(a) Every applicant or permittee must submit a detailed, written estimate of the cost, in current dollars, for implementing the closure plan as required by section 383-6.3(b)(2)(i) of this Subpart. The cost estimate must be approved by the department and based on the cost of implementing the closure plan as approved or amended by the terms and conditions of the permit. The cost estimate must include the costs of:

1. (1) decontamination and dismantlement of land disposal facility structures; and
2. (2) closure of the land disposal facility so that the need for ongoing active maintenance is eliminated to the extent practicable and only minor custodial care, surveillance, and monitoring are required;
3. (3) implementation of the closure plan based on the costs of hiring a third party to implement the closure plan; and
4. (4) implementation of the closure plan reflecting the costs of closure at the estimated point in the land disposal facility's operation period when the extent and manner of operation and inventory of wastes would make closure the most expensive, as indicated by the closure plan.