                    FOR PUBLICATION

  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT


PIT RIVER TRIBE; NATIVE                 No. 17-15616
COALITION FOR MEDICINE
LAKE HIGHLANDS DEFENSE;                   D.C. Nos.
MOUNT SHASTA                       2:04-cv-00956-JAM-AC
BIOREGIONAL ECOLOGY                2:04-cv-00969-JAM-AC
CENTER; SAVE MEDICINE
LAKE COALITION; MEDICINE
LAKE CITIZENS FOR QUALITY                 OPINION
ENVIRONMENT,
         Plaintiffs-Appellees,

              v.

BUREAU OF LAND
MANAGEMENT; U.S.
DEPARTMENT OF THE
INTERIOR,
      Defendants-Appellants.


      Appeal from the United States District Court
          for the Eastern District of California
       John A. Mendez, District Judge, Presiding

          Argued and Submitted May 14, 2019
                 Seattle, Washington

                   Filed September 19, 2019
2                    PIT RIVER TRIBE V. BLM

Before: William A. Fletcher and Morgan Christen, Circuit
      Judges, and Roslyn O. Silver,* District Judge.

                    Opinion by Judge Christen


                            SUMMARY**


          Geothermal Steam Act / Federal Leases

    The panel affirmed the district court’s summary judgment
in favor of Pit River Tribe and several environmental
organizations in their action against federal agencies
responsible for administering twenty-six unproven
geothermal leases located in California’s Medicine Lake
Highlands.

    Pit River alleged that the Bureau of Land Management’s
decision to continue the terms of the unproven leases for up
to forty years violated the Geothermal Steam Act (“GSA”).

    Section 1017 of the GSA authorizes the Secretary of the
Interior to approve cooperative or unit plans to manage
multiple geothermal leases as a unit, and the Secretary must
review such unit plans every five years and eliminate any
lease not reasonably necessary for unit operations under the
plan. Section 1005(a) of the GSA provides that geothermal


    *
      The Honorable Roslyn O. Silver, United States District Judge for the
District of Arizona, sitting by designation.
    **
       This summary constitutes no part of the opinion of the court. It has
been prepared by court staff for the convenience of the reader.
                  PIT RIVER TRIBE V. BLM                    3

leases on federal land have primary lease terms of ten years,
and allows the leases to be continued for as long as
geothermal steam is produced in commercial quantities.
Section 1005(c) states that leases subject to “unit plans” may
be extended even if not productive during the initial ten-year
term under certain conditions.

    The panel held that the statutory meaning of 30 U.S.C.
§ 1005(a) was clear and unambiguous. The panel held that
the provision permitted production-based forty-year
continuations at the end of the primary term only on a lease-
by-lease basis, not on a unit-wide basis. It was BLM’s
burden to provide a compelling reason for the court to depart
from the plain language of § 1005(a), and the panel
concluded that it had not met that burden here.


                        COUNSEL

Mary Gabrielle Sprague (argued) and Ellen J. Durkee,
Appellate Section; Eric Grant, Deputy Assistant Attorney
General; Jeffrey Bossert Clark, Acting Assistant Attorney
General; Environment and Natural Resources Division,
United States Department of Justice, Washington, D.C.; for
Defendants-Appellants.

Samuel Lazerwitz (argued) and Caleb G. Wright (argued),
Certified Law Students; Alicia E. Thesing, Isaac C. Cheng,
and Deborah Ann Sivas, Supervising Attorneys;
Environmental Law Clinic, Mills Legal Clinic at Stanford
Law School, Stanford, California; for Plaintiffs-Appellees.
4                    PIT RIVER TRIBE V. BLM

                              OPINION

CHRISTEN, Circuit Judge:

    The Bureau of Land Management and the Department of
the Interior (collectively, BLM) appeal the district court’s
order granting summary judgment in favor of the Pit River
Tribe and several local and regional environmental
organizations (collectively, Pit River). We have jurisdiction
pursuant to 28 U.S.C. § 1291 and we affirm the district
court’s judgment.

                           I. Background

    Pit River filed this action against the federal agencies
responsible for administering twenty-six unproven
geothermal leases located in California’s Medicine Lake
Highlands. We refer to these leases as “unproven” because
BLM has not determined that they are capable of producing
geothermal steam in commercial quantities. See Pit River
Tribe v. Bureau of Land Mgmt., 793 F.3d 1147, 1149–50 (9th
Cir. 2015) (Pit River III).1 Calpine Corporation, the current
leaseholder, was also named as a defendant but it did not
appeal the judgment the district court entered on remand from
our court. The operative complaint alleges that BLM’s
decision to continue the terms of the unproven leases for up
to forty years violated the Geothermal Steam Act (GSA), the
National Environmental Policy Act (NEPA), the National




   1
     Our decision in Pit River III provides a detailed history of the case.
We recount that history only as necessary to resolve this appeal.
                      PIT RIVER TRIBE V. BLM                               5

Historic Preservation Act (NHPA), and the Indian-fiduciary-
trust doctrine.2 Id. at 1148.

