                                                                              FILED
                                                                  United States Court of Appeals
                                       PUBLISH                            Tenth Circuit

                      UNITED STATES COURT OF APPEALS                     March 5, 2019

                                                                      Elisabeth A. Shumaker
                            FOR THE TENTH CIRCUIT                         Clerk of Court
                        _________________________________

 ROCKWOOD CASUALTY INSURANCE
 COMPANY, insurer of Hidden Splendor
 Resources, Inc.,

       Petitioner,

 v.                                                           No. 18-9520

 DIRECTOR, OFFICE OF WORKERS’
 COMPENSATION PROGRAMS,
 UNITED STATES DEPARTMENT OF
 LABOR; TONY KOURIANOS,

       Respondents.
                        _________________________________

          Petition for Review from an Order of the Benefits Review Board
                            (Benefits No. 17-0323 BLA)
                       _________________________________

Cheryl L. Intravaia, Feirich/Mager/Green/Ryan, Carbondale, Illinois, for Petitioner.

Victoria S. Herman (Joseph E. Wolfe, with her on the brief), Wolfe Williams &
Reynolds, Norton, Virginia, for Tony N. Kourianos, Respondent.

William M. Bush (Kate S. O’Scannlain, Solicitor of Labor, Kevin Lyskowski, Associate
Solicitor, Gary K. Stearman, Counsel for Appellate Litigation, and Rita A. Roppolo,
Attorney, on the brief), U.S. Department of Labor, Washington, D.C., for Director, Office
of Workers’ Compensation Programs, Respondent.

                        _________________________________
Before BRISCOE, MATHESON, and BACHARACH, Circuit Judges.

                         _________________________________

MATHESON, Circuit Judge.
                   _________________________________

       Congress enacted the Black Lung Benefits Act (“BLBA”), 30 U.S.C. §§ 901-944,

in 1969 to compensate miners with pneumoconiosis, commonly known as “black lung

disease.” Antelope Coal Co./Rio Tinto Energy Am. v. Goodin, 743 F.3d 1331, 1335 (10th

Cir. 2014). The BLBA provides benefits to coal miners who become totally disabled

from pneumoconiosis caused by their mining work. Id.

       Tony N. Kourianos worked as a coal miner for more than 27 years before filing a

claim for benefits under the BLBA. His claim was reviewed through a three-tiered

administrative process. Ultimately, the Benefits Review Board (“BRB”) found that he

was entitled to benefits. The BRB also found that Mr. Kourianos’s last employer, Hidden

Splendor Resources, Inc. (“Hidden Splendor”), was the “responsible operator” liable for

paying those benefits. Hidden Splendor’s insurer, Rockwood Casualty Insurance

Company (“Rockwood”), petitions this court for review of the BRB’s decision. Along

with Mr. Kourianos, the Director of the Office of Workers’ Compensation Programs

(“OWCP” or “Director”) is a respondent in this case. See 20 C.F.R. § 725.360(a)(5)

(stating that the Director will be a party “in all proceedings relating to a claim for

benefits”).




                                              2
       Rockwood challenges the BRB’s decision on two grounds. First, it argues the

BRB incorrectly affirmed the administrative law judge’s (“ALJ”) decision prohibiting

Hidden Splendor from withdrawing its responsible operator stipulation. Second, it argues

the BRB incorrectly found that Mr. Kourianos was totally disabled and entitled to

benefits.

       Exercising jurisdiction under 30 U.S.C. § 932(a) and 33 U.S.C. § 921(c), we deny

Rockwood’s petition.

                                    I. BACKGROUND

       We describe the legal framework governing Mr. Kourianos’s claim for benefits

and then recount the specific factual and procedural history of his case.

                                   A. Legal Background

       A claim for BLBA benefits contemplates two critical questions. First, which

operator is responsible for paying benefits under the BLBA? Second, is the claimant

entitled to benefits under the Act? The following presents the law applicable to these two

questions and the Department of Labor’s three-tiered administrative process for deciding

BLBA claims.

1. The Responsible Operator Determination

       The BLBA provides that individual coal mine operators are liable for a miner’s

benefits if the miner’s disability or death arose “at least in part” from coal mine




                                              3
employment with the operator. 30 U.S.C. § 932(c); 20 C.F.R. § 725.494(a).1 To ensure

coal mine operators can pay their miners’ benefits, Congress imposed workers’

compensation insurance requirements on them. 30 U.S.C. § 933(a); 20 C.F.R. § 726.1.

As a fallback alternative, Congress created the Black Lung Disability Trust Fund, which

assumes liability for miners’ benefits if “there is no operator who is liable for the

payment of such benefits.” 26 U.S.C. § 9501(d)(1)(B).

       To implement the BLBA, Congress directed the Department of Labor to

promulgate regulations “for determining whether pneumoconiosis arose out of

employment in a particular coal mine or mines.” 30 U.S.C. § 932(h). Under the

regulations, a coal mine operator is a “potentially liable operator” if (i) the miner’s

disability or death arose out of employment with the operator; (ii) the entity was an

operator after June 30, 1973; (iii) the miner worked for the operator for at least one year;

(iv) the miner’s employment with the operator included at least one working day after

December 31, 1969; and (v) the operator is financially capable of assuming liability for

the claim. 20 C.F.R. § 725.494(a)-(e). The regulations state that the “operator

responsible for the payment of benefits . . . shall be the potentially liable operator . . . that

most recently employed the miner.” Id. § 725.495(a)(1).


       1
         Because Mr. Kourianos filed his claim after January 19, 2001, the current version
of the BLBA regulations apply to his claim. 20 C.F.R. § 725.2 (“This part applies to all
claims filed after January 19, 2001 and all benefits payments made on such claims.”); see
Antelope Coal, 743 F.3d at 1341-42 (holding that 2013 amendments to BLBA regulations
applied retroactively to claim filed before amendments were promulgated); see also
Consolidation Coal Co. v. Dir., OWCP, 864 F.3d 1142, 1151 (10th Cir. 2017).
                                              4
       The BLBA defines a miner as “any individual who works or has worked in or

around a coal mine or coal preparation facility in the extraction or preparation of coal.”

30 U.S.C. § 902(d); see also 20 C.F.R. § 725.202(a). To meet the statutory definition of

a “miner,” the claimant must establish that he or she (1) worked “in or around a

statutorily defined coal mine (the ‘situs’ test),” and (2) performed “duties involv[ing] the

extraction or preparation of coal, or involv[ing] appropriate coal mine construction or

transportation (the ‘function’ test).” Falcon Coal Co. v. Clemons, 873 F.2d 916, 921 (6th

Cir. 1989) (citing 30 U.S.C. § 802(h)(2) and surveying case law).2

       In sum, under the BLBA, the responsible operator is the last coal mine operator to

have employed the claimant as a “miner” for more than one year. 20 C.F.R.

§§ 725.494(c), 725.495(a)(1).

2. The Benefits Determination

       To obtain benefits under the BLBA, a claimant must prove

              (1)    he or she suffers from pneumoconiosis (disease),

              (2)    the pneumoconiosis arose out of coal mining
                     employment (disease causation),

              (3)    he or she is totally disabled due to a respiratory or
                     pulmonary impairment (disability), and

              (4)    pneumoconiosis is a substantially contributing cause of
                     the total disability (disability causation).

       2
        We applied the “situs” and “function” tests in Wackenhut Corp. v. Hansen ex rel.
Hansen, 560 F. App’x 747, 750 (10th Cir. 2014) (unpublished) (cited for persuasive
value under Fed. R. App. P. 32.1, 10th Cir. R. 32.1).

                                              5
Energy W. Mining Co. v. Estate of Blackburn, 857 F.3d 817, 822 (10th Cir. 2017); see

also 30 U.S.C. §§ 902, 921; 20 C.F.R. §§ 725.202(d)(2), 718.204(c)(1).

       Below, we discuss four additional aspects of a BLBA claim: (a) the “15-year

presumption,” (b) the difference between clinical and legal pneumoconiosis, (c) the

10-year presumption and the disease causation element, and (d) the showing necessary to

demonstrate a “total disability.”

       a. The 15-year presumption and rebuttal

       The BLBA created a rebuttable “presumption that a miner is disabled due to

pneumoconiosis when he or she has worked for 15 years in underground coal mines or

substantially similar conditions and is totally disabled from a respiratory or pulmonary

condition (the ‘15-year presumption’).” Antelope Coal, 743 F.3d at 1335; see 30 U.S.C.

