(1) The owner or operator of a Class II or Class IV landfill unit shall install a final cover system that is designed to minimize infiltration and erosion. The final cover system must be designed and constructed to:
(a) have a permeability no greater than to the permeability of any bottom liner system or natural subsoils present, or a permeability no greater than 1×10-5 cm/sec, whichever is less;
(b) minimize infiltration through the closed Class II or Class IV landfill unit by the use of an infiltration layer that contains at least 18 inches of earthen material; and
(c) minimize erosion of the final cover by the use of an erosion layer that contains at least six inches of earthen material that is capable of sustaining native plant growth.
(2) The department may approve an alternative final cover design for a Class II or Class IV landfill unit that includes:
(a) an infiltration layer that achieves a reduction in infiltration equivalent to the infiltration layer specified in (1)(a) and (b); and
(b) an erosion layer that provides protection from wind and water erosion equivalent to the erosion layer specified in (1)(c).
(3) An owner or operator of a Class II or Class IV landfill unit that disposes of 20 tons or less of solid waste per day, based on an annual average, shall comply with alternative requirements for the infiltration barrier that may be established by the department after public review and comment. An alternative requirement established under this subsection must:
(a) consider the unique characteristics of small communities;
(b) take into account climatic and hydrogeologic conditions; and
(c) protect human health and the environment.
(4) The owner or operator of a Class II or Class IV landfill unit, or a lateral expansion of an existing Class II or Class IV landfill unit, shall submit a closure plan to the department for approval that describes the steps necessary to close all Class II and Class IV landfill units and lateral expansions at the facility at any point during their active life in accordance with the cover design requirements in (1) or (2), as applicable. The closure plan must include, at a minimum, the following information:
(a) a description of the final cover, designed in accordance with (1), and the methods and procedures to be used to install the cover;
(b) an estimate of the largest area of the Class II or Class IV landfill unit ever requiring a final cover, as required under (1), at any time during the active life of the unit;
(c) an estimate of the maximum inventory of wastes ever on-site over the active life of the landfill facility; and
(d) a schedule for completing all activities necessary to satisfy the closure criteria in this rule.
(5) For all closure construction, the owner or operator shall submit for department approval plans, specifications, reports, and certifications, to the same extent as required in ARM 17.50.1205.
(6) The owner or operator shall notify the department that a closure plan has been prepared and placed in the operating record no later than February 12, 2010, or by the initial receipt of waste, whichever is later.
(7) Prior to beginning closure of each Class II or Class IV landfill unit as specified in (8), an owner or operator of a facility shall submit to the department a notice of the intent to close the unit and place the notice in the operating record.
(8) The owner or operator of a Class II or Class IV landfill unit shall begin closure activities of that unit no later than 30 days after the date on which the unit receives the known final receipt of wastes or, if the unit has remaining capacity and there is a reasonable likelihood that the unit will receive additional wastes, no later than one year after the most recent receipt of wastes. Extensions beyond the one-year deadline for beginning closure may be granted by the department if the owner or operator demonstrates that the unit has the capacity to receive additional wastes and the owner or operator has taken, and will continue to take, all steps necessary to prevent threats to human health and the environment from the unclosed unit.
(9) The owner or operator of a Class II or Class IV landfill unit shall complete closure activities of the unit in accordance with the closure plan within 180 days following the beginning of closure, as specified in (8). Extensions of the closure period may be granted by the department if the owner or operator demonstrates that closure will, of necessity, take longer than 180 days and that the owner or operator has taken, and will continue to take, all steps to prevent threats to human health and the environment from the unclosed unit.
(10) Following closure of a Class II or Class IV landfill unit, the owner or operator shall notify the department that a certification, signed by an independent licensed professional engineer, verifying that closure has been completed in accordance with the closure plan, has been placed in the operating record. A unit is not considered closed until the department has conducted an inspection and approved the certification.
(11) The owner or operator may request permission from the department to remove the notation from the deed if all wastes have been removed from the facility.