 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued November 12, 2019           Decided February 14, 2020

                        No. 19-5131

                  GOVERNMENT OF GUAM,
                       APPELLEE

                              v.

                UNITED STATES OF AMERICA,
                       APPELLANT


        Appeal from the United States District Court
                for the District of Columbia
                    (No. 1:17-cv-02487)


    Rachel Heron, Attorney, U.S. Department of Justice,
argued the cause for appellant United States of America. With
her on the briefs were Eric Grant, Deputy Assistant Attorney
General, and Evelyn Ying and Michael Augustini, Attorneys.

    John D.S. Gilmour argued the cause for plaintiff-appellee.
With him on the brief were Bezalel A. Stern, William J.
Jackson, and Mark Donatiello. Fabio Dworschak entered an
appearance.

    Before: HENDERSON and TATEL, Circuit Judges, and
GINSBURG, Senior Circuit Judge.

    Opinion for the Court filed by Circuit Judge TATEL.
                               2

     TATEL, Circuit Judge: For nearly half a century, the United
States Navy operated a landfill on the island of Guam. Home
to discarded munitions, chemicals, and everyday garbage, the
so-called Ordot Dump lacked any sort of environmental
safeguards. At bottom, this case concerns whether Guam or the
Navy is financially responsible for the environmental hazards
arising from the Ordot Dump. The answer to that question turns
on the interaction between two provisions of the
Comprehensive Environmental Response, Compensation, and
Liability Act (CERCLA): section 107, the act’s “cost-
recovery” provision, and section 113, its “contribution”
provision. See 42 U.S.C. §§ 9607, 9613(f). If Guam must
proceed under section 113, then its suit against the Navy for
costs related to the dump is now time-barred. But if it may
utilize section 107, then its suit remains timely. As explained
below, we conclude that a 2004 consent decree with EPA
triggered Guam’s right to pursue a contribution claim under
section 113, precluding it from now pursuing a claim under
section 107. We therefore reverse the district court’s contrary
conclusion and remand with instructions to dismiss.

                               I.

     Congress enacted CERCLA, 42 U.S.C. §§ 9601 et seq., “in
response to the serious environmental and health risks posed
by industrial pollution,” United States v. Bestfoods, 524 U.S.
51, 55 (1998). Seeking to enable the “prompt cleanup of
hazardous waste sites and to ensure that responsible parties foot
the bill,” General Electric Co. v. Jackson, 610 F.3d 110, 114
(D.C. Cir. 2010), CERCLA directs that any potentially
responsible party— “PRP” for short—“shall be liable” for the
costs associated with the release of hazardous substances and
subsequent cleanup of polluted sites, CERCLA § 107(a).
                                3
     Remediation at Superfund sites is, unsurprisingly,
expensive. Central to CERCLA’s operation is a mechanism for
entities to seek recoupment of any cleanup costs incurred from
other responsible parties. As originally drafted, CERCLA
provided that “any person” potentially responsible for
hazardous waste “shall be liable for . . . all costs of removal or
remedial action incurred by the United States Government or a
State or an Indian tribe,” CERCLA § 107(a)(4)(A), as well as
“any other necessary costs of response incurred by any other
person,” id. § 107(a)(4)(B) (emphasis added). While CERCLA
“did not mandate ‘joint and several’ liability in every case,”
Burlington Northern & Santa Fe Railway Co. v. United States,
556 U.S. 599, 613 (2009), “[t]he practical effect of placing the
burden on defendants has been that responsible parties rarely
escape joint and several liability,” O’Neil v. Picillo, 883 F.2d
176, 178–79 (1st Cir. 1989), meaning that any one PRP may be
held responsible for the entire cost of a cleanup.

     Although multiple entities may be responsible for a
superfund site, only one may have actually “incurred” “costs of
response”—a necessary predicate to bringing a section 107
claim. CERCLA § 107(a)(4)(A), (B). Following CERCLA’s
passage in 1980, “litigation arose over whether § 107, in
addition to allowing the Government and certain private parties
to recover costs from PRPs, also allowed a PRP that had
incurred response costs”—that is, a PRP that had paid out but
not actually done a cleanup itself—“to recover costs from other
PRPs.” Cooper Industries, Inc. v. Aviall Services, Inc., 543
U.S. 157, 161 (2004). At common law, tortfeasors like PRPs
were typically entitled to “contribution”—a “right to collect
from joint tortfeasors when, and to the extent that, the tortfeasor
has paid more than his or her proportionate share to the injured
party, the shares being determined as percentages of causal
fault.” Contribution, Black’s Law Dictionary (11th ed. 2019).
But as originally passed, “CERCLA contained no provision
                                4
expressly providing for a right of action for contribution;” in
fact, it made no mention of “contribution” at all. Cooper, 543
U.S. at 162.

