/ The special use permit in this case was issued to MRI on July 21, 1986, after the district court affirmed the Forest Service's decision and shortly after this case was argued before the court of appeals. We have lodged a copy of the two-part special use permit with the Clerk of the Court. /45/ Many of the provisions contained therein are contained in every special use permit for a ski area development. See Early Winters Study, App. I (Sample Special Use Permit), paras. 46, 49, 53, 54, 56. /46/ Congress has substantially revised the permitting process through enactment of the National Forest Ski Area Permit Act of 1986, 16 U.S.C. (Supp. IV) 497b. See note 2, supra. The Forest Service issued the special use permit in this case prior to enactment of that statute. In any event, the new enactment preserves the government's broad discretion to determine appropriate permit conditions by providing that a ski area permit "shall be subject to such reasonable terms and conditions as the Secretary (of Agriculture) deems appropriate" (16 U.S.C. (Supp. IV) 497b(b)(7)). /47/ The terms of this broad grant of authority also refute the court of appeals' conclusion (Pet. App. 16a) that 16 U.S.C. 497 is an independent source of mitigation requirements. Nothing in Section 497's language directs the Secretary to mitigate environmental damage absent a determination by the Secretary, by regulation or otherwise, that such mitigation is appropriate. /48/ See, e.g., 1963 Forest Service Manual Section 2140.1 (in planning special uses, the agency's objective is to manage and protect resources and to minimize adverse effects to projects); Section 2134 (special use permits must contain stipulations that ensure maintenance of productivity of land and resolution of conflicts with other planned or prospective uses). /49/ The regulations were promulgated to implement provisions of the Federal Land Policy and Management Act of 1976 (FLPMA), 43 U.S.C. 1701 et seq., dealing with "rights-of-way" on federal lands. See 45 Fed. Reg. 38,324 (1980). "Procedures for authorizing other kinds of special uses are not significantly changed" (ibid.). Notably, the FLPMA provisions specifically exclude from their coverage rights-of-way "constructed and maintained in connection with commercial recreation facilities on lands in the National Forest System" (43 U.S.C. 1761(a)(6)). The Forest Service is in the process of promulgating regulations, pursuant to the National Forest Ski Area Permit Act, specifically addressing ski area special use permits. See 16 U.S.C. (Supp. IV) 497b(c). /50/ Furthermore, the Forest Service has never interpreted these regulations as allowing it to require, as a condition contained in a special use permit, that a ski area developer mitigate effects on third-party lands. Thus, it was especially inappropriate for the court of appeals to construe these regulations as requiring the development of a "complete mitigation plan" that would address both on-site and off-site environmental impacts. /51/ On remand, the agency would be obligated to prepare a supplemental statement providing further elaboration on alternatives to the proposal and the proposal's impacts on air quality in the Pasayten Wilderness. See note 20, supra. APPENDIX