§ 921(c)(4). “In other words, a miner who proves 15 years of coal mine work and total

disability is entitled to a presumption that the remaining elements of his claim are

established.” Antelope Coal, 743 F.3d at 1335; see Blackburn, 857 F.3d at 822 (stating

that a claimant’s burden is “soften[ed]” when he has worked for at least 15 years as a

miner).

       The party opposing an award of benefits under the BLBA may rebut the 15-year

presumption by establishing that (1) the claimant does not have pneumoconiosis or

(2) pneumoconiosis did not cause any part of the miner’s respiratory or pulmonary total

disability. 20 C.F.R. § 718.305(d). In other words, once a claimant establishes the


                                             6
15-year presumption, the operator must rebut the existence of (1) the disease, or (2) the

disease or disability causation. Blackburn, 857 F.3d at 822. “The presumption must not

be considered rebutted on the basis of evidence demonstrating the existence of a totally

disabling obstructive respiratory or pulmonary disease of unknown origin.” 20 C.F.R.

§ 718.305(d).

         b. Clinical and legal pneumoconiosis

         “The BLBA recognizes two types of pneumoconiosis: clinical and legal.”

Antelope Coal, 743 F.3d at 1335. The 15-year presumption applies to both classifications

of the disease. Consolidation Coal Co. v. Dir., OWCP, 864 F.3d 1142, 1144 (10th Cir.

2017).

         Clinical pneumoconiosis refers to diseases the medical community has recognized

as pneumoconiosis, including “conditions characterized by . . . the fibrotic reaction of the

lung tissue to . . . deposition [of particulate matter] caused by dust exposure in coal mine

employment.” 20 C.F.R. § 718.201(a)(1).

         Legal pneumoconiosis, on the other hand, is defined as any “chronic dust disease

of the lung and its sequelae, including respiratory and pulmonary impairments, arising

out of coal mine employment.” 30 U.S.C. § 902(b); see 20 C.F.R. § 718.201(a)(2) (“This

definition includes, but is not limited to, any chronic restrictive or obstructive pulmonary

disease arising out of coal mine employment.”). To show legal pneumoconiosis, a

claimant therefore “must satisfy both the Disease and Disease causation elements” of a

BLBA claim. Blackburn, 857 F.3d 817. Legal pneumoconiosis encompasses “a broader

                                              7
class of lung diseases that are not pneumoconiosis as the term is used by the medical

community.” Andersen v. Dir., OWCP, 455 F.3d 1102, 1104 (10th Cir. 2006). In other

words, a claimant may have legal pneumoconiosis without ever receiving a formal

medical diagnosis of “pneumoconiosis.” See id.

       c. The 10-year presumption and disease causation

       The 15-year presumption establishes the second element of a BLBA claim—the

pneumoconiosis arose out of coal mining employment. See Blackburn, 857 F.3d at 822.

The second element also may be established under the BLBA’s 10-year presumption.

See 30 U.S.C. § 921(c)(1).

       “Arising out of coal mine employment” means the relevant lung disease or

impairment is “significantly related to, or substantially aggravated by, dust exposure in

coal mine employment.” 20 C.F.R. § 718.201(b). “If a miner who is suffering or

suffered from pneumoconiosis was employed for ten years or more in one or more coal

mines there shall be a rebuttable presumption that his pneumoconiosis arose out of such

employment.” 30 U.S.C. § 921(c)(1); see 20 C.F.R. § 718.203(b). The 10-year

presumption overlaps with the 15-year presumption because both presumptions shift the

burden to the employer to submit evidence to disprove that a claimant’s pneumoconiosis

arose out of coal mine employment. Because the 15-year presumption addresses the

element of disability causation in addition to disease causation, however, the 10-year

presumption is effectively subsumed by the 15-year presumption.



                                             8
       d. Total disability

       One of the elements to establish the 15-year presumption is proof of total

disability from a respiratory or pulmonary condition. A miner is considered “totally

disabled” if he or she has “a pulmonary or respiratory impairment which,” on its own,

prevents the miner from (i) “performing his or her usual coal mine work” and

(ii) “engaging in gainful employment in the immediate area of his or her residence

requiring the skills or abilities comparable to those of any employment in a mine or

mines in which he or she previously engaged with some regularity over a substantial

period of time.” 20 C.F.R. § 718.204(b)(1).

       The BLBA regulations provide that a miner can qualify for a total disability

determination by submitting evidence from (1) pulmonary function tests, (2) arterial

blood gas tests, or (3) medical evidence of right-side congestive heart failure. 20 C.F.R.

§ 718.204(b). In addition, when total disability cannot be shown by these three

categories of testing, the regulations provide that “total disability may nevertheless be

found if a physician exercising reasoned medical judgment, based on medically

acceptable clinical and laboratory diagnostic techniques, concludes that a miner’s

respiratory or pulmonary condition prevents . . . the miner from engaging in [the

claimant’s usual] employment.” 20 C.F.R. § 718.204(b)(2). Arterial blood gas studies

and medical opinions provide the key evidence of “impairment” in this case.

       The BLBA regulations provide standards for evaluating arterial blood gas studies.

See 20 C.F.R. pt. 718, App. C. These standards are depicted in “Appendix C,” which

                                              9
“contains three tables of ‘qualifying’ values for arterial-blood gas studies . . . . A test that

produces ‘qualifying’ values is deemed, in the absence of contrary evidence, indicative of

a totally disabling respiratory or pulmonary impairment.” Regulations Implementing the

Byrd Amendments to the Black Lung Benefits Act: Determining Coal Miners’ and

Survivors’ Entitlement to Benefits, 77 Fed. Reg. 19456, 19464 (Mar. 30, 2012).

       Appendix C incorporates three categories of data: (1) the altitude at which the test

was taken, (2) a partial pressure of oxygen (“PO2”) reading, and (3) a partial pressure of

carbon dioxide (“PCO2”) reading. See 20 C.F.R. pt. 718, App. C. First, Appendix C

consists of three charts, each based on a different altitude range and each with a different

set of PO2 and PCO2 values: (1) 0 to 2,999; (2) 3,000 to 5,999; and (3) 6,000 or more

feet above sea level. Id. Second, Appendix C compares the blood’s carbon dioxide

pressure levels (PCO2) with the oxygen pressure levels (PO2) to determine how fast the

subject’s lungs are producing oxygen. See id.; Suppl. App. 17-18. Third, at each PCO2

reading in the chart, Appendix C sets a “qualifying” PO2 value, below which the miner

will be deemed impaired in the absence of contrary evidence. Id. For example, in the

3,000-to-5,999-foot altitude range, a claimant with a PCO2 level of 26 would qualify as

“impaired” if his or her PO2 level was 69 or lower. We reproduce the chart for the

3,000-to-5,999 category below:




                                              10
20 C.F.R. Pt. 718, App. C.

3. Procedures for Claims Under the BLBA

      Claims under the BLBA are subject to three levels of administrative review.3

First, the OWCP district director4 receives and develops documentary evidence and

issues a proposed decision and order (“PDO”) regarding benefits and liability. 20 C.F.R.

§§ 725.414, 725.418. Second, if a party wishes to challenge the PDO, it may request a

hearing before an ALJ who reviews evidence—including oral testimony—and issues a


      3
        The Secretary of Labor has a discretionary right to undertake a fourth level of
review, but he did not do so here. See 20 C.F.R. § 726.317(a).
      4
        The “district director” should not be confused with the Director of OWCP, the
Department of Labor official charged with administering the BLBA program. See 20
C.F.R. § 1.1(a).

                                            11
“decision and order.” Id. §§ 725.419(a), 725.476. Third, a party dissatisfied with the

ALJ’s decision may appeal to the BRB, which reviews the hearing record for error and

issues its own decision. 33 U.S.C. § 921(b)(3); 20 C.F.R. § 725.481. Aggrieved

parties-in-interest may appeal BRB orders to an appropriate circuit court. See 33 U.S.C.

§ 921(c); 30 U.S.C. § 932(a); 20 C.F.R. § 725.482.

       a. District director review

       Once a miner files a claim for benefits under the BLBA, the OWCP district

director investigates the claim and determines whether one or more operators are

potentially liable. 20 C.F.R. § 725.407(a). The district director then notifies each

potentially liable operator of the claim and sends “a copy of the claimant’s application

and a copy of all evidence obtained by the district director relating to the miner’s

employment.” Id. § 725.407(c).

       Each notified operator has 30 days to accept or contest its designation as a

potentially liable operator. Id. § 725.408(a)(1). “If the operator contests its

identification, it shall . . . state the precise nature of its disagreement” in its response. Id.

