198 F.3d 862 (D.C. Cir. 1999)
City of Alexandria, Virginia, et al.,Appelleesv.Rodney E. Slater, Secretary, U.S. Department of Transportation, et al.,Appellants
No. 99-5220
United States Court of AppealsFOR THE DISTRICT OF COLUMBIA CIRCUIT
Argued October 26, 1999Decided December 17, 1999

Appeal from the United States District Court for the District of Columbia(98cv00251)
Daria J. Zane, Assistant United States Attorney, argued  the cause for appellants.  With her on the briefs were Wilma  A. Lewis, United States Attorney, R. Craig Lawrence, Assistant United States Attorney, Nancy E. McFadden, General  Counsel, United States Department of Transportation, and  Paul M. Geier, Assistant General Counsel.
Barry M. Hartman and Lance W. High were on the brief  for amicus curiae Greater Washington Board of Trade.
Richard L. Walton, Jr., Senior Assistant Attorney General,  State of Virginia, was on the brief for amicus curiae the  Commonwealth of Virginia, Virginia Department of Transportation.
Kathleen A. Morse and Carolyn Moses Frank, Assistant  Attorneys General, State of Maryland, were on the brief for  amicus curiae Maryland State Highway Administration.
S. William Livingston, Jr., argued the cause for appellees. With him on the brief were Mitchell F. Dolin and Thomas L.  Cubbage, III.  John N. Hanson entered an appearance.
Hope M. Babcock, Thomas R. Lotterman, Paul W.  Edmondson, and Elizabeth S. Merritt were on the joint brief  for amicus curiae the National Trust for Historic Preservation in the United States, Preservation Alliance of Virginia,  and Sierra Club.
Before:  Silberman, Williams, and Randolph, Circuit  Judges.
Opinion for the Court filed by Circuit Judge Silberman.
Silberman, Circuit Judge:


1
Appellees challenged the Federal Highway Administration's approval of plans to replace the  Woodrow Wilson Memorial Bridge.  The district court held  that the Administration violated the National Environmental  Policy Act and the National Historic Preservation Act.  We  reverse.

I.

2
The Woodrow Wilson Memorial Bridge is a microcosm of  the Washington, D.C. metropolitan area's traffic congestion  problems.  Built in 1961, the six-lane structure carries the  Capital Beltway over the Potomac River, connecting the City  of Alexandria, Virginia, to Prince George's County, Maryland; originally intended to serve as a Washington bypass for  interstate travelers, it became increasingly used by commuters as the region's population grew.  As a result, traffic  volume on the Bridge has increased to over 160,000 vehicles  per day, more than twice the capacity the structure was  designed to accommodate;  congestion is particularly acute  during peak hours, where the configuration of an eight-lane  Beltway feeding into a six-lane bridge--in addition to steadily  increasing local traffic in the surrounding communities--has  produced one of the worst rush-hour "bottlenecks" in the  region.  These congestion problems have created harmful  collateral consequences:  the heavy volume on the Bridge has  contributed to an accident rate nearly double that of similar  facilities in the region, and has expedited the deterioration of  the Bridge's structure to the point where the Bridge is  projected to be structurally unsound by 2004.


3
Efforts to replace the Bridge began over ten years ago,  when the Federal Highway Administration, in cooperation  with its coordinate agencies in Maryland, Virginia, and the  District of Columbia, began examining alternative approaches  to solving the Bridge's capacity and structural problems. The Administration began to study the potential effects of  rebuilding the Bridge on the surrounding communities early  in the project's development, commissioning surveys of historic and archaeological resources in areas likely to be affected  by the projects.  The Commission also started the process,  mandated by the National Environmental Policy Act (NEPA),  42 U.S.C. § 4321 et seq. (1994), of considering the environmental impacts of alternative project designs.  In 1991 the  Administration issued a draft Environmental Impact Statement (EIS) for public comment;  this statement suggested  and compared five proposals for replacing the Bridge.  Each  of the alternatives in the draft proposed expanding the river  crossing from six to twelve lanes, and included a similar  expansion of the five-mile Beltway corridor approaching the  river crossing from the east and west.1


4
Reaction to the draft was less than enthusiastic;  the Administration was criticized for assessing inadequately the  environmental and cultural impacts of its proposal, and for  failing to coordinate its work with that of interested governmental agencies and community groups.  By its own admission concerned that "a region-wide consensus about the new  bridge had not been reached," the Administration went back  to the drawing board.  In response the Administration organized a "Coordination Committee" composed of elected and  administrative officials from the region to enhance community  and intergovernmental cooperation.  The Committee revisited  the entire process of developing alternative Bridge designs,  ultimately soliciting and considering over 350 proposals from  interested individuals and organizations, and increased the  Administration's public outreach efforts in affected communities.  In the meantime, pursuant to its obligations under  section 106 of the National Historic Preservation Act, 16  U.S.C. § 470f (1985 & Supp.), and section 4(f) of the Department of Transportation Act, 49 U.S.C. § 303 (1997), the  Administration continued to assess the project's potential impacts on historic, archaeological, and cultural resources in  the area.


