its liability for the payment of continuing benefits,” see id. § 725.492(a)(4), and there is no “successor operator” liable for the payment of benefits, see id. § 725.493(a)(2), then the next most recent employer satisfying the definition “shall be considered” the responsible operator, see id. § 725.493(a)(4). “[I]f no responsible operator can be identified, benefits are paid by the Black Lung Disability Trust Fund.” Id. § 725.1(d) (2001). And under the regulations applicable to this case, it is the Director’s burden to develop evidence sufficient to support the conclusion that a potentially responsible operator is incapable of assuming liability and consequently does not qualify as the responsible operator. See Director, OWCP v. Trace Fork Coal Co., 67 F.3d 503, 507 (4th Cir.1995) (<HOLDING>); see also id. at 506-07 (stating that “[w]e
holding that a state agency was not an operator solely by conducting inspections and issuing permits holding that partys failure to develop issue in argument section constitutes waiver of issue holding that the applicable regulations give the director not the designated responsible operator the power to develop evidence on the responsible operator issue holding that the trial court must give due consideration to the applicable law and facts holding that a medicare provider was responsible for familiarizing itself with the legal requirements of cost reimbursement and obtaining an agency interpretation of the applicable regulations