Opinion for the Court filed by Circuit Judge SENTELLE.
Petitioner FPL Energy Maine Hydro LLC (FPL), a hydroelectric facility, petitions this Court, for review of two orders by the Federal Energy Regulatory Commission (FERC), the first determining that FPL is subject to licensing because the Messalonskee Stream on which FPL is located is “navigable” under 16 U.S.C. § 796(8), the second denying FPL’s request for rehearing. Because we find that FERC’s interpretation of the statute governing navigability is a reasonable one and that its navigability finding was supported by substantial evidence, we deny the petitions.
I. Background
The Messalonskee Stream (Stream) is a tributary of the Kennebec River (Kenne-bec) located in central Maine. It runs approximately ten miles from the Messal-onskee Lake to the Kennebec, with four dams located along its stretch. The southernmost dam is the Union Gas Project, located approximately one mile up the Stream from the confluence of the Stream and the Kennebec. In between the dam and the Kennebec, beginning from the dam and progressing downstream, are two sets of rapids or “rips,” a bridge, a third set of rips, and two islands that together span approximately 200 feet downstream with a shallow shoal on the east side of the islands and a narrow and rocky channel on the west side. Below the islands the Stream widens and deepens as it encounters the backwater of the Kennebec. The Kennebec, itself a navigable water, empties into the Atlantic Ocean.
Pursuant to section 23(b)(1) of the Federal Power Act (FPA), 16 U.S.C. § 817(1), a non-federal hydroelectric project must be licensed if it is located on a navigable water of the United States, as defined by 16 U.S.C. § 796(8), or if other criteria not relevant to this case are met. Because the four dams constitute one development unit, if one project requires a license, then they all must be licensed.
See Kennebec Water District,
Section 3(8) of the FPA defines navigable waters as
those parts of streams ... which either in their natural or improved condition notwithstanding interruptions between the navigable parts of such streams or waters by falls, shallows, or rapids compelling land carriage, are used or suitable for use for the transportation of persons or property in interstate or foreign commerce....
16 U.S.C. § 796(8). This means that, to be navigable for purposes of the FPA a waterway must form a highway for commerce with other states or with foreign countries, by itself or by connecting with other waters.
See The Montello,
87 U.S. (20 Wall.)
*1155
480, 439,
II. Proceedings Below
The Union Gas Project is currently licensed by FPL (as successor in interest to Central Maine Power Company — the original licensee of the project). The original license for the project was issued in 1968 and expired in 1993. Since that time, the project has been operating on annual licenses. As part of a jurisdictional examination of several projects for which licensing might not have been required,
1
the Office of Hydropower Licensing conducted a navigation report on the Stream in 1996. This report indicated that the Stream was not navigable because there was “no evidence of usage of the stream as a water highway, a continuous link for interstate commerce, either commercial or recreational, from above the project sites, past the projects, to the Kennebec River.” Following a review of comments to the report, the Acting Director of the Office of Hydro-power Licensing issued an order finding that the Union Gas Project was located on a navigable waterway and therefore required a license.
See Kennebec Water District,
III. Analysis
This case requires us to answer two questions: first, whether FERC’s interpretation of “navigability” under the FPA was reasonable; second, if so, whether FERC’s navigability finding was supported by substantial evidence. We answer both questions affirmatively.
A. “Navigability” Interpretation
FPL argues that FERC departed from the statutory “suitable for use ... in ... commerce” test set forth at 16 U.S.C. § 796(8)
(see also Rochester Gas,
We reject each of FPL’s arguments. Where an administrative agency is tasked with interpreting an ambiguous statute that it administers, a court will defer to that agency’s interpretation so long as it is reasonable.
See Chevron U.S.A., Inc. v. Natural Res. Def. Council, Inc.,
At the outset, we may quickly reject FPL’s argument that it was improper for FERC to rely on the flow created when the Union Gas Project is generating to create navigability. FPL confuses a finding of whether a waterway has always been navigable because an improvement
could
be made if reasonable in cost, with a finding of whether a waterway, together with its improvements, is presently “suitable for use.”
See Rochester Gas,
*1157 Turning next to FPL’s primary argument, FPL contends that FERC’s “possibility of passage” test: 1) ignored the fact that the Stream has never been used, either historically or presently, for eommer-cial or private purposes, and 2) deviated from past decisions wherein FERC denied a finding of navigability when the only evidence of actual use was specialized, recreational boating.
All parties agree that the Stream has never been used for commercial traffic. But just because a body of water has not been used for commercial use does not mean that it is not
susceptible
to commercial use.