5
In 1997, the Administration issued its Final Environmental  Impact Statement (the "Final EIS").  The Final EIS gave  detailed consideration to eight alternative proposals (seven  "build" alternatives and a baseline "no build" alternative),  comparing them on a range of criteria including vehicle  capacity, cost, and extent of environmental impacts.  As was  the case with the draft each of the "build" alternatives  scrutinized in the Final EIS had twelve lanes;  each alternative also had a lane configuration that separated local and  express traffic, and contained a lane dedicated for High  Occupancy Vehicle usage.  The critical difference among the  proposed alternatives was the type of river crossing;  the  seven "build" alternatives included a range of tunnel and  bridge designs.  Although the Final EIS discussed narrower  eight and ten-lane options, it did not afford them full treatment as formal "alternatives" because the Administration  concluded, on the basis of traffic projections, that narrower river crossings would fall short of meeting the Bridge's long term traffic needs.  Among the eight options the Administration designated a "Preferred Alternative" that would replace  the Bridge with two parallel six-lane drawbridges (one drawbridge for eastbound and one for westbound traffic) clearing  the Potomac's navigational channel by seventy feet at their  highest points.  The Administration also included in the Final  EIS a sixty-page "Section 4(f) Evaluation" identifying and  offering plans to mitigate the effects of the Preferred Alternative and all other build alternatives on public parks, wildlife  refuges, and historic sites.


6
After a brief comment period the Administration approved  the Preferred Alternative in a Record of Decision and submitted, as is required by section 106 of the National Historic  Preservation Act, a Memorandum of Agreement evidencing  the Administration's cooperation with state historic preservation officers in identifying historic sites that might be impacted.  The Memorandum identified and offered mitigation plans  for several historic sites, but it also noted that the Administration had not yet identified properties to be used for  "construction staging, dredge disposal, wetland mitigation, or  other ancillary activities" during the period of the Bridge's  construction.


7
The City of Alexandria filed an action in the district court  challenging the Administration's approval of the project, and  the district court permitted three Alexandria-based organizations that opposed the Administration's proposed alternative  (collectively the "Alexandria Coalition" or "appellees") to  intervene as plaintiffs.  The City alleged that the Administration had violated a host of regulatory provisions, including the  National Environmental Policy Act, section 106 of the National Historic Preservation Act, and section 4(f) of the Department of Transportation Act.2  After both sides had filed for  summary judgment the City of Alexandria settled its claim with the Administration, leaving the Alexandria Coalition as  the only remaining plaintiffs.


8
The district court ruled in favor of the Alexandria Coalition. See City of Alexandria v. Slater, 46 F. Supp. 2d 35 (D.D.C.  1999).  The court concluded that the Administration had  violated NEPA by not affording detailed consideration to a  ten-lane river crossing as a "reasonable alternative" in the  Final EIS, and that the Final EIS' treatment of the temporary environmental impact of the construction phase of the  project was too cursory to satisfy NEPA.  Relying upon our  recent decision in Corridor H Alternatives, Inc. v. Slater, 166  F.3d 368 (D.C. Cir. 1999), the district court also determined  that the Administration had violated section 106's requirement that an agency "take into account" the effects of a  proposed project on protected historic properties by postponing the identification of the sites that were to be used for  construction-related "ancillary activities."  Because an agency  must complete the section 106 identification process before it  can satisfy section 4(f)'s requirement that an agency use "all  possible planning to minimize harm" to historic sites, the  court concluded that the Administration had necessarily failed  to comply with section 4(f) as well.  The district court remanded the project to the Administration;  the Administration appealed, as it is entitled to do.  See Occidental Petroleum Corp. v. SEC, 873 F.2d 325, 330 (1989) (when district  court remand obliges agency to take further actions under an  arguably incorrect legal standard an immediate appeal is  appropriate).

II.
A.

9
The National Environmental Policy Act's mandate "is essentially procedural," Vermont Yankee Nuclear Power Corp.  v. Natural Resources Defense Council, Inc., 435 U.S. 519, 558  (U.S. 1978);  the statute requires that agencies assess the  environmental consequences of federal projects by following  certain procedures during the decision-making process.  See  Citizens Against Burlington, Inc. v. Busey, 938 F.2d 190, 193-94 (D.C. Cir. 1991).  Before approving a project, an  agency must prepare a "detailed statement ... [on] the  environmental impact of the proposed action, any adverse  environmental effects which cannot be avoided should the  proposal be implemented, [and] alternatives to the proposed  action."  42 U.S.C. § 4332(2)(C)(i)-(iii).  These general prescriptions are given sharper focus in the Council on Environmental Quality's regulations,3 which require agencies to prepare environmental impact statements;  at the "heart of the  environmental impact statement" is the requirement that an  agency "rigorously explore and objectively evaluate" the projected environmental impacts of all "reasonable alternatives"  for completing the proposed action.  40 C.F.R. § 1502.14.


