 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued April 5, 2016               Decided August 16, 2016

                       No. 15-1050

           RUSH UNIVERSITY MEDICAL CENTER,
                     PETITIONER

                             v.

           NATIONAL LABOR RELATIONS BOARD,
                     RESPONDENT

 INTERNATIONAL BROTHERHOOD OF TEAMSTERS LOCAL 743,
                    INTERVENOR


                Consolidated with 15-1097


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


    Kenneth F. Sparks argued the cause for petitioner. With
him on the briefs was Mark L. Stolzenburg.

     Jacqueline M. Holmes and Jeffrey G. Micklos were on the
brief for amici curiae American Hospital Association and the
Federation of American Hospitals in support of petitioner.
                              2
     Elizabeth A. Heaney, Supervisory Attorney, National
Labor Relations Board, argued the cause for respondent.
With her on the brief were Richard F. Griffin, Jr., General
Counsel, John H. Ferguson, Associate General Counsel,
Linda Dreeben, Deputy Associate General Counsel, and
Elliott Becker, Attorney.

James B. Coppess argued the cause for intervenor. With him
on the brief was Joel A. D’Alba. Gary S. Witlen entered an
appearance.

    Before: GRIFFITH, SRINIVASAN and WILKINS, Circuit
Judges.

    Opinion for the Court filed by Circuit Judge SRINIVASAN.

     SRINIVASAN, Circuit Judge: In 1989, the National Labor
Relations Board promulgated a rule aimed to address
concerns about the undue proliferation of collective
bargaining units in health care facilities.           Excessive
fragmentation of bargaining units was viewed to increase the
potential for labor unrest, which could be particularly harmful
to the public in the health care setting. The resulting rule,
known as the Health Care Rule, established eight standardized
bargaining units for acute-care hospitals.         The list of
standardized units includes, for instance, registered nurses,
skilled maintenance employees, and guards. On a prospective
basis, the Rule deems the eight enumerated units to be the
only appropriate bargaining units in acute-care hospitals.

     This case concerns the application of the Health Care
Rule on a retrospective basis—in particular, to preexisting
bargaining units that did not conform to the eight standardized
units set forth in the Rule. The Rule calls for the Board to
address preexisting nonconforming units through case-by-
                               3
case adjudication. But the Rule prescribes that, if there is a
petition to represent an additional unit in a hospital with
preexisting nonconforming units, the Board may find the
additional unit appropriate only if it comports, to the extent
practicable, with one of the eight standardized units.

     The Board understands that aspect of the Rule to apply as
follows: in any representation election that would create a
new bargaining unit, the new unit must include all
unrepresented employees who would be grouped together in
one of the Rule’s standardized units. So, for instance, if the
new bargaining unit would include any unrepresented
registered nurses, the new unit must include all unrepresented
registered nurses, not just some of them. That approach tends
to minimize the number of employees who would be left
unrepresented, thereby limiting the potential for further
proliferation of bargaining units in the future.

     The question in this case is whether the same
understanding of the Rule governs in the case of an election to
add unrepresented employees to a preexisting bargaining unit,
as opposed to an election to create a new bargaining unit. In
other words, when a union seeks to add unrepresented
employees to a preexisting nonconforming unit, must the unit
embrace all (and not just some) of the unrepresented
employees who would fit within the same standardized unit in
the Rule? The Board’s answer is no. The Board reasons that
the addition of employees to an already existing unit—unlike
the creation of a new unit—necessarily keeps the number of
bargaining units constant. It therefore does not implicate the
core concern of the Rule, i.e., proliferation of additional
bargaining units.

     The petitioner in this case, an acute-care facility, argues
that the Board’s distinction between preexisting units and new
                               4
units under the Rule is arbitrary and incompatible with the
Board’s own precedent. We disagree. We therefore uphold
the Board’s understanding that the Rule is inapplicable in the
context of elections to add employees to a preexisting unit.

                               I.

                              A.