    The subject leases are located within the Glass Mountain
Unit Plan. The parties agree that the GSA requires that any
lease be allowed to continue if it is producing geothermal
steam in commercial quantities, or is shown to be capable of
doing so, within its primary ten-year term. See 30 U.S.C.
§ 1005(a) (1994).3 The parties’ dispute centers on whether all
leases committed to a “unit plan” may be collectively
continued for up to forty years if any single lease in the unit
becomes productive during the primary term. Pit River
argues that § 1005(a) allows production-based continuations
to be granted only on an individual basis. BLM argues that
§ 1005(a) allows production-based continuations to be
granted to all leases in a unit if any one of them becomes
productive during the primary term. BLM’s interpretation of
the GSA is heavily informed by its view that the Mineral
Leasing Act (MLA), 30 U.S.C. §§ 221i–236a (1964),
provides an important backdrop against which the GSA must
be analyzed.4




    2
      The complaint also alleges a violation of the Freedom of
Information Act (FOIA), but the district court’s ruling on the FOIA issue
was not appealed.
    3
       Unless otherwise specified, all citations to the GSA refer to the 1994
edition of the United States Code because the parties agree that this
iteration of the GSA applies to their dispute.
    4
      Unless otherwise noted, all citations to the MLA’s provisions are to
the 1964 edition of the United States Code, which was in effect when the
GSA was enacted.
6                 PIT RIVER TRIBE V. BLM

                  II. Procedural History

    This is the second time our court has addressed the
controversy concerning the duration of the leases in the Glass
Mountain Unit. See Pit River III, 793 F.3d at 1148. In July
of 2013, the district court granted judgment on the pleadings
in favor of BLM on the grounds that Pit River lacked
prudential standing to assert its GSA claim. Id. at 1154–55.
We reversed the district court’s judgment, ruling that Pit
River’s claim fell within the GSA’s “zone of interests,” id. at
1155–58, and we remanded to the district court so it could
consider the merits of the claims.

    On remand from Pit River III, the district court granted
summary judgment in favor of Pit River. The court ruled
that, as it was written in 1994, the GSA’s primary term
provision was unambiguous and did not authorize BLM to
continue the twenty-six unproven leases for forty years
simply because they were part of a unit that contained a
single proven lease. The district court reasoned that because
Congress referred to “unit plans” in § 1005(c) and (g), but
omitted this term from § 1005(a), “Congress did not
contemplate the additional [forty]-year term for
nonproductive leases committed to a unit plan under
[§] 1005(a).” In an amended judgment, the district court
vacated and set aside BLM’s May 18, 1998 decision granting
the lease continuations, and remanded the proceedings to the
agency to determine whether to extend or cancel the twenty-
six leases pursuant to the GSA and the implementing
regulations in effect as of May 1998. The district court
observed that its judgment did not affect BLM’s decision to
continue the single proven lease, and that Pit River’s NEPA,
NHPA, and fiduciary duty claims were mooted by the court’s
                  PIT RIVER TRIBE V. BLM                      7

vacatur of BLM’s 1998 decision letters. BLM appeals the
district court’s judgment.

                  III. Standard of Review

   We review de novo an order granting summary judgment.
Cty. of Amador v. U.S. Dep’t of the Interior, 872 F.3d 1012,
1020 (9th Cir. 2017).

                      IV. Jurisdiction

    We must first assure ourselves of our jurisdiction to hear
this appeal because the district court’s order granting
summary judgment vacated BLM’s 1998 decision letters and
remanded to the agency. See Pit River Tribe v. U.S. Forest
Serv., 615 F.3d 1069, 1075 (9th Cir. 2010). “[R]emand
orders are generally not ‘final’ decisions for purposes of
section 1291[,]” id., but a remand order is considered final
and appealable where: “(1) the district court conclusively
resolves a separable legal issue, (2) the remand order forces
the agency to apply a potentially erroneous rule which may
result in a wasted proceeding, and (3) review would, as a
practical matter, be foreclosed if an immediate appeal were
unavailable.” Id. (quoting Alsea Valley All. v. Dep’t of
Commerce, 358 F.3d 1181, 1184 (9th Cir. 2004)). Here,
because the district court determined that 30 U.S.C. § 1005(a)
did not authorize BLM to continue the unproven leases based
on the single proven lease, BLM will be constrained by this
interpretation on remand. If the district court’s interpretation
is incorrect, the remand will result in a wasted proceeding.
Moreover, review of the district court’s interpretation will be
foreclosed absent immediate appeal because, after remand to
the agency, BLM cannot later appeal the result of its own
agency decision. See Alsea Valley All., 358 F.3d at 1184;
8                 PIT RIVER TRIBE V. BLM

Chugach Alaska Corp. v. Lujan, 915 F.2d 454, 457 (9th Cir.
1990). For these reasons, we conclude that we have
jurisdiction to hear this appeal.

                        V. Discussion

    A. The Geothermal Steam Act

    This appeal requires us to interpret the GSA, 30 U.S.C.
§§ 1001–1028 (1994). Congress enacted the GSA in 1970 “to
promote the development of geothermal leases on federal
lands.” Geo-Energy Partners-1983 Ltd. v. Salazar, 613 F.3d
946, 949 (9th Cir. 2010). Geothermal resources include “the
heat or energy found in steam, hot water, or geothermal
formations.” Id. The GSA was adopted in the wake of the
MLA, which governs oil and gas leases on federal lands. BP
Am. Prod. Co. v. Burton, 549 U.S. 84, 87 (2006). A brief
explanation of the MLA’s unitization provision provides
helpful background.