§ 725.408(a)(2). The operator may submit documentary evidence in support of its

disagreement within 90 days of receiving the OWCP notice. Id. § 725.408(b)(1). The

regulations further provide, “No documentary evidence relevant to [the operator’s

potential liability] may be admitted in any further proceedings unless it is submitted

within” the 90-day time limit. Id. § 725.408(b)(2).



                                               12
       After receiving a potentially liable operator’s response, the district director

develops and reviews the relevant medical evidence and issues a “schedule for the

submission of additional evidence” (“SSAE”), which includes a preliminary

determination of the miner’s entitlement to benefits. Id. § 725.410(a). The SSAE also

states which of the potentially liable operators has been identified as the responsible

operator for the claim. Id. § 725.410(a)(3). Once identified, the designated responsible

operator has 30 days to accept or contest its designation. Id. § 725.412(a)(1). If the

operator accepts its responsible operator designation or fails to file a timely response, the

operator “shall be deemed to have accepted the district director’s designation with respect

to its liability, and to have waived its right to contest its liability in any further proceeding

conducted with respect to the claim.” Id. § 725.412(a)(2).

       At the end of this initial level of proceedings, the district director makes a final

recommendation of entitlement to benefits, designates the responsible operator, and

issues a written proposed decision and order (“PDO”). 20 C.F.R. § 725.418(d). When it

issues the PDO, the district director must “dismiss, as parties to the claim, all other

potentially liable operators.” Id.

       b. Administrative law judge proceedings

       Parties-in-interest who wish to contest a PDO’s findings or conclusions may

request a hearing before an ALJ. Id. § 725.419(a). Upon receiving a party’s request, the

district director refers the case to the Office of Administrative Law Judges. Id. An ALJ

then holds a formal hearing and may take oral testimony. Id. § 725.455. With one

                                               13
exception not relevant here, “[t]he district director may not notify additional operators of

their potential liability after a case has been referred to the Office of Administrative Law

Judges.” Id. § 725.407(d).

       “Except as otherwise provided in this section, the hearing shall be confined to

those contested issues which have been identified by the district director or any other

issue raised in writing before the district director.” Id. § 725.463(a) (citation omitted).

One exception is critical here:

              An administrative law judge may consider a new issue only if
              such issue was not reasonably ascertainable by the parties at
              the time the claim was before the district director. Such new
              issue may be raised upon application of any party, or upon an
              administrative law judge’s own motion, with notice to all
              parties, at any time after a claim has been transmitted by the
              district director to the Office of Administrative Law Judges
              and prior to decision by an administrative law judge. If a new
              issue is raised, the administrative law judge may, in his or her
              discretion, either remand the case to the district director with
              instructions for further proceedings, hear and resolve the new
              issue, or refuse to consider such new issue.

20 C.F.R. § 725.463(b) (emphasis added).

       After the hearing, the ALJ issues a decision and order resolving the claim. Id.

§ 725.476.

       c. Proceedings before the BRB

       “Any party dissatisfied with a decision and order issued by an [ALJ] may . . .

appeal the decision and order to the [BRB.]” Id. § 725.481. The BRB does not receive

new evidence. 33 U.S.C. § 921(b)(3); 20 C.F.R. § 802.301(b). Instead, a panel of three


                                              14
ALJs considers the record and issues a decision. See 20 C.F.R. §§ 802.301-802.309. The

panel may hold oral argument, but it need not do so. Id. § 802.304. The Secretary of

Labor has discretion to review the BRB’s decisions. Id. § 726.317(a).

                                 B. Procedural History

      In 2012, Mr. Kourianos’s claim started making its way through the three-tiered

administrative review outlined above.

1. Proceedings Before the OWCP District Director

      After receiving the claim, the OWCP district director used Mr. Kourianos’s Social

Security earnings report to identify two potentially liable operators: Hidden Splendor and

West Ridge Resources, Inc. Suppl. App. at 47-52.5 The district director then sent each

potentially liable operator a “Notice of Claim.” Id. Hidden Splendor initially denied it

was the responsible operator, arguing that it employed Mr. Kourianos as a miner for less

than one year. Approximately one month after its initial response, however, Hidden

Splendor filed an amended response admitting that it was “the responsible operator

within the meaning of the [BLBA].” Id. at 58.

      On February 6, 2013, approximately three months after its amended response, a

Hidden Splendor “senior staff accountant” faxed the district director a document with the



      5
         The Government filed a Supplemental Appendix (“Suppl. App.”) containing the
key documents from the administrative review process. Within the administrative record,
we cite the director’s exhibits as “DX” and the Employer’s (Rockwood/Hidden
Splendor’s) exhibits as “EX.” We cite the transcript of the ALJ’s hearing as “ALJ Hrg.
Tr.”

                                            15
heading “Hire Dates for Tony Kourianos.” Id. at 46. The one-page document listed three

periods of employment for Mr. Kourianos: (1) “December 26, 2006 to April 11, 2007 –

In the Mine”; (2) “November 16, 2010 to January 21, 2011 – In the Mine”; and

(3) “April 5, 2011 to October 14, 2011 – Outside at the Loadout.” Id.

       After reviewing the documentary evidence, the district director issued an SSAE,

which made the following preliminary conclusions: (1) Mr. Kourianos “would be

entitled to benefits if [the district director] issued a decision at this time,” and (2) Hidden

Splendor “is the responsible operator liable for the payment of benefits.” Id. at 60.

Hidden Splendor responded to the SSAE, stating, “You will find Hidden Splendor has

accepted the designation of Responsible Operator but contests Claimant’s entitlement for

benefits.” Id. at 73. The district director then issued its PDO, which adopted the

preliminary conclusions in the SSAE and dismissed West Ridge as a potentially

responsible operator.

       Hidden Splendor sought ALJ review of the district director’s determination that

Mr. Kourianos was entitled to benefits. In its “statement of contested issues,” Hidden

Splendor “advise[d] the parties that [it] does not dispute its designation as the

Responsible Operator in this claim.” Id. at 83 (emphasis in original).




                                              16
2. Proceedings Before the ALJ

       The ALJ issued two orders, one confirming Hidden Splendor’s designation as the

responsible operator and a second finding Mr. Kourianos was entitled to benefits.

       a. Responsible operator determination

       The ALJ held a formal hearing in Price, Utah, on August 12, 2014. Mr. Kourianos

testified and explained his job duties at Hidden Splendor. He testified that during the first

two periods with the company listed on the staff accountant’s fax, he worked as an

instructor and a fire boss in the mine. During the last period of employment, however, he

worked “at the loadout,” Suppl. App. at 46, performing “night watchman” duties to

ensure that people did not trespass or take materials from the mine. ALJ Hrg. Tr. at 51,

55. He noted that he did not mine or provide instruction to miners during that time. For

some of his time as a night watchman, the mine was not operational.

       Because Mr. Kourianos’s testimony suggested that he did not work as a “miner”

for a full year at Hidden Splendor, Rockwood’s counsel moved to withdraw the

stipulation that Hidden Splendor was the responsible operator for the claim. The ALJ

permitted the parties to file supplemental briefing on whether Hidden Splendor should be

allowed to withdraw its responsible operator stipulation.

       The ALJ denied Rockwood’s motion. He applied 20 C.F.R. § 725.463(b), which,

as noted above, states that an ALJ “may consider a new issue only if such issue was not

reasonably ascertainable by the parties at the time the claim was before the district

director.” Suppl. App. at 2-3. The ALJ found that the evidence of Mr. Kourianos’s work

                                             17
was “reasonably ascertainable” when the claim was pending before the district director,

noting:

               While I appreciate that Claimant’s testimony at the hearing
               concerning his job duties for Employer came as a surprise, I
               note that one significant piece of written documentation
               related to the [responsible operator] issue, the “Hire Dates for
               Tony Kourianos” fax, was submitted by Employer.
               Furthermore, this piece of evidence, which Employer states in
               its brief was prepared by Employer’s “staff accountant,”
               distinguished between the periods when Claimant worked “in
               the mine” and “at the Loadout.” Thus, Employer might have
               ascertained what job duties Claimant performed, and thereby
               determined whether Hidden Splendor should have been
               named the [responsible operator], by interviewing its own
               agent regarding the evidence it submitted.

Suppl. App. at 3 (citations omitted).

        b. Entitlement to benefits

        The ALJ issued his Decision and Order on February 28, 2017. The order

addressed the following issues:

               (1)    The length of Mr. Kourianos’s coal mine employment;

               (2)    Whether Mr. Kourianos suffer[ed] from
                      pneumoconiosis, as defined by the Act and
                      regulations;

               (3)    If so, whether Mr. Kourianos’s pneumoconiosis arose
                      from his coal mine employment;

               (4)    Whether Mr. Kourianos [was] totally disabled; and

               (5)    If so, whether Mr. Kourianos [was] totally disabled
                      due to pneumoconiosis.