See United States v. Utah,
In the past, FERC has often relied on evidence of recreational use as a proxy for commercial suitability. Here, however, there is no evidence of recreational use of the Stream. In fact, the only evidence indicating actual use of the Stream comes from the three trips made for the purpose of litigation. Echoing the ALJ, FPL argues that this evidence is insufficient to serve as a proxy for commercial suitability. Instead, FPL argues that FERC precedent requires a navigability finding to be based on “regular and substantial recreational use” in the absence of actual commercial use. We disagree. The statute and the case law make clear that evidence of
actual use
is not necessary for a navigability determination. “[T]he test [is] whether the river ... is used, or
capable of being used
as a highway for commerce, over which trade and travel is or may be conducted in the customary modes of trade and travel on water.”
Economy Light & Power Co. v. United States,
FPL nonetheless argues that the test trips were of a type of specialized, recreational boating that FERC has previously
*1158
disregarded when making navigability determinations. The eases on which FPL relies, however, are distinguishable from the facts before us. For example, in
Pennsylvania Elec. Co.,
FPL further argues that FERC’s navigability test was flawed because FERC failed to identify the possible commercial use to which the Stream may be put. We see no reason why FERC must identify the precise commercial use to which a previously unused waterway may be put in order for the Commission’s finding of navigability to be upheld. The test is whether the waterway is presently “suitable for use for the transportation of persons or property in interstate or foreign commerce,” not whether the waterway is presently suitable for a specific type of commercial activity named by FERC and approved of by an opposing party. 16 U.S.C. § 796(8);
see also PacifiCorp,
Even more important to our analysis, FERC did not rely on the test canoe trips alone when finding that the Stream was navigable. FERC also looked to the Stream’s physical characteristics when making its navigability determination.
See United States v. Utah,
For the reasons stated, we find that FERC’s interpretation of the FPA’s navigability test was reasonable insofar as it necessarily relied on test canoe trips and the Stream’s physical characteristics in the absence of past or present commercial and *1159 recreational use of the waterway. It is therefore entitled to deference.
B. Substantial Evidence
As our discussion of FERC’s deference-worthy interpretation of the navigability test may suggest, we also conclude that FERC’s finding of navigability is supported by substantial evidence. 16 U.S.C. § 825Z(b) (“The finding of the Commission as to the facts, if supported by substantial evidence, shall be conclusive.”).
The “experimental” test canoe trips provide sufficient evidence that the Stream is navigable. Three witnesses, all with differing interests in the litigation, successfully navigated downstream without incident, and two attempted and succeeded in navigating upstream, albeit with some difficulty. Although FPL made much of the difficulty associated with this upstream travel both in its brief and at oral argument, FPL failed to provide any explanation as to why an upstream trip&emdash;either made with ease or with difficulty&emdash;is necessary for a navigability finding when the evidence of successful downstream trips is clear. Nowhere in the statute or accompanying case law does it state that the transport of persons or property in interstate or foreign commerce must include two-way transport. We do not view this case as an opportunity to suggest otherwise.
In addition to relying on the three test trips, FERC made a separate determination that the physical characteristics of the Stream rendered it suitable for commercial navigation. The Supreme Court has held that a water’s “capacity [for commercial navigation] may be shown by physical characteristics and experimentation as well as by the uses to which the streams have been put.”
United States v. Utah,
The record includes sufficient evidence regarding the Stream's physical characteristics on which FERC relied in making its navigability determination. FERC noted that the Stream has a very slight gradient, has a depth of approximately three and a half to four feet when the dam is generating (although slightly shallower around the two islands), is wide enough to support passage up and down the Stream and around the two islands, and has few obstacles (e.g., boulders and fallen trees) that a canoeist may steer around without difficulty. Kennebec Water District,
FPL attempts to bolster its argument with evidence that the test trips upon which FERC relied were made during periods of unusual water conditions. FPL argues that this should negate FERC’s navigability finding. That is, FPL argues that since “susceptibility of use as a highway for commerce should not be confined to exceptional conditions or short periods of temporary high water,” the canoe test trips do not show the stream to be navigable.
Loving,
We acknowledge that the evidence of navigability is not overwhelming. But to uphold FERC’s navigability determination, we need only find that the evidence on which the finding is based is substantial. 16 U.S.C. § 8251(b); see
Consolidated Hydro, Inc. v. FERC,
IV. Conclusion
FERC’s reliance on test canoe trips and the physical characteristics of the Stream, in the absence of historical or present commercial or recreational use, is a reasonable interpretation of the navigability test set forth in the Federal Power Act and is therefore entitled to deference by this Court. Moreover, the record includes substantial evidence to support FERC’s navigability finding. Three witnesses were able to successfully navigate down the Stream, and the physical characteristics of the Stream support a finding of navigability. For these reasons, the petitions for review are denied.
Notes
. Union Gas was previously required to be licensed pursuant to FERC’s incorrect interpretation of a different section of the FPA.