    When Congress enacted the MLA, oil and gas were
extracted under the common-law “rule of capture,” which
encouraged landowners to drill wells on individual leases to
capture as much oil or gas as possible. See Frank Sylvester
& Robert W. Malmsheimer, Oil and Gas Spacing and Forced
Pooling Requirements: How States Balance Energy
Development and Landowner Rights, 40 U. Dayton L. Rev.
47, 49 (2015). The rule of capture encouraged overdrilling
that dissipated reservoir pressure and ultimately led to
inefficient oil and gas recovery. See Northcutt Ely, The
Conservation of Oil, 51 Harv. L. Rev. 1209, 1219–22 (1938).
The practice of unitization emerged in response to these
inefficiencies. See Sylvester, et al., supra at 49–50.
Unitization allows an entire oil or gas field “to be operated as
                      PIT RIVER TRIBE V. BLM                               9

a single entity, without regard to surface boundary issues,”
see Norfolk Energy, Inc. v. Hodel, 898 F.2d 1435, 1438 (9th
Cir. 1990) (internal quotation marks omitted), i.e., it allows
drilling and production operations occurring on a single lease
within a unit to be deemed performed on all other leases
within the unit for purposes of showing that bona fide
development efforts have been made, or for sharing royalties.
See, e.g., 30 U.S.C. § 1017; 30 U.S.C. § 226(j); 43 C.F.R.
§§ 3280–3287 (1997). By limiting the need to drill on each
lease within a unit, unitization lessens the likelihood that an
oil or gas reservoir will suffer from overdrilling and depleted
reservoir pressure. Congress incorporated the unitization
concept into the MLA, granting the Secretary of the Interior
the authority to approve unit plans of development when
doing so is in the public interest. See Pub. L. No. 71-853, 46
Stat. 1523. Although significant differences exist between
the MLA and the GSA, the GSA also permits lessees to join
together under unit plans of development. See 30 U.S.C.
§ 1017; 43 C.F.R. § 3280.0–2 (1997).

    The GSA refers to production-based “continuations” and
drilling-based “extensions”—concepts articulated in the
MLA—but neither the MLA nor the GSA explicitly define
these terms. See 30 U.S.C. §§ 221i–236a; 30 U.S.C. § 1001.
The parties agreed at oral argument that, like the MLA, the
GSA allows for lease continuations based on production, and
lease extensions based on exploratory drilling activities.5



    5
       We note that the Interior Board of Land Appeals generally interprets
a continuation based on production as a prolonged lease term that is
“indefinite and is allowed when a lease is presently capable of producing
oil or gas” in commercial quantities, while an “‘extension by drilling’ . . .
requires that a lessee conduct actual drilling operations on the last day of
10                 PIT RIVER TRIBE V. BLM

    Pit River’s claims implicate §§ 1005 and 1017 of the
GSA, so we discuss these provisions in some detail. Section
1017 governs unit plans. Section 1005 governs the duration
of geothermal lease terms.

        1. 30 U.S.C. § 1017: The Unitization Provision

    Section 1017 of the GSA authorizes the Secretary of the
Interior to approve cooperative or unit plans to manage
multiple leases as a unit “[f]or the purpose of properly
conserving the natural resources of any geothermal pool,
field, or like area.” 30 U.S.C. § 1017. The Secretary must
review such unit plans every five years “and, after notice and
opportunity for comment, eliminate from inclusion in such
plan any lease or part of a lease not regarded as reasonably
necessary to cooperative or unit operations under the plan.”
Pit River III, 793 F.3d at 1150 (quoting 30 U.S.C. § 1017).

        2. 30 U.S.C. § 1005:             The Lease Duration
           Provisions

    Section 1005(a) of the GSA provides that geothermal
leases on federal land have primary lease terms of ten years.
30 U.S.C. § 1005(a). If geothermal steam is produced in
commercial quantities during the ten-year primary term,
§ 1005(a) allows the lease to be continued for as long as
geothermal steam is produced in commercial quantities, not




the lease term with an intent to complete a producing well.” Coastal
Petroleum Co., 190 IBLA 347, 352, 2017 WL 3263839, at *4 (July 25,
2017).
                       PIT RIVER TRIBE V. BLM                               11

to exceed an additional forty years.6 Id. At the end of the
first forty-year term granted pursuant to § 1005(a), the GSA
affords a preferential right of renewal for a second forty-year
term if geothermal steam is still being produced in
commercial quantities and the land is not needed for other
purposes. 30 U.S.C. § 1005(b).

