 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT




Argued March 21, 2017                  Decided May 19, 2017

                         No. 15-1318

 WILKES-BARRE HOSPITAL COMPANY, LLC, DOING BUSINESS
         AS WILKES-BARRE GENERAL HOSPITAL,
                    PETITIONER

                              v.

            NATIONAL LABOR RELATIONS BOARD,
                      RESPONDENT

PENNSYLVANIA ASSOCIATION OF STAFF NURSES AND ALLIED
                 PROFESSIONALS,
                   INTERVENOR


                 Consolidated with 15-1384

        On Petition for Review and Cross-Application
               for Enforcement of an Order of
             the National Labor Relations Board


     Kaitlin Kaseta argued the cause for petitioner. With her
on the briefs was Bryan T. Carmody.

    Kellie J. Isbell, Attorney, National Labor Relations Board,
argued the cause for respondent. On the brief were Richard F.
Griffin, Jr., General Counsel, John H. Ferguson, Associate
                               2
General Counsel, Linda Dreeben, Deputy Associate General
Counsel, Elizabeth Heaney, Supervisory Attorney, and
Michael R. Hickson, Attorney.

   Before: PILLARD, Circuit Judge, and EDWARDS and
SENTELLE, Senior Circuit Judges.

   Opinion for the Court filed by Senior Circuit Judge
SENTELLE.

     SENTELLE, Senior Circuit Judge: Petitioner Wilkes-Barre
Hospital Company, LLC d/b/a Wilkes-Barre General Hospital
(the “Hospital”) petitions for review of the National Labor
Relations Board’s (“NLRB” or the “Board”) decision and order
finding that the Hospital violated section 8(a)(1) and (a)(5) of
the National Labor Relations Act (the “Act”), 29 U.S.C.
§ 158(a)(1), (5), by unilaterally ceasing the payment of
longevity-based wage increases to its nurses after the
expiration of the parties’ collective bargaining agreement. See
generally Litton Fin. Printing Div. v. NLRB, 501 U.S. 190
(1991); NLRB v. Katz, 369 U.S. 736 (1962). The NLRB
cross-applies for enforcement of its decision and order. The
Hospital argues that the language of the agreement and the
parties’ shared understanding of that language demonstrate that
the Hospital was not obligated to continue paying
longevity-based increases upon expiration of the agreement.
Relying on NLRB v. Noel Canning, 134 S. Ct. 2550 (2014), the
Hospital also challenges the NLRB Regional Director’s
authority to issue and prosecute the underlying complaint
against the Hospital. For the reasons set forth below, we deny
the Hospital’s petition for review and grant the NLRB’s
cross-application for enforcement.
                               3
                               I.

            The Collective Bargaining Agreements

    Petitioner operates an acute care facility in Wilkes-Barre,
Pennsylvania. The Hospital’s full-time and part-time graduate
and registered nurses are represented by the Pennsylvania
Association of Staff Nurses and Allied Professionals,
AFL-CIO (the “Union”). The Union is the exclusive collective
bargaining representative for a bargaining unit of
approximately 450 of the Hospital’s nurses.

     In or around May 2009, the Union negotiated with the new
owner of the Hospital a memorandum of agreement that served
as the parties’ collective bargaining agreement through June
30, 2009 (“2009 CBA”). The 2009 CBA incorporated by
reference certain terms of the prior collective bargaining
agreement between the Hospital’s former owner and the Union
(“2005 CBA”), including Article 25, which provided nurses
with annual across-the-board raises and longevity-based wage
increases. After the 2009 CBA expired on July 1, 2009, the
parties began negotiations but did not reach a successor
collective bargaining agreement until April 30, 2011 (“2011
CBA”). Accordingly, the parties were without a collective
bargaining agreement from July 1, 2009, to April 30, 2011. No
wage increases, including the longevity-based increases, were
paid to the nurses in January 2010 or January 2011.

     In response to the Hospital’s failure to pay longevity-based
increases in January 2010, the Union filed an unfair labor
practice charge with the NLRB’s Regional Office. The
NLRB’s Regional Director dismissed the charge and the
General Counsel upheld the dismissal. The Union did not file
an unfair labor practice charge in connection with the
                               4
Hospital’s failure to pay longevity-based increases in January
2011.

     The 2011 CBA became effective on April 30, 2011, and
expired on April 30, 2013. The new CBA, like the 2009 CBA,
provides that a nurse’s minimum base hourly rate would be
determined by his/her experience level. The seven experience
levels were grouped as follows: 0-2 years; 3-4 years; 5-9 years;
10-14 years; 15-19 years; 20-24 years; and 25+ years. Similar
to the 2005 CBA and the 2009 CBA, Article 25 and Appendix
A of the 2011 CBA provide for two types of wage increases:
across-the-board raises and longevity-based increases.

     Sections 1 through 3 of Article 25 describe the
across-the-board raises, which were provided to nurses on three
dates certain. After the 2011 CBA became effective on April
30, 2011, nurses received a catch-up increase in their base
hourly rate in May 2011. Nurses then received a 2.75%
increase in base hourly rate on January 27, 2012, and a further
2.00% increase on January 27, 2013.