     Although established in 1935, the National Labor
Relations Board’s first major foray into formal rulemaking
did not come until its promulgation of the Health Care Rule
more than five decades later, in 1989. Am. Hosp. Ass’n v.
NLRB, 499 U.S. 606, 608 (1991); San Miguel Hosp. Corp. v.
NLRB, 697 F.3d 1181, 1184 (D.C. Cir. 2012). As relevant
here, the Rule addressed Congress’s concerns about undue
proliferation of bargaining units in health care facilities. See
Am. Hosp. Ass’n, 499 U.S. at 615-17; S. Rep. No. 93-766
(1974), as reprinted in 1974 U.S.C.C.A.N. 3946, 3950;
Collective-Bargaining Units in the Health Care Industry, 54
Fed. Reg. 16,336-01, 16,345-46 (Apr. 21, 1989) (to be
codified at 29 C.F.R. pt. 103). An excessive number of
bargaining units increases the prospect of jurisdictional
disputes and work stoppages, potentially impairing the
provision of health care services to the public.             See
Collective-Bargaining Units in the Health Care Industry, 53
Fed. Reg. 33900-01, 33906 (Sept. 1, 1988); Am. Hosp. Ass’n,
499 U.S. at 615.

     In response, the Health Care Rule established the
following eight standardized bargaining units for acute-care
hospitals: registered nurses, physicians, professionals other
than registered nurses and physicians, technical employees,
skilled maintenance employees, business office clerical
employees, guards, and all other nonprofessional employees.
                                 5
29 C.F.R. § 103.30(a); San Miguel Hosp. Corp., 697 F.3d at
1183. Under the Rule, the collective bargaining units in an
acute-care hospital can consist of those eight—and only those
eight—units. Am. Hosp. Ass’n, 499 U.S. at 608.

     The Rule, however, included an exception from that
mandate for nonconforming units already in existence at the
time of the Rule’s promulgation. See 29 C.F.R. § 103.30(a).
Preexisting nonconforming units were left for the Board to
address on a case-by-case basis through adjudication. See id.
§ 103.30(b).       In undertaking those adjudications, the
governing regulations cabin the Board’s discretion in one
respect of relevance here: when “there are existing non-
conforming units . . . and a petition for additional units is
filed . . . the Board shall find appropriate only units which
comport, insofar as practicable, with the appropriate unit”
from the eight standardized units. Id. § 103.30(c).

     In adjudications construing that language, the Board has
explained that, “[b]y its terms, Section 103.30(c) applies only
to petitions for ‘additional units,’ that is, petitions to represent
a new unit of previously unrepresented employees, which
would be an addition to the existing units at a facility.”
Kaiser Found. Hosps., 312 NLRB 933, 934 (1993); accord
Crittenton Hosp., 328 NLRB 879, 880 (1999). And when a
union brings a petition to represent such a new unit of
previously unrepresented employees (who are referred to as
“residual employees”), the Board has further determined that
the additional unit must include all residual employees who
would fit within the same standardized unit under the Rule.
See St. Mary’s Duluth Clinic Health Sys., 332 NLRB 1419,
1420-22 (2000).

    As an example, the Board applied that understanding of
Section 103.30(c) in a situation in which there was a
                               6
preexisting nonconforming bargaining unit that included some
of the facility’s skilled maintenance employees (which, as
noted, is one of the eight standardized categories of
employees). The Board explained that, if a union sought to
represent a new unit that would include unrepresented skilled
maintenance workers, the union could not “represent yet
another separate, residual unit that included only a portion of
the remaining unrepresented skilled maintenance employees,”
but would be “required to include all unrepresented
employees residual to the existing unit of skilled maintenance
employees.” St. Vincent Charity Med. Ctr., 357 NLRB 854,
856 (2011) (emphases added).

     The Board does not apply the same understanding,
however, if a union seeks to add residual employees to an
already existing unit rather than to create a new unit. The
mechanism by which a union adds employees to an existing
unit is known as an Armour-Globe, or self-determination,
election. See generally Armour & Co., 40 NLRB 1333
(1942); Globe Mach. & Stamping Co., 3 NLRB 294 (1937).
In its decision in St. Vincent, the Board exempted Armour-
Globe elections from Section 103.30(c) in particular and from
the Health Care Rule more generally.

     The Board explained that an “Armour-Globe self-
determination election . . . undeniably avoids any proliferation
of units, much less undue proliferation, because it does not
result in the creation of and election in a separate, additional
unit.” St. Vincent, 357 NLRB at 855. Instead, “an Armour-
Globe election permits employees sharing a community of
interest with an already represented unit of employees to vote
whether they wish to be added to the existing unit.” Id. In
that sense, a self-determination election “further[s] the
petitioned-for employees’ interest in obtaining representation
                               7
while avoiding any undue proliferation of units,” the principal
concern of the Health Care Rule. Id. at 856.