    Neither § 1005(a) nor § 1005(b) refer to “unit plans,” but
§ 1005(c) does. It is entitled “Cooperative or unit plan for
drilling operations; extension of term; renewal.” 30 U.S.C.
§ 1005(c). Section 1005(c) states that leases subject to unit
plans may be extended, even if the leases have not been
productive during their initial ten-year primary terms, if
actual drilling operations begin prior to the end of the primary
lease terms and are being diligently prosecuted.7 Id. For
leases still not producing steam nor shown to be capable of
producing in commercial quantities by the end of an
extension granted pursuant to § 1005(c), the agency may


    6
        30 U.S.C. § 1005(a) specifies that “[i]f geothermal steam is
produced or utilized in commercial quantities within this term, such lease
shall continue for so long thereafter as geothermal steam is produced or
utilized in commercial quantities, but such continuation shall not exceed
an additional forty years.” In turn, 30 U.S.C. § 1005(d) defines “produced
or utilized in commercial quantities” to include a showing that a well is
“capable of producing geothermal steam in commercial quantities.”
(emphasis added).
    7
        30 U.S.C. § 1005(c) provides, inter alia, that a lease for which:

           actual drilling operations were commenced prior to the
           end of its primary term and are being diligently
           prosecuted at that time shall be extended for five years
           and so long thereafter, but not more than thirty-five
           years, as geothermal steam is produced or utilized in
           commercial quantities.
12                      PIT RIVER TRIBE V. BLM

authorize one or two additional five-year extensions if the
lessee has made certain bona fide efforts.8 30 U.S.C.
§ 1005(g)(1). Notably, § 1005(g)(1) also expressly refers to
leases operated under “approved cooperative or unit plan[s]
of development.” Id. If a lease extended pursuant to
§ 1005(g)(1) begins producing geothermal steam in
commercial quantities during a § 1005(g)(1) extension,
§ 1005(g)(2) provides that the lease shall be continued for up
to twenty-five additional years if it was previously extended
under § 1005(c), “for a total of [fifty] years,” or for up to
thirty additional years (but not to exceed a total of fifty years)




     8
         30 U.S.C. § 1005(g)(1) states:

            (1) Any geothermal lease issued pursuant to this
            chapter for land on which, or for which under an
            approved cooperative or unit plan of development or
            operation, geothermal steam has not been produced or
            utilized in commercial quantities by the end of its
            primary term, or by the end of any extension provided
            by subsection (c) of this section, may be extended for
            successive 5-year periods, but totaling not more than
            10 years, if the Secretary determines that the lessee has
            met the bona fide effort requirement of subsection (h)
            of this section, and either of the following:

                (A) [T]he payment in lieu of commercial quantities
                production requirement of subsection (i) of this
                section.

                (B) The significant expenditure requirement of
                subsection (j) of this section.
                        PIT RIVER TRIBE V. BLM                           13

if it was only previously extended pursuant to § 1005(g)(1).9
30 U.S.C. § 1005(g)(2).

    B. The Glass Mountain Leases

    Three years after Congress enacted the GSA, BLM
promulgated regulations authorizing holders of geothermal
leases to enter into unit agreements for the development of
geothermal resources. See 38 Fed. Reg. 35,068, 35,073–75
(Dec. 21, 1973); see also 43 C.F.R. §§ 3280.0–1 to 3286.1
(1997). These regulations included a model unit agreement.
See 38 Fed. Reg. at 35,075–80; see also 43 C.F.R. § 3286.1
(1997). In 1982, Calpine’s predecessors entered into the
Glass Mountain Unit Agreement, which tracked the
regulations’ model agreement.10

    The twenty-six unproven leases at issue in this
appeal—plus a twenty-seventh “proven lease” that BLM
determined was capable of producing geothermal steam in
commercial quantities—were eventually committed to the
Glass Mountain Unit Agreement. Pit River III, 793 F.3d
at 1149–51. The Agreement established a “Unit Area” and

    9
        30 U.S.C. § 1005(g)(2) provides:

           (2) A lease extended pursuant to paragraph (1) shall
           continue so long thereafter as geothermal steam is
           produced or utilized in commercial quantities, but such
           continuation shall not exceed an additional 25 years, for
           a total of 50 years, if such lease was also the subject of
           an extension under subsection (c) of this section or an
           additional 30 years, for a total of 50 years, if such lease
           is only extended pursuant to paragraph (1).
    10
       We do not separately identify Calpine’s predecessors to avoid
confusion and because the predecessors’ actions do not affect our analysis.
14                PIT RIVER TRIBE V. BLM

“Participating Area.” The Unit Area is the area comprised of
all leases subject to the Agreement, and the Participating Area
is the “part of the Unit Area which is deemed to be
productive,” i.e., it is “all land then regarded as reasonably
proved to be productive from a pool or deposit discovered or
developed[.]” By the fifth anniversary of the Participating
Area’s effective date, the Agreement requires that all portions
of unitized lands not entitled to be included in the
Participating Area must be automatically eliminated from the
Agreement and from the Unit Area, unless drilling operations
are in progress on an exploratory well and these operations
continue diligently.