     Sections 4 and 5 of Article 25 provide for the
longevity-based increases. Section 4 explains that wage
minimums were “based upon the employee’s length of
continuous service as a registered nurse,” and Section 5 states
that longevity-based increases were to be paid on “January 27th
of the year following the employee’s anniversary date.” Nurses
received longevity-based increases as they advanced from one
experience level to the next (e.g., 0-2 years level to 3-4 years
level), resulting in an increase in their hourly pay rate the
following January 27th.

     The initial wage scale and the subsequent increases during
the term of the 2011 CBA were set forth in Appendix A in the
                             5
following chart showing minimum hourly wage rates for nurses
in the seven experience levels:




“Reading across, the chart shows the three annual
across-the-board raises; reading down, the chart shows the
longevity-based wage increases.” Wilkes-Barre Hosp. Co.,
362 N.L.R.B. No. 148, at *4 (July 14, 2015).

       The Hospital’s Failure to Pay Longevity-Based
                     Increases in 2014

    The parties began negotiations for a successor collective
bargaining agreement in February 2013. The 2011 CBA
expired on April 30, 2013, and the parties bargained without
impasse through July 2014. Following the expiration of the
2011 CBA, the Hospital did not pay any wage increases in
January 2014. The Hospital does not dispute that it neither
gave the Union prior notice of its intention to cease paying
longevity-based increases in 2014 nor afforded the Union the
opportunity to bargain over that decision.
                               6
     The Union filed charges with the NLRB’s Regional
Director, including its contention that the Hospital’s failure to
pay longevity-based increases in January 2014 violated section
8(a)(1) and (a)(5) of the Act. The Union did not assert that the
nurses were entitled to additional across-the-board raises. The
General Counsel, through Dennis P. Walsh, the Regional
Director of Region 4, issued a consolidated complaint on April
23, 2014.

              The Board Proceedings and Order

     An administrative law judge considered charges that the
Hospital violated section 8(a)(1) and (a)(5) by ceasing to pay
longevity-based increases to nurses in January 2014. See
Wilkes-Barre Hosp. Co., Case 04-CA-123748, 2014 WL
6386518 (Nov. 17, 2014). The complaint charged that, under
the rule first articulated in NLRB v. Katz, 369 U.S. 736 (1962),
when the 2011 CBA expired, the Hospital had a statutory
obligation to maintain the status quo as to its nurses’ terms and
conditions of employment. See, e.g., Honeywell Int’l, Inc. v.
NLRB, 253 F.3d 125, 127, 131 (D.C. Cir. 2001). The Hospital
argued that, within the status quo, the longevity-based
increases operated in tandem with the across-the-board raises.
The Hospital further argued that the evidence established that
past practice permitted it to pretermit the payment of the
longevity-based increases after the expiration of the CBA.

     The ALJ accepted the General Counsel’s position that the
across-the-board raises and the longevity-based increases were
“distinct rights” that did not “go hand-in-hand” and found it
“quite simple” for the Hospital to apply “the terms that already
existed in the contract and grant[] hourly wage rate increases
as specified in appendix A” after the agreement’s expiration.
She therefore concluded that the Hospital violated its statutory
                               7
duty to bargain by failing to pay longevity-based increases in
January 2014.

     She explained that the 2011 CBA did not include language
either “specifically limiting the applicability of” the
longevity-based increases to the term of the agreement or
clearly and unmistakably waiving the nurses’ statutory right to
receive those increases.        Thus, the ALJ held, the
longevity-based increase provision “continue[d] in effect” after
the agreement’s expiration. She also rejected the Hospital’s
past practice argument, finding that the evidence did not
establish that the parties had a longstanding practice of the
Hospital’s unilateral changes going unchallenged by the
Union.

     The Hospital also moved to dismiss on the ground that
Director Walsh had been improperly appointed by an
unconstitutionally constituted Board and therefore did not have
the authority to issue the complaint upon which the proceeding
was held. The ALJ denied this motion, citing the record fact
that a later, lawfully constituted Board had ratified the
Director’s appointment. The NLRB summarily affirmed the
ALJ’s rulings, findings, and conclusions, and adopted her
recommended order with slight modifications. Wilkes-Barre
Hosp., 362 N.L.R.B. No. 148, at *1.

    The Hospital timely filed the present petition for review,
and the NLRB filed a cross-application for enforcement. We
have jurisdiction pursuant to 29 U.S.C. § 160(e), (f).

                              II.

    Before considering the merits of the Board’s order, we
must address the threshold question raised by the Hospital’s
motion to dismiss. The Hospital argues that all the acts of
                               8
Regional Director Walsh were ultra vires, as his appointment
was invalid. The NLRB had appointed him as Regional
Director on March 10, 2013. In NLRB v. Noel Canning, 134 S.
Ct. 2550 (2014), the Supreme Court invalidated the recess
appointments of three of the Board’s five members. As a result,
the Board lacked a valid quorum between January 2012 and
August 2013. Therefore, argues the Hospital, Walsh had no
authority to issue the complaints against it. See ManorCare of
Kingston PA, LLC v. NLRB, 823 F.3d 81, 89 (D.C. Cir. 2016);
Advanced Disposal Servs. E., Inc. v. NLRB, 820 F.3d 592, 596
& n.1 (3d Cir. 2016).