      Congress addressed this gap in the statutory scheme when
it amended CERCLA through the Superfund Amendments and
Reauthorization Act of 1986, Pub. L. 99–499, 100 Stat. 1613.
Specifically, it added a new section to the Act—section 113—
which “provide[d] two express avenues for contribution.”
Cooper, 543 U.S. at 167. The first, section 113(f)(1), provides
that “[a]ny person may seek contribution from any other person
who is liable or potentially liable under section [107(a)] of this
title, during or following any civil action . . . under section
[107(a)] of this title.” CERCLA § 113(f)(1). The second new
avenue, section 113(f)(3)(B), provides that a party that “has
resolved its liability to the United States or a State for some or
all of a response action or for some or all of the costs of such
action in an administrative or judicially approved settlement
may seek contribution from any person who is not party to a
settlement.” Section 113 also creates special incentives for
PRPs to settle with enforcement authorities. Although that
section broadly allows PRPs to seek contribution from other
PRPs, “[a] person who has resolved its liability to the United
States or a State in an administrative or judicially approved
settlement shall not be liable for claims for contribution
regarding matters addressed in the settlement.” Id. § 113(f)(2).
Settlement with EPA or state authorities therefore inoculates a
party from further contribution liability.

     The upshot is that CERCLA now offers two potential
causes of action for an entity seeking recovery from a PRP: a
section 107 “cost-recovery” action, available for recoupment
of cleanup costs, and a section 113(f) “contribution” action,
available for recoupment of funds paid out pursuant to a section
107 action, a settlement, or another contribution action. Central
                                5
to this case, the statute of limitations for a contribution action
is three years, see CERCLA § 113(g)(3); the statute of
limitations for a remedial section 107 action is six, id.
§ 113(g)(2)(B).

                               II.

     Nearly a century before CERCLA’s passage, the United
States captured the island of Guam following the Spanish-
American War. See Paul Carano & Pedro C. Sanchez, A
Complete History of Guam 169–83 (1964) (describing how
Guam became an American possession). From 1903 until
World War II, the United States treated Guam as a US Naval
ship—the “USS Guam”—and maintained military rule until
the passage of the Guam Organic Act in 1950. Robert F.
Rogers, Destiny’s Landfall: A History of Guam 126, 226
(1995). That act marked the formal transfer of power from the
United States to Guam’s newly formed civilian government, id.
at 226, but until the 1960s, visiting Guam required a military
security clearance, see Exec. Order No. 11045, 3 C.F.R. 238,
238–39 (1962) (discontinuing the Guam Island Naval
Defensive Sea Area and Guam Island Naval Airspace
Reservation). Guam remained, as it had been since the Treaty
of Paris in 1898, an “unincorporated territory of the United
States.” 48 U.S.C. § 1421a.

     Against this colonial backdrop, the Navy constructed and
operated the Ordot Dump for the disposal of municipal and
military waste sometime in the 1940s. Even after relinquishing
sovereignty over the island, however, the Navy continued to
take advantage of the dump. Throughout the Korean and
Vietnam Wars, the Navy used the Ordot Dump for the disposal
of munitions and chemicals, allegedly including
Dichlorodiphenyltrichloroethane—DDT—and Agent Orange,
Am. Compl. ¶ 11. It was “the only sited and operational dump
                                6
on Guam” until the 1970s, and the only public landfill on the
island until its closure in 2011. Id. And as the Navy continued
to use the Ordot Dump, it continued growing; “[w]hat was once
a valley,” the District Court of Guam explained, “is now at least
a 280-foot mountain of trash.” United States v. Guam, No.02-
00022, slip op. at 1 (D. Guam Jan. 24, 2008).

     Despite its extensive use, the Ordot Dump lacked basic
environmental safeguards. “[U]nlined on its bottom and
uncapped at its top,” the landfill absorbed rain and surface
water, which percolated through the landfill and mixed with
contaminants. Am. Compl. ¶ 12. These contaminants released
into the nearby Lonfit River, which flows into the Pago River,
and ultimately into the Pacific Ocean at Pago Bay. Id.

    The Ordot Dump has long attracted the attention of the
United States as regulator. EPA added the Ordot Dump to its
National Priorities List in 1983, and, in 1988, issued a Record
of Decision designating the Navy as a potentially responsible
party for the site. Id. ¶ 13. But having relinquished sovereignty
over the island, the Navy no longer owned and operated the
Ordot Dump—Guam did. And, beginning in 1986, EPA
repeatedly ordered Guam to devise plans for containing and
disposing of waste at the landfill.

     Unsatisfied with Guam’s remediation attempts, EPA sued
Guam in 2002 under the Clean Water Act, 33 U.S.C. §§ 1251
et seq., asserting that Guam violated that act by “discharging
pollutants . . . into waters of the United States without obtaining
a permit.” Complaint for Injunctive Relief, United States v.
Guam, No. 02-00022, at ¶ 26 (D. Guam) (CWA Compl.), Joint
Appendix (J.A.) 86. As EPA explained in its complaint, the
Clean Water Act defines “waters of the United States” as
“including the territorial seas,” id. at ¶ 14, J.A. 85 (quoting 33
U.S.C. § 1362(7), and it alleged that Guam “has routinely
                                7
discharged untreated leachate from the Ordot [Dump] into the
Lonfit River and two of its tributaries,” id. at ¶ 21, J.A. 85. EPA
sought an injunction ordering Guam to comply with the Clean
Water Act, by, among other things, “submit[ting] plans and a
compliance schedule for a cover system for the Ordot Landfill”
and “complet[ing] construction of the cover system to
eliminate discharges of untreated leachate.” Id. ¶ 29, J.A. 86.

