dissenting:
I respectfully dissent and would grant the petition because the Commission has erected an unreasonably high barrier to good cause for late intervention, and without explanation or justification has departed from its own precedent of routinely granting late intervention where there is no risk of prejudice. In denying Petitioners’ motions for late intervention, the Federal Energy Regulatory Commission (“the Commission”) has arbitrarily imposed a good cause requirement far more stringent than indicated by analogous precedent and at odds with the liberal standard it has applied consistently in similar cases. Moreover, it should not go unnoticed that in denying leave to intexvene, the Commission has silenced any party wishing to advance Petitioners’ environmental concerns. It is a salient fact that there are no parties remaining besides the dam operators and the FERC, and the Commission’s ruling prevents anyone from challenging whether its decision to issue an Environmental Assessment (“EA”) rather than a more comprehensive Environmental Impact Statement (“EIS”) violates the National Environmental Policy Act. The Commission may be happy as a clam to have no party able to challenge its judgment, giving it in effect totally unconstrained discretion, but in such a case the real loser is the public which will not have environmental issues aix-ed as they might have been raised by an intervenor. The Commission does not explain why it has departed from its prior precedent, and I choose not to be complicit in its denial of late intervention, which impedes the public’s interest in considering the environmental issues in this case. This is not to say that the environmental considerations favor one side or the other on the merits, but only that the responsible Petitioners should not be shut out of the courthouse.
The record shows that Petitioners’ intervention would not offend any of the factors normally considered by the Commission in these cases, factors which together ask whether the late intervention would create prejudice. See 18 C.F.R. § 385.214(d)(1). The majority does not dispute that Petitioners satisfy all three prejudice factors. Petitioners’ involvement would not disrupt the px'oceedings in any way; no other party represents the Petitioners’ interests; and there would be no additional burden upon the existing parties.
In any common sense assessment, there is strong cause for the conduct of the Petitioners in seeking late intervention and little justification on the other side for denying it. Petitioners seek late intexvention because 1) facts discovered intensified the import of the issue to be challenged through intexvention; 2) the Commission issued an EA rather than a more detailed *1027EIS, thereby eliminating what would have been an automatic path for intervention; and 3) the Commission denied intervention to another interested federal agency, the National Marine Fisheries Service, which would have been in the position to advance environmental issues, such as those raised by Petitioners. There is little precedent available in our circuit concerning the meaning of “good cause” which might inform our assessment of the Commission’s interpretation of the good cause requirement for late intervention. However, the phrase “good cause” is used throughout our legal system, and often it means little more than that there is a good reason for the action proposed to be taken.1 Certainly, prior precedent does not favor a rule that to have good cause to intervene one must show that facts have developed permitting a new issue to be raised that could not have been identified before those facts surfaced.2 It should be sufficient if the new facts make the resolution of an issue more important and enhance the impact of a resolution on the parties and the public. Further, the precedent that exists suggests that the meaning of good cause varies depending on the degree of prejudice that would attend an action, so that when prejudice is greater, the cause to justify the action must be greater. The Commission’s own precedents apply this type of sliding scale test and, as shown below, have not insisted on a substantial showing of good cause when there was no prejudice.
The majority asserts, without citation to FERC case law, that under FERC regulations a late petitioner must both show good cause and prove that late intervention would not cause prejudice. Op. at 1021-22. The Commission, however, has interpreted its own regulations differently; it does not require independent showings of both good cause and lack of prejudice. Rather, FERC precedent shows that the agency regularly permits late intervention without requiring a showing of good cause, when intervention would not cause prejudice.
In my view, the Commission should have followed its precedent of Alaska Power & *1028Telephone Co., 98 F.E.R.C. ¶ 61092 (2002), in which it said that it “has generally-adopted a liberal approach to late intervention in hydroelectric proceedings, if doing so will not delay the proceeding or result in prejudice to other parties. In such cases, the Commission often has made no finding of whether the movant has demonstrated good cause for the late request.” Id. ¶ 61276.3 Alaska Power & Telephone establishes that in hydroelectric cases, the Commission in practice does not impose a good cause requirement on late intervention when there is no risk of prejudice. This case is also a hydroelectric case,4 but here the Commission without explanation departs from its “liberal approach to late intervention in hydroelectric proceedings” by imposing a rigorous “good cause” requirement on Petitioners despite the lack of prejudice that would result from late intervention. 98 F.E.R.C. at ¶ 61276.
The cases cited by the majority further support the conclusion that the Commission regularly does not require a meaningful showing of good cause for late intervention when there is no prejudice. See Op. at 1023-24. The majority asserts that the liberal intervention policy announced in Cameron LNG, LLC, 118 F.E.R.C. ¶ 61,-019 (2007), and Columbia Gas Transmission Corp., 113 F.E.R.C. ¶ 61,118, 61,438 (2005), is limited only to natural gas cases. However, not only does Alaska Power & Telephone apply this policy to hydroelectric cases, but the Commission justifies its liberal late intervention policy in cases involving natural gas not because of anything specific to natural gas, but because “late intervention at the early stages of natural gas certificate proceedings will neither disrupt the proceedings nor prejudice the interests of any other party.” Brad-wood Landing LLC NorthemStar Energy LLC, 126 F.E.R.C. ¶ 61035 (2009).