     While the Hospital’s argument is correct in its basic
assumptions, events have overtaken it since the initial
invalidity of Walsh’s appointment and his unlawful issuance of
complaints. After the period of invalid Board operation
recognized in Noel Canning, the President made valid
appointments to create a quorum on the Board. The
reconstituted Board ratified the appointment of Walsh as
Director, among many other actions. Walsh, as Director,
thereafter ratified his own prior invalid actions. Because both
the Board and Director Walsh ratified the actions taken during
the period in which the Board lacked a valid quorum, we
conclude that the Hospital’s motion was properly denied.

     In general, “[r]atification occurs when a principal
sanctions the prior actions of its purported agent.” Doolin Sec.
Sav. Bank, F.S.B. v. Office of Thrift Supervision, 139 F.3d 203,
212 (D.C. Cir. 1998), superseded by statute on other grounds,
Federal Vacancies Reform Act of 1998, Pub. L. No. 105-277,
122 Stat. 2681 (1998), as recognized in SW Gen., Inc. v. NLRB,
796 F.3d 67, 70–71 (D.C. Cir. 2015), aff’d 137 S. Ct. 929
(2017). Our precedents establish that ratification can remedy a
defect arising from the decision of “an improperly appointed
official . . . when . . . . a properly appointed official has the
                               9
power to conduct an independent evaluation of the merits and
does so.” See Intercollegiate Broad. Sys., Inc. v. Copyright
Royalty Bd., 796 F.3d 111, 117–21, 124 (D.C. Cir. 2015)
(citing Doolin Sec., 139 F.3d at 213–14; FEC v. Legi-Tech, 75
F.3d 704, 708–09 (D.C. Cir. 1996)). Relevant to this case, we
previously suggested that “a properly constituted Board” could
ratify the decisions of an improperly constituted Board. See
Laurel Baye Healthcare of Lake Lanier, Inc. v. NLRB, 564 F.3d
469, 476 (D.C. Cir. 2009); see also Allied Aviation Serv. Co. of
N.J. v. NLRB, ___ F.3d ___, 2017 WL 1379517, at *6 (D.C.
Cir. 2017).

     On July 18, 2014, after the Supreme Court’s decision in
Noel Canning, all five members of a properly constituted Board
adopted and ratified “all administrative, personnel, and
procurement matters approved by the Board or taken by or on
behalf of the Board between January 4, 2012, and August 5,
2013,” inclusive. Wilkes-Barre Hosp., 362 N.L.R.B. No. 148,
at *5. The Board expressly authorized Director Walsh’s
appointment, and Director Walsh affirmed and ratified his own
actions in a separate order on July 30, 2014.

     After considering relevant materials, the properly
constituted Board expressly ratified its appointment of Director
Walsh as a Regional Director. The Hospital presents no
evidence to suggest that the Board failed “to conduct an
independent evaluation of the merits,” Intercollegiate Broad.,
796 F.3d at 117, or make “a detached and considered
judgment,” Doolin Sec., 139 F.3d at 213, when it ratified
Director Walsh’s appointment. The Hospital argues that the
Board’s ratification was an improper attempt to “insulate the
Board from the invalidity of the original appointments and the
actions taken thereunder.” This argument fails. Ratification
can remedy defects arising from the decisions of improperly
appointed officials. See, e.g., Intercollegiate Broad., 796 F.3d
                               10
at 117–18. Therefore, the properly constituted Board’s
ratification remedied any defect arising from the quorum
violation.

     Because he acted as “both the principal and the agent,” the
propriety of Director Walsh’s ratification of his own actions
presents a more difficult question. See Advanced Disposal, 820
F.3d at 602–03. After considering the applicable law and the
facts of this case, we conclude that Director Walsh’s
ratification was sufficient to remedy the defect. As an initial
matter, we note that the only evidence presented by the
Hospital on the invalidity of Director Walsh’s ratification is a
memorandum from the Board’s Office of Inspector General
concluding that probable cause existed to find that Director
Walsh violated the Standards of Ethical Conduct for
Employees of the Executive Branch by participating in certain
prohibited fundraising activities. As the violation is unrelated
to the Hospital or Director Walsh’s issuance of complaints
during the period in which the Board lacked a quorum, we fail
to see the relevancy of this information to the question
presented in this case.

     The Hospital’s primary argument is that Director Walsh’s
“self-ratification” was improper because “human nature”
makes it impossible for an individual to be disinterested in his
own prior decision-making. Although we have not been
confronted with this precise situation, our precedents shed
some light on the question. In Doolin Security, for example,
we applied our ratification precedents even though the situation
was “not easily characterized as between a principal . . . and an
agent.” See 139 F.3d at 213–14. We further explained in
Legi-Tech that, “given human nature,” forcing a properly
appointed official to start at the beginning of the process does
not necessarily promise a “more detached and ‘pure’
consideration of the merits of the case . . . .” 75 F.3d at 709.
                               11

     We note that other circuits have held that ratification can
be effective even where the same party is both the agent and
the principal. In Advanced Disposal, the Third Circuit
considered the question in a context so directly parallel to the
present case that the same Director Walsh was the
agent/principal in both. See 820 F.3d at 602–03. Citing our
decision in Doolin Security, and analyzing the question that
lingers, the Third Circuit ruled that Director Walsh’s filing of
a complaint necessarily affirmed the validity of his earlier
action. Id. at 605.