Id. at 7.

                                             18
              i. Employment and smoking history

       The ALJ found that Mr. Kourianos was a miner for 27.27 years.6 During this

time, Mr. Kourianos “worked in various capacities as a coal miner,” but his “usual coal

mine work” was working as a “fire boss.” Suppl. App. at 14-15. As a fire boss, Mr.

Kourianos conducted frequent examinations of the mine and carried a tool belt that

weighed at least 30 to 32 pounds. Accordingly, the ALJ found that Mr. Kourianos’s

usual mine work qualified as “medium work” under 20 C.F.R. § 404.1567(c) (describing

classifications of physical stress involved in different kinds of work). The ALJ further

found that Mr. Kourianos smoked an average of 7.5 cigarettes per day for approximately

44 years.

       Rockwood’s petition does not contest the ALJ’s employment classification or Mr.

Kourianos’s smoking history.

              ii. Medical tests

       The ALJ considered X-rays, which showed no pulmonary irregularities. He also

reviewed “pulmonary function tests,” which likewise did not show evidence of legal

pneumoconiosis. Id. at 17.




       6
        The ALJ did not include Mr. Kourianos’s time as a Hidden Splendor “security
guard” in this calculation. Suppl. App. at 9.

                                            19
       The ALJ next examined Mr. Kourianos’s “arterial blood gas studies,” which

measure the ability of the lungs to oxygenate blood. Under 20 C.F.R. § 718.204(b)(2)(ii),

such tests may be used to establish total disability. The ALJ explained,

                A defect will manifest itself primarily as a fall in arterial
                oxygen tension either at rest or during exercise. The blood
                sample is analyzed for the partial pressure of oxygen (“PO2”)
                and the partial pressure of carbon dioxide (“PCO2”) in the
                blood. A lower level of oxygen (“O2”) compared to carbon
                dioxide (“CO2”) indicates a deficiency in the transfer of gases
                through the alveoli which may leave the miner disabled.

Id. at 17-18.

       As discussed above, Appendix C provided the framework for the ALJ’s analysis

of Mr. Kourianos’s arterial blood gas studies. 20 C.F.R. pt. 718, App. C. To read the

results of these studies, the ALJ (1) selected the correct altitude range from Appendix C,

(2) identified Mr. Kourianos’s PCO2 readings, and (3) identified the threshold PO2 value

corresponding to the PCO2 reading. If Mr. Kourianos’s PO2 level was below the

threshold value, he would qualify as “impair[ed].” See id. If it fell above the impairment

threshold, he would not.

       The ALJ considered results from two sets of Mr. Kourianos’s arterial blood gas

tests taken at Castleview Hospital in Price, Utah. Price sits at approximately 5,566 feet

above sea level, and the tests therefore accounted for an altitude of 3,000-5,999 feet. Mr.

Kourianos’s 2010 test yielded a PO2 level of 60 at rest, which, when measured against

his PCO2 level of 43, did not qualify him as impaired under Appendix C (the threshold

impairment level was a PO2 level of 55). His 2012 test showed a resting PCO2 level of

                                              20
39 and a corresponding PO2 level of 68, which also did not qualify him as impaired

under Appendix C because the threshold PO2 level was 56. Id. But the 2012 test

revealed a PO2 level of 59 after exercise, which fell below the threshold of 62 (at a PCO2

level of 33) announced in Appendix C and therefore qualified him as impaired. Id.

      The ALJ detailed the results in the following chart:




Suppl. App. at 18.

             iii. Medical reports and opinions

      The ALJ also considered reports and depositions from three doctors. Mr.

Kourianos selected Dr. Shane Gagon to perform the medical screening for his BLBA

claim. Rockwood engaged Drs. George Zaldivar and Jeff Selby to examine and comment

on Mr. Kourianos’s medical records. Neither Dr. Zaldivar nor Dr. Selby examined Mr.

Kourianos in person.

      In brief, Dr. Gagon concluded that Mr. Kourianos was totally disabled, while Drs.

Zaldivar and Selby opined that Mr. Kourianos did not suffer from pneumoconiosis and

was not totally disabled. Drs. Zaldivar and Selby further attributed Mr. Kourianos’s

respiratory issues to his history of smoking, while Dr. Gagon believed that smoking and

                                           21
coal mine work contributed equally to Mr. Kourianos’s respiratory impairment. After

receiving Dr. Zaldivar’s report, Dr. Gagon filed a supplemental report, discussed below.

                     1) Dr. Gagon

       Dr. Gagon examined Mr. Kourianos in August 2012, conducted arterial blood gas

testing, and issued his report shortly thereafter. Dr. Gagon found that Mr. Kourianos

“suffered from moderate impairment with subjective chronic shortness of breath with

minimal exertion and PO2 with exercise.” Suppl. App. at 18 (quotations omitted). He

diagnosed Mr. Kourianos with chronic bronchitis and a significant drop in PO2 levels

with exercise. Dr. Gagon concluded the bronchitis was likely caused by “coal dust

exposure and smoking” and that both factors “probably” contributed equally to the

impairment. Id. (quotations omitted).

       Dr. Gagon initially opined that Mr. Kourianos “would be able to work in the coal

mine” but “not at the same degree with someone with no abnormalities” and “as long as

his job was fairly sedentary.” Suppl. App. at 19 (quotations and brackets omitted). The

ALJ summarized Dr. Gagon’s disability determination: “But based on Claimant’s

description of the more physical job he performed in his usual coal mine work as a fire

boss . . . Claimant would not be able to perform the described job duties.” Id.

       Dr. Gagon performed the 2012 arterial gas tests on Mr. Kourianos. In his

deposition, Dr. Gagon affirmed that the results were “normal” for Price, Utah. EX 12

at 12. But he affirmed that “it was abnormal that the PO2s dropped” so much from

resting to exercise. Id.

                                            22
       Dr. Gagon submitted a supplemental report. It stated: (1) the blood gas studies

took into account the altitude of Price, Utah; (2) the barometric pressure for the blood gas

test was likely incorrect, but the error was probably a scrivener’s error that would not

change the results of the test; (3) the blood gas equipment reads the results of the test at

the altitude of Price, Utah, and there had been no errors in the past; (4) “[t]he ABG values

indicate hypoxemia with exercise meeting the requirements of disability set forth by

Black Lung [regulations] at the altitude of Price, UT”; (5) Dr. Saldivar “seems to be

contradicting himself” by stating that smoking was probably the cause of Mr.

Kourianos’s low O2 levels because, “with the miner’s significant exposure to coal dust,

this is also a significant contributing factor”; (6) Mr. Kourianos’s bronchiolitis could be

caused by coal dust or by smoking; (7) “Mr. Kourianos could work as long as the work is

sedentary” but that “with his significant hypoxemia with exercise, he would be limited

with any exertion”; and (8) “[b]ased on the table set forth [in Appendix C,] he meets the

requirments [sic] of disability based on his hypoxemia at the altitude range of 3000-

5999.” Doc. 10612740 at 4-8.7

                     2) Dr. Zaldivar

       Dr. Zaldivar did not examine Mr. Kourianos in person. The opinions in his report

and deposition were based on a review of Mr. Kourianos’s medical records, which did




       7
        The Director submitted this document in response to this court’s sua sponte order
because it was missing from the original appendix.

                                              23
not include a work history. Dr. Zaldivar stated, “My opinion[] considering the totality of

the case is that pneumoconiosis is not present.” Suppl. App. at 20 (quotations omitted).

He said that “if there is any pulmonary condition at all, it is bronchiolitis caused by

smoking.” Id. (quotations omitted). In support, he explained that “coal miners are

human beings subject to all diseases and conditions of human beings and are affected by

habits such as smoking just as the population at large is affected by it.” Id. (quotations

omitted). Thus, if Mr. Kourianos suffered from chronic bronchitis, Dr. Zaldivar

concluded that it was caused by smoking. Id. at 21.

       Dr. Zaldivar also concluded that Mr. Kourianos was not disabled. In response to

Dr. Gagon’s report and Mr. Kourianos’s arterial blood gas studies, Dr. Zaldivar

acknowledged that Mr. Kourianos’s blood gas PO2 levels appeared “very low” but noted

they “were not [low] when taking into consideration the altitude of Price, UT.” Id. at 19

(quotations omitted). He “explained that normal PO2 values are expected to drop linearly

as altitude increases.” Id. at 24. Therefore, as the ALJ recounted, Dr. Zaldivar opined

that the Department of Labor regulations did not “accurately reflect the drop in PO2

values that occurs at higher altitudes.” Id. at 21.