Public Utility District No. 1 of Okanogan County, 63 F.E.R.C. ¶ 61,337, 63,202 (1993), which is not a natural gas case, further undercuts the Commission’s decision against Petitioners because there too the Commission allowed a late intervention after determining that it would not disrupt proceedings or cause prejudice. The majority acknowledges that in Public Utility District the Commission did not explicitly impose a separate good cause requirement. The most natural reading of Public Utility District, Alaska Power & Telephone, and the natural gas cases, one that unifies them into a consistent standard, is that the Commission does not require any substantial showing of good cause when there is no evidence of prejudice or disruption.5
*1029I conclude that the Commission should have allowed Petitioners to intervene both because good cause was shown for a late intervention, and because intervention was permissible in any event under the Commission’s usual policy of dispensing with the good cause requirement when, as here, there was no risk of prejudice or disruption to other parties. Here, however, the Commission without explanation departed from its own precedent and required Petitioners to make a substantial showing of good cause. This deviation was an arbitrary departure from prior agency rules of decision and is prohibited by our precedent. See Cal. Trucking Ass’n v. Interstate Commerce Comm’n, 900 F.2d 208, 212 (9th Cir.1990) (stating that an agency “may not depart, sub silentio, from its usual rules of decision to reach a different, unexplained result in a single case” (quotation omitted)). By denying Petitioners’ attempt to intervene, the Commission has ensured that no group can challenge in court whether the Commission’s actions in this case comply with federal environmental law. There is no good reason why those who wish to advance important environmental issues should be practically silenced, in the sense that they have submitted materials for the agency to review but are left with no court process for an appeal of the decision of the Commission. I respectfully dissent and would hold that the Commission acted in an arbitrary and capricious manner by failing to follow its own precedent.
. For example, Federal Rule of Civil Procedure 6(b) provides that courts "for good cause” may extend the time limits imposed by the rules of civil procedure. Interpreting this language, courts have said that the good cause standard and an extension "normally will be granted in the absence of bad faith on the part of the party seeking relief or prejudice to the adverse party.” 4B Charles Alan Wright & Arthur R. Miller, Federal Practice and Procedure § 1154 (3d ed.1998). Even when the extension is sought after the time limit has expired, the good cause standard is satisfied merely upon a showing of excusable neglect. Fed.R.Civ.P. 6(b)(2). Similarly, a liberal good cause standard applies when setting aside an entry of default. Fed. R. Civ P. 55(c). Motions under this rule “are frequently granted,” and good cause is generally found when "the court finds that the default was not the result of gross neglect, that the nondefaulting party will not be substantially prejudiced by the reopening, and the party in default has a meritorious defense.” 10A Wright, Miller & Kane § 2696 (footnotes omitted). Similarly, Black's Law Dictionary defines "good cause” as "a legally sufficient reason .... to show why a request should be granted or an action excused,” and certainly that and more was shown here. Black’s Law Dictionary 235 (8th ed.2004).
. The fact that good cause has been liberally interpreted in other contexts does not necessarily control how good cause should be interpreted in under the FERC’s late intervention regulations, 18 C.F.R. §§ 385.214(b) & (d), for it is settled law that "[t]he same or similar words may have different meanings when used in different statutes motivated by different legislative purposes." Singh v. Ashcroft, 386 F.3d 1228, 1233 n. 8 (9th Cir.2004). Nonetheless, as Justice Jackson once observed, "the mere fact that a path is a beaten one is a persuasive reason for following it.” Robert H. Jackson, Full Faith and Credit— The Lawyer’s Clause of the Constitution, 45 Colum. L.Rev. 1, 26 (1945).
. The Commission denied the late intervention request because it had already issued a dispositive final order, after which "extraordinary grounds” must be present to allow for late intervention because "the prejudice to other parties and burden on the Commission of granting late intervention can be substantial.” Alaska Power and Tel., 98 F.E.R.C. ¶ 61277. By contrast, here the Commission has not issued a final order, and no prejudice would result from allowing late intervention.
. This case concerns water flow through a dam and involves a license issued under the Federal Power Act. Such licenses permit the operation of dams and other hydroelectric projects. See 16 U.S.C. § 797(e); Op. at 1013.
. The majority contends that the Commission "has steadfastly and consistently held” that a petitioner who intervenes late despite having notice that might justify an earlier intervention lacks good cause. Op. at 1025. However, in each of the six cases the majority cites for this claim, the Commission also determined that late intervention would cause prejudice or that another party already represented the late petitioner's interests. See, e.g., Bradwood Landing LLC, 126 F.E.R.C-¶ 61,035 (2009) ("Allowing late intervention at this point in the proceeding brings very little benefit to the proceeding and potentially would create prejudice and additional burdens on the Commission, other parties, and the applicants.”); Cent. Neb. Pub. Power & Irngation *1029Dist., 125 F.E.R.C.i 61,192 (2008) (denying intervention after the Commission issued a dispositive order because “[o]nce a dispositive order has been issued in a proceeding ... the prejudice to other parties and the burden on the Commission of granting late intervention are substantial”); Crown Landing LLC, 117 F.E.R.C. ¶ 61,209 (2006) (''[Late Petitioner] claims no intention to inject any new argument into this proceeding beyond those offered by [an existing party].”).