     Similarly, in CFPB v. Gordon, 819 F.3d 1179 (9th Cir.
2016), the Ninth Circuit considered the effect of the CFPB
Director’s ratification of his own prior invalid actions. See id.
at 1185–86, 1190–91. The Director, like the NLRB in the case
before us, was serving under an unconstitutional recess
appointment at the time he made the initial actions. That
circuit, relying on our decision in Legi-Tech, concluded that
“even if the subsequent . . . ‘review’ was ‘nothing more than a
rubberstamp,’” it “resolve[d] any Appointments Clause
deficiencies.” See id. at 1191–92 (quoting Legi-Tech, 75 F.3d
at 709); see also Intercollegiate Broad., 796 F.3d at 118 & n.1
(suggesting that ratification may be sufficient even if the
subsequent decision rubberstamped the previous decision).

     In this case, the Hospital presented no evidence suggesting
that Director Walsh failed to make a detached and considered
judgment or that he was “actually biased” against the Hospital.
Legi-Tech, 75 F.3d at 709. It also appears that forcing Director
Walsh to reissue the complaint in this case would likely “do
nothing but give the [Hospital] the benefit of delay.” See
Doolin Sec., 139 F.3d at 214. We also note that the Hospital
has failed to assert any “continuing prejudice” from the
violation. See Legi-Tech, 75 F.3d at 708–09. Consistent with
                               12
precedent, we conclude that “the better course” is to take his
ratification “at face value and treat it as an adequate remedy.”
Id. at 709. In short, the bare fact that Director Walsh ratified
his own actions, without more, does not make his ratification
insufficient. In any event, it is the General Counsel who has
final authority over the issuance of complaints, see 29 U.S.C.
§ 153(d), and Director Walsh was acting on behalf of General
Counsel Richard Griffin, who had been duly confirmed when
the complaint against the Hospital issued on April 23, 2014.
We conclude that Director Walsh’s ratification of his own
action remedied the defect in his original issuance of the
complaint. We therefore proceed to review the merits of the
petition.

                              III.

                               A.

     Our review of the Board’s unfair labor practice
determination is limited. Brewers & Maltsters, Local Union
No. 6 v. NLRB, 414 F.3d 36, 42 (D.C. Cir. 2005). “We . . . must
sustain the Board’s decision unless, reviewing the record as a
whole, it appears that the Board’s factual findings are not
supported by substantial evidence, or that the Board acted
arbitrarily or otherwise erred in applying established law to the
facts at issue.” S. Nuclear Operating Co. v. NLRB, 524 F.3d
1350, 1355 (D.C. Cir. 2008) (citation and internal quotation
marks omitted). We also defer to the Board’s reasonable
construction of section 8(a)(5) and (d), 29 U.S.C. § 158(a)(5),
(d). See Brewers & Maltsters, 414 F.3d at 41–42.

    While the Board has authority to interpret collective
bargaining agreements to resolve unfair labor practice charges,
NLRB v. U.S. Postal Serv., 8 F.3d 832, 837 (D.C. Cir. 1993),
we owe “no deference to the Board’s interpretation of a
                               13
disputed collective bargaining agreement,” Commonwealth
Commc’ns, Inc. v. NLRB, 312 F.3d 465, 468 (D.C. Cir. 2002).
Federal courts, not the Board, are the primary source of
authority in interpreting collective bargaining agreements.
Litton Fin. Printing Div. v. NLRB, 501 U.S. 190, 202–03
(1991); Enloe Med. Ctr. v. NLRB, 433 F.3d 834, 837–38 (D.C.
Cir. 2005); see also Chicago Tribune Co. v. NLRB, 974 F.2d
933, 937–38 (7th Cir. 1992) (“The Board is not an expert in
contract interpretation.”). We therefore interpret the 2011
CBA de novo. See Postal Serv., 8 F.3d at 837. When
interpreting a collective bargaining agreement, we generally
apply “ordinary principles of contract law.” M&G Polymers
USA, LLC v. Tackett, 135 S. Ct. 926, 933 (2015).

                               B.

               The Unilateral Change Doctrine

     “Section[] 8(a)(5) and 8(d) of the [Act] require parties in a
collective bargaining relationship to negotiate in good faith
over ‘wages, hours, and other terms and conditions of
employment.’” Daily News of L.A. v. NLRB, 73 F.3d 406, 410
(D.C. Cir. 1996) (quoting 29 U.S.C. § 158(d)); see also 29
U.S.C. § 158(a)(5). Section 8(a)(1) makes it an unfair labor
practice for an employer to interfere with its employees’
exercise of their rights under the Act. 29 U.S.C. § 158(a)(1).
Thus, an employer’s violation of section 8(a)(5)’s duty to
bargain also violates section 8(a)(1). Enter. Leasing Co. of Fla.
v. NLRB, 831 F.3d 534, 546 (D.C. Cir. 2016).