                               B.

     Petitioner Rush University Medical Center is an acute-
care teaching hospital located in Chicago, Illinois. The
International Brotherhood of Teamsters, Local 743 (the
Union) has long represented a unit of employees in different
nonprofessional job classes at Rush. The unit is a preexisting
nonconforming unit under the Health Care Rule because it
includes employees from two of the eight enumerated
categories—“other nonprofessional” employees and “skilled
maintenance” employees—but it does not include all of
Rush’s employees in either category.

    In 2014, the Union petitioned for a special election that
would enable Rush’s unrepresented Patient Care Technicians
(PCTs) to vote to be included in the preexisting
nonconforming unit. PCTs qualify as “other nonprofessional”
employees for purposes of the standardized units set forth in
the Health Care Rule. The proposed voting group for the
Armour-Globe election consisted of the roughly 245
unrepresented PCTs. Rush opposed the proposed voting
group on the ground that it was underinclusive. In Rush’s
view, the voting group, to comply with the Health Care Rule,
needed to encompass all unrepresented nonprofessional
employees (who numbered between 700 and 800), not just
PCTs.

    The Regional Director rejected Rush’s arguments and
found that the petitioned-for voting group was appropriate.
The Board then denied Rush’s request for review. The Board
considered the case to be controlled by its prior decision in St.
                                8
Vincent, which, as explained, held that Armour-Globe
elections need not conform to the Health Care Rule.

     In the ensuing election, the residual PCTs voted to be
included in the preexisting nonconforming unit. In order to
test the certification, Rush refused to bargain. The Union
filed a complaint with the Board, and the Board subsequently
found that the refusal to bargain violated the National Labor
Relations Act. Rush Univ. Med. Ctr., 362 NLRB No. 23, at
*2-3 (Feb. 27, 2015). Rush now petitions this court for
review, and the Board cross-applies for enforcement of its
order.

                              II.

     Rush contends that the Board’s bargaining unit
determination in this case relied on an impermissible
interpretation of the Health Care Rule. In Rush’s view,
Section 103.30(c)’s requirement to conform to the Rule
“insofar as practicable” should operate no differently in an
Armour-Globe self-determination election than in an election
that would add a new bargaining unit. In the former situation
no less than the latter, Rush submits, a union must add all—
not just some—residual employees who would be grouped
within the same standardized unit under the Rule. According
to Rush, the Board’s contrary conclusion in St. Vincent, to
which it adhered in this case, is arbitrary and inconsistent with
the Board’s prior decisions.

     We reject Rush’s challenge to the Board’s interpretation
and application of its own regulation. This Court will
overturn the Board’s determination of an appropriate
collective bargaining unit only if “it is arbitrary or not
supported by substantial evidence in the record.” Country
Ford Trucks, Inc. v. NLRB, 229 F.3d 1184, 1189 (D.C. Cir.
                               9
2000). We “accord the Board an especially ‘wide degree of
discretion’” on questions of representation.           Randell
Warehouse of Ariz., Inc. v. NLRB, 252 F.3d 445, 447-48 (D.C.
Cir. 2001) (quoting NLRB v. A.J. Tower Co., 329 U.S. 324,
330 (1946)). When, as here, we review an agency’s
interpretation of its own regulations, we do not “decide which
among several competing interpretations best serves the
regulatory purpose.” Thomas Jefferson Univ. v. Shalala, 512
U.S. 504, 512 (1994). Rather, we “give controlling weight to
the Board’s interpretation of its own rule unless it is plainly
erroneous or inconsistent with the regulation itself.” Alldata
Corp. v. NLRB, 245 F.3d 803, 807 (D.C. Cir. 2001).

      Here, the Board’s interpretation of the Health Care Rule
in St. Vincent is fully consistent “with the regulation itself.”
Id. The regulation’s pertinent language says that, when “there
are existing non-conforming units” and “a petition for
additional units is filed,” the “Board shall find appropriate
only units which comport, insofar as practicable, with the
appropriate unit” from the eight standardized units defined by
the Rule. 29 C.F.R. § 103.30(c). That regulation, as the
Board has explained, applies by its terms to “a petition for
additional units.” Id. (emphasis added). An Armour-Globe
self-determination election, by its nature, does not involve the
creation of any “additional units.” Rather, it involves the
inclusion of additional unrepresented employees in an
already-existing unit. Consequently, the Board’s exemption
of Armour-Globe elections from Section 103.30(c) is entirely
compatible with the regulation’s terms.