     Rather than litigate these claims, Guam and EPA entered
into a consent decree in 2004, which the District Court of Guam
approved. See Consent Decree, United States v. Guam, No. 02-
00022 (D. Guam) (Consent Decree), J.A. 90. That Decree
required Guam, among other things, to pay a civil penalty,
close the Ordot Dump, and design and install a “dump cover
system.” Id. at 5–12, J.A. 94–101. The Decree expressly states
that it “shall apply and be binding upon the Government of
Guam . . . and on the United States on behalf of U.S. EPA,”
and was “based on the pleadings, before taking testimony or
adjudicating any issue of fact or law, and without any finding
or admission of liability against or by the Government of
Guam,” id. at 3, J.A. 92. Although cleanup continues, Guam
officially closed the Ordot Dump in 2011 pursuant to the
Decree.

     Guam initiated this action against the United States in
2017, arguing that the Navy was responsible for the Ordot
Dump’s contamination and seeking to recoup its landfill-
closure and remediation costs. Alleging that the costs of the
Ordot Dump’s required remediation would “exceed
approximately $160,000,000,” Am. Compl. ¶ 15, Guam
brought two causes of action relevant here: a CERCLA section
107(a) claim seeking “removal and remediation costs” related
to the landfill, id. ¶ 25, and, “[i]n the alternative,” a section
113(f) contribution action, id. ¶ 31.
                               8
     The United States moved to dismiss under Federal Rule of
Civil Procedure 12(b)(6), arguing that Guam could not avail
itself of CERCLA section 107(a) because section 113(f)(3)(B)
is “the exclusive CERCLA remedy for the costs a liable party
is compelled to incur pursuant to a judicially-approved
settlement with the United States.” Mot. to Dismiss 18.
Pointing to the 2004 Consent Decree, the United States argued
that Guam had resolved its liability for a response action, and
so had to proceed under section 113 rather than 107. And,
because CERCLA section 113 “imposes a three-year statute of
limitations on contribution claims” that runs from a consent
decree’s entry, the United States argued that Guam was time-
barred from pursuing that claim. Id. at 17, J.A. 61.

     The district court, accepting the premise that “Guam is
permitted to proceed against the United States for full cost
recovery under section 107(a) only if Guam’s right to
contribution under section 113(f)(3)(B) has not been
triggered,” explained that “the key question[] that the pending
motion to dismiss presents is whether the 2004 Consent Decree
‘resolve[d] [Guam’s] liability’ for the response action or
response costs that Guam undertook with respect to the Ordot
Landfill and also qualifies as a ‘settlement’ within the meaning
of” CERCLA’s contribution provision. Guam v. United States,
341 F. Supp. 3d 74, 84 (D.D.C. 2018) (quoting CERCLA
§ 113(f)(3)(B)) (alterations in original). In a thorough opinion,
the district court explained that “whether or not an agreement
for the removal or remediation of hazardous waste ‘resolves’
liability for section 113(f)(3)(B) purposes turns on the terms of
the agreement,” and concluded that “the 2004 Consent Decree
did not resolve Guam’s liability for the Ordot Landfill
cleanup.” Id. Because the Decree failed to meet the “statutorily
prescribed conditions for bringing a contribution claim under
section 113(f)(3)(B),” the court ruled that Guam could
                                 9
maintain its section 107(a) claim against the United States and
denied the United States’ motion to dismiss. Id.

      The United States sought interlocutory appeal of the
district court’s order pursuant to 28 U.S.C. § 1292(b). The
district court, noting that “the courts of appeals diverge . . . with
respect to how one best interprets agreement language” of the
kind presented here, concluded that “there is substantial ground
for difference of opinion regarding at least one controlling
issue of law . . . , and that allowing the United States to appeal
. . . could materially advance this litigation,” and certified the
interlocutory appeal of the order. Guam v. United States, No.
1:17-CV-2487, 2019 WL 1003606, at *1 (D.D.C. Feb. 28,
2019) (internal quotation marks omitted). We granted the
request for interlocutory review. “We review de novo the
District Court’s legal conclusions denying a motion to
dismiss.” Liff v. Office of Inspector General for U.S.
Department of Labor, 881 F.3d 912, 918 (D.C. Cir. 2018).

                                III.

     The first question we must decide, as it underlies this
dispute, is whether CERCLA sections 107 and 113 are
mutually exclusive. That is, if a party incurs costs pursuant to
a settlement and therefore has a cause of action under section
113, is it precluded from seeking cost-recovery under section
107?

     While the differences between CERCLA sections 107 and
113 seem clear in theory, the supposedly sharp distinction
between cost-recovery and contribution does not always play
out in practice. Although the two actions are separate, some
situations ostensibly fall under both CERCLA provisions. As
the Supreme Court explained in United States v. Atlantic
Research Corp., 551 U.S. 128 (2007), “a PRP may sustain
                               10
expenses pursuant to a consent decree” that involve cleanup
costs. Id. at 139 n.6. “In such a case, the PRP does not incur
costs voluntarily,” as one would while undertaking a cleanup,
“but [also] does not reimburse the costs of another party,” as
one would in a traditional contribution action. Id. Having
settled with the Government, the PRP is authorized to pursue a
section 113(f)(3)(B) contribution action, but because it has
incurred cleanup costs, the recoupment of those funds would
arguably also fall within section 107. In other words, given that
“neither remedy swallows the other,” id., both cost-recovery
and contribution actions appear available.