10
Appellees argue, and the district court agreed, that the  Administration violated NEPA by failing to deem a ten-lane  bridge a "reasonable alternative" in the Final EIS.  They  observe that a ten-lane bridge would constitute a significant  improvement over the existing six-lane structure, and would  reduce congestion with considerably less impact on environmental and cultural resources than each of the twelve-lane  alternatives compared by the Administration.  In addition to  having a narrower river crossing, appellees point out that a  ten-lane alternative would have a smaller construction "footprint" along the entire five-mile stretch of the Beltway that  will be under construction, and would require smaller interchanges at each of the four points of access to the Beltway in  the project corridor.  The Administration responds that the  ten-lane alternative favored by appellees was excluded after  studies determined that it did not meet the traffic capacity  needs of the project.  The Administration also argues that the difference between the environmental impacts of the two  projects is less than appellees suggest;  a ten-lane bridge  would impact only 1.6 fewer acres of parkland and 12.9 fewer  acres of natural resources over the entire length of the  project corridor, and would have an identical impact on  cultural resources.


11
How are the merits of appellees' argument to be assessed? After all, the phrase "reasonable alternative," standing alone,  offers no guidance to a reviewing court.  Something can only  be an "alternative" by reference to something else;  "the term  'alternatives' is not self-defining."  Vermont Yankee, 435 U.S.  at 551.  The Council on Environmental Quality, for its part,  does little to clarify the baseline against which a "reasonable  alternative" is to be measured;  its regulations at times appear to contrast the "alternatives" to the "proposal," suggesting that the range of reasonable alternatives are to be  selected by reference to the project implemented.  See 40  C.F.R. § 1502.14.  But that approach would seem to bias the  process.  See, e.g., Calvert Cliffs' Coordinating Comm., Inc. v.  U.S. Atomic Energy Comm'n, 449 F.2d 1109, 1114 (D.C. Cir.  1971).  And even if we were to understand an "alternative" to  be defined by reference to the proposal actually selected, our  interpretive task would hardly be easier, as "the adjective  'reasonable' is no more self-defining than the noun that it  modifies." Citizens Against Burlington, 938 F.2d at 195.


12
We have resolved this difficulty by evaluating an agency's  choice of "reasonable alternatives" in light of the objectives of  the federal action;  as then-Judge Thomas put it in Citizens  Against Burlington, "[t]he goals of an action delimit the  universe of the action's reasonable alternatives."  Id.  But  that approach of course requires that we first consider whether the agency has reasonably identified and defined its objectives.  The agency's choice of alternatives are, then, evaluated  in light of these stated objectives;  an alternative is properly  excluded from consideration in an environmental impact  statement only if it would be reasonable for the agency to  conclude that the alternative does not "bring about the ends  of the federal action."  Id.  We engage in both of these  inquiries--whether an agency's objectives are reasonable, and whether a particular alternative is reasonable in light of these  objectives--with considerable deference to the agency's expertise and policy-making role.  Id. at 196.


13
The district court's opinion suggests that the Administration improperly defined its objectives, criticizing the Administration for narrowing its choice of alternatives "based on a set  of criteria that focused primarily on transportation and safety  issues."  City of Alexandria, 46 F. Supp. 2d at 44.  This  description of the Administration's objectives is an accurate  one;  while the "Statement of Purpose and Need" in the Final  EIS references several objectives (including protecting the  environment), it focuses on the region's traffic needs.  But it  hardly follows that the Administration violated NEPA.  As  mentioned above, NEPA's injunction that agencies consider  the environmental impacts of "all reasonable alternatives"  does not substantively constrain an agency's choice of objectives;  to the contrary, it is those very objectives that provide  the point of reference for a determination whether an alternative is "reasonable" in the first place.  By suggesting that the  Administration violated NEPA because it did not sufficiently  prioritize environmental goals, the district court subtly--and  impermissibly--transformed a procedural statute into a substantive one.  See Baltimore Gas & Elec. Co. v. Natural  Resources Defense Council, Inc., 462 U.S. 87, 97 (1983)  ("Congress in enacting NEPA ... did not require agencies to  elevate environmental concerns over other appropriate considerations.")  The proper question to ask at the outset of a  NEPA inquiry is not whether the Administration focused on  environmental goals but rather--as we noted--whether its  stated objectives were reasonable.  It seems rather obvious  to us that it is not unreasonable in articulating its objectives  for an agency to "focus primarily on transportation and safety  issues" when replacing a massively congested and structurally  unsound bridge.  Cf. Corridor H, 166 F.3d at 374 (affirming  the Administration's rejection of highway alternatives that  did not meet the transportation and safety needs of the  region).


