Petition for Review from an Order of the Federal Mine Safety
and Health Review Commission (MSHR Nos. WEST 2015-64, WEST
Henry Moore, II (Patrick W. Dennison with him on the briefs),
Jackson Kelly PLLC, Pittsburgh, Pennsylvania, for Petitioner.
Toler Scott, Attorney (Nicholas C. Geale, Acting Solicitor of
Labor; April E. Nelson, Associate Solicitor; and Ali A.
Beydoun, Counsel, Appellate Litigation, with her on the
brief), United States Department of Labor, Office of the
Solicitor, Arlington, Virginia, for Respondents.
BRISCOE, BALDOCK, and EID, Circuit Judges.
Twentymile Mining, LLC ("Peabody Twentymile")
operates the Foidel Creek Mine, a large underground coal mine
in Colorado. The mine uses over one thousand ventilation
stoppings to separate the fresh intake air from the air
flowing out of the mine that has been circulated through
areas where extraction is occurring. Federal law requires
permanent ventilation stoppings to be "constructed in a
traditionally accepted method and of materials that have been
demonstrated to perform adequately." 30 C.F.R. §
75.333(e)(1)(i). In 2014, an inspector for the Mine Safety
and Health Administration ("MSHA") issued a
citation to Peabody Twentymile for a violation of this safety
standard because it had used polyurethane spray foam to seal
the perimeter of a permanent concrete block ventilation
Twentymile unsuccessfully contested the citation and civil
penalty before an administrative law judge ("ALJ").
The ALJ relied on the preamble to the ventilation stopping
regulation, which listed six "traditionally accepted
construction methods," to determine that Peabody
Twentymile's method of constructing concrete block
stoppings was not "traditionally accepted" and was
subject to a $162 fine. Peabody Twentymile then petitioned
the Federal Mine Safety and Health Review Commission (the
"Commission") for review, and the Commission issued
an evenly split decision, causing the ALJ's decision to
stand. Peabody Twentymile now petitions for judicial review
of the ALJ's decision. Exercising jurisdiction under 30
U.S.C. § 816(a)(1), we grant Peabody Twentymile's
petition for review. Because we conclude that Peabody
Twentymile's construction method was "traditionally
accepted" by MSHA under the unambiguous meaning of that
phrase, we reverse the ALJ's decision and vacate the
101(a) of the Federal Mine Safety and Health Act of 1977, 30
U.S.C. § 811(a), directs the Secretary of Labor to
establish mandatory health and safety standards for mines.
Under this authority the Secretary has promulgated a set of
regulations governing underground-coal-mine
ventilation." Plateau Mining Corp. v. Fed. Mine
Safety & Health Review Comm'n, 519 F.3d 1176,
1180 (10th Cir. 2008) (citing 30 C.F.R. §§
75.300-75.389). These regulations set forth generally
applicable standards for mine ventilation systems and require
each mine operator to develop and follow a mine-specific
ventilation control plan, which must be approved by an MSHA
district manager. See id. (citing 30 C.F.R. §
the relevant regulation, 30 C.F.R. § 75.333(e)(1)(i),
concerns the construction of mine ventilation stoppings.
Ventilation stoppings protect miners from noxious air and
help maintain the integrity of the mine's escapeways by
separating clean intake air from polluted outgoing air. The
Except as provided in paragraphs (e)(2), (3) and (4) of this
section all . . . permanent stoppings . . . installed after
June 10, 1996, shall be constructed in a traditionally
accepted method and of materials that have been
demonstrated to perform adequately or in a method and of
materials that have been tested and shown to have a minimum
strength equal to or greater than the traditionally accepted
30 C.F.R. § 75.333(e)(1)(i) (emphasis added). MSHA
promulgated this version of the rule in 1996 and published a
preamble to the standard. Safety Standards for Underground
Coal Mine Ventilation, 61 Fed. Reg. 9764, 9783-84 (Mar. 11,
1996). The standard itself does not define the methods or
materials that have been "traditionally accepted,"
but the preamble notes that, "[s]ince the inception of
the Mine Act, a number of traditionally accepted construction
methods have performed adequately and have served their
intended function of separating air courses." Joint
Appendix ("JA") at 211 (61 Fed. Reg. 9783). The
preamble goes on to list "traditionally accepted
construction methods," including:
 8-inch and 6-inch concrete blocks (both hollow-core and
solid) with mortared joints;
 8-inch and 6-inch concrete blocks dry-stacked and coated
on both sides with a strength enhancing sealant suitable for
 8-inch and 6-inch concrete blocks dry-stacked and coated
on the high pressure side with a strength enhancing sealant
suitable for dry-stacked stoppings;
 steel stoppings (minimum 20-gauge) with seams sealed
using manufacturer's recommended tape and with the tape
and perimeter of the metal stopping coated with suitable mine
 lightweight incombustible cementatious masonry blocks
coated on the joints and perimeter with a strength enhancing
sealant suitable for dry-stacked stoppings.