     In Atlantic Research, the Supreme Court “d[id] not decide
whether these compelled costs of response are recoverable
under § 113(f), § 107(a), or both.” Id. To date, neither have we.
But “every federal court of appeals to have considered the
question since Atlantic Research . . . has said that a party who
may bring a contribution action for certain expenses must use
the contribution action, even if a cost recovery action would
otherwise be available.” Whittaker Corp. v. United States, 825
F.3d 1002, 1007 (9th Cir. 2016); see id. at 1007 n.5 (collecting
cases).

     Today we join our sister circuits. The entire purpose of
section 113(f)(3)(B) is to “permit[] private parties to seek
contribution after they have settled their liability with the
Government.” Atlantic Research Corp., 551 U.S. at 132 n.1.
Allowing a PRP that has settled with the government to instead
seek recoupment through a section 107 cost-recovery claim
would render section 113(f)(3)(B) superfluous; if a PRP could
choose whether to sue under section 107 or section 113, “a
rational PRP would prefer to file an action under § 107(a)[] in
every case.” Hobart Corp. v. Waste Management of Ohio, Inc.,
758 F.3d 757, 767 (6th Cir. 2014). Like any statute, CERCLA
must be “read as a whole,” King v. St. Vincent’s Hospital, 502
                                11
U.S. 215, 221 (1991), and we decline to interpret section
113(f)(3)(B) as providing superfluous relief to a party that has
settled with the United States or a State.

     Having concluded that section 113(f)(3)(B) and section
107 are mutually exclusive, we must address one more
threshold issue. Section 113(f)(3)(B) reads: “A person who has
resolved its liability to the United States . . . for some or all of
a response action or for some or all of the costs of such action
in a[] . . . judicially approved settlement may seek contribution
from any person who is not party to a settlement referred to in
paragraph (2).” CERCLA § 113(f)(3)(B) (emphasis added).
Paragraph (2), in turn, provides that “[a] person who has
resolved its liability to the United States or a State in an
administrative or judicially approved settlement shall not be
liable for claims for contribution regarding matters addressed
in the settlement.” Id. § 113(f)(2). Here, we face an unusual
situation: the United States, through the Navy, is a potentially
responsible party, but the United States, through EPA, is also
the regulator that has brought the enforcement action. At first
blush, the “not party to a settlement” language would seem to
preclude a contribution suit by Guam against the United States
regardless of whether the settlement otherwise triggers
section 113(f)(3)(B); after all, the United States is a “party to a
settlement” with Guam.

     CERCLA “is not a model of legislative draftsmanship,”
Exxon Corp. v. Hunt, 475 U.S. 355, 363 (1986), and, read
literally, section 113(f)(3)(B)’s “not party to a settlement”
language could create non-sensical results. For example,
imagine hypothetical Company X settles with EPA for the
costs of response actions for a contaminated site in California
in 1990. By virtue of becoming “party to a settlement,”
Company X would gain immunity from any future section
113(f)(3)(B) action, even if that action were to arise decades
                               12
later for an entirely unrelated site in Massachusetts. The very
first time an agency of the United States settled with a
potentially responsible party at any site, moreover, that agency
would become wholly immune to section 113(f)(3)(B) claims
at every site where it may be a responsible party. “A fair
reading of legislation demands a fair understanding of the
legislative plan,” King v. Burwell, 135 S. Ct. 2480, 2496
(2015), and given that section 113 clearly seeks to incentivize
private parties to settle with the United States, we decline to
read the “not party to a settlement” language as forever
foreclosing contribution actions against any party that has ever
settled any qualifying claim.

      The United States offers two alternative interpretations.
First, it argues that reading sections 113(f)(2) and 113(f)(3)(B)
together demonstrates that the phrase “any person who is not
party to a settlement referred to in paragraph (2)” simply means
any person not insulated from such a contribution claim by a
section 113(f)(2) settlement. Appellant’s Suppl. Br. 7.
Alternatively, it argues that, even if the phrase means that a
contribution action could not be brought against any party to
any settlement whatsoever, it does not matter here because the
Consent Decree was a settlement between Guam and the EPA
and Guam’s contribution action is against the Navy—a
different federal agency. Id. at 7-9. Because we agree with the
first alternative, we need not address the second.

      Congress enacted Section 113(f) to bring PRPs “to the
bargaining table at an early date.” Asarco LLC v. Atl. Richfield
Co., 866 F.3d 1108, 1117 (9th Cir. 2017) (quoting Whittaker
Corp., 825 F.3d at 1013 (Owens, J., concurring)). Section
113(f) accomplishes this goal by providing two benefits to such
PRPs: a “defensive benefit” to PRPs who decide to resolve
their liability by entering a settlement with the United States or
with a State and are thereby protected against contribution
                               13
actions brought by other PRPs regarding matters included in
the settlement, see CERCLA § 113(f)(2); and an “offensive
benefit” to those same PRPs who, again, in exchange for
resolving their liability, can pursue other PRPs for contribution,
see id. § 113(f)(3)(B).