14
More in keeping with our precedent, the district court also  determined that a ten-lane alternative was reasonable--and therefore should have been given greater attention--in light  of these objectives.  The district court arrived at this conclusion by characterizing the Administration as "articulat[ing]  the problem as one of addressing the future transportation  needs of the region."  "Such a broad statement of purpose  and need," the district court explained, "hardly provides an  unequivocal basis for eliminating ten-lane alternatives from  consideration."  City of Alexandria, 46 F. Supp. 2d at 44.This might be so, had the Administration truly characterized  its objectives in such general terms.  But it did not.  As is  required by statute, see 23 U.S.C. § 109(b), the Administration instead focused specifically--in its Statement of Purpose  and Need and elsewhere--on the traffic needs that will exist  twenty years after the project's approval, and its analyses  based on 2020 traffic projections demonstrate that a ten-lane  bridge would be insufficient.  The Administration's studies  show that appellees' preferred design (a ten-lane configuration without an HOV lane) would be able to accommodate less  than half of the per-hour capacity of the Administration's  preferred alternative, causing peak-hour traffic queues of  significantly greater length and extended duration;  accident  rates would also be markedly higher on a ten-lane structure.


15
The district court ignored this data, instead focusing exclusively on an Administration study showing that a ten-lane  bridge would be able to accommodate up to 295,000 vehicles  per day, a number only slightly smaller than the projected  daily traffic flow on the Bridge in 2020.  City of Alexandria,  46 F. Supp. 2d at 44.  But that study apparently assumed an  even flow of traffic throughout the day (which, of course, is  unrealistic).  Whatever the total number of vehicles that will  cross in a 24-hour period, the relevant question is how long  during peak commuting hours it will take to cross the bridge. Appellees also do not seriously challenge the Administration's  findings, instead protesting that these studies establish little  more than the "truism ... that a ten-lane bridge would carry  somewhat less traffic than a twelve-lane bridge."  It is not  apparent to us why this proposition has less force in the case  because it is a "truism."


16
Appellees' more fundamental argument is that, regardless  of its shortcomings in satisfying future traffic needs, we must  hold a ten-lane bridge to be a reasonable alternative in light  of our statement in Natural Resources Defense Council, Inc.  v. Morton that an agency should not "disregard alternatives  merely because they do not offer a complete solution to the  problem."  458 F.2d 827, 836 (D.C. Cir. 1972).  Appellees  over read Morton.  In that case an environmental group  challenged the Secretary of the Interior's proposed sale of oil  and gas leases to submerged lands in the Gulf of Mexico;  the  Secretary sought to sell these properties as part of a cross agency effort, initiated by the President, to increase American energy supplies.  We held that the Secretary's environmental impact statement violated NEPA because it failed to  consider alternatives outside of the Department of the Interior's jurisdiction;  we also noted that the agency could not  exclude alternatives "supplying only part of the energy that  the lease sale would yield."  Id. at 836.  This broad articulation of "reasonable alternatives" was compelled by the national scope of the problem being addressed:  "When the proposed action is an integral part of a coordinated plan to deal  with a broad problem, the range of alternatives that must be  evaluated is broadened."  Id. at 835.


17
Morton thus stands for the same proposition as Citizens  Against Burlington:  namely, that a "reasonable alternative"  is defined by reference to a project's objectives.  Morton  explained that, within the context of a coordinated effort to  solve a problem of national scope, a solution that lies outside  of an agency's jurisdiction might be a "reasonable alternative";  so might an alternative within that agency's jurisdiction  that solves only a portion of the problem, given that other  agencies might be able to provide the remainder of the  solution.  Such a holistic definition of "reasonable alternatives" would, however, make little sense for a discrete project  within the jurisdiction of one federal agency, as we recognized  in Morton when we contrasted the Secretary's action with  that of building "a single canal or dam."4  Id.  Concerned with severe traffic conditions in the Capital Region, Congress  has authorized the Administration to replace the Woodrow  Wilson Memorial Bridge.  The Administration has sole responsibility for solving this problem;  were it to build a tenlane bridge, no one else would step in and alleviate the  congestion that would result.5  In this context, it is simply a  non sequitur to call a proposal that does not "offer a complete  solution to the problem" a "reasonable alternative."