     Nor is the Board’s understanding arbitrarily at odds with
the regulation’s object. The Health Care Rule guards against
undue proliferation of bargaining units in acute-care hospitals.
An Armour-Globe self-determination election, by definition,
involves no proliferation of bargaining units at any facility.
                               10
See St. Vincent, 357 NLRB at 855. Rather, the number of
bargaining units remains constant. To be sure, the Board
could elect to require that the bargaining unit in an Armour-
Globe election, just like in a representation election to create a
new unit, must encompass all residual employees who would
fit within the same unit among the Rule’s standardized units.
But the Board did not act arbitrarily by drawing a distinction
between the two types of elections. Instead, as the Board
explained in St. Vincent, its interpretation “further[s] the
petitioned-for employees’ interest in obtaining representation”
through a self-determination election “while avoiding any
undue proliferation of units.” Id. at 856.

     Rush’s principal argument is not that the Board’s
interpretation in St. Vincent conflicts with the regulation’s text
or objectives. Rather, Rush devotes the bulk of its attention to
contending that St. Vincent is arbitrary because it departs,
without reasoned explanation, from the Board’s prior decision
in St. John’s Hospital, 307 NLRB 767 (1992). Rush’s
argument lacks merit.

     In St. John’s, there were nonconforming units predating
the Health Care Rule that included some of the hospital’s
skilled maintenance employees.          An incumbent union
petitioned for a representation election that would have added
a new bargaining unit encompassing some (but not all) of the
unrepresented skilled maintenance workers. The Board
declined to allow the representation election. The Board
explained that, in the context of a hospital with a preexisting
nonconforming unit, a union desiring to add a new unit must
include within the unit “all unrepresented employees residual
to the existing unit.” Id. at 768. Moreover, because the case
involved not a new union but instead an “incumbent wishing
to represent employees residual to those in its existing unit,”
the union was required to “do so by adding them to the
                              11
existing unit” rather than creating a new unit, “usually by
means of a self-determination election.” Id. The Board
therefore remanded “to the Regional Director for direction of
a self-determination election.” Id.

     Rush seizes on the Board’s apparent understanding of the
scope of the proposed bargaining unit for the self-
determination election that was to be conducted on remand.
The Board assumed that the union would represent “all the
remaining skilled maintenance employees as part of its
existing unit.” Id. (emphasis added). As Rush sees it, St.
John’s thereby established an inexorable command that,
whenever a union conducts an Armour-Globe self-
determination election to add unrepresented employees to a
preexisting nonconforming unit, the union must seek to add
“all”—not just some—of the residual employees who fit
within the standardized bargaining unit. St. John’s need not
be read in that fashion, however.

     To the contrary, the Board in St. Vincent gave a reasoned
explanation of why it did not understand St. John’s to have
established a blanket requirement that a union, when seeking
a self-determination election to add employees to a
preexisting unit, must include all residual employees
belonging to the same standardized unit. St. John’s involved
an effort to create “an additional, residual unit.” St. Vincent,
357 NLRB at 856. In St. Vincent (as in this case), by contrast,
the union sought to add employees “to its existing unit in a
self-determination election.” Id. Moreover, although the
Board in St. John’s remanded for the potential conduct of a
self-determination election that would encompass “all
remaining unrepresented skilled maintenance employees”—
not just some of those residual employees—the Board “did
not specifically address whether” it was correct to “includ[e]
the skilled maintenance employees not originally sought by
                              12
the” union when it petitioned for an election to create a new
unit. Id.

     In other words, the Board explained in St. Vincent, the
decision in St. John’s had assumed that a self-determination
election on remand would include all residual employees, but
without deciding whether that assumed scope was correct,
much less compelled. That assumption had arisen in St.
John’s because the Regional Director would have allowed a
representation election to add a new unit, but only if the new
unit included all residual employees. See id. And when the
employer sought review by the Board of the Regional
Director’s allowance of an election to create a new unit, the
employer did not dispute that, if the union were to seek to add
employees to a preexisting unit rather than create a new unit,
the self-determination election would—consistent with the
Regional Director’s contemplated election of a new unit—
include all residual skilled maintenance workers. As the
Board observed in St. Vincent, there was “no indication [in St.
John’s] that any party requested that the Board reconsider the
Regional Director’s inclusion of all remaining unrepresented
skilled maintenance employees if an election”—either a self-
determination election or an election to add a new unit—
“were to be held.” Id.