      Reading these two sections in pari materia, we interpret
the phrase “any person who is not party to a settlement referred
to in paragraph (2)” in section 113(f)(3)(B) to mean that one
benefit does not cancel out the other. See Motion Picture
Association of America, Inc. v. F.C.C., 309 F.3d 796, 801 (D.C.
Cir. 2002) (“Statutory provisions in pari materia normally are
construed together to discern their meaning.”). Section
113(f)(3)(B) provides that a person who has resolved its
liability with the United States or a State can pursue a
contribution action against any person but it notes that the right
to seek contribution does not erase the protection provided
under section 113(f)(2). For example, if Company A resolves
its liability for a response action with the United States, it is
protected under section 113(f)(2) from future contribution
actions related to its settlement with the United States. The fact
that Company B subsequently also resolves its liability to the
United States in a related action—and can thereby initiate a
contribution action against “any person” under section
113(f)(3)(B)—cannot mean that Company A’s protection
under section 113(f)(2) is forfeited, leaving it vulnerable to a
contribution suit by Company B. This is what the phrase “any
person who is not party to a settlement referred to in paragraph
(2)” clarifies. Another way to view the two provisions working
in tandem is to think of the above hypothetical in reverse. As
the Third Circuit has explained, “[i]t appears that the statute
allows the government to immunize a late settlor from an early
settlor’s contribution suit by settling with the government.”
United States v. Alcan Aluminum, Inc., 25 F.3d 1174, 1186 (3d
Cir. 1994); see also J. Whitney Pesnell, The Contribution Bar
                               14
in CERCLA Settlements and Its Effect on the Liability of
Nonsettlors, 58 La. L. Rev. 167, 231 (1997) (“[Section
113(f)(2)] provides, in no uncertain terms, that parties who
have resolved their liability to the government in a judicially
approved settlement, such as the parties to the second
settlement, shall not be liable for claims for contribution
regarding matters addressed in the settlement.”).

     This interpretation is supported by the fact that Congress
chose to reference “paragraph (2)” within section 113(f)(3)(B).
“[W]e are obliged to give effect, if possible, to every word
Congress used.” Reiter v. Sonotone Corp., 442 U.S. 330, 339
(1979). In section 113(f)(3)(B), Congress did not state “any
person who is not party to a settlement” alone; instead, it
specifically stated “any person who is not a party to a
settlement referred to in paragraph (2).” CERCLA
§ 113(f)(3)(B) (emphasis added). A settlement included in
“paragraph (2)” means a settlement entered into by a person to
resolve its liability to the United States or a State in order to
secure protection from a contribution action. Therefore, giving
effect to section 113(f)(3)(B)’s express reference to section
113(f)(2) and reading that section in harmony with section
113(f)(3)(B), we think it quite clear that section 113(f)(3)(B)
allows a person to seek contribution from any person other than
those persons protected by their own settlement under section
113(f)(2). Put differently, a person may not use section
113(f)(3)(B) to seek contribution against a person who has
resolved its liability through a settlement agreement under
section 113(f)(2) to the extent the contribution action involves
matters addressed in that settlement.

     Here, the “any person who is not a party” language in
section 113(f)(3)(B) does nothing to prohibit Guam’s
contribution action. Guam is not attempting to pursue a
contribution action against a PRP that has already resolved its
                                15
liability to the United States or a State and is thus protected by
section 113(f)(2). The key inquiry, then, is this: did the 2004
Consent Decree “resolve [Guam’s] liability” for a response
action within the meaning of section 113(f)(3)(b), thus
triggering Guam’s right to seek contribution and precluding it
from seeking cost-recovery under section 107? It is to that
question we now turn.

                                A.

     In order to trigger CERCLA section 113(f)(3)(B), a party
must have “resolved its liability to the United States or a State
for some or all of a response action or for some or all of the
costs of such action in a[] . . . judicially approved settlement.”
CERCLA § 113(f)(3)(B). Guam contends that the 2004
Consent Decree cannot qualify as a settlement under CERCLA
because it settled an action brought by EPA under the Clean
Water Act, not CERCLA. In Guam’s view, the Consent Decree
“requires reference to CERCLA to trigger a Section
113(f)(3)(B) claim.” Appellee’s Br. 26 n.11.