                     3) Dr. Selby

       Dr. Selby also did not examine Mr. Kourianos. The ALJ noted that, after

reviewing medical records, Dr. Selby similarly concluded that Mr. Kourianos “did not

suffer from clinical or legal pneumoconiosis.” Id. at 22. Dr. Selby acknowledged that

the PO2 level was “a bit low at first glance at rest, and then the PO2 decreased with

                                              24
exercise.” Id. (quotations omitted). Like Dr. Zaldivar, he concluded that, given the

altitude in Price, Utah, the range of disability “would be more accurately defined toward

the PO2 of 57 value.” Id. at 21 (quotations omitted). In other words, he believed that the

Appendix C threshold was too high when applied to the altitude of Price.

       Dr. Selby stated that the low PO2 values could be “undiagnosed asthma,” “chronic

bronchitis from smoking,” or “congestive heart failure.” Id. at 22 (quotations omitted).

He also stated that the drop in Mr. Kourianos’s PO2 values could mean he suffered from

“some form of disease,” but he discounted the severity of the disease because the PO2

levels were normal for the altitude of Price. Id. at 22 (quotations omitted). Dr. Selby

also stated that “working in coal mines prohibits the inhalation of cigarette smoking, thus

actually protecting the lungs.” Id. at 26 (quotations omitted).

              iv. Analysis of evidence

                     1) Total disability and 15-year presumption

       Based on the evidence described above, the ALJ found that Mr. Kourianos was

totally disabled. The ALJ noted that the “pulmonary function tests and the arterial blood

gas studies yield equivocal results.” Id. at 24. Regarding the medical opinions, he stated

as follows:

              I find that the medical opinion evidence does establish that
              Claimant is totally disabled from working as a fire boss. I
              give great weight to Dr. Gagon’s opinion, because he is the
              only physician who discussed (in his deposition) the specific
              duties Claimant performed as a fire boss. His opinion
              regarding disability is well-documented and well-reasoned,
              and he was in a better position to determine whether Claimant

                                             25
             could exert the physical effort required to perform a fire
             boss’s duties than the other physicians. See Killman v.
             Director, OWCP, 415 F.3d 716, 722 (7th Cir. 2005).

                     I give little weight to Dr. Zaldivar’s and Dr. Selby’s
             findings that Mr. Kourianos is not disabled. Neither doctor's
             finding was informed by details of Claimant’s usual coal
             mine employment. Furthermore, Dr. Zaldivar and Dr. Selby
             both stated in their reports and testified at their depositions
             that the arterial blood gas studies did not properly account for
             Price, Utah’s altitude: because the test was conducted at a
             relatively high altitude, they stated, and because PO2 values
             could be expected to drop linearly as altitude increased, the
             low PO2 value should not be considered to show disability.
             Appendix C to 20 C.F.R. Part 718, however, requires that
             administrative law judges analyze arterial blood gas studies
             according to three ranges of altitude: from sea level to 2,999
             above sea level; from 3,000 to 5,999 above sea level; and
             over 6,000 feet above sea level. The testing was performed in
             the second range, from 3,000 to 5,999 feet above sea level.
             The regulations do not contemplate further dividing testing
             results into narrower ranges, nor am I permitted to do so.
             Because Dr. Zaldivar’s and Dr. Selby’s statements are
             inconsistent with the regulations, I give their opinions
             regarding Claimant’s disability little weight.

Id. at 24. Thus, he found that Mr. Kourianos had met element three of a BLBA claim—

the disability element. Because he found that Mr. Kourianos was totally disabled and had

worked as a miner for more than 15 years, the ALJ applied the 15-year presumption.

                    2) No rebuttal of presumption

      Element One—the ALJ initially found that Hidden Splendor had rebutted the

presumption of clinical pneumoconiosis because Mr. Kourianos did not submit evidence

of clinical pneumoconiosis. But based on Dr. Gagon’s diagnosis of chronic bronchitis

that was caused in part by coal dust, the ALJ concluded that Hidden Splendor could not

                                           26
rebut the presumption that Mr. Kourianos suffered from legal pneumoconiosis (the

disease element).

       Although Mr. Kourianos had a history of smoking, the ALJ found that none of the

doctors established a sufficiently precise connection between smoking and Mr.

Kourianos’s respiratory problems. Specifically, the ALJ gave “little weight to Dr.

Gagon’s conclusion that coal dust exposure and cigarette smoke equally contributed to

his respiratory condition, because his diagnosis is conclusory and not well documented.”

Id. at 26. The ALJ also “g[a]ve little weight to Dr. Zaldivar’s conclusion that Claimant’s

respiratory condition was caused solely by smoking” because (1) Dr. Zaldivar implied

that “blood gas studies alone could not indicate the presence of coal workers’

pneumoconiosis, but that pneumoconiosis must be seen via pulmonary function testing or

x-rays—a position inconsistent with the regulations”; and (2) his conclusions about

smoking were “based on an analysis of the general population, and not on an analysis

specific to the miner.” Id. Finally, the ALJ gave “little weight to Dr. Selby’s finding that

Mr. Kourianos suffered from asthma and that his asthma was unrelated to his coal mining

and exacerbated by his smoking” for two reasons: (1) Dr. Selby was the only doctor to

diagnose Mr. Kourianos with asthma, and he did not adequately document or explain his

diagnosis; and (2) “Dr. Selby’s statement that ‘working in coal mines prohibits the

inhalation of cigarette smoking, thus actually protecting the lungs’ is contrary to the

central purpose and function of the [BLBA].” Id.



                                             27
       Element Two—because Hidden Splendor argued only that Mr. Kourianos did not

have pneumoconiosis (disease) and did not dispute that coal mining caused his

pneumoconiosis (disease causation), the ALJ found that it had not rebutted the

presumption of disease causation. In doing so, the ALJ acknowledged the 10-year

presumption,8 noting that the BLBA “regulations provide for a rebuttable presumption

that pneumoconiosis arose out of coal mine employment if a miner with pneumoconiosis

was employed in the mines for ten or more years.” Id. at 27 (citing 30 U.S.C. § 92l(c)(l);

20 C.F.R. § 718.203(b)).

       Element Four9—the ALJ found that Hidden Splendor had not rebutted the

presumption that pneumoconiosis caused Mr. Kourianos’s disabling respiratory or

pulmonary impairment (disability causation). Id. at 27. The ALJ reasoned, “[N]either

Dr. Zaldivar nor Dr. Selby diagnosed pneumoconiosis, and Employer has pointed to no

other evidence to rebut the presumption that Mr. Kourianos’s pneumoconiosis caused his

total disability.” Id. In other words, because Hidden Splendor’s arguments challenged

only the existence of a total disability (disability), it did not argue against the disability

causation presumption in the alternative.




       8
        As noted above, a claimant who has established the 15-year presumption does
not need the benefit of the 10-year presumption.
       9
         As noted above, the ALJ found that element three—total disability—had been
satisfied. Together with Mr. Kourianos’s 27 years as a coal miner, this established the
15-year presumption, prompting the need for Hidden Splendor to rebut elements one,
two, or four.
                                           28
       Finding that Mr. Kourianos had satisfied the four elements of a BLBA claim, the

ALJ awarded Mr. Kourianos benefits and found Hidden Splendor liable for those benefits

as the responsible operator.

3. Proceedings before the BRB

       Hidden Splendor appealed to the BRB, arguing the ALJ erred in finding that

(1) Hidden Splendor was the responsible operator; (2) the evidence established total

disability under 20 C.F.R. § 718.204(b)(2); (3) Mr. Kourianos was entitled to the 15-year

presumption; and (4) Hidden Splendor did not rebut the presumption. Id. at 30-31.

       In deciding the appeal, the BRB first recited the standard of review, explaining

that the ALJ’s Decision and Order “must be affirmed if it is rational, supported by

substantial evidence, and in accordance with applicable law.” Id. at 32 (citing 33 U.S.C.

§ 921(b)(3), as incorporated by 30 U.S.C. § 932(a)). It unanimously affirmed on all

grounds.10




       10
          One member of the panel concurred in the judgment, highlighting that the ALJ
did not rely solely on Appendix C of the regulations in making his determination:
“Given that he accurately characterized their opinions and provided a rational basis for
rejecting them, his additional statement that he was not ‘permitted’ to consider further
altitude adjustments was, at worst, a harmless error, in my view.” Suppl. App. at 44.