    In 1989, BLM determined that a single lease in the Glass
Mountain Unit was capable of producing geothermal steam
in commercial quantities. Pit River III, 793 F.3d at 1151. In
1991 and 1992, at the request of Calpine’s predecessors,
BLM’s California State Office extended the terms of twenty-
four unproven leases in the Glass Mountain Unit for five
years pursuant to § 1005(g)(1). BLM continued the term of
the single proven lease for up to forty additional years
pursuant to § 1005(a). Id. In the process of responding to the
predecessors’ requests, BLM’s California State Office
communicated with the Nevada State Office, “which advised
that [forty]-year lease continuations should be granted to all
of the unproven Glass Mountain leases[.]” Id. The California
Office disagreed. Id. It concluded that “the ‘[forty-]year
extension [under § 1005(a)] may only be applied to the lease
with the well capable of production and not to the other
committed leases in the unit.’” Id. (second alteration in
original). The California Office noted that § 1005(a) did not
refer to unit plans. Id.
                    PIT RIVER TRIBE V. BLM                           15

    In 1995, BLM sent Calpine’s predecessor a letter stating
that the predecessor was “in default of meeting reasonable
diligence in the unit,” and that the Glass Mountain Unit was
“no longer of any significant benefit to the BLM or Forest
Service” because “[t]he unit has become an impediment to
development by causing operators to select drilling targets on
the basis of whether a lease is or is not committed to the unit
instead of the area with the greatest potential to support a
development project.” On June 3, 1996, BLM notified
Calpine’s predecessor via an additional letter that a proposed
Participating Area should have been submitted in 1989, but
that due to agency delay and other circumstances, BLM
would allow submission of a proposed Participating Area
within sixty days of receipt of the letter. Calpine’s
predecessor submitted a proposed Participating Area on
August 15, 1996.11

    BLM’s California State Office changed its interpretation
of § 1005(a) in 1998. The California Office’s Program Lead,
Sean Hagerty, circulated an internal memo that sheds light on
the reasons for BLM’s changed position. Hagerty’s memo
described the prior disagreement between BLM’s California
and Nevada Offices and explained that the California Office
was concerned about allowing the Glass Mountain Unit to
continue for an indefinite period of time merely based on the
single proven lease. In particular, “BLM was concerned over
how the Unit could be managed without any effective way of
requiring the unit operator . . . to conduct additional activities
in the Unit prior to the submission of the initial Participating
Area (PA).” The memo explained that BLM was initially
uncertain whether the single proven lease, which was deemed

    11
       This information was not part of the record in Pit River III, 793
F.3d at 1152 n.6.
16                  PIT RIVER TRIBE V. BLM

capable of production but had not actually commenced
production, was legally sufficient to require Calpine’s
predecessor to submit an initial Participating Area. Because
BLM subsequently decided that a well capable of production
was equivalent to a well actually in production, it requested
and received a proposed Participating Area from Calpine’s
predecessor. Hagerty’s memo concluded that, because the
Participating Area had been designated, “the Glass Mountain
Unit boundary would contract down to the boundary of the
[Participating Area],” and therefore “the Glass Mountain Unit
Agreement no longer had an indefinite lifespan and could
now be managed in the public interest.”               Hagerty
recommended that BLM grant an additional term of up to
forty years to all leases committed to the Glass Mountain
Unit.

    On May 18, 1998—five days after Hagerty circulated his
memo—BLM’s California Office issued decision letters
vacating the 1991 and 1992 lease extensions for the unproven
leases and continuing them for up to forty years pursuant to
§ 1005(a).12 Pit River III, 793 F.3d at 1152. BLM explained
that the decision to grant the five-year lease extensions
pursuant to the regulation implementing § 1005(g)(1) “was in
error.” BLM further explained that all leases committed to
the Glass Mountain Unit should have been granted additional
lease terms based on the paying-well determination for the
single proven lease pursuant to the regulation implementing
§ 1005(a) and (d).




     12
        In total, BLM continued twenty-six unproven leases, which
included two leases that were not previously extended in 1991 or 1992.
Pit River III, 793 F.3d at 1152 n.8.
                  PIT RIVER TRIBE V. BLM                   17

   C. Statutory Analysis

    It is clear that the GSA authorizes “continuations” based
on production, see 30 U.S.C. § 1005(a), and there is no
dispute that the GSA authorizes five-year “extensions” based
on actual drilling or bona fide efforts. See § 1005(c), (g).
Both parties argue that 30 U.S.C. § 1005(a) is clear and
unambiguous, but they advocate for opposite interpretations.
BLM argues that § 1005(a), read in light of the GSA as a
whole and against the backdrop of the MLA, authorizes forty-
year continuations on a unit-wide basis once a single lease in
a unit is deemed productive. Pit River argues that § 1005(a)
unambiguously authorizes forty-year continuations at the end
of a primary term only on a lease-by-lease basis, not on a
unitized basis.

    “We interpret a federal statute by ascertaining the intent
of Congress and by giving effect to its legislative will[,]”
beginning with the statute’s language. Artichoke Joe’s Cal.
Grand Casino v. Norton, 353 F.3d 712, 720 (9th Cir. 2003)
(internal quotation marks omitted). We “presume that [the]
legislature says in a statute what it means and means in a
statute what it says.” BedRoc Ltd., LLC v. United States,
541 U.S. 176, 183 (2004) (internal quotation marks omitted).
“The plainness or ambiguity of statutory language is
determined by reference to the language itself, the specific
context in which the language is used, and the broader
context of the statute as a whole.” Geo-Energy Partners-
1983 Ltd., 613 F.3d at 956 (internal quotation marks omitted).
If “the language is not dispositive, we look to the
congressional intent revealed in the history and purposes of
the statutory scheme.” Artichoke Joe’s, 353 F.3d at 720
(internal quotation marks omitted). “[I]f we find that the
statutory meaning is plain and unambiguous, then our ‘sole
18                 PIT RIVER TRIBE V. BLM