     “Whether a non-[CERCLA] settlement agreement may
give rise to a contribution action has split the circuits,” three to
one. Asarco, 866 F.3d at 1119. As the Ninth Circuit recently
explained, both it and the Third Circuit have concluded that
“Congress did not intend to limit § 113(f)(3)(B) to response
actions and costs incurred under CERCLA settlements,” and
that “a non-[CERCLA] settlement agreement may form the
necessary predicate for a § 113(f)(3)(B) contribution action.”
Id. at 1120–21; see also Trinity Industries, Inc. v. Chicago
Bridge & Iron Co., 735 F.3d 131, 136 (3d Cir. 2013) (same).
The Seventh Circuit has recently concluded the same. See
Refined Metals Corp. v. NL Industries Inc., 937 F.3d 928, 932
(7th Cir. 2019) (“[Section] 113(f)(3)(B) . . . does not limit
covered settlements to those that specifically mention
                               16
CERCLA.”). The Second Circuit has gone the other way,
holding that section 113(f)(3)(B) creates a “contribution right
only when liability for CERCLA claims . . . is resolved.”
Consolidated Edison Co. of New York, Inc. v. UGI Utilities,
Inc., 423 F.3d 90, 95 (2d Cir. 2005). More recently, however,
the Second Circuit cast doubt on that holding, noting that EPA
“understandably takes issue” with that case and that “there is a
great deal of force to [its] argument.” Niagara Mohawk Power
Corp. v. Chevron USA, Inc., 596 F.3d 112, 126 n.15 (2d Cir.
2010).

      We agree with the Third, Seventh, and Ninth Circuits that
section 113(f)(3)(B) does not require a CERCLA-specific
settlement. As the Seventh and Ninth have pointed out, another
provision of section 113—paragraph (f)(1)—expressly
requires that a party first be sued under CERCLA section 106
or 107 before pursuing contribution. See CERCLA § 113(f)(1)
(“Any person may seek contribution from any other person
who is liable or potentially liable under section [1]07(a) of this
title, during or following any civil action under section [1]06
of this title or under section [1]07(a) of this title.”) (emphasis
added). But section 113(f)(3)(B) contains no such CERCLA-
specific language, and “where 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 Congress
acts intentionally and purposely in the disparate inclusion or
exclusion,” Russello v. United States, 464 U.S. 16, 23 (1983)
(internal citation, alterations and quotation marks omitted). We
therefore conclude that a settlement agreement can trigger
section 113(f)(3)(B) even if it never mentions CERCLA.

                               B.

   But that conclusion gets us only so far. The fact that a non-
CERCLA settlement can trigger section 113(f)(3)(B) tells us
                               17
little about whether the 2004 Consent Decree, in fact,
“resolve[d] [Guam’s] liability” for some or all of the response
action or response costs that Guam undertook with respect to
the Ordot Dump. “Whether or not liability is resolved through
a settlement” is unanswerable by a “universal rule;” it instead
requires examination of “the terms of the settlement on a case-
by-case basis.” Bernstein v. Bankert, 733 F.3d 190, 213 (7th
Cir. 2013). Because “a consent decree . . . is essentially a
contract,” a court’s “construction of a consent decree is
essentially a matter of contract law,” Segar v. Mukasey, 508
F.3d 16, 21 (D.C. Cir. 2007) (internal quotation marks
omitted), and where, as here, that consent decree binds the
United States, that contract is “governed exclusively by federal
law,” Boyle v. United Technologies Corp., 487 U.S. 500, 504
(1988).

     We begin with CERCLA’s text. The phrase “resolved its
liability” is nowhere defined in the statute, meaning our
interpretation of these words should start “with their ordinary
meaning.” BP American Production Co. v. Burton, 549 U.S.
84, 91 (2006). The word “resolve” usually means “to deal with
successfully,” “reach a firm decision about,” or “work out the
resolution” of something. Resolve, Merriam-Webster’s
Collegiate Dictionary 997 (10th ed. 1997). Our sister circuits
have likewise concluded that in the context of section
113(f)(3)(B), “resolved” means “decided, determined, or
settled—finished, with no need to revisit,” Bernstein, 733 F.3d
at 211, that is, a “firm decision” that is no longer “susceptible
to further dispute or negotiation,” Asarco, 866 F.3d at 1122
(internal quotation marks omitted). The word “[l]iability,” in
turn, means an “obligat[ion] according to law or equity.”
Liability, Merriam-Webster’s Collegiate Dictionary 670 (10th
ed. 1997); see also Liability, Black’s Law Dictionary (11th ed.
2019) (“the quality, state, or condition of being legally
obligated or accountable; legal responsibility to another or to
                              18
society, enforceable by civil remedy or criminal punishment.”);
Asarco, 866 F.3d at 1124 (“a settlement agreement must
determine a PRP's compliance obligations”) (emphasis added).
Taking the phrase “resolved its liability” as a whole, we think
it clear that “a PRP’s liability must be decided, determined, or
settled, at least in part, by way of agreement with the EPA.”
Bernstein, 733 F.3d at 212 (emphasis in original removed).