18
One other point merits brief discussion.  In finding a tenlane alternative reasonable, the district court noted that the  Administration only conducted a Clean Air Act conformity  analysis for the use of ten lanes on the Bridge.  See City of  Alexandria, 46 F. Supp. 2d at 45.  If the Administration only  expects ten lanes to be open, the district court reasoned, how  can it fail to consider a ten-lane bridge as a reasonable  alternative under NEPA?  The answer is that the Clean Air  Act and NEPA inquiries have different time horizons;  while a  project must show conformity with the Clean Air Act at the  time it is approved, see 42 U.S.C. § 7506(c)(1) (1995), the  consideration of reasonable alternatives under NEPA requires, as mentioned above, an assessment of traffic needs in  2020.  Accordingly the Administration did not violate the National Environmental Policy Act by failing to include a tenlane bridge proposal as a "reasonable alternative" in its Final  Environmental Impact Statement.

B.

19
Once an agency identifies the "reasonable alternatives" to a  proposed action, NEPA and Council on Environmental Quality regulations also require an agency to identify the "adverse  environmental effects" of each alternative.  See 42 U.S.C.  § 4332(2)(C)(ii);  40 C.F.R. § 1502.16.  The district court  found fault with the Administration's treatment of the temporary "construction impacts" that would arise during the period that the Bridge was being built.  Again, we disagree.


20
The district court focused on the brevity of the "Construction Impacts" section of the Final EIS, which covers only four  pages and, according to the district court, "is of such a broad  and generic nature that it could apply to practically any  construction project undertaken by the [Administration]."City of Alexandria, 46 F. Supp. 2d at 45.  While the Administration's discussion might have been more thorough, we think  the district court's assessment of the Administration's treatment of these issues too harsh.  The Administration addresses a range of expected construction impacts, including the  construction's likely effect on local traffic, air quality, area  noise levels, water quality and wetlands, cultural resources,  and visual effects.  The level of detail of these assessments  varies;  it is worth noting, in light of the district court's focus  on the terseness of the Administration's analysis, that some of  the shorter analyses are the most eminently reasonable. Take, for instance, the Administration's discussion of traffic  impacts.  The Administration acknowledges that the construction project will affect traffic flow on several Alexandria  roadways, and may also cause potential delays in the delivery  of emergency services.  It also offers a range of mitigation  strategies:  six lanes of the Bridge will be kept open at all  times to minimize rush-hour congestion;  some access (even if  circuitously routed) will be maintained to all roads and areas; there will be no disruption of marine traffic on the Potomac;  the public will be notified of temporary road closings through  the news media, the posting of signs, and the creation of a  "project activities" hotline.  Perhaps appellees would prefer  the Administration to set forth in the Final EIS a comprehensive plan detailing precisely which streets will be closed, and  which alternative routes will be established, but that is not  mandated by NEPA.  See, e.g., Robertson v. Methow Valley  Citizens Council, 490 U.S. 332, 353 (1989) ("[I]t would be  inconsistent with NEPA[ ] ... to demand the presence of a  fully developed plan that will mitigate environmental harm  before an agency can act.").


21
We think the terseness of the Administration's discussion  of construction impacts is justified for other reasons as well. The Administration typically delays the identification of "construction staging" sites--locations used to store materials and  equipment during project construction--until the design  stage of the project.  As will be discussed infra, this practice  is permissible under the statute and is arguably required by  the Administration's governing regulations.  Since the Administration did not identify the location of these areas, it of  course could not identify the accompanying environmental  impacts with precision.  But this does not mean that the  Administration did not consider, on a more general level,  what those impacts would be;  the Final EIS identifies several  potential staging areas, and notes that each of these sites are  in "previously disturbed" areas with "minimal natural resources."  The Administration's brevity is particularly understandable given the numerous regulatory constraints that will  limit the extent of construction activities.  As the Administration notes, Maryland and Virginia require construction contractors to limit noise levels in "noise sensitive areas adjacent  to the project area" to eighty decibels--a noise level comparable to that currently produced by traffic on some stretches of  the highway.  Similar federal and state regulatory provisions  require the mitigation of any short-term construction impacts  on wetland and aquatic resources, constrain the emissions of  dust from construction-related activities and equipment, and  limit the Administration's selection of construction staging  areas.  The Final EIS' reference of these provisions is important, as it indicates the Administration's awareness of the  maximum impact that the construction may cause.