Id. (61 Fed. Reg. 9783).
Twentymile's Foidel Creek Mine utilizes two types of
ventilation stoppings: (1) temporary metal panel stoppings;
and (2) permanent concrete block stoppings. The concrete
block stoppings are constructed at Peabody Twentymile by
stacking concrete blocks, covering the blocks on their face
with a strength-enhancing bonding agent, and sealing the
sides and tops of the stoppings with polyurethane foam.
Twentymile has been utilizing this method to construct block
stoppings since at least 1991. Further, Peabody Twentymile
has included its use of polyurethane foam to seal the
perimeters of ventilation stoppings in its ventilation plans
since 1991. These ventilation plans have been reviewed and
approved by the Secretary of Labor (the
"Secretary") at least once every six months.
See 30 U.S.C. § 863(o); 30 C.F.R. §
an August 5, 2014, inspection of the Foidel Creek Mine, an
MSHA inspector and MSHA assistant district manager noticed
that the perimeter of one concrete block stopping was sealed
with Touch 'n Seal polyurethane foam and lacked any
strength-enhancing sealant around the perimeter behind the
foam. After the inspection, the MSHA inspector issued a
citation alleging a violation of 30 C.F.R. §
75.333(e)(1)(i) with regard to the concrete block stopping.
The citation read, in part:
stopping was not built in a traditionally accepted method
that has demonstrated to perform adequately. The following
conditions were observed;
1.) The perimeter of the stopping was not sealed with mortar.
2.) The perimeter of the stopping was sealed [wi]th touch N
seal foam measuring approximately 0 to 6 inches along the
ribs and roof.
JA at 198. There is no dispute the MSHA had never issued a
citation to Peabody Twentymile for its use of polyurethane
foam prior to the 2014 citation.
Twentymile contested the citation before a Commission ALJ.
After a hearing on the merits, the ALJ issued a decision
upholding the citation for violating 30 C.F.R. §
75.333(e)(1)(i) as well as the $162 penalty imposed against
Peabody Twentymile for the violation. The ALJ found the
traditionally accepted construction methods listed in the
regulation's preamble to be exhaustive and not inclusive
of the construction method Peabody Twentymile used for its
concrete block stoppings.
Twentymile petitioned the Commission for discretionary review
of the ALJ's decision, and the Commission granted review.
Two Commission members voted to affirm the ALJ's
decision, and two Commissioners voted to reverse the
ALJ's decision. The two affirming Commissioners disagreed
about the degree of deference owed to the Secretary's
interpretation of § 75.333(e)(1)(i). They both found,
however, that the Secretary's interpretation was entitled
to deference and voted to affirm the ALJ's findings that
Peabody Twentymile had not constructed the concrete block
stoppings using a "traditionally accepted method"
in violation of § 75.333(e)(1)(i).
reversing Commissioners found that "traditionally
accepted method" has a plain meaning and that MSHA had
"traditionally accepted" Peabody Twentymile's
use of polyurethane foam to seal the perimeter of its block
stoppings because it had not issued previous citations for
the practice and had consistently approved the mine's
ventilation plans. The reversing Commissioners noted,
[I]t strains credulity to characterize MSHA's continuous
approval of Peabody Twentymile's use of polyurethane foam
for over 31 years as 'an error' when that approval
took the form of explicit approval of its ventilation plans,
at least 60 reviews of that plan, and hundreds of inspections
covering hundreds of block stoppings without issuing a single
JA at 264. They also concluded that "it defies credulity
to assert that MSHA allowed an unsafe practice to exist for
three decades in a large and important underground coal
mine." Id. The reversing Commissioners noted
that, even if 30 C.F.R. § 75.333 were ambiguous, the
Secretary's interpretation should not be entitled to
deference because neither the regulation nor the preamble
prohibits the method and the Secretary's enforcement
practices prior to 2014 do not align with the Secretary's
result of the Commissioners' split decision, the
ALJ's decision stood as though affirmed. See Plateau
Mining Corp., 519 F.3d at 1191; Sec'y of Labor,
Mine Safety & Health Admin. v. Penn. Elec. Co., 12
FMSHRC 1562, 1563-65 (1990), aff'd on other
grounds, 969 F.2d 1501 (3d Cir. 1992).
there is no majority decision from the Commission, we review
the ALJ's factual findings for substantial evidence and
legal conclusions de novo. Plateau Mining Corp., 519
F.3d at 1191. Questions of statutory and regulatory
interpretation are also reviewed de novo. Bridger Coal
Co. v. Dir., Office of Workers' Comp. Programs, U.S.
