(1) Contaminated soils are considered remediated when:

(a) contaminant concentrations listed in Montana Risk-based Corrective Action Guidance for Petroleum Releases, Table 1 (February 2024) are permanently reduced to the residential RSBL concentrations. 

(2) When contaminated soil remediation in a treatment zone is complete, the owner or operator of a landfarm facility may:

(a) remove the remediated material and replace it with additional contaminated soils for treatment;

(b) apply an additional lift to the treatment zone for treatment if:

(i) the maximum depth of remediated soil within the treatment cell, including the additional lift, does not exceed a depth of five feet; and

(ii) BTZ sampling is conducted pursuant to ARM 17.50.1613; or

(c) close and reclaim the treatment cell.

(3) If the contaminant concentration standards in (1) cannot be attained, the department may approve post-remediation uses for these contaminated soils if the owner or operator of a landfarm facility submits a request to the department that:

(a) demonstrates through analytical results that contaminant degradation has reached a maximum using the analytical methods and standards outlined in ARM 17.50.1612 and 17.50.1613; and

(b) verifies the treatment cell and treatment zone are in compliance with this subchapter.

(4) The owner or operator of a landfarm facility may not supply or use soils for any purpose exceeding the contaminant concentrations specified in Montana Risk-based Corrective Action Guidance for Petroleum Releases, Table 1 (February 2024).

(5) The owner or operator of a landfarm facility may not supply, and a person may not use, remediated soils in any location that threaten human health and the environment, for residential topsoil, or for any purpose in school playgrounds or daycare centers.