     So far, so good—but liability for what? Recall that
section 113(f)(3)(B) kicks in where a party has resolved its
liability for “some or all of a response action” or for some or
all “of the costs of such action.” CERCLA § 113(f)(3)(B)
(emphasis added). As Guam readily admits, “‘[r]esponse’ is a
term of art in CERCLA,” Appellee’s Br. 9, and it entails a wide
range of actions. Specifically, “response” is defined as any
“removal . . . and remedial action; [and] all such terms
(including the terms ‘removal’ and ‘remedial action’) include
enforcement activities related thereto.” CERCLA § 101(25).
“Removal,” in turn, is defined as “the cleanup or removal of
released hazardous substances from the environment,” “such
actions as may be necessary to monitor, assess, and evaluate
the release or threat of release of hazardous substances,” “the
disposal of removed material,” or “other actions as may be
necessary to prevent, minimize, or mitigate damage to the
public health or welfare or to the environment.” Id. § 101(23).
And “remedy” or “remedial action” means “actions consistent
with permanent remedy taken instead of or in addition to
removal actions in the event of a release or threatened release
of a hazardous substance into the environment,” or actions “to
prevent or minimize the release of hazardous substances so that
they do not migrate to cause substantial danger to present or
future public health or welfare or the environment.” Id.
§ 101(24). And there is more: remedial action includes
“storage, confinement, perimeter protection using dikes,
trenches, or ditches, clay cover, neutralization, cleanup of
                              19
released hazardous substances and associated contaminated
materials, recycling or reuse, diversion, destruction,
segregation of reactive wastes, dredging or excavations,” as
well as the “repair or replacement of leaking containers,
collection of leachate and runoff, onsite treatment or
incineration, provision of alternative water supplies, and any
monitoring reasonably required to assure that such actions
protect the public health and welfare and the environment.” Id.
Section 113(f)(3)(B) comes into play, therefore, when a party
has resolved its liability for “some or all” of any of the above
actions.

     By its plain terms, the 2004 Consent Decree “resolve[d]”
Guam’s liability for “some . . . of a response action.” The
Consent Decree provides that it “shall be in full settlement and
satisfaction of the civil judicial claims of the United States
against the Government of Guam as alleged in the Complaint
filed in this action.” Consent Decree ¶ 45, J.A. 112. EPA’s
Complaint, in turn, sought an injunction requiring Guam to
comply with the Clean Water Act, by, among other things,
“submit[ting] plans and a compliance schedule for a cover
system for the Ordot Landfill” and for “complet[ing]
construction of the cover system to eliminate discharges of
untreated leachate.” CWA Complaint ¶ 29, J.A. 86. The
Consent Decree further obligates Guam to design and install a
“dump cover system.” Consent Decree ¶ 8, J.A. 94.
Construction and installation of a cover falls squarely within
the definition of a “remedial action,” which includes the
“confinement” of substances and the “repair or replacement of
leaking containers.” CERCLA § 101(24). EPA’s Clean Water
Act lawsuit, in other words, sought injunctive relief for Guam
to take action that qualified as a “response action,” and the
2004 Consent Decree released Guam from legal exposure for
that claim in exchange for Guam’s commitment to perform
work that qualified as a “response action.”
                                20

     That “construction of the cover system to eliminate
discharges of untreated leachate” “resolv[ed] [Guam’s]
liability . . . for some or all of a response action” within the
meaning of CERCLA section 113(f)(3)(B), triggering that
section and precluding Guam from seeking cost-recovery
under section 107.
                                C.

     Despite the clarity of the Consent Decree, Guam insists
that, for several reasons, the Decree did not “resolve” Guam’s
liability to the United States. We are unpersuaded.

     Guam first argues that because “the US broadly and
unconditionally reserved all of its rights, including its rights to
pursue CERCLA claims,” the Consent Decree is “replete with
ongoing legal exposure for Guam” and therefore “did not
resolve liability with the requisite finality to trigger a Section
113(f)(3)(B) contribution claim.” Appellee’s Br. 25; 28–29.
True, the Consent Decree provides that “[n]othing . . . shall
limit the ability of the United States to enforce any and all
provisions of applicable federal laws and regulations.” Consent
Decree ¶ 46, J.A. 112. But that provision applies only to
“violations unrelated to the claims in the Complaint.” Id.
(emphasis added). This reservation of rights tells us nothing
about what the complaint and the consent decree do or do not
resolve under CERCLA. Section 113(f)(3)(B) is clear,
moreover, that it requires merely the resolution of liability for
“some” of a response action. In order to trigger section
113(f)(3)(B), a decree need not decisively determine every
action that a party may one day be required to perform at the
relevant site. What matters is whether what it does require
qualifies as “some” of a “response action.” And as explained
above, supra at 16–20, Guam’s construction obligations for the
Ordot Dump—agreed to under the threat of injunctive relief—
                                21
qualified as “some of” a “response action” under CERCLA.
The consent decree’s reservation of rights for unrelated claims
does nothing to alter that analysis.

     Guam next contends that the Consent Decree cannot have
triggered section 113(f)(3)(B) because “it only releases Guam
from . . . liability upon full implementation of the settlement’s
requirements, and performance is ongoing.” Appellee’s Br. 19.
Such a reading, however, would nullify section 113(f)(3)(B) in
a host of cases. According to section 113’s statute of
limitations, a party must bring a contribution action “no more
than 3 years after . . . entry of a judicially approved settlement.”
CERCLA § 113(g)(3)(B) (emphasis added). The clock starts to
run, in other words, on entry of the settlement, not when
liability is “resolved.” But under Guam’s theory, liability may
not be “resolved” for quite some time. For example, the Decree
requires Guam to perform within “44 months”—nearly four
years. Consent Decree ¶ 9, J.A. 100. Guam’s view—that
liability is not “resolved” until that performance is complete—
would produce an absurd result: Guam’s cause of action under
section 113 would not accrue until after the statute of
limitations runs. See Asarco, 866 F.3d at 1124 n.8 (rejecting
such a reading of CERCLA). And Guam would hardly be
alone. A different CERCLA provision, section 122, provides
that “[a] covenant not to sue concerning future liability to the
United States shall not take effect until the President certifies
that remedial action has been completed.” CERCLA
§ 122(f)(3). If parties “resolve” their liability only following
full performance and Presidential certification, most PRPs
would find themselves barred by the statute of limitations by
the time they gained the ability to sue under section
113(f)(3)(B). Congress could not have intended such a result.