                                            29
                                    III. DISCUSSION

       Rockwood raises two issues on appeal.11 First, did the ALJ err in denying Hidden

Splendor’s motion to withdraw its responsible operator stipulation? Second, did

substantial evidence support the ALJ’s determination that Mr. Kourianos is entitled to

benefits?

       This case has three parties. Rockwood is the petitioner acting as Hidden

Splendor’s legal representative and agent. Mr. Kourianos and the Director are both

respondents. Mr. Kourianos defends both issues on appeal but requests that if “Employer

is not the properly named responsible operator,” this court should name the Black Lung

Trust Fund as liable for his benefits. Kourianos Br. at 11. To defend the interests of the

Trust Fund, the Director disputes only the responsible operator issue and takes no

position on Mr. Kourianos’s eligibility for benefits.

                                  A. Standard of Review

       On the first appeal issue—the ALJ’s denial of Rockwood’s motion to withdraw its

responsible operator stipulation—the parties state that our standard of review is abuse of

discretion. See Pet’r’s Br. at 5-6; OWCP’s Br. at 20; Kourianos’s Br. at 9. But as our




       11
          Rockwood also filed a contested motion to supplement the record with an
agreed order between the Director and Consolidated Coal in a separate case. The agreed
order was not before the ALJ in this case and we therefore deny Rockwood’s motion to
supplement the record. See In re United States, 138 S. Ct. 371, 372 (2017) (explaining
that the administrative record consists of materials relied upon and considered by agency
decision makers).

                                             30
discussion of this issue shows, Rockwood’s argument appears to challenge not only the

ALJ’s application of the regulations but also his interpretation of them. Courts review

the latter de novo but grant deference to the agency’s interpretation of its own

regulations. See Antelope Coal, 743 F.3d at 1341; Andersen, 455 F.3d at 1103. We need

not analyze the standard of review further because, under either abuse of discretion or de

novo review, we affirm the ALJ’s decision on this issue.

       On the second appeal issue—the ALJ’s benefits determination—we review

whether “substantial evidence” supported the ALJ’s decision. Hansen v. Dir., OWCP,

984 F.2d 364, 368 (10th Cir. 1993). Substantial evidence is “such relevant evidence as a

reasonable mind might accept as adequate to support a conclusion.” Consol. Edison Co.

v. NLRB, 305 U.S. 197, 229 (1938); see Energy W. Mining Co. v. Oliver, 555 F.3d 1211,

1217 (10th Cir. 2009). We do not reweigh the evidence presented to the ALJ. Antelope

Coal, 743 F.3d at 1341. “[W]here medical professionals . . . disagree[ ], the trier of fact

is in a unique position to determine credibility and weigh the evidence.” Id. (quotations

omitted). Thus, “the task of weighing conflicting medical evidence is within the sole

province of the ALJ.” Hansen, 984 F.2d at 368.12




       12
         Although we formally review the BRB’s decision, the BRB’s deferential
standard of review of ALJ decisions requires us to examine the ALJ’s findings of fact.
Antelope Coal, 743 F.3d at 1341 n.13; Blackburn, 857 F.3d at 822; see also 33 U.S.C.
§ 921(b)(3) (stating that on review by the BRB, the ALJ’s findings of fact are “conclusive
if supported by substantial evidence”).

                                             31
                       B. The Responsible Operator Determination

       The ALJ did not determine whether Mr. Kourianos worked as a miner at Hidden

Splendor for a full year. Rather, Hidden Splendor admitted to the Director that it was the

responsible operator, and the ALJ accepted that admission as conclusive. Rockwood

therefore challenges the ALJ’s refusal to allow Hidden Splendor to withdraw its

stipulation.

1. Additional Legal Background

       The Department of Labor’s regulations prescribe the process for determining the

responsible operator. They generally call for the district director—not the ALJ—to

decide the responsible operator question. See 20 C.F.R. § 725.418(d) (providing that the

district director must “dismiss, as parties to the claim, all other potentially liable

operators” when it issues its PDO); id. § 725.407(d) (prohibiting the district director from

“notify[ing] additional operators of their potential liability after a case has been referred”

to an ALJ). The Department of Labor explained the rationale for this rule when it

promulgated updated BLBA regulations in 2010:

               The Department agrees that the revised regulations place
               additional burdens on coal mine operators who have, in the
               past, routinely filed form controversions of their liability for
               benefits and waited until the case was referred to the Office of
               Administrative Law Judges to develop their defenses. . . . As
               revised, the regulations will permit the district director to
               refer a case to the Office of Administrative Law Judges with
               no more than one operator as a party to the claim, the
               responsible operator as finally designated by the district
               director. The regulations prohibit the remand of cases for the
               identification of additional potentially liable operators, or to

                                              32
              allow the district director to designate a new responsible
              operator, thereby reducing delay in the adjudication of the
              merits of a claimant’s entitlement. This change also places
              the risk that the district director has not named the proper
              operator on the Black Lung Disability Trust Fund, however.
              The Department believes that the additional demands placed
              upon potentially liable operators are not unreasonable. In
              addition, the Department does not accept the criticism that the
              regulation sets traps for unwary litigants. The nature of the
              evidence required by the Department, and the time limits for
              submitting that evidence, are clearly set forth in the
              regulations, and will be communicated to potentially liable
              operators who are notified of a claim by the district director.

Regulations Implementing the Federal Coal Mine Health and Safety Act of 1969, as

Amended, 65 Fed. Reg. 79920-01, 79985 (Dec. 20, 2000) (citations omitted).

       Accordingly, even if the district director incorrectly identifies the responsible

operator and refers the case to an ALJ, a new responsible operator may not be named.

Appleton & Ratliff Coal Corp. v. Ratliff, 664 F. App’x 470, 473 (6th Cir. 2016)

(unpublished) (“The appeal to an ALJ is the point of no return on the responsible operator

designation.”). “If subsequent proceedings determine the director’s designation is not

supported, the matter is not remanded to find a different responsible operator and,

instead, the Trust Fund pays benefits.” Id.

       Against this backdrop, we apply the general rule that “stipulations and concessions

bind those who make them.” Consolidation Coal Co. v. Dir., OWCP (“Burris”), 732

F.3d 723, 730 (7th Cir. 2013). In this case, the potential exception to that rule is

20 C.F.R. § 725.463(b), which provides that “[a]n administrative law judge may consider

a new issue only if such issue was not reasonably ascertainable by the parties at the time

                                              33
the claim was before the district director.” See also Marfork Coal Co. v. Weis, 251 F.

App’x 229, 236 (4th Cir. 2007) (denying operator’s motion to belatedly introduce x-ray

evidence because the x-ray was not previously hidden; it “was waiting to be found”).

2. Analysis

       Hidden Splendor conceded its responsible operator status (1) in its amended

response to the district director’s notice of claim, in which it stated that it was “the

responsible operator within the meaning of the [BLBA],” Suppl. App. at 58; (2) in its

response to the district director’s SSAE, in which it stated that “Hidden Splendor has

accepted the designation of Responsible Operator,” id. at 73; and (3) in its initial

submission to the ALJ, in which it stated that Hidden Splendor “does not dispute its

designation as the Responsible Operator,” id. at 83.

       As the ALJ noted, Hidden Splendor’s senior staff accountant had reported in a fax

to the district director that Mr. Kourianos worked “outside at the loadout”—not “in the

mine”—during his last months at Hidden Splendor. Id. at 46. But notwithstanding the

fax’s suggestion that Mr. Kourianos was not “in the mine” for a full year at Hidden

Splendor, Rockwood failed to investigate Mr. Kourianos’s employment and did not

dispute the responsible operator question until the ALJ’s hearing more than two years

after Mr. Kourianos filed his claim. These facts undercut any argument that responsible

operator evidence was not “reasonably ascertainable” while Mr. Kourianos’s claim was

pending before the district director. 20 C.F.R. § 725.463(b).



                                              34
       Hidden Splendor could have “reasonably ascertain[ed]” Mr. Kourianos’s job

duties in a number of ways. See id. As the BRB noted, Hidden Splendor “determined the

terms of claimant’s work and therefore normally would have records relevant to the

nature of his employment (job title, etc.). Employer has not averred that it had no records

or access to relevant personnel with the requisite information.” Suppl. App. at 34 n.5. In

addition, neither Hidden Splendor nor Rockwood has suggested that they sought to speak

to Mr. Kourianos or his co-workers about his duties at Hidden Splendor. Moreover, if

Hidden Splendor had checked its operating records, it would have found its mine was

closed for part of the time that Mr. Kourianos worked there. Any of these steps would

have been reasonable, but Rockwood did not take them. Mr. Kourianos’s employment

was not only “reasonably ascertainable” but was easily ascertainable through a simple

phone call or a review of Hidden Splendor’s records. 20 C.F.R. § 725.463(b).

