(1) For purposes of closure of a landfarm facility, the owner or operator of a landfarm facility shall submit a closure plan that documents the following: 

(a) all contaminated soils were remediated pursuant to ARM 17.50.1617 standards;

(b) concentrations of TCLP metals in all remediated soils remaining at the facility are below the limits specified in ARM 17.50.1613, Table 4 and concentrations of nitrates or phosphorous are below the annual agronomic uptake rate for the established vegetation;

(c) one of the following requirements was satisfied:

(i) all contaminated soils were remediated and removed in accordance with ARM 17.50.1617 standards;

(ii) all contaminated soils were remediated to ARM 17.50.1617 standards and were subsequently spread and contoured in place; or

(iii) all contaminated soils were remediated to Table 1 residential RSBL concentrations in the Montana Risk-based Corrective Action Guidance for Petroleum Releases, (February 2024) and are capable of supporting native vegetation;

(d) all facility structures, such as cell, berms, and ditches, were reclaimed to pre-operation conditions;

(e) disturbed areas were revegetated with native plant growth or other department-approved species;

(f) final surface grades prevent ponding and erosion; and

(g) any ground water wells not intended for post-closure use were abandoned pursuant to ARM 17.50.1305.

(2) The owner or operator of a landfarm facility shall complete all closure activities within 180 days after commencing closure. Extension of the closure period may be granted by the department if the owner or operator demonstrates that closure will take longer than 180 days and that measures necessary to protect human health and the environment are maintained.

(3) Upon completion of all activities in the closure plan, the owner or operator of the landfarm facility shall provide written notification to the department that the facility has closed. Final closure is not complete until the department has completed final site inspection verifying the provisions of (1).