(1) Closure criteria for Class II landfills are as follows:

(a) Owners or operators of all Class II landfill units must install a final cover system that is designed to minimize infiltration and erosion.   The final cover system must be designed and constructed to:

(i) minimize infiltration through the closed unit by the use of an infiltration layer that contains a minimum 18 inches of earthen material and have a permeability less than or equal to the permeability of any bottom liner, barrier layer, or natural subsoils present, or a permeability no greater than 1 x 10^-5 cm/sec, whichever is less;

(ii) minimize erosion of the final cover by the use of a seed bed layer that contains a minimum of 6 inches of earthen material that is capable of sustaining native plant growth and protecting the infiltration layer from frost effects and rooting damage; and

(iii) revegetate the final cover with native plant growth within 1 year of placement of the final cover.   The department may approve alternative revegetation plant species or an extension in the time requirement for revegetation.

(b) The department may approve an alternative final cover design that includes:

(i) an infiltration layer that achieves reduction in infiltration at least equivalent to the infiltration layer specified in (1) (a) (i) and (ii) above; and

(ii) an erosion layer that provides protection from wind and water erosion equivalent to the erosion layer specified in (1) (a) (ii) and (iii) above.

(c) The owner or operator must prepare a written closure plan that describes the steps necessary to close all landfill units at any point during their active life in accordance with the cover design requirements in (1) (a) or (b) above, as applicable.   The closure plan, at a minimum, must include the following information:

(i) a description of the final cover, designed in accordance with (1) (a) or (b) above, and the methods and procedures to be used to install the cover;

(ii) an estimate of the area of the Class II landfill that the department determines to be the largest active portion in the facility requiring a final cover as required under (1) (a) above during the active life of the facility;

(iii) an estimate of the maximum inventory of wastes ever on-site over the active life of the landfill facility; and

(iv) a schedule for completing all activities necessary to satisfy the closure criteria in (1) (a) above.

(d) The owner or operator must submit a closure plan to the department for approval and place it in the operating record no later than October 9, 1993, or at the time of application for license for a new landfill, the placement of wastes in a new Class II landfill unit, or the lateral expansion of an existing unit.

(e) Prior to beginning closure of each landfill unit as specified in (1) (a) or (b) above, an owner or operator must notify the department that a notice of the intent to close the unit has been placed in the operating record.

(f) The owner or operator must begin closure activities of each Class II landfill unit no later than 30 days after the date on which the Class II landfill unit receives the known final receipt of wastes or, if the Class II landfill unit has remaining capacity and there is a reasonable likelihood that the Class II landfill unit will receive additional wastes, no later than 1 year after the most recent receipt of wastes.   Extensions beyond the 1-year deadline for beginning closure may be granted by the department if the owner or operator demonstrates that the Class II landfill 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 Class II landfill unit.   Any portion of a Class II landfill unit that will not receive additional waste within 90 days must have an intermediate cover of at least 1 foot of approved earthen materials.

(g) The owner or operator of all Class II landfill units must complete closure activities of each Class II unit in accordance with the closure plan within 180 days following the beginning of closure as specified in (1) (f) above.   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 he has taken and will continue to take all steps to prevent threats to human health and the environment from the unclosed Class II landfill unit.

(h) Following closure of each Class II landfill unit, the owner or operator must notify the department that closure has been completed in accordance with the closure plan.   A certification, signed by an independent registered professional engineer, or the department, verifying that closure has been completed in accordance with the closure plan, must be placed in the operating record.   Upon receipt of the notification of closure the department will:

(i) place the landfill in interim closure status and hold in abeyance any fees due under ARM 17.50.410 until closure compliance is verified by the department; and

(ii) schedule an inspection to verify closure plan compliance.

(i) Following closure of all Class II landfill units, the owner or operator must record a notation on the deed to the landfill facility property, or some other instrument that is normally examined during title search, and notify the department that the notation has been recorded and a copy has been placed in the operating record.   The notation on the deed must in perpetuity notify any potential purchaser of the property that:

(i) the land has been used as a landfill facility; and

(ii) its use is restricted under ARM 17.50.531(1) (c) (iii) .

(j) The owner or operator may request permission from the department to remove the notation from the deed if all wastes are removed from the facility.

(2) Class III landfill units must be closed under a department approved plan that includes at a minimum:

(a) two feet of final cover; and

(b) grading and seeding to prevent erosion.

(c) the deed notation specified in (1) (i) (i) of this rule, unless all wastes are removed from the facility and the owner or operator requests permission from the department to remove the notation from the deed.

(3) The closure requirements for Class IV units are as follows:

(a) Owners or operators of all Class IV landfill units must install a final cover system that is designed to minimize infiltration and erosion.   The final cover system must be designed and constructed to:

(i) minimize infiltration through the closed unit by the use of an infiltration layer that contains a minimum 18 inches of earthen material and has a permeability no greater than 1x10^-5 cm/sec;

(ii) minimize erosion of the final cover by the use of a seed bed layer that contains a minimum of 6 inches of earthen material that is capable of sustaining native plant growth and protecting the infiltration layer from frost effects and rooting damage; and

(iii) revegetate the final cover with native plant growth within 1 year of placement of the final cover.

(b) The department shall approve an alternative final cover design if it includes:

(i) an infiltration layer that achieves reduction in infiltration at least equivalent to the infiltration layer specified in (3) (a) (i) and (ii) above; and

(ii) an erosion layer or alternative revegetation plant species that provide protection from wind and water erosion equivalent to the erosion layer specified in (3) (a) (ii) and (iii) above.

(c) The owner or operator must prepare a written closure plan that describes the steps necessary to close all landfill units at any point during their active life in accordance with the cover design requirements in (3) (a) or (b) above, as applicable. The closure plan, at a minimum, must include the following information:

(i) a description of the final cover, designed in accordance with (3) (a) or (b) above, and the methods and procedures to be used to install the cover;

(ii) an estimate of the area of the Class IV landfill unit that the department determines to be the largest active portion in the facility ever requiring a final cover as required under (3) (a) above during the active life of the facility;

(iii) an estimate of the maximum inventory of wastes ever on-site over the active life of the landfill facility; and

(iv) a schedule for completing all activities necessary to satisfy the closure criteria in (3) (a) above.

(d) The owner or operator must submit a closure plan to the department for approval and place it in the operating record when applying for a license for a Class IV landfill, before   placing wastes in a Class IV unit at a licensed Class II facility, and/or before the lateral expansion of an existing unit.

(e) Prior to beginning closure of each landfill unit, an owner or operator must notify the department that a notice of the intent to close the unit has been placed in the operating record.

(f) The owner or operator must begin closure activities of each Class IV landfill unit no later than 30 days after the date on which the landfill 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 1 year after the most recent receipt of wastes.   Extensions beyond the 1-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.   Any portion of a Class IV landfill unit that will not receive additional waste within 180 days must have an intermediate cover of at least 1 foot of approved earthen materials.

(g) An owner or operator of Class IV landfill units must complete closure of each unit in accordance with the closure plan within 180 days following the beginning of closure as specified in (3) (f) above.   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 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 Class IV landfill unit.