       Rockwood’s excuses for Hidden Splendor’s failure to investigate are not

convincing. Rockwood appears to argue that the regulations’ timeline prevented it from

submitting new evidence after 90 days of receiving the district director’s notice of claim.

See Pet’r’s Br. at 18. The regulations show otherwise. See 20 C.F.R. § 725.417(b) (“In

appropriate cases, the district director may permit a reasonable time for the submission of

additional evidence following a conference . . . .”); id. § 725.410(b) (“The [SSAE] shall

allow all parties not less than 60 days within which to submit additional evidence,

including evidence relevant to the claimant’s eligibility for benefits and evidence relevant

to the liability of the designated responsible operator.” (emphasis added)). In addition,

                                            35
Hidden Splendor did not ask to submit additional evidence or suggest that it wanted to

challenge its responsible operator status before the district director.

       Rockwood also suggests that the available documentary evidence about Mr.

Kourianos’s employment was misleading. It was not. Mr. Kourianos’s Social Security

earnings statement showed that he was a Hidden Splendor employee and stated how

much money he made working for the company, but it said nothing about his job duties.

In addition, the accountant’s “Hire Dates for Tony Kourianos” fax showed that Mr.

Kourianos did not work “in the mine” for at least part of his time with the company.

Suppl. App. at 46.

       Finally, Rockwood’s reliance on Morrison v. Hurst Drilling Co., 512 P.2d 438,

439-40 (Kan. 1973) is misplaced. In Morrison, an employee’s wife filled out her

husband’s workers’ compensation claim and erroneously listed the place of injury as

Kansas. Id. at 440-41. Relying on the employee’s wife’s statement, the defendant

employer stipulated that the injury occurred in Kansas. Id. at 440. After the employee’s

testimony and other documentation revealed the injury had occurred at a work site in

Oklahoma (a finding that deprived the Kansas court of jurisdiction), the employer sought

to withdraw its stipulation. Id. The claim examiner granted the employer’s motion.

       On appeal, the Kansas Supreme Court recited the applicable rule as follows:

              The general rule is that a stipulation having all the binding
              force of a contract cannot be set aside on grounds other than
              those justifying the setting aside of contracts generally, such,
              for instance, as fraud, collusion, mistake, accident, surprise,
              undue influence, false representations innocently made,

                                              36
              inadvertence or improvidence in making the stipulation, or
              some other ground of the same nature.

Id. at 441 (quotations omitted). Applying that rule, the court then held that the defendant

relied on the employee’s wife’s misstatement when it entered the stipulation, noted that

the plaintiff would not suffer any prejudice from an order withdrawing the stipulation

because he could simply re-file his workers compensation claim in Oklahoma, and

allowed the defendant to withdraw its stipulation. Id. at 442.

       Unlike the employee in Morrison, 512 P.2d at 440, whose wife misstated a

material fact in the workers’ compensation claim, Mr. Kourianos never suggested that he

was a coal miner the entire time he worked at Hidden Splendor. To the contrary, he

stated at the hearing that he “kn[e]w by law that we have to blame [Hidden Splendor]”

for his disability, but he explained forthrightly that he did not do “miner” work for a full

year with the company. ALJ Hrg. Tr. at 35, 56-62.

       In addition, Rockwood’s discussion of Morrison is misguided because Mr.

Kourianos’s claim involved the application of the BLBA regulations rather than state

common law. As discussed above, the regulations place the burden on employers to

challenge their responsible operator designation before the district director. See Ratliff,

664 F. App’x at 473. If they fail to do so and the ALJ ultimately finds they were wrongly

named as the responsible operator, that decision does not shift liability to another

operator. Id. Instead, the Black Lung Trust Fund must step in to replace the operator as

the party liable for paying the miner’s benefits. See 26 U.S.C. § 9501(d)(1). Under this


                                             37
statutory scheme, the Department of Labor has declared—through its regulations—that

the district director should resolve responsible operator issues in the first instance, see

20 C.F.R. § 725.407(d), and the ALJ properly applied the Department’s regulations, see

Suppl. App. at 2-3.

                                    *      *        *     *

       In sum, the nature of Mr. Kourianos’s employment at Hidden Splendor was

“reasonably ascertainable” the entire time his claim was pending before the district

director. See 20 C.F.R. § 725.463(b). With due diligence, Hidden Splendor could have

obtained all the necessary information about Mr. Kourianos’s work responsibilities

before the claim ever reached the ALJ. Because it failed to do so, the ALJ did not err in

denying Hidden Splendor’s motion to withdraw its responsible operator stipulation.13

                        C. The Benefits Eligibility Determination

       The ALJ’s benefits eligibility determination rests on factual findings. We uphold

those findings when substantial evidence supports them. See Antelope Coal, 743 F.3d

at 1341.




       13
           We decline to address the Director’s argument that responsible operator liability
can never be raised as a “new issue” in the ALJ hearing when the operator has conceded
liability before the district director. See OWCP Br. at 25-26. We hold only that, in this
case, the ALJ properly denied Rockwood’s motion to re-open the issue under the “new
issue” rule. 20 C.F.R. § 725.463(b).

                                               38
1. BLBA Claims Framework

      As previously discussed, to prevail on a BLBA benefits claim, the claimant must

establish four elements:

             (1)    the claimant suffers from pneumoconiosis (disease),

             2)     the claimant’s pneumoconiosis arose out of coal mine
                    employment (disease causation),

             (3)    the claimant is totally disabled because of a respiratory
                    or pulmonary impairment (disability), and

             (4)    claimant’s pneumoconiosis is a substantially
                    contributing cause of the miner’s total disability
                    (disability causation).

Blackburn, 857 F.3d at 821.

      Mr. Kourianos worked as a miner for more than 27 years. To invoke the 15-year

presumption, therefore, he needs to show only that he suffered from a totally disabling

respiratory or pulmonary impairment. 20 C.F.R. §§ 718.204, 718.305(b)(1); see Antelope

Coal, 743 F.3d at 1344. And once he has done so, the other three elements of a BLBA

claim are presumptively established. The presumption therefore “softens [Mr.

Kourianos’s] burden” and places a heavier burden on Rockwood. Blackburn, 857 F.3d

at 822. On appeal, Rockwood primarily seeks to avoid the application of the 15-year

presumption by arguing the ALJ incorrectly determined that Mr. Kourianos was totally

disabled due to a respiratory or pulmonary impairment.

      The following analysis concludes that substantial evidence supported the ALJ’s

determination that the 15-year presumption applied to Mr. Kourianos’s claim. We further

                                            39
conclude that Hidden Splendor did not rebut the presumption by disproving that

(1) pneumoconiosis caused Mr. Kourianos’s pulmonary impairment or that (2) Mr.

Kourianos’s pneumoconiosis caused his total disability.

2. Analysis

       a. Total disability

       As noted above, the ALJ relied on two types of evidence in reaching his total

disability determination. First, he considered arterial blood gas studies under 20 C.F.R.

§ 718.204(b)(2)(ii). Second, finding the studies “equivocal,” he considered the medical

opinions discussed above. Id. § 718.204(b)(2)(iv).

              i. Arterial blood gas testing

       Mr. Kourianos’s 2012 arterial blood gas test yielded a PCO2 level of 33 and a PO2

level of 59 during exercise, thus bringing him below the impairment threshold PO2 level

of 62 on the Appendix C chart. All three doctors, however, including Dr. Gagon, stated

that Mr. Kourianos’s PO2 value of 59 at Price, Utah, was “normal.” See EX 12 at 11-12;

Suppl. App. at 38. This view stemmed from the altitude of Price, Utah, falling in the

upper end of the 3,000-5,999-foot range and the fact that “normal PO2 levels are

expected to drop linearly as altitude increases.” Suppl. App. at 38. Accordingly,

Rockwood argues that the blood gas studies did not provide evidence of Mr. Kourianos’s

disability and could not support the ALJ’s finding that the medical tests were

“equivocal.” Pet’r’s Br. at 28. We disagree.