    “The Board has taken the position that it is difficult to
bargain if, during negotiations, an employer is free to alter the
very terms and conditions that are the subject of those
negotiations.” Litton Fin., 501 U.S. at 198. Indeed, the
Supreme Court has equated an employer’s unilateral change to
                              14
terms and conditions of employment to “a flat refusal” to
bargain.     NLRB v. Katz, 369 U.S. 736, 743 (1962).
Accordingly, absent impasse or waiver, an employer violates
both section 8(a)(1) and (a)(5) by unilaterally changing terms
and conditions of employment. Honeywell Int’l, Inc. v. NLRB,
253 F.3d 125, 127, 131 (D.C. Cir. 2001) (citing Litton Fin., 501
U.S. 190; Katz, 369 U.S. 736). This “unilateral change
doctrine” extends to cases “where, as here, an existing
agreement has expired and negotiations on a new one have yet
to be completed.” Id. at 127–28 (quoting Litton Fin., 501 U.S.
at 198); see also More Truck Lines, Inc. v. NLRB, 324 F.3d 735,
738–39 (D.C. Cir. 2003); Sw. Steel & Supply, Inc. v. NLRB,
806 F.2d 1111, 1113 (D.C. Cir. 1986).

               Status Quo under the 2011 CBA

     To avoid running afoul of the unilateral change doctrine,
an employer must maintain the status quo as to terms and
conditions of employment after the expiration of a collective
bargaining agreement. See Laborers Health & Welfare Trust
Fund for N. Cal. v. Advanced Lightweight Concrete Co., 484
U.S. 539, 543–44 nn.5–6 (1988). The primary dispute in this
case concerns the proper determination of the post-expiration
status quo. Because an employer’s obligation to maintain the
status quo derives from the Act, not from the agreement, see
More Truck Lines, 324 F.3d at 738-39; Honeywell Int’l, 253
F.3d at 128, 131, certain terms of an expired agreement extend
beyond the agreement’s expiration and continue to “define the
status quo,” Litton Fin., 501 U.S. at 206 (emphasis omitted).
Otherwise put, the unilateral change doctrine requires
employers “to honor the terms and conditions of an expired
collective-bargaining agreement.” Laborers Health & Welfare
Trust Fund, 484 U.S. at 544 n.6. In defining the post-expiration
status quo in this case, therefore, we look to the substantive
terms of the 2011 CBA. See NLRB v. Cauthorne, 691 F.2d
                               15
1023, 1025 (D.C. Cir. 1982); E.I. Du Pont De Nemours, 364
N.L.R.B. No. 113, at *5 (Aug. 26, 2016); see also
Intermountain Rural Elec. Ass’n v. NLRB, 984 F.2d 1562, 1567
(10th Cir. 1993) (noting that “the contract language itself . . .
defines the [post-expiration] status quo”).

     In considering an unfair labor practice charge premised on
the unilateral change doctrine, “the relevant inquiry . . . is
whether any established employment term on a mandatory
subject of bargaining has been unilaterally changed.” Daily
News, 73 F.3d at 411. In this case, the longevity-based wage
increase provision was a mandatory subject of bargaining, see
29 U.S.C. § 158(d); More Truck Lines, 324 F.3d at 738–39, and
an established term of the 2011 CBA that survived the
agreement’s expiration. It is undisputed that the parties did not
bargain to lawful impasse and that the Hospital did not notify
the Union of its intention to cease paying longevity-based
increases. Accordingly, upon expiration of the 2011 CBA, the
Hospital was obligated to continue paying longevity-based
increases absent lawful impasse or a new agreement with the
Union. See Honeywell Int’l, 253 F.3d at 127–28, 131–32.

     The Hospital counters that the longevity-based increases
were paid “exclusively in conjunction with” the
across-the-board raises, which were expressly limited to the
term of the agreement and thus cannot define the
post-expiration status quo. The Hospital argues that during the
term of the agreement, nurses were given a single wage rate
increase on each of three specific dates consisting of a
combination of an across-the-board raise and a longevity-based
increase, if applicable. According to the Hospital, therefore,
cessation of all wage increases represents the post-expiration
status quo. The Hospital’s argument misses the mark.
                               16
     In essence, the Hospital seeks to define the status quo by
taking a snapshot of each individual nurse’s pay rate at the
moment the 2011 CBA expired. But the terms of the expired
agreement define the post-expiration status quo, see, e.g.,
Litton Fin., 501 U.S. at 206; Sw. Steel, 806 F.2d at 1113, not
each individual employee’s circumstance at the time of
expiration, see Daily News, 73 F.3d at 409, 412–13 (stating that
employer must continue merit-increase program after the
agreement’s expiration even though the increases were
“discretionary as to the precise amount”).

