These petitions for review under 16 U.S.C. § 825(b) of orders of the Federal Power Commission authorizing construction of an electrical transmission line by the Power Authority of the State of New York and declining to award attorneys’ fees and other litigation expenses to various intervenors provide the fourth occasion for this court to review aspects of PASNY’s efforts to construct a 35 mile power line through the scenic Durham Valley in Greene County.1 The Commission issued its opinion and order on January 29, 1976, and on April 27, 1976 it denied a motion to reopen the record.
The Greene County Planning Board and the Town of Greenville (hereinafter “Greene County”) assert that the Commission violated its duties under the National Environmental Policy Act of 1969, 42 U.S.C. §§ 4321 et seq., and under the Federal Power Act, 16 U.S.C. §§ 791a et seq., by improperly limiting its analysis of benefits and adverse impacts rather than considering related, pending projects and broader systematic concerns and alternatives. Moreover, petitioners claim the Commission should have reopened the record to consider newly-available data on electricity consumption and other evidence tending to rebut its conclusion that the power line is necessary. They also make various complaints about the adequacy of the Commission’s environmental impact statement and the fairness of the hearing conducted by the administrative law judge. We conclude that the Commission has fulfilled its obligations under NEPA and the FPA, and that none of petitioners’ other claims warrant reversal.
The Town of Durham and the Association for the Preservation of Durham Valley, intervenors before the Commission who were successful in urging the selection of an alternative route for the power line, join with Greene County in asking us to reverse the Commission’s refusal to pay for their litigation expenses. Since recent rulings by the Comptroller General indicate that the FPC has authority to grant these reimbursements in appropriate circumstances, we remand to the Commission for further consideration of this issue.
I.
The history of this case dates back to August 1968 when the PASNY applied for approval from the FPC for construction of an 1100-megawatt pumped storage facility near Gilboa, New York. Under 16 U.S.C. § 797(e) the FPC has licensing jurisdiction over such a hydroelectric project and over any transmission lines that are designed for the primary purpose of serving the project. The plan for the Gilboa project was approved by the Commission in June 1969, and it envisaged three 345 kilovolt transmission lines, specifications for each of which would be subject to final review by the Commission. One line was to run southwest to Dehli, one northeast to New Scotland (near Albany), and one southeast for 35 miles to Leeds. Plans for these lines were soon submitted, and the Dehli and New Scotland lines were promptly approved without arousing significant opposition. Environmental controversy arose over the proposed Leeds line, however, and various opponents ultimately received permission from the Commission to intervene. After some reworking of the Leeds proposal by the PAS-NY, a hearing before Administrative Law Judge William C. Levy commenced on November 9, 1971.
*1231The hearing continued until interrupted by order of this court on January 17, 1972. In Greene County Planning Board v. FPC (Greene County I), 455 F.2d 412 (2d Cir.), cert. denied, 409 U.S. 849, 93 S.Ct. 56, 34 L.Ed.2d 90 (1972), we ruled that the FPC was violating NEPA by conducting hearings in reliance on the environmental report submitted by the PASNY, instead of first having prepared its own environmental impact statement. Id. at 422. The FPC staff was ordered to prepare its own impact statement to serve as a foundation for cross-examination of PASNY and FPC witnesses at the hearing. In Greene County I we also cautioned the Commission not to ignore broad but potentially relevant considerations such as future power demand and supply, alternative sources of power, and impending plans for further power facility construction.
After its petition for certiorari had been denied, the FPC set about the task of complying with this court’s mandate by drafting an impact statement, soliciting comments, and preparing a final impact statement. The hearing then recommenced2 and ran for two and a half months before the record was closed on October 27, 1973. Considerable expert engineering testimony on the need for the transmission line and testimony on its environmental impact was adduced from the PASNY employees charged with the planning and evaluating of the line and also from the employees of the FPC who had prepared the environmental impact statement. The Durham intervenors put on their own environmental experts to testify against the PASNY’s preference for a route running through the Durham Valley, which is an especially scenic part of Greene County. The Greene County intervenors sought to call as their own expert witness an environmental engineer employed with the Office of Environmental Planning of the New York State Public Service Commission, but Judge Levy ruled that the state was not required to furnish such expert testimony. On July 1, 1974, Judge Levy issued his opinion authorizing construction of a Gilboa-Leeds line and selecting as environmentally least harmful a route that skirted the Durham Valley, twenty-nine months later the Commission affirmed.