                                              40
       First, Mr. Kourianos’s 2012 arterial blood gas testing yielded a PO2 level that

qualified him for impairment under the regulations. See Erie Boulevard Hydropower, LP

v. FERC, 878 F.3d 258, 269 (D.C. Cir. 2017) (“It is axiomatic that an agency is bound by

its own regulations.” (quotations and alterations omitted)). As Dr. Gagon stated in his

supplemental report, “I cannot change the ‘rules of the game.’ Based on the table set

forth [in Appendix C], [Mr. Kourianos] meets the requirements of disability based on his

hypoxemia at the altitude range of 3000-5999.” Doc. 10612740 at 8. Irrespective of how

altitude may affect test results within a range, Appendix C still qualified Mr. Kourianos

for a pulmonary or respiratory impairment. The ALJ therefore properly considered

Appendix C—as well as the medical opinions—in making his ultimate disability

determination. See Bosco v. Twin Pines Coal Co., 892 F.2d 1473, 1479 (10th Cir. 1989)

(declaring that “an ALJ must consider all evidence relevant to the issue of total

disability” in deciding whether 15-year presumption applies).

       Second, Dr. Gagon testified that “it was abnormal that the PO2s dropped” with

exercise, and neither of the other doctors contested his conclusion. EX 12 at 11-12; see

EX 5 at 10-11; EX 2 at 8-9.14 Accordingly, even if the PO2 levels were “normal” for




       14
         In this respect, Rockwood misconstrues the record when it states that “all of Mr.
Kourianos’[s] testing values were normal.” Pet’r’s Br. at 45. Mr. Kourianos’s arterial
blood gas testing was abnormal under the regulations, and the drop in his PO2 values
from resting to exercise was also “abnormal.” Suppl. App. at 37-38 & n.13.

                                            41
Price, Utah, the test still revealed a notable abnormality that suggested some degree of

respiratory impairment.

              ii. Medical opinions

       The ALJ appeared to rely in part on the arterial blood gas studies for his total

disability decision, but because he also found them to be “equivocal,” and not sufficient

to find total disability on their own, he relied further on the three doctors’ medical

opinions for his ultimate disability determination. Suppl. App. at 24; see 20 C.F.R.

§ 718.204(b)(2)(iv). As we discuss below, substantial evidence supported the ALJ’s

evaluation of the medical opinions. See Hansen, 984 F.2d at 368 (“[T]he task of

weighing conflicting medical evidence is within the sole province of the ALJ.”).

       All three doctors found that Mr. Kourianos had respiratory problems, which

qualified his impairment as legal pneumoconiosis to the extent they were “chronic.” See

Antelope Coal, 743 F.3d at 1335; 20 C.F.R. § 718.201(a)(2) (legal pneumoconiosis

includes “any chronic restrictive or obstructive pulmonary disease arising out of coal

mine employment” (quotations omitted)). Dr. Gagon diagnosed Mr. Kourianos with

chronic bronchitis, a chronic productive cough, and a significant drop in PO2 levels with

exercise. Suppl. App. at 18. Dr. Zaldivar noted that Mr. Kourianos showed “symptoms

of chronic bronchitis for one-and-a-half years and night wheezing” and explained that his

“[l]ungs showed decreased breath sounds.” Id. at 19 (quotations omitted). Dr. Selby

noted that Mr. Kourianos’s symptoms of “wheezing, productive cough, and decreased

PO2, indicated a very strong presentation for the diagnosis of asthma.” Id. at 21

                                             42
(quotations omitted). The doctors therefore disagreed about the severity rather than the

existence of Mr. Kourianos’s impairment.

       The ALJ compared Mr. Kourianos’s disability to his job duties, as 20 C.F.R.

§ 718.204(b)(1) required. Weighing the evidence, he gave greater weight to Dr. Gagon’s

testimony because “he [was] the only physician who discussed (in his deposition) the

specific duties Claimant performed as a fire boss.” Suppl. App. at 24. He discounted Dr.

Zaldivar’s and Dr. Selby’s findings that Mr. Kourianos was not disabled because their

opinions were not “informed by details of Claimant’s usual coal mine employment.” Id.

We do not reweigh evidence, and the ALJ considered all the evidence before him and

explained his conclusion fully. See Blackburn, 857 F.3d at 826-28 (upholding BRB

decision when ALJ credited one doctor’s causation testimony against the testimony of

two other doctors); see also Hansen, 984 F.2d at 368 (noting that the ALJ is in a unique

position to judge the credibility of medical professionals). The total disability

determination was supported by substantial evidence. See 33 U.S.C. § 921(b)(3).

       b. Rockwood has not overcome the 15-year presumption

       Because substantial evidence supported the ALJ’s total disability determination—

the third element of a BLBA claim—the 15-year presumption provided that the disease,

disease causation, and disability causation elements were presumptively met. The burden

thus shifted to Rockwood to disprove any of those elements. We conclude it failed to do

so.



                                             43
              i. No rebuttal of presumption of pneumoconiosis or disease causation

       Because substantial evidence supported the ALJ’s determination that Mr.

Kourianos was totally disabled and because Mr. Kourianos worked for more than 27

years as a coal miner, the ALJ was required to presume that he had legal pneumoconiosis

caused by his coal mine work.

       Rockwood attempts to rebut the presumptions that Mr. Kourianos suffered from

pneumoconiosis and that it arose from coal mining by pointing to Mr. Kourianos’s

history of smoking as an alternative cause of his impairment. All three doctors suggested

that smoking contributed, at least in part, to Mr. Kourianos’s respiratory problems.

Suppl. App. at 26. But the ALJ gave limited weight to their opinions because they all

spoke about the general dangers of smoking without linking smoking to any of Mr.

Kourianos’s particular problems.

       The ALJ noted that Dr. Gagon’s opinion that smoking and coal dust were equal

contributors to Mr. Kourianos’s problems was “conclusory and not well-documented.”

Id. The ALJ discredited Dr. Zaldivar’s causation opinion because it was “based on an

analysis of the general population, and not on an analysis specific to the miner.” See id.

at 26. And he discredited Dr. Selby’s opinion, in part because his “statement that

‘working in the coal mines prohibits the inhalation of cigarette smoking, thus actually

protecting the lungs’ [was] contrary to the central purpose and function of the act.” Id.

(quoting Dr. Selby Depo.). The ALJ did not find this reasoning convincing, and we do

not disturb that determination when it is based on reasoned judgment. See Antelope Coal,

                                            44
743 F.3d at 1345-46 (upholding ALJ’s rejection of an operator’s reliance on statistical

data to prove the effects of smoking on a coal miner); see also Blackburn, 857 F.3d

at 826-28 (upholding ALJ’s determination that employer did not rebut presumption of

pneumoconiosis when doctors provided inconsistent testimony about smoking).

      The 15-year presumption shifts the burden to the employer, who must present

evidence to rebut the existence of or the causation of pneumoconiosis. The ALJ

concluded Hidden Splendor did not rebut these presumptions. We find that substantial

evidence supported that decision. See 20 C.F.R. § 718.305(d) (“The presumption must

not be considered rebutted on the basis of evidence demonstrating the existence of a

totally disabling obstructive respiratory or pulmonary disease of unknown origin.”).

             ii. No rebuttal of presumption of total disability due to pneumoconiosis

      Rockwood also argues that Mr. Kourianos’s disability cannot be attributed to

pneumoconiosis, but it relies on the same arguments it uses to challenge that Mr.

Kourianos is totally disabled. We have rejected these arguments. Moreover, Rockwood

does not point to evidence of any other ailment—e.g., lung cancer from cigarettes—that

might have caused Mr. Kourianos’s total disability. As the ALJ noted, “Employer has

pointed to no other evidence to rebut the presumption that Mr. Kourianos’s

pneumoconiosis caused his total disability.” Suppl. App. at 27. We find that substantial

evidence supports this determination.




                                            45
                                  *      *        *    *

       In sum, the ALJ properly found that the 15-year presumption applied because Mr.

Kourianos was (1) totally disabled as a result of a respiratory impairment and (2) worked

for more than 15 years in a mine. See Antelope Coal, 743 F.3d at 1335. The burden thus

fell on Rockwood to rebut the presumptions that Mr. Kourianos had pneumoconiosis, that

coal mining caused it, and that his pneumoconiosis caused his total disability. See id.

at 1336. The ALJ concluded that it had not done so, and we find that substantial

evidence supports that conclusion.

                                  III. CONCLUSION

       Because the ALJ did not err in denying Hidden Splendor’s motion to withdraw its

responsible operator stipulation, and because the ALJ’s substantive benefits

determination was well reasoned and supported by substantial evidence, we deny

Rockwood’s petition.




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