     The 2011 CBA, through its language and structure,
establishes two distinct types of wage increases:
across-the-board raises and longevity-based increases.
Sections 1, 2, and 3 of Article 25 set forth the across-the-board
raises. These raises resulted in a percentage increase in each
nurse’s base minimum hourly rate and were provided to all of
the Hospital’s nurses on three specific dates during the term of
the agreement. Sections 4 and 5 of Article 25 provide for the
longevity-based increases, which were paid to individual
nurses who advanced from one experience level to the next.
The longevity-based increases, unlike the across-the-board
raises, were tied to an individual nurse’s anniversary date, not
to the term of the agreement. Specifically, the agreement states
that longevity-based increases were to be paid on “January 27th
of the year following the employee’s anniversary date.” Thus,
as the Board held, the across-the-board raises and
longevity-based increases were “distinct rights,” and nurses
had a continued “right to wage rate increases when they
advanced to the next experience level.” Wilkes-Barre Hosp.,
362 N.L.R.B. No. 148, at *7.

     The Hospital argues that the chart in Appendix A
illustrates the interplay between the two wage increases,
asserting that the chart combines the five wage sections in
                               17
Article 25 “into one, singular wage increase table.” Appendix
A, however, does not support the Hospital’s contention. As the
Board explained: “Reading across, the chart shows the three
annual across-the-board raises; reading down, the chart shows
the longevity-based wage increases.” Id. at *4. It is undisputed
that the wage rates included in the chart froze at the January
2013 levels upon the agreement’s expiration, meaning that
nurses were not entitled to an across-the-board raise in their
base minimum hourly rates in January 2014. Although the
wage rates froze, each individual nurse could still move up the
steps of the chart based on his/her experience level until a new
agreement or lawful impasse was reached. Appendix A
therefore reflected the nurses’ ongoing right to receive
post-expiration longevity-based increases, as set forth in
Sections 4 and 5 of Article 25. We agree with the Board that
when a nurse reached one of the milestone work anniversaries,
“the longevity-based scale at appendix A” can easily be applied
without any “concomitant across-the-board raises.” Id. at *7.

     The Hospital also directs our attention to the language
accompanying the chart, which explains that the wage scale
and subsequent wage increases set forth in the 2011 CBA
applied “[d]uring the term of th[e] Agreement.” This
durational clause, the Hospital argues, removed any
uncertainty as to whether longevity-based increases survived
the 2011 CBA’s expiration. But the durational clause in
Appendix A speaks to the nurses’ contractual rights, not to their
statutory rights. See, e.g., Litton Fin., 501 U.S. at 207 (noting
“the distinction between contractual obligations and
postexpiration terms imposed by the [Act]”). Without more,
such a general durational clause cannot defeat the unilateral
change doctrine. See Honeywell Int’l, 253 F.3d at 128, 132–
33.
                               18
     The Hospital makes a secondary argument based on the
past practice of the parties to the 2011 CBA. An employer may
implement unilateral changes to terms and conditions of
employment when such changes are in line with its
longstanding practice. See E.I. Du Pont De Nemours & Co. v.
NLRB, 682 F.3d 65, 67–70 (D.C. Cir. 2012); Int’l Bhd. of Elec.
Workers Local 1466 v. NLRB, 795 F.2d 150, 153 (D.C. Cir.
1986). Rather than constitute an unlawful unilateral change, an
action taken pursuant to an established practice actually
preserves the status quo. See Katz, 369 U.S. at 746; E.I. Du
Pont, 682 F.3d at 67–68; see also Aaron Bros. Co. v. NLRB,
661 F.2d 750, 753 (9th Cir. 1981) (“Wage changes that merely
reflect continuations of past company policy are not considered
changes in existing work conditions, and thus fall outside the
Katz rule.”). To support its past practice argument, the
Hospital points to the Union’s failure to file an unfair labor
practice charge in connection with the Hospital’s non-payment
of longevity-based increases in January 2011, after the
expiration of the 2009 CBA. But a union’s one-time failure to
challenge an employer’s unilateral change does not qualify as
an established practice. See Brewers & Maltsters, 414 F.3d at
45.

    In conclusion, the terms of the 2011 CBA establish that the
payment of longevity-based increases represents the
post-expiration status quo between the Hospital and the Union.

        The Contract Coverage Doctrine and Waiver

     Having concluded that the Act “does not shield” the
Hospital’s unilateral decision to cease payment of
longevity-based increases, we turn to the Hospital’s argument
that the Union “surrendered the[] right to bargain over the . . .
change[] through either waiver or contract.” S. Nuclear
Operating, 524 F.3d at 1357. First, invoking the “contract
                              19
coverage doctrine,” the Hospital asserts that the parties agreed
in the 2011 CBA that the payment of all wage increases would
cease upon the expiration of the agreement. Second, the
Hospital contends that it demonstrated that the Union clearly
and unmistakably waived the nurses’ right to post-expiration
longevity-based increases. We reject both arguments.

     There are important distinctions between the contract
coverage doctrine and waiver—a point we have repeatedly
stressed. See generally Heartland Plymouth Court MI, LLC v.
NLRB, 838 F.3d 16 (D.C. Cir. 2016). Because “the question of
contractual coverage, one of contractual interpretation, is
antecedent to the waiver question,” id. at 19 n.1, we first
consider whether the Hospital’s decision to cease paying
longevity-based increases was covered by the 2011 CBA.