function . . . is to enforce it according to its terms.’”
Hernandez v. Williams, Zinman & Parham PC, 829 F.3d
1068, 1072 (9th Cir. 2016) (alteration in original) (quoting
United States v. Ron Pair Enters., 489 U.S. 235, 241 (1989));
see Chevron, U.S.A., Inc. v. Nat. Res. Def. Council, Inc.,
467 U.S. 837, 842–43 (1984) (“If the intent of Congress is
clear, that is the end of the matter; for the court, as well as the
agency, must give effect to the unambiguously expressed
intent of Congress.”).

    We begin with the GSA’s text, and observe that § 1005(a)
does not include the term “unit plan.” See 30 U.S.C.
§ 1005(a). It is not our practice to read words into statutory
provisions, see United States v. Watkins, 278 F.3d 961, 965
(9th Cir. 2002), as a statute’s plain language is “our primary
guide to Congress’ preferred policy.” Sandoz Inc. v. Amgen
Inc., 137 S. Ct. 1664, 1678 (2017) (internal quotation marks
omitted). Relatedly, we have observed that:

        It is a well-established canon of statutory
        interpretation that the use of different words
        or terms within a statute demonstrates that
        Congress intended to convey a different
        meaning for those words. Congress’s explicit
        decision to use one word over another in
        drafting a statute is material. It is a decision
        that is imbued with legal significance and
        should not be presumed to be random or
        devoid of meaning.

SEC v. McCarthy, 322 F.3d 650, 656 (9th Cir. 2003) (internal
citations omitted). “[W]hen Congress includes particular
language in one section of a statute but omits it in another
section of the same Act, it is generally presumed that
                  PIT RIVER TRIBE V. BLM                     19

Congress acts intentionally and purposely in the disparate
inclusion or exclusion.” Barnhart v. Sigmon Coal Co.,
534 U.S. 438, 452 (2002) (internal quotation marks omitted).
We conclude that the use of “unit plan” in § 1005(c) and
(g)(1) expressly memorialized congressional intent to make
short lease extensions available on a unit-wide basis if leases
do not become productive during their primary terms but
lease operators can show that drilling has commenced or
other bona fide efforts have been made. In other words, we
conclude that the omission of the term “unit plan” in
§ 1005(a) is “imbued with legal significance.” McCarthy,
322 F.3d at 656.

    BLM argues that Congress’s omission of the term “unit
plan” from § 1005(a) is not a rejection of the unitization
principle because the subsection must be read in conjunction
with the GSA as a whole and against the historical backdrop
of the MLA. This argument is premised on BLM’s unstated
assertion that geothermal steam reservoirs function in the
same way that underground pools of oil and gas do. Prior to
oral argument, the record contained no support for this
assertion. After oral argument, BLM submitted a letter
explaining that overdrilling in geothermal fields results in a
loss of well pressure, just like oil and gas fields. As support,
BLM’s letter cited a public document that reported on the
rapid development of a northern California hydrothermal
system and the resulting loss of production well pressure. Pit
River has not had a chance to respond, but even assuming that
geothermal reservoirs function the same way as oil and gas
reservoirs do, the general framework Congress adopted in the
MLA does not overcome the plain language Congress chose
for the GSA’s primary term and unitization provisions.
20                PIT RIVER TRIBE V. BLM

    BLM argues that the MLA provides important context
and that the incorporation of the unitization principle into the
MLA suggests Congress intended to adopt the same statutory
scheme for the GSA. We disagree. Congress enacted the
MLA decades before it enacted the GSA, and we assume
Congress is knowledgeable about existing law when it enacts
new legislation. See Miles v. Apex Marine Corp., 498 U.S.
19, 32 (1990); see also Cty. of Amador, 872 F.3d at 1022
(“[U]nderstanding the historical context in which a statute
was passed can help to elucidate the statute’s purpose and the
meaning of statutory terms and phrases.”). The GSA’s
sponsor understood the 1970 bill to generally permit the
Secretary of Interior to lease public lands in “much the same
manner” as the Secretary was authorized to do by the MLA.
S. Rep. No. 91-1160, at 4 (1970). But Congress recognized
that efforts to harness geothermal steam in an emerging
market posed unique challenges. See H.R. Rep. No. 91-1544,
at 3–4 (1970). By 1970, the MLA was in its fiftieth year of
regulating oil and gas leasing but the geothermal steam
industry was still in its infancy. Congress acknowledged that
the mining and mineral leasing statutes “lack many of the
requirements necessary to encourage [geothermal steam’s]
orderly development.” Id. at 5. The hope was that the GSA
would “establish a framework that will make this risk-laden,
relatively untried industry an attractive investment in the
public interest.” S. Rep. No. 91-1160, at 9. Recognizing the
need to encourage geothermal exploration by allowing
leaseholders time to get the resource to market—or to bring
the market to the geothermal steam by building
infrastructure—the GSA’s original sponsor acknowledged
“there may be some reasonable delay beyond the expiration
of the primary term before a generating facility can be
installed to receive the steam and commence actual power
                     PIT RIVER TRIBE V. BLM                          21

production.”13 S. Rep. No. 91-1160, at 8. Contrary to BLM’s
argument, the text of the GSA, read as a whole, demonstrates
that Congress deviated from the MLA when it adopted the
GSA, perhaps because it was aware of the need to
accommodate the uniquely-situated geothermal steam
technology and developing market.