     Next, Guam directs us to the Consent Decree’s disclaimer
of liability, which provides that the parties’ agreement is
                               22
“based on the pleadings, before taking testimony or
adjudicating any issue of fact or law, and without any finding
or admission of liability against or by the Government of
Guam.” Consent Decree 3, J.A. 92. Pointing to what it calls this
“clear and unambiguous” language, Guam urges us to take the
disclaimer at its word. Appellee’s Br. 16–17. To be sure, a
disclaimer of liability may weigh against the conclusion that
the parties intended to resolve liability within the meaning of
section 113(f)(3)(B). See, e.g., Florida Power Corp. v.
FirstEnergy Corp., 810 F.3d 996, 1002 (6th Cir. 2015) (finding
that consent decree did not resolve the plaintiff’s liability, in
part because “the plaintiff had not conceded the question of its
liability”). As other circuits faced with similar language have
observed, however, “parties often expressly refuse to concede
liability under a settlement agreement, even while assuming
obligations consistent with a finding of liability.” Asarco, 866
F.3d at 1123. Accordingly, “the mere fact that [a party] refused
to admit liability is not enough to exempt [a consent] [d]ecree
from the reach of section 113(f)(3)(B).” Refined Metals Corp.,
937 F.3d at 931. Here, the disclaimer of liability, standing
alone, cannot overcome the Consent Decree’s substantive
provisions. And because we have concluded that those
substantive terms do, in fact, “resolve” Guam’s “liability” to
the United States “for some . . . of a response action,” supra at
16–20, the Consent Decree triggers section 113(f)(3)(B)
despite the disclaimer.

     Guam nonetheless asserts that the consent decree falls
outside CERCLA’s provisions because the statute covers
“[c]ontamination involving ‘hazardous substances’” and the
Clean Water Act violations alleged in EPA’s Complaint
concerned “non-CERCLA pollutant discharges only.”
Appellee’s Br. 42. But the Complaint demanded that Guam
“complete construction of [a] cover system to eliminate
discharges of untreated leachate,” CWA Compl. ¶ 29, and
                               23
CERCLA expressly identifies the “collection of leachate and
runoff” as a “remedial action,” CERCLA § 101(24).

     And finally, Guam argues that denying it the right to seek
recovery under section 107 presents constitutional concerns.
“[A]s to non-settling PRPs,” Guam insists, “the right to
contribution is a property interest, which cannot be
extinguished without due process of law.” Appellee’s Br. 49
(internal quotations omitted). Because a qualifying section
113(f)(3)(B) settlement insulates Guam from further
contribution suits, Guam argues that other PRPs lack notice,
and “[a]llowing the [Clean Water Act] and [Consent Decree] at
issue here to trigger contribution rights equates to silently
extinguishing the property interest of anyone who might have
a potential claim against a settling party without due process of
law.” Id. Although it is far from clear whether Guam could
assert this claim on behalf of absent third parties, because
Guam failed to raise it in the district court, “it is forfeited.”
Keepseagle v. Vilsack, 815 F.3d 28, 36 (D.C. Cir. 2016). And
as to Guam’s own rights, Guam lost the ability to bring a
contribution claim not because it was deprived of due process,
but because the statute of limitations ran.

                               IV.

     From Guam’s perspective, the result we reach today is
harsh. “[A]ccept[ing] as true,” as we must at this stage, “all
material allegations of the complaint,” Barker v. Conroy, 921
F.3d 1118, 1121 (D.C. Cir. 2019) (internal quotations omitted),
the United States deposited dangerous munitions and
chemicals at the Ordot Dump for decades and left Guam to foot
the bill. The practical effect of our decision is that Guam cannot
now seek recoupment from the United States for that
contamination because its cause of action for contribution
expired in 2007. Unfortunately for Guam, however, “where a
                              24
statute is clear, the courts are not at liberty to construe the
statute other than according to its terms, or to depart from its
clear requirements.” Hirshfeld v. District of Columbia, 254
F.2d 774, 775 (D.C. Cir. 1958) (internal citations omitted). And
while offering little consolation to Guam, EPA has reduced the
likelihood that these circumstances will reoccur by since
revising its model settlement language to include an express
statement that the parties “agree that this Settlement Agreement
constitutes an administrative settlement for purposes of Section
113(f)(3)(B) of CERCLA.” Florida Power Corp., 810 F.3d at
1009.

     For the foregoing reasons, we reverse the district court’s
denial of the United States’ motion to dismiss and remand with
instructions to dismiss the complaint.
                                                    So ordered.
