Mont. Code Ann. § 82-4-234

The operator shall commence the reclamation of the area of land affected by the operator's operation as soon as possible after the beginning of strip mining or underground mining of that area in accordance with plans previously approved by the department. Those grading, backfilling, subsidence stabilization, topsoiling, and water management practices that are approved in the plans must be kept current with the operation as defined by rules of the department, and a permit or supplement to a permit may not be issued if, in the discretion of the department, these practices are not current.