    A comparison of the GSA’s primary term provision,
§ 1005(a), and the MLA’s primary term provision, 30 U.S.C.
§ 226(e), reveals notable differences. Section 226(e) is
entitled “Primary terms” and it expressly incorporates the
phrase “unit plan.” Section 226(e) governs primary lease
term continuations and extensions thereafter. Congress did
not adopt § 226(e) wholesale when it enacted the GSA;
rather, it split this provision into two subsections. Section
1005(a) authorizes primary term continuations and § 1005(c)
separately authorizes post-primary term extensions and
production-based continuations. BLM describes the decision
to divide § 226(e) into § 1005(a) and (c) in the GSA as a
stylistic choice, but we are mindful that Congress could have
replicated the MLA’s primary term provision (including the
“unit plan” language) directly into the statutory text of GSA
§ 1005(a), and it did not do so.

    BLM goes on to argue that the GSA provision authorizing
unit plans, 30 U.S.C. § 1017, authorizes § 1005(a)’s
production-based continuations to be granted on a unit-wide


    13
       Indeed, even as of 1988, Congress acknowledged the challenges
involved in harnessing geothermal energy. H.R. Rep. No. 100-664, at 6
(1988) (“Unlike coal, oil and gas which can be transported to power
production facilities, the steam from a geothermal well cannot be
transported more than two miles because of heat dissipation,” and must be
converted to electricity at or near the well site.).
22                   PIT RIVER TRIBE V. BLM

basis because § 1017 is fairly read to broadly incorporate the
MLA’s unitization framework into the GSA. We are not
persuaded that so much can be read into § 1017. First,
BLM’s reasoning “would require us to assume that Congress
chose a surprisingly indirect route to convey an important and
easily expressed message.” Landgraf v. USI Film Prods.,
511 U.S. 244, 262 (1994). See generally Zachary v. Cal.
Bank & Tr., 811 F.3d 1191, 1198–99 (9th Cir. 2016)
(rejecting statutory reading that reflected a policy choice
Congress could have made “in a far more straightforward
manner”). Section 1017 authorizes unit agreements and
constriction of unit plans, requiring that, no more than five
years after approval of a unit plan (and at least every five
years thereafter), the Secretary of the Interior must eliminate
leases “not regarded as reasonably necessary to . . . unit
operations.”14 30 U.S.C. § 1017. Section 1017 further
provides that leases eliminated from a unit by the constriction
process may receive extensions pursuant to § 1005(c) and (g)
only if they separately qualify.15 Id. The language in § 1017
represents a significant departure from the MLA’s corollary
provision governing unit plans, MLA § 226(j). The MLA
allows lessees to form unit plans for development, but it
expressly allows leases to be continued indefinitely on a unit-
wide basis—for as long as production continues. See
30 U.S.C. § 226(j). Setting aside renewals authorized by


     14
       Section 1017 also provides that this “elimination shall be based on
scientific evidence, and shall occur only when it is determined by the
Secretary to be for the purpose of conserving and properly managing the
geothermal resource.”
     15
       BLM argues that this language reaffirms the unitization principle.
But the impact of this language is limited. It merely confirms that leases
constricted from a unit plan must individually qualify for extensions under
§ 1005(c) or (g); it says nothing about continuations under § 1005(a).
                  PIT RIVER TRIBE V. BLM                    23

§ 1005(b) and (g)(3), all GSA lease terms are capped at fifty
years. The MLA also differs from the GSA by not requiring
plan review every five years for constriction of the unit plan.
See id. In sum, we agree that the MLA provides context for
considering the terms of the GSA, but it cannot be doubted
that Congress varied from the MLA when it fashioned
§§ 1005 and 1017, and the MLA’s unitization framework
does not require the conclusion BLM urges us to reach.

   BLM next argues that the following language in
§ 1005(g)(1) demonstrates that § 1005(a) authorizes
continuations on a unit-wide basis:

       Any geothermal lease issued pursuant to this
       chapter for land on which, or for which under
       an approved cooperative or unit plan of
       development or operation, geothermal steam
       has not been produced or utilized in
       commercial quantities by the end of its
       primary term, or by the end of any extension
       provided by subsection (c) . . . may be
       extended for successive 5-year periods[.]