The Commission’s finding of need for the transmission line rested on substantial evidence that the line is necessary if the PAS-NY is to make optimal use of the Gilboa power storage facility. Engineering opinion was unanimous that the Gilboa-Leeds line would significantly improve the “reliability and stability” of power transmission from the Gilboa project, as well as increasing the “transfer capability” of the overall PASNY network. Thus, the line would ensure access to readily available and inexpensive Gilboa power at times of peak consumption in New York City and other parts of the state, and it would also increase the PASNY’s capacity to meet localized peak demands by transferring power as needed to and from various points within eastern New York.
The Commission also decided that the 345 kv transmission line should be constructed with the capability of being expanded to two 345 kv lines or a 765 kv line if the need for the additional transmitting capacity were to arise in the future. The second 345 kv circuit would be most useful if a second hydroelectric storage project presently under PASNY and FPC consideration were to be constructed in the vicinity of Gilboa; upgrading the line to 765 kv would be called for if the PASNY decided to go forward with its plans to upgrade its overall network of lines with which the GilboaLeeds line connects; and the Commission concluded that convertibility of the 345 kv line would result in substantia] environmental and construction cost savings if either of these likely contingencies were to develop.
The Commission rejected Greene County’s motion that it reopen the record in order to consider recent data indicating *1232that electricity consumption in New York City and the rest of the state has significantly and unexpectedly declined, and also that since its construction in 1973 the Gil-boa facility has been able to function without mishap and at full capacity by using just the Gilboa-New Scotland and Gilboa-Dehli transmission lines. The Commission said that this new information would not require any modification of its order for the construction of the Gilboa-Leeds line.
II.
The purposes of NEPA are frustrated when consideration of alternatives and collateral effects is unreasonably constricted. This can result if proposed agency actions are evaluated in artificial isolation from one another. Accordingly, an agency is required to consider the full implications of each decision in light of other potential developments in the area, and to prepare a comprehensive impact statement if several projects are significantly interdependent. Kleppe v. Sierra Club, 427 U.S. 390, 408, 96 S.Ct. 2718, 2730, 49 L.Ed.2d 576, 590 (1976); Chelsea Neighborhood Ass’n v. United States Postal Service, 516 F.2d 378, 388 (2d Cir. 1975); Natural Resources Defense Counsel v. Calloway, 524 F.2d 79, 87-90 (2d Cir. 1975). A balance must sometimes be struck between the importance of going forward with a project presently under consideration and the danger of improperly “piggybacking” several related projects by justifying each of them on the assumption that the others are to be constructed, only to discover later that the overall combination of the projects may do more harm than good.
With these principles in mind, we concur in the FPC’s conclusion that the Gilboa-Leeds transmission line is an appropriate unit for an impact statement. On the basis of substantial evidence, the Commission found that the line is necessary in order for the state to make optimal use of the existing Gilboa storage facility. Since the line was justified on this ground alone, there was no need for the impact statement to encompass other present and future PASNY proposals for which the line would have additional utility. Of course, under NEPA as well as under the long-range planning requirements of the Federal Power Act, 16 U.S.C. § 803(a), the Commission still had an obligation to take these related contingencies into account — as it did, for example, in providing for the possibility of a future doubling or upgrading of the initial 345 kv line — but it was not compelled to postpone for years its decision on the Gil-boa-Leeds line while waiting for all these related plans to become fixed.