22
We also note that agencies are enjoined by the Council on  Economic Quality to develop environmental impact statements that are "no longer than absolutely necessary" and that  discuss impacts "in proportion to their significance."  40  C.F.R.  1502.2(b)-(c).  The Administration points out that  each of the seven "build" alternatives would have similar  construction impacts, thus making a detailed discussion of  each of their effects redundant.  More fundamentally, while  the disruption caused by the construction of a project as  significant as this one is by no means trivial, it is relatively  modest in both scope and duration when compared to the  environmental impact of the project as a whole.  To be sure,  there is a point at which an agency's analysis ventures from  the "tolerably terse to the intolerably mute," Greater Boston  Television Corp. v. FCC, 444 F.2d 841, 852 (D.C. Cir. 1970),  but we simply do not think that the Administration's analysis  of construction impacts reaches that point.

III.
A.

23
The district court concluded that the Administration also  failed to identify adequately the effect that its preferred  alternative will have on historic resources in the project area,  as is required under two distinct but overlapping statutes:section 106 of the National Historic Preservation Act and  section 4(f) of the Department of Transportation Act.  Section 106, like NEPA, is essentially a procedural statute;  it  requires that agencies "take into account the effect of [an]  undertaking on any district, site, building, structure, or object  that is included in or eligible for inclusion in the National  Register [of Historic Places]."  16 U.S.C. § 470f.  To comply  with section 106, an agency must consult with state historic  preservation officers to ensure that historic properties in the  project area are thoroughly identified and the effects that the  project will have on them fully assessed.  See 36 C.F.R. § 800.4-.5.6  The usual product of this consultation process is  a Memorandum of Agreement among the consulting parties  signifying agreement upon how the detrimental effects will be  "taken into account."  Even where disagreement precludes  the completion of a Memorandum of Agreement an agency  may implement a project after receiving and considering  comments from the Advisory Council on Historic Preservation.  See id. at 800.6(c).


24
On the other hand, section 4(f), unlike the other statutes at  issue in this case, imposes a substantive mandate on the  Administration:  It prohibits the agency from taking an action  that "uses" a historic resource unless there is "no prudent  and feasible alternative to using that land" and the agency  engages in "all possible planning" to "minimize harm" to the  sites.7  49 U.S.C. § 303(c);  see also Citizens to Preserve  Overton Park v. Volpe, 401 U.S. 402 (1971).  Department of  Transportation regulations require the Administration to  "make the section 4(f) approval" at the same time that it  approves its final EIS or issues its Record of Decision, 23  C.F.R. § 771.135(l);  the Administration ordinarily complies  with this requirement by publishing a separate "Section 4(f)  Evaluation" along with its final EIS, which identifies the  project's effects on historic properties in the project area and  the efforts the agency has taken to mitigate those effects.  In  order to comply with 4(f)'s substantive requirements, it is of  course necessary first to identify historic sites in the project  area;  accordingly, we have observed that compliance with  section 4(f) is predicated upon completion of the section 106  process.  See Corridor H Alternatives, Inc. v. Slater, 166  F.3d 368, 371 (1999).


25
The central dispute between the parties is not about whether, but about when, the Administration must complete its  identification of historic properties.  The Administration has  been "taking into account" the effect of the proposed project  on historic sites since the project's inception, conducting  several surveys which led to the identification of 23 National  Register-listed or National Register-eligible properties, and  36 underwater or terrestrial archaeological sites in the project area.  The Administration also identified and visited each  National Register-listed property in Alexandria for the purpose of determining, among other things, the "visual impacts"  that various alternative bridge proposals would have on each  site.  The result was publication of a Memorandum of Agreement and a Section 4(f) Evaluation with or prior to the  Administration's approval of the project;  these documents  identify seven historic sites that will be affected by the  project and another six that may be, and offers plans to  minimize and mitigate the project's impact on these properties.


26
The district court did not question the overall legitimacy or  thoroughness of these studies.8 (Indeed, appellees cannot  identify a single historic resource in the project area that the  Administration failed to "take into account."9)  Instead, the district court concluded that the Administration violated section 106 by deciding to postpone the identification of sites  where it would conduct certain construction-related activities,  including construction staging areas (the locations where  contractors will store materials and mobilize construction  activities), wetland mitigation areas, and dredge disposal  sites.  While the likely impact of these activities, which the  Administration describes as "ancillary," are minimal when  compared to those of the project as a whole, it is at least  conceivable that they could ultimately affect section 106 properties.  Acknowledging this possibility, but noting that it  usually defers the identification of such properties until the  "design stage" of a large highway project, the Administration  included promissory language in its Memorandum of Agreement binding it to fulfill its section 106 responsibilities when  selecting these sites.  The district court thought that these  prospective terms ran afoul of our recent decision in Corridor  H Alternatives, Inc. v. Slater, 166 F.3d 368 (D.C. Cir. 1999),  in which we held that the Administration could not postpone  the entire section 106 process until after it issued its Record  of Decision.