Dep't of Labor, 669 F.3d 1183, 1190 (10th Cir.
"first step in interpreting a statute is to determine
whether the language at issue has a plain and unambiguous
meaning with regard to the particular dispute in the
case." Ceco Concrete Constr., LLC v. Centennial
State Carpenters Pension Tr., 821 F.3d 1250, 1258 (10th
Cir. 2016) (quoting Robinson v. Shell Oil Co., 519
U.S. 337, 340 (1997)). When interpreting an administrative
regulation, "we apply the same rules we use to interpret
statutes. We begin by examining the plain language of the
text, giving each word its ordinary and customary meaning.
If, after engaging in this textual analysis, the meaning of
the regulations is clear, our analysis is at an end."
Mitchell v. Comm'r, 775 F.3d 1243, 1249 (10th
Cir. 2015) (citations omitted). If the regulation is
unambiguous, we will enforce it in accordance with its plain
meaning, giving no deference to a contrary interpretation by
the Secretary of Labor. See id.
case turns on the meaning of 30 C.F.R. §
75.333(e)(1)(i), which requires permanent ventilation
stoppings to "be constructed in a traditionally accepted
method and of materials that have been demonstrated to
perform adequately or in a method and of materials that have
been tested and shown to have a minimum strength equal to or
greater than the traditionally accepted in-mine
controls." The "method" at issue in this case
is the use of polyurethane foam to seal the perimeters of
concrete block stoppings. The parties acknowledge that
Peabody Twentymile's method for constructing block
stoppings has not undergone strength testing,  and Peabody
Twentymile does not argue that its method complies with any
of the five methods for stopping construction listed in the
regulation's preamble. As a result, Peabody
Twentymile's use of foam must be within the meaning of
"traditionally accepted method" as that phrase
appears in the regulation itself.
question in this case, then, is what constitutes a
"traditionally accepted method" of construction as
that term is used in § 75.333(e)(1)(i). The terms
"traditionally" and "accepted" are not
defined in the standard. The absence of a definition in the
standard, however, does not necessarily make the term
ambiguous. In these circumstances, we apply the ordinary or
dictionary definitions of the terms. Jones v.
Comm'r, 560 F.3d 1196, 1200-01 (10th Cir. 2009)
(applying plain meaning of 26 U.S.C. § 1221(a)(3)(B) to
conclude taxpayer's charitable donation of discovery
material to museum, which was "prepared or
produced" for the taxpayer, could not be used to claim
around 1996 when the regulation was promulgated,
"traditionally" was defined as: "[i]n a
traditional manner; by, in the way of, or according to
tradition." Oxford English Dictionary (2d ed. 1989). The
plain and ordinary meaning of "tradition" was
"[a] long established and generally accepted custom or
method of procedure, having almost the force of a law."
Id. "Tradition" was also defined as
"[a] time-honored practice." The American Heritage
Dictionary of the English Language (3d ed. 1996).
"Accepted" was defined as "[w]idely
encountered, used, or recognized," id., and as
"[r]eceived as offered; well-received; approved" or
"[h]ence, satisfactory, acceptable," Oxford English
Dictionary (2d ed. 1989). "Traditionally accepted,"
therefore, means "approved of in a customary manner or
regularly over a period of time." Under this
interpretation, a method that was repeatedly accepted by MHSA
inspectors over a considerable period of time would satisfy
the definition of "traditionally accepted."
Secretary disagrees with this definition of
"traditionally accepted" and argues that a method
can only be "traditionally accepted" if it appears
on the list of methods in the preamble of the regulations.
The problem with the Secretary's interpretation, however,
is that it is inconsistent with the plain language of the
regulation. The regulation's plain language is broader
than the Secretary suggests and points to a definition of
"traditionally accepted" as a method approved of
over a period of time. There is nothing in the language of
the regulation that suggests that a traditionally accepted
method is somehow further limited. Indeed, as the Secretary
points out, there could be many ways in which a method could
become traditionally accepted under the plain language of the
regulation. Aple. Br. at 19. For example, a method could be
accepted by MHSA inspections over a considerable period of
time, through long-recognized industry standards, or by
regulations that limit or define such methods. See
id. The broad language of the regulation would permit
all of these methods to qualify as "traditionally
Secretary points out, and we acknowledge, that a regulation
is "ambiguous if it is reasonably susceptible to more
than one interpretation or capable of being understood in two
or more possible senses or ways." Nat'l Credit
Union Admin. Bd. v. Nomura Home Equity Loan, Inc., 764
F.3d 1199, 1226 (10th Cir. 2014) (quotation marks omitted).
But that is not the case here. The term "traditionally