Petitioners also criticize the FPC for failing to consider the special environmental impacts associated with 765 kv transmission. We agree with the Commission, however, that detailed analysis of this ancillary subject would not have been productive. In ordering that the 345 kv line be designed so as to be upgradable to 765 kv if necessary, the Commission did not pass on the ultimate merits of 765 kv circuitry; it simply took into account the reasonable possibility that such upgrading may be desirable at some future date. It appears that inclusion of this capability represents a relatively minor modification of the primary 345 kv structure, and that it in no sense compels future upgrading. Hence, provision for upgrading would seem to be appropriate regardless of what might be said at some future time about the adverse environmental effects of 745 kv transmission. Under these circumstances there was no necessity for extensive environmental analysis of 745 kv transmission in the present licensing proceedings.
Another contention of petitioners is that the FPC’s consideration of alternative routes was inadequate. Although the impact statement discusses five routes from Gilboa to Leeds as well as the possibility of relying on existing rights-of-way for more circuitous routes to the north or the south, petitioners suggest that alternatives not involving Gilboa and Leeds termini should also have been considered. The record reveals, however, that a third 345 kv line is necessary for maximum reliability of transmission from Gilboa. It also seems clear *1233that, given the existing PASNY network, having Leeds as the other terminus of this third line from Gilboa is the only way to ensure reliable power flow from Gilboa to both upstate New York or New York City. Since the need for an additional circuit from Gilboa to Leeds was thus established, we are satisfied that consideration of “systems alternatives” involving other termini was unnecessary.
Nor did the Commission abuse its discretion in refusing to reopen the record to consider new evidence. While an agency does have an obligation to make corrections when it has been relying on erroneous factual assumptions, especially where broad public interests are at stake, see Hudson River Fishermen’s Ass’n v. FPC, 498 F.2d 827, 833 (2d Cir. 1974), an agency’s refusal to reopen the record cannot be deemed arbitrary and capricious unless the new evidence offered, if true, would clearly mandate a change in result, see ICC v. Jersey, 322 U.S. 503, 514-15, 64 S.Ct. 1129, 88 L.Ed. 1420 (1944). Although the decline in New York power consumption levels and the successful operation of the Gilboa facility without the Gilboa-Leeds line do tend to undercut the Commission’s conclusion that the additional line is necessary for optimal reliability of power transmission from Gilboa, the undercutting is at best only partial. Consequently, we cannot quarrel with the reasonableness of the Commission’s conclusion that neither of these new facts would affect its determination regarding the need for a Gilboa-Leeds line.
Petitioners assert that the record was also incomplete due to the improper exclusion of evidence by Judge Levy. They object specifically to two rulings: (1) the refusal to allow them to use a state employee as their own expert witness, and (2) the refusal to order the FPC to produce a potentially relevant staff report.
With respect to the first ruling, we do not agree with respondent’s assertion that employees of applicants can never be subpoenaed to furnish expert testimony before the FPC. The Administrative Procedure Act, 5 U.S.C. § 555(d), provides that agency subpoenas shall issue “on a statement or showing of general relevance and reasonable scope of the evidence sought.” The agency must determine what constitutes “reasonable scope” in each case. See, e. g., Independent Directory Corp. v. FTC, 188 F.2d 468, 470-71 (2d Cir. 1951). Although Virginia Petroleum Jobbers Ass’n v. FPC, 110 U.S.App.D.C. 339, 293 F.2d 527, 529 cert. denied, 368 U.S. 940, 82 S.Ct. 377, 7 L.Ed.2d 339 (1961), indicates that opponents of an application are not routinely entitled to free run of the applicant’s experts, this does not mean that subpoenas of experts are never appropriate where, for example, the parties seeking the subpoena are unable to afford their own experts, the expert testimony sought would be highly relevant, and the employer-applicant is itself a government entity with a corresponding obligation to serve the broad public interest. Nonetheless, since substantial environmental evidence was already in the record and since the witness, Frank Brugraff, was expert only in the environmental effects of transmission lines, there is little reason to believe that his expert testimony would have affected the Commission’s ultimate finding of need for the line. In light of this consideration, we cannot say that curtailment of Burgraff’s examination was an abuse of discretion.