27
We think that district court misconstrued our holding in  Corridor H. In that case, the Administration postponed the  entire section 106 process for a major highway corridor;  its  Record of Decision instead adopted a "Programmatic Agreement" dividing the highway into fourteen segments, and promised that it would not begin construction of a particular  segment before completing the section 106 process for that  segment.  We held that this Agreement impermissibly abrogated the Administration's responsibility to assess the project's impact on historic properties during the planning stages  of the project.  See 166 F.3d at 373.  But that is not the case  here, since the Administration has identified historic properties along the entire project corridor and documented its  findings prior to approval in both a Memorandum of Agreement and a Section 4(f) Evaluation.  All that has been  deferred is the identification of sites that might be impacted  by a small number of "ancillary activities."  This is quite  distinguishable from the "Programmatic Agreement" we proscribed in Corridor H.


28
The Administration did not postpone the identification of  these properties "merely to avoid having to complete its 4(f)  and 106 analyses," as the district court said.  46 F. Supp. 2d  at 47.  As the Administration points out, the precise identification of these sites requires "substantial engineering work"  that is not conducted until the design stage of the project; indeed the Administration is required to conduct such "final  design activities" after it completes its Final EIS.  23 C.F.R.  § 771.113(a)(iii).  Furthermore, then-existing Council regulations explicitly encouraged flexible, staged planning in the  section 106 process.  See 36 C.F.R. § 800.3(b) (section 106  procedures "may be implemented ... in a flexible manner");36 C.F.R. § 800.3(c) (section 106 regulations should not be  interpreted to "prohibit phased compliance at different stages  in planning.").  Appellees respond that the Administration  could nonetheless "feasibly" identify these sites without doing  "final design" plans for the project.  But the standard of  "feasibility," while relevant to whether an agency may use 4(f)  properties, has no application in determining when the agency  must identify them.  We think that, particularly where the  sites postponed are merely ancillary to the project, section  106 and the identification prerequisites of section 4(f) do not  forbid the rational planning process adhered to by the Administration.

B.

29
We also think that the Administration satisfied section  4(f)'s substantive provisions.  Appellees barely bother to argue that the Administration did not comply with section  4(f)(1)'s requirement that it consider all "prudent and feasible  alternative[s]" to using protected properties.  The reason for  this gap in appellees' otherwise vigorous presentation is obvious enough.  For while the Administration is required to give  the protection of 4(f) property "paramount importance" in  determining whether an alternative is "prudent," Overton  Park, 401 U.S. at 412-13, we have squarely held that an  alternative cannot be a prudent one if it does not satisfy the  transportation needs of the project.  See Citizens Against  Burlington, 938 F.2d at 204.  In light of this limitation,  appellees can only win under section 4(f)(1) if they establish  one of two propositions:  They must show that a narrower  Bridge satisfies the transportation needs of the project, or  they must offer a "prudent" project alternative that does not  impact the 4(f) properties used by the Administration's preferred design.  The former question we have already resolved  in the Administration's favor, and appellees do not advance an  alternative highway route that has a less significant impact on  4(f) properties.


30
Appellees do argue with greater enthusiasm that the Administration violated section 4(f)(2)'s requirement that the  agency engage in "all possible planning" to minimize harm to  4(f) properties, but this argument is equally unpersuasive.To begin at the broadest level of generality, appellees do not  question the Administration's express findings that, among  the seven "prudent and feasible" alternatives compared in the  Final EIS, the preferred alternative"results in the least  overall impact to section 4(f) resources."  Cf. Druid Hills  Civic Ass'n, Inc.  v. FHWA, 772 F.2d. 700, 716 (11th Cir.  1985) (noting that "section 4(f)(2) requires a simple balancing  process which totals the harm caused by each alternate route  to section 4(f) areas and selects the option which does the  least harm").  At the site-specific level, the Administration  made several significant project modifications to avoid or  minimize impacts to section 4(f) properties, including altering an interchange design to avoid impacting a schoolground and  eliminating the construction of a temporary Beltway overpass  to minimize the risk of harm to Freedman's Cemetery. Where the Administration could identify no feasible and  prudent plan for avoiding impact to a 4(f) site, it offered plans  to mitigate that impact;  for instance, it proposed substantial  improvements to Jones Point Park, arguably the most significant 4(f) property impacted by the project.  Further recitation of the Administration's mitigation efforts is possible, but  unnecessary;  suffice it to say that, after a thorough review of  the record, we have little difficulty concluding that the Administration complied with its responsibilities under section  4(f) of the Department of Transportation Act.10


31
* * * *


32
During the course of our consideration of this case, appellees have attempted to bolster their position by pointing to  the opposition of prominent legislators to the project, and by  noting the hurdles to ultimate congressional approval that  still lie in the Administration's path.  These political impediments are irrelevant to us but they indicate where appellees  should concentrate their efforts.  We have been admonished  by the Supreme Court with respect to the very statute that is  at the heart of this case to avoid using its requirements as a  vehicle to impose our own judgment.  Vermont Yankee, 435  U.S. at 554.  Our obligation is not to further our beau ideal of  a bridge design, but merely to ensure that the procedures  mandated by these statutes have been complied with.  We  hold that the Administration has satisfied the requirements of NEPA, the National Historic Preservation Act, and the Department of Transportation Act, and reverse.