     The duty to bargain does not prevent a union from
“exercis[ing] its right to bargain about a particular subject by
negotiating for a provision in a collective bargaining contract
that fixes the parties’ rights and forecloses further mandatory
bargaining as to that subject.” Postal Serv., 8 F.3d at 836
(quoting Local Union No. 47, Int’l Bhd. of Elec. Workers v.
NLRB, 927 F.2d 635, 640 (D.C. Cir. 1991)); see also S. Nuclear
Operating, 524 F.3d at 1358. Thus, pursuant to the contract
coverage doctrine, an employer is “free to make unilateral
changes . . . without running afoul of the Act” when those
changes are “covered by the collective bargaining agreement.”
Enter. Leasing, 831 F.3d at 547 (citations and internal
quotation marks omitted).

     A dispute regarding a subject that is “covered by” a
collective bargaining agreement presents “an issue of contract
interpretation,” Bath Marine Draftsmen’s Ass’n v. NLRB, 475
F.3d 14, 23 (1st Cir. 2007) (citing Postal Serv., 8 F.3d at 836–
37), and when parties negotiate for a contractual provision
                                20
limiting the union’s statutory rights, “we will give full effect to
the plain meaning of such provision,” Local Union No. 47, 927
F.2d at 641; see also Postal Serv., 8 F.3d at 836 (“[T]he courts
are bound to enforce lawful labor agreements as written . . . .”).
Importantly, a subject may be covered by an agreement even if
the agreement does not clearly and unmistakably address that
particular subject. See Enloe Med., 433 F.3d at 837–38; Postal
Serv., 8 F.3d at 838; Connors v. Link Coal Co., 970 F.2d 902,
906 (D.C. Cir. 1992); Local Union No. 47, 927 F.2d at 641.
Accordingly, in analyzing whether the Hospital’s decision to
cease paying longevity-based increases upon the expiration of
the 2011 CBA was covered by that agreement, we consider
whether that subject was “within the compass of” the terms of
the agreement. Postal Serv., 8 F.3d at 838.

     We begin by noting that the Board improperly collapsed
the contract coverage and waiver questions. The Board found
that the 2011 CBA did not “specifically limit[]” the
applicability of the longevity-based increases to the
agreement’s term or clearly and unmistakably waive the
Union’s statutory rights. Wilkes-Barre Hosp., 362 N.L.R.B.
No. 148, at *6. In determining whether an employer’s
unilateral decision is covered by a collective bargaining
agreement, we consistently have rejected the Board’s attempts
to require the agreement to “specifically mention,” Enloe Med.,
433 F.3d at 839, “specifically refer[]” to, Postal Serv., 8 F.3d
at 838, or “specifically address,” Connors, 970 F.2d at 906, that
decision. As we previously explained, the Board’s approach
fails to recognize that “bargaining parties [cannot] anticipate
every hypothetical grievance and purport to address it in their
contract,” Postal Serv., 8 F.3d at 838, and “imposes an
artificially high burden on an employer,” Enloe Med., 433 F.3d
at 837.
                                 21
     Nevertheless, after reviewing the terms of the 2011 CBA,
we conclude that the Hospital’s decision to cease paying
longevity-based increases after the agreement’s expiration is
not covered by the agreement. The Hospital argues that,
because the 2011 CBA expressly limited the across-the-board
raises to the term of the agreement, the agreement necessarily
limited the Hospital’s statutory obligation to pay
longevity-based increases to the term of the agreement as well.
As explained above, however, the across-the-board raises and
the longevity-based increases are distinct rights that operate
independently of each other. And unlike the across-the-board
raises, the longevity-based increases were “not limited to a time
certain.” See Honeywell Int’l, 253 F.3d at 128, 132–33. The
durational clause in Appendix A, which stated that the initial
wage scale and subsequent wage increases applied “[d]uring
the term of th[e] Agreement,” does not change this conclusion.
Because the unilateral change doctrine “presupposes the end of
a collective bargaining agreement,” the standard durational
clause in Appendix A, without more, cannot “‘cover[]’ and
[thereby] vitiate[] [the] Union’s statutory claim to continued”
longevity-based increases. See id. at 128, 132–33. We
therefore conclude that the Hospital’s decision to cease paying
longevity-based increases in January 2014 is not covered by the
terms of the 2011 CBA.

     The Hospital also argues that the Union clearly and
unmistakably waived the nurses’ statutory right to receive
longevity-based increases after the expiration of the 2011
CBA. “A waiver occurs when a union knowingly and
voluntarily relinquishes its right to bargain about a matter . . . .”
Postal Serv., 8 F.3d at 836 (citation and emphasis omitted). By
waiving the right to bargain over a particular matter, a union
“surrenders the opportunity to create a set of contractual rules
that bind the employer, and instead cedes full discretion to the
employer on that matter.” S. Nuclear Operating, 524 F.3d at
                              22
1357 (citation and internal quotation marks omitted). It follows
that “an employer’s unilateral change to contract terms on that
subject does not violate the Act.” Enter. Leasing, 831 F.3d at
546. For this reason, unlike the contract coverage doctrine, a
waiver “must be ‘clear and unmistakable.’” Honeywell Int’l,
253 F.3d at 133 (quoting Metro. Edison Co. v. NLRB, 460 U.S.
693, 703 (1983)).