     That assumption explains the Board’s statement in St.
John’s that, “in the circumstances presented here, because the
[union] already represents a nonconforming unit of skilled
maintenance employees, if the [union] seeks to represent any
of the remaining unrepresented skilled maintenance
employees, the [union] must represent all the remaining
skilled maintenance employees as part of its existing unit.”
St. John’s, 307 NLRB at 768. The reference to “all the
remaining skilled maintenance employees” did not establish a
requirement that every self-determination election necessarily
                               13
encompass all residual employees. Rather, the reference
merely captured the assumed scope of the bargaining unit in
that case, which none of the parties had challenged before the
Board. The primary point of the quoted statement was instead
to establish that the union, as an incumbent union, would need
to add “the remaining skilled maintenance employees as part
of its existing unit” rather than create a new unit. Id.

     In St. Vincent, the Board described its prior decision in St.
John’s in just those terms. See St. Vincent, 357 NLRB at 856
& n.12. As a result, the Board in St. Vincent remained free to
conclude—as it did—that an Armour-Globe self-
determination election falls outside the Health Care Rule, and
thus need not include all residual employees who would fit in
the same standardized unit.

     Indeed, any contrary conclusion in St. Vincent would
have been highly difficult to square with the Board’s
intervening decisions after St. John’s. In two decisions, the
Board specifically construed Section 130.30(c) to apply only
in circumstances involving creation of an additional, new unit.
See Crittenton, 328 NLRB at 880; Kaiser, 312 NLRB at 934.
In both decisions, accordingly, the Board declined to apply
Section 130.30(c) because the circumstances did not involve
any new unit. See Crittenton, 328 NLRB at 880; Kaiser, 312
NLRB at 934. St. Vincent likewise involved no new unit.
Against the backdrop of the decisions in Crittenton and
Kaiser, the Board would have been hard-pressed to conclude
in St. Vincent that, in an Armour-Globe election in which
there necessarily is no new bargaining unit, Section 130.30(c)
nonetheless somehow applies. The Board reasonably decided
otherwise. In short, because St. Vincent reasonably found
Armour-Globe elections to fall outside the scope of Section
103.30(c), and because this case involves an Armour-Globe
                              14
election, we reject Rush’s argument that the bargaining unit in
this case impermissibly conflicted with Section 103.30(c).

     This brings us, finally, to Rush’s contention that, even if
the bargaining unit need not have encompassed all residual
nonprofessional employees, it at least needed to include
employees in the job classification of Nurse Assistant II.
Those employees, Rush urges, have highly similar job duties
to the PCTs who cast votes in the self-determination election.
The Nurse Assistant IIs thus should have been included in the
voting group, Rush asserts.         The Board rejected that
argument, and we perceive no basis for overturning the
Board’s determination.

     When considering petitions for Armour-Globe elections,
the Board looks to the proposed voting group to “determine
the extent to which the employees to be included share a
community of interest with unit employees, as well as
whether the employees to be added constitute an identifiable,
distinct segment so as to constitute an appropriate voting
group.” Warner-Lambert Co., 298 NLRB 993, 995 (1990).
In declining in this case to include Nurse Assistant IIs in the
proposed voting group, the Board relied on Rhode Island
Hospital, 313 NLRB 343 (1993). There, the Board focused
on certain characteristics of the employees in the challenged
voting group when assessing the relevant community of
interest. In particular, members had no requirement that they
be enrolled in school to maintain employment; members
received employment benefits; and members’ pay rates were
affected by performance evaluations. Id. at 365. Because the
excluded employees did not have those characteristics, the
Board found they did not share a community of interest with
the voting group. Id. at 364-65. In this case, precisely the
same three factors distinguish Nurse Assistant IIs from PCTs.
Consequently, the Board’s decision to uphold the Regional
                              15
Director’s determination that Nurse Assistant IIs did not share
a community of interest with PCTs was neither arbitrary nor
unsupported by substantial evidence.

                      *   *   *    *   *

     For the foregoing reasons, we deny Rush’s petition for
review and grant the Board’s cross-application for
enforcement.
                                               So ordered.