33
So ordered.



Notes:


1
 More specifically, the project would widen the Beltway to twelve  lanes between Telegraph Road in Alexandria and Route 210 in  Prince George's County.


2
 The City also alleged that the Administration violated the Clean  Air Act by failing to conduct a conformity analysis for the twelve lane preferred alternative.  The district court agreed, but the  Administration does not appeal this finding.


3
 The Council on Environmental Quality has no express regulatory authority under the National Environmental Policy Act;  instead,  the Council was empowered to promulgate binding regulations by  President Carter's Executive Order No. 11991, 42 Fed. Reg. 26,967  (1977).  Because the Administration does not challenge the Council's regulatory authority, we treat the Council's regulations as  binding on the agency.  But see Scott C. Whitney, The Role of the  President's Council on Environmental Quality in the 1990s and  Beyond, 6 J. Envtl. L. & Lit. 81 (1991).


4
 We doubt the continuing vitality of the rather expansive view of  NEPA we expressed in Morton, since subsequent Supreme Court cases have directly criticized us for overreading that statute's  mandate.  See Baltimore Gas & Elec. Co., 462 U.S. at 97;  Vermont  Yankee, 435 U.S. at 554;  Kleppe v. Sierra Club, 427 U.S. 390 (1976).Morton, after all, suggested that the Secretary should have deemed  as "reasonable alternatives" Congress' ability to reduce oil import  quotas and the Federal Power Commission's authority to change its  natural gas pricing policies.  458 F.2d at 835, 837.  To be sure,  Vermont Yankee cited with approval our statement in Morton  stressing the limits of an agency's obligations under NEPA, 435  U.S. at 551, but we wonder whether Morton's holding can be  squared with Vermont Yankee's injunction that "the 'detailed statement of alternatives' cannot be found wanting simply because the  agency failed to include every alternative device and thought conceivable by the mind of man."  Id.


5
 As the Administration determined, there are no apparent and  feasible independent rail transit options that could be combined to a  ten-lane bridge to satisfy transportation needs.


6
 The Council has recently promulgated regulations revising the  section 106 process.  64 Fed. Reg. 27,044 (1999).  Our citations are  to the regulations as they existed at the time the Administration  approved the project.


7
 In addition to historical sites, other properties--including parks,  recreational areas, and wildlife preserves--are protected by section  4(f).


8
 Appellees point to the Administration's decision to reduce the  size of the "Area of Potential Effects" in 1997, and suggest that the  Administration reduced this Area in an attempt to evade section  106's obligations.  The Administration offers a perfectly innocent  explanation, which we have no reason to question:  The Area of  Potential Effects was originally drawn with a range of alternatives  in mind, including taller bridge designs with far more extensive  "visual effects" in Alexandria.  It was then reduced to encompass  only those areas affected by the preferred alternative.  Notably,  appellees do not point to any properties outside of the new "reduced" Area of Potential Effects that will actually be affected by  the project.


9
 Amicus Sierra Club rather inventively argues that the Administration failed to treat as a section 106/4(f) property the Hunting  Terrace apartment complex in Alexandria, but it is not eligible for  inclusion in the National Register of Historic Places, and therefore  is not a protected property under either section 106 or section 4(f).See 23 C.F.R. § 771.135(e);  36 C.F.R. § 800.2(e).  Showing similar  ingenuity, appellees argue that the Administration violated sections  106 and 4(f) because "the boundaries of Freedman's Cemetery ...  have still not yet been determined."  They apparently believe that  since the site's precise location is unknown (and, it seems, unknowable), it is by definition impossible to know for certain the "effect"  that the construction will have on the site, thus placing the Administration in violation of sections 106 and 4(f).  To set forth the logic of  this argument is to refute it.  Cf. Hoonah Indian Ass'n v. Morrison, 170 F.3d 1223, 1231-32 (9th Cir.1999) (inability of Forest  Service to identify location of Indian march justified decision not to  designate it a section 106 property).


10
 Appellees correctly note that section 4(f)'s substantive requirements can only be complied with after section 4(f) properties have  been identified.  We remind the Administration that our holding  that it could defer the identification of section 4(f) properties that  might be impacted by construction staging and dredge disposal  activities in no way absolves it of its responsibility to conduct a 4(f)  analysis when selecting these sites during the design stage of the  project.