§ 1005(g)(1). Congress added this provision in 1988 to help
non-productive leases withstand adverse market conditions
created by a world energy glut. See H.R. Rep. No. 100-664,
at 6 (1988). As BLM’s argument goes, because § 1005(g)(1)
allows unproductive leases in unit plans to be extended for
five years on a unit-wide basis if they remain unproductive at
the end of their primary terms, and because it also provides
that leases are ineligible for § 1005(g)(1) extensions if they
have received § 1005(a) continuations, then § 1005(g)(1)
must be read as confirmation that § 1005(a) authorizes
production-based continuations on a unit-wide basis. Again,
24                PIT RIVER TRIBE V. BLM

we are not persuaded. BLM’s reasoning overlooks the most
straightforward reading of the statute: Regardless of the
combination of primary term, continuations or extensions,
Congress capped the terms of geothermal leases at fifty years.
Consistent with this scheme, leases that receive forty-year
continuations under § 1005(a) after becoming productive
during their ten-year primary terms are ineligible for the
shorter extensions allowed for unproven leases. BLM also
overlooks that § 1005(a) says nothing about unit plans, and
that § 1005(g)(1) only authorizes extensions, on an individual
or a unit-wide basis, for leases that do not become productive
during their primary terms or § 1005(c) extensions. Contrary
to BLM’s conclusion, it was entirely consistent for Congress
to have provided short unit-wide extensions under § 1005(c)
and (g)(1) for unproductive leases that do not individually
qualify for lengthy continuations during their primary terms.

     BLM also argues that because GSA § 1005(c) and (g)(2)
authorize continuations on a unit-wide basis for leases that
produce steam in commercial quantities during extended
terms, it “defies logic” to think that Congress did not intend
to provide unit-wide rewards for production achieved during
initial primary lease terms. The reason Congress chose not to
incorporate the unitization principle into the GSA’s primary
term provision is not fully explained by the statute, but in the
ordinary case, “our obligation is to apply the statute as
Congress wrote it.” Hubbard v. United States, 514 U.S. 695,
703 (1995). We have explained why we are not persuaded by
BLM’s premise that § 1005(a) must allow continuations on
a unitized basis because the GSA’s primary term provision
was modeled after the MLA’s primary term provision.
Further, given the nature of the emerging geothermal steam
market, Congress may have opted against unit-wide
continuations during primary terms as a way of incentivizing
                  PIT RIVER TRIBE V. BLM                    25

exploration on all leases to define the contours of the
productive area during the primary term. The decision not to
incorporate unit-wide continuations during the primary term
still allows leaseholders to benefit from unitization through
cost and royalty sharing. It is also consistent with § 1017’s
mandatory review of unit plans every five years, and with the
requirement that unit areas be constricted to eliminate leases
not reasonably necessary to unit operations. See 30 U.S.C.
§ 1017. Congress may have been concerned that granting
unit-wide continuations during the initial ten-year term would
impede development by encouraging operators to select
drilling targets based on whether leases were committed to
units, rather than on the areas with the greatest potential for
production. This is the very concern BLM expressed in 1995.
Whatever the case, on the record before us, we do not agree
with BLM’s assertion that it defies logic to conclude that
Congress did not intend to authorize production-based
continuations on a unitized basis during primary terms.

    BLM’s final argument is that § 1005(a)’s legislative
history shows that Congress intended the terms of all leases
in a unit to benefit if any one of them becomes productive
during the primary term. BLM points us to a 1970 House
Report:

       Section 6 of the bill provides that each
       geothermal lease shall be for a primary term
       of 10 years. If steam is produced or utilized
       in commercial quantities within this term the
       lease will continue for so long thereafter as
       such production or utilization continues, but
       not to exceed an additional 40 years. If at the
       end of such 40 years steam continues to be
       produced in commercial quantities, and the
26                  PIT RIVER TRIBE V. BLM

        land is not needed for other purposes, the
        lessee is given a preferential right to a renewal
        of the lease for a second 40-year period in
        accordance with such terms and conditions as
        the Secretary deems appropriate. Comparable
        provision is also made respecting lands leased
        for development under approved cooperative
        and unit plans.

H.R. Rep. No. 91-1544, at 7 (1970) (emphasis added). BLM
argues that the “comparable provision” for leases committed
to unit plans must be § 1017. But it is equally likely that,
when Congress passed the GSA in 1970, this passage was
intended to differentiate § 1005(a) from § 1005(c), the only
provision then authorizing development on a unit-wide
basis.16 In other words, the passage that BLM relies on may
highlight that Congress adopted a lease-by-lease approach for
production-based continuations during the primary term in
§ 1005(a), and that § 1005(c) authorized a separate but
comparable unit-wide approach for five-year extensions
granted after primary terms, based on drilling. Absent further
context or explanation in the House Report, we find its
reference to “comparable provision” to be inconclusive. See
Flores-Arellano v. INS, 5 F.3d 360, 362 (9th Cir. 1993)
(ruling that inconclusive legislative history was insufficient
to overcome unambiguous statutory text). It is BLM’s burden
to provide a compelling reason for us to depart from the plain
language of § 1005(a), and we conclude it has not met that
burden here.




    16
       Section 1005(g)—the other provision authorizing development on
a unit-wide basis—was not added to the GSA until 1988.
                 PIT RIVER TRIBE V. BLM                   27

                      VI. Conclusion

    The statutory meaning of 30 U.S.C. § 1005(a) is clear and
unambiguous. It only permits production-based continuations
on a lease-by-lease basis, not on a unit-wide basis. We
therefore affirm the district court’s order granting summary
judgment in favor of the appellees.

   AFFIRMED.