The document at issue in the second ruling was a 1969 internal agency report prepared by the FPC staff which concluded that the Gilboa-Leeds line would function for the primary purpose of serving the Gilboa hydroelectric facility and would therefore be subject to FPC jurisdiction under 16 U.S.C. § 797(e). Certainly, the standards for discovery in an administrative proceeding should not be more restrictive than the standards for disclosure under the Freedom of Information Act, 5 U.S.C. § 552. See generally Note, The Freedom of Information Act and the Exemption for Intra-Agency Memoranda, 86 Harv.L.Rev. 1047 (1973). Subject to such considerations as confidentiality and the need for unencumbered intra-agency circulation of preliminary views, see International Paper Co. *1234v. FPC, 438 F.2d 1349, 1358-59 (2d Cir.), cert. denied, 404 U.S. 827, 92 S.Ct. 61, 30 L.Ed.2d 56 (1971); Ackerley v. Ley, 137 U.S.App.D.C. 133, 420 F.2d 1336, 1341 (1969), approved staff reports that are relevant should generally be made available to parties in an agency proceeding. See, e. g., GSA v. Benson, 415 F.2d 878, 880-81 (9th Cir. 1969). Nevertheless, any failure of discovery here does not warrant reversal since the “primary line” report would have been merely cumulative of the substantial evidence already in the record on this function of the Gilboa-Leeds line.
Petitioners also allege that the environmental impact statement is not based on sufficient independent staff analysis, see C.F.R. § 281(b), fails to use an interdisciplinary approach, and is too abstract and too argumentative. We disagree. At the hearing the FPC staff experts testified that, as required by NEPA, see Greene County I, 455 F.2d at 420, they had conducted their own evaluation of the need for, and impact of, the transmission line; their reliance on PASNY computer studies and on power-flow data routinely recorded by the PASNY and other electric utilities was not an unreasonable abrogation of their analytical responsibilities. As for the other criticisms, we have read the impact statement and find them to be unpersuasive.
III.
With respect to the intervenors’ attorneys’ fees and witness expenses the Commission denied all requests for reimbursement, holding that it lacked the authority to make such payments and that none of the intervenors deserved such compensation in any event since they had only been “protecting their own interests.” When the same matter was before us in Greene County I, we had declined to order the FPC to reimburse intervenors in the absence of express Congressional authorization. 455 F.2d at 426. ■ ■
While this appeal has been pending, however, the Office of the Comptroller General has announced that in its opinion the FPC does have authority to pay for intervenors’ expenses. In Matter of Costs of Intervention — Nuclear Regulatory Commission, Decision B-92288 (February 19, 1976), the Comptroller General ruled that the NRC has implied authority to reimburse impecunious intervenors. A letter of May 10,1976 from the Comptroller General to the Oversight and Investigations Subcommittee of the House Committee on Interstate and Foreign Commerce indicates that this decision is equally applicable to the FPC and eight other agencies: “appropriated funds of each agency may be used to finance the costs of participants in agency hearings whenever the agency finds that (1) it cannot make the required determination unless it extends financial assistance to certain interested parties who require it, and whose representation is necessary to dispose of the matter before it; and (2) the party is indigent or otherwise unable to finance its participation.” 3 .
Since the Comptroller General is Congress’s agent for the purpose of determining the legality of administrative expenditures, see 31 U.S.C. § 65(d), his decision “upon any question involving a payment to be made by [an agency] . shall govern the General Accounting Office in passing upon the account containing such disbursement.” 31 U.S.C. § 74. The Comptroller General’s decision is authoritative and cannot be reversed by a court unless clearly contrary to law. See Brunswick v. Elliott, 70 App.D.C. 45, 103 F.2d 746, 749 (1939).4
*1235Although express statutory authorization is required before either a court or a regulatory commission can order one litigant to pay a prevailing litigant’s expenses on the ground that the prevailing litigant represents the public interest, Alyeska Pipeline Service Co. v. Wilderness Society, 421 U.S. 240, 95 S.Ct. 1612, 44 L.Ed.2d 141 (1975); Turner v. FCC, 169 U.S.App.D.C. 113, 514 F.2d 1354 (1975), the Comptroller General has concluded that fee reimbursement is distinguishable from fee shifting because it involves no exercise of compulsion against a private party.
