At the closure of a tank system, the owner or operator shall remove or decontaminate all waste residues, contaminated containment system components, contaminated soils, and structures and equipment contaminated with waste, and manage them as hazardous waste, unless COMAR 26.13.02.03D applies. An owner or operator shall ensure that the closure plan, closure activities, cost estimates for closure, and financial responsibility for tank systems meet all of the requirements specified in Regulations .07 and .08 of this chapter. If an owner or operator demonstrates that not all contaminated soils can be practicably removed or decontaminated as required in §A of this regulation, then the owner or operator shall close the tank system and perform post-closure care in accordance with the closure and post-closure care requirements of Regulation .14J of this chapter which apply to landfills. In addition, for the purposes of closure, post-closure, and financial responsibility, the tank system is then considered to be landfill, and the owner or operator shall meet all of the requirements for landfills specified in Regulations .07 and .08 of this chapter. If an owner or operator has a tank system that does not have secondary containment that meets the requirements of Regulations .10-4B—F of this chapter, and has not been granted a variance from the secondary containment requirements in accordance with Regulation .10-5 of this chapter, then the owner or operator shall: Include in the closure plan for the tank system a: Plan for complying with §A of this regulation; and Contingent plan for complying with §C of this regulation; Prepare and submit as part of the permit application a contingent post-closure plan for complying with §C of this regulation; Reflect, in the cost estimates calculated for closure and post-closure care, the costs of complying with the contingent closure plan and the contingent post-closure plan, if those costs are greater than the costs of complying with the closure plan prepared for the expected closure under §A of this regulation; Base financial assurance on the cost estimates developed in accordance with §D(3) of this regulation; and Ensure that the contingent closure and post-closure plans meet all of the closure, post-closure, and financial responsibility requirements for landfills under Regulations .07 and .08 of this chapter.