     In determining whether the Union waived its statutory
rights, we consider the language of the 2011 CBA as well as
the parties’ course of conduct. See S. Nuclear Operating, 524
F.3d at 1357–58; Honeywell Int’l, 253 F.3d at 133–34. An
employer bears the burden of showing that a union clearly and
unmistakably waived its statutory rights. Sw. Steel, 806 F.2d
at 1114–15. To satisfy its burden, the Hospital must establish
that the parties “consciously explored or fully discussed the
matter on which the union has consciously yielded its rights.”
S. Nuclear Operating, 524 F.3d at 1357–58 (citation and
internal quotation marks omitted).

     The Hospital contends that the language of the 2011 CBA
establishes that the Union clearly and unmistakably waived the
nurses’ right to post-expiration longevity-based increases.
“[G]enerally speaking, waivers of statutory rights must be
demonstrated by an express statement in the contract to that
effect.” Gannett Rochester Newspapers v. NLRB, 988 F.2d
198, 203–04 (D.C. Cir. 1993) (citations, internal quotation
marks, and alteration omitted). Consequently, employers
cannot rely on contractual silence. Id. at 203; S-B Mfg. Co.,
270 N.L.R.B. 485, 490 (1984). Nor can “general contractual
provision[s],” Gannett Rochester, 988 F.2d at 203, or
“[e]quivocal, ambiguous language in a bargaining agreement,”
NLRB v. Gen. Tire & Rubber Co., 795 F.2d 585, 588 (6th Cir.
1986), meet that standard. We also have noted that when a
particular subject is not “covered by” a collective bargaining
                              23
agreement, that agreement generally will not “clearly and
unmistakably waive bargaining over that matter.” Heartland
Plymouth, 838 F.3d at 26. This case is no exception.

     The Hospital fails to identify any express language in the
2011 CBA to support its waiver defense, arguing instead that
the agreement’s language does not affirmatively “point to an
ongoing statutory obligation” to pay longevity-based increases.
The Hospital’s argument fails to consider that, pursuant to the
unilateral change doctrine, wage rates established in a
collective bargaining agreement continue in effect “even after
an employer is released from any contractual obligations.” See
More Truck Lines, 324 F.3d at 738–39; see also Honeywell
Int’l, 253 F.3d at 134. Moreover, as noted above, the 2011
CBA’s silence on the Hospital’s statutory obligation to
continue paying longevity-based increases after the
agreement’s expiration as part of the status quo is insufficient
to establish waiver. Gannett Rochester, 988 F.2d at 203.
While a contract duration clause that expressly authorizes the
employer to terminate its statutory obligations upon expiration
is sufficient to establish waiver, see Local Joint Exec. Bd. of
Las Vegas v. NLRB, 540 F.3d 1072, 1080–82 (9th Cir. 2008);
Honeywell Int’l, 253 F.3d at 133–34; Staffco of Brooklyn, LLC,
364 N.L.R.B. No. 102, at *2–4 & n.8 (Aug. 26, 2016), the 2011
CBA does not contain such a clause. The durational clause in
Appendix A “makes it clear that the Union’s contractual right”
to longevity-based increases ended on April 30, 2013, but it “is
silent on the Union’s [post-expiration] statutory rights.”
Honeywell Int’l, 253 F.3d at 134. Accordingly, the durational
clause “in no way evinces a clear and unmistakable waiver by
the Union.” Id.

     The Hospital also fails to establish through “other
contextual factors” that the Union waived the nurses’ statutory
right to longevity-based increases. See Regal Cinemas, Inc. v.
                               24
NLRB, 317 F.3d 300, 312–14 (D.C. Cir. 2003). The record
does not reveal any evidence concerning the parties’ bargaining
history. Instead, the Hospital once again relies on the Union’s
failure to bring an unfair labor practice charge in January 2011,
arguing that this failure illustrates that the parties agreed that
the Hospital could cease the payment of longevity-based
increases upon expiration. But the Union’s one-time failure to
challenge the Hospital’s cessation of longevity-based increases
in January 2011 “does not estop subsequent assertion of that
right.” S. Nuclear Operating, 524 F.3d at 1358; see also
Brewers & Maltsters, 414 F.3d at 45. We note that the
Supreme Court has held that two instances of a union’s silence
did not “establish a pattern of decisions clear enough to convert
the union’s silence into binding waiver.” See Metro. Edison,
460 U.S. at 707–10. In sum, nothing in the record establishes
that the Union fully discussed the nurses’ right to receive
longevity-based increases after the 2011 CBA’s expiration and
then “voluntarily relinquished [its] right to bargain over them.”
S. Nuclear Operating, 524 F.3d at 1358.

                              ***

     For the reasons stated, we conclude that the Hospital
violated section 8(a)(1) and (a)(5) by unilaterally ceasing the
payment of longevity-based wage increases to nurses after the
expiration of the parties’ collective bargaining agreement.
Accordingly, we deny the Hospital’s petition for review and
grant the Board’s cross-application for enforcement.

                                                     So ordered.