Since public hearings are integral to the functioning of an agency such as the FPC, authorization for reimbursement of indigent intervenors who make important contributions in these hearings can reasonably be found in the agency’s general statutory mandate. See 16 U.S.C. § 793 (“The commission may make such expenditures as are necessary to execute its functions.”). On this basis the Comptroller General’s decision is not clearly incorrect and as a consequence the FPC now appears to have authorization to pay intervenors’ expenses.5
Still, the Commission has implied that even if it had the authority it would not grant fees and expenses to the petitioners because they were only “protecting their own interests,” and it is argued that we should affirm on this ground. However, we have some doubts about the fairness of withholding funds from these particular intervenors. All intervenors in agency proceedings are engaged in protecting their perceived self-interests; otherwise they would not bother to intervene. Although the intervenors were acting in their own interests, they were at the same time serving the broader public interest in the preservation of unspoiled scenic countryside. They seem to have played an essential role in the proceedings: it was their evidence and advocacy that appears to have been responsible for persuading the Commission to reject the preference of its own staff and the PASNY for the slightly shorter route running through the Durham Valley.6 Thus, the Commission was substantially aided in making its determination by the action of the intervenors. Where environmental issues are involved, a salutary public interest is served if the parties affected have the opportunity to express their views. Otherwise, the Commission could be limited to the information made available to it by the power companies and business interests directly involved. Moreover, it seems quite possible that the Durham and Greene County petitioners could qualify as “indigent” in that their litigation obligations may be unreasonably large in comparison to their financial resources.
Under these circumstances, where there is a good chance that the intervenors may meet the standards approved by the Comptroller General, we believe the equitable course is to remand to the Commission for reconsideration of its holding in light of the Comptroller General’s recent decisions.
We leave it to the Commission to determine whether compensation is appropriate and, if so, what further proceedings are appropriate here in order to provide fair consideration of the petitioners’ reimbursement request.7
All petitions for review are denied except that we remand to the Commission for fur*1236ther consideration of the petitioners’ requests for reasonable reimbursement of their litigation expenses.
. Greene County Planning Board v. FPC, 455 F.2d 412 (2d Cir.), cert. denied, 409 U.S. 849, 93 S.Ct. 56, 34 L.Ed.2d 90 (1972); Greene County Planning Board v. FPC, 490 F.2d 256 (2d Cir. 1973); Greene County Planning Board v. FPC, 528 F.2d 38 (2d Cir. 1975).
. The intervenors again sought a stay of the hearing from this court, this time on the basis of inadequacies in the impact statement; but these challenges were rejected as premature in Greene County Planning Commission v. FPC (Greene County II), 490 F.2d 256 (2d Cir. 1973).
. It appears from the record that neither of the Comptroller General’s rulings were considered by the Commission when it reached its decision in the instant case. The February 19 ruling on the NRC was issued just one week before Durham’s petition for rehearing was filed, and no reference is made to the NRC ruling in either the rehearing petition or the Commission’s denial of that petition. The May 10 letter, which dealt with the FPC specifically, postdates all of the Commission’s.decisions on reimbursement in this case.
. Miguel v. McCarl, 291 U.S. 442, 54 S.Ct. 465, 78 L.Ed. 901 (1934), and McCarl v. Cox, 56 App.D.C. 27, 8 F.2d 669, 671 (1925), cited by *1235Judge Van Graafeiland in his dissent, were cases where the Comptroller General’s rulings were clearly contrary to law.
. Reasonable reimbursement should include reimbursement for out-of-pocket expenses incurred by the intervenors, reimbursement for experts’ fees and expenses, payment of reasonable attorneys’ fees to intervenors’ counsel, and reimbursement for out-of-pocket expenses and disbursements incurred by counsel.
. The intervenors also may deserve some credit for the Commission’s decision to use single rather than double sets of towers and a narrower right-of-way.
. We recognize that the task of developing detailed standards for awards to intervenors may best be accomplished through rulemaking or through legislation, but this does not mean that the Durham petitioners are not entitled at least to a reasoned explanation for the withholding of reimbursement in their case.