(1) The department may not approve a postmining land use of cropland unless the following criteria are met:
(a) prior to mining, all soils within the proposed cropland reclamation area must have been at least capability class IV, based on U.S. natural resources conservation service criteria;
(b) soils proposed for use must have the following properties:
(i) loamy texture, as defined by the U.S. soil conservation service in the Soil Survey Manual, chapter 4 as revised May, 1981, pp. 4-56 and 4-57;
(ii) rock fragment (gravels, cobbles, and channers only) contents less than 20% in the first lift and less than 35% in the second lift;
(iii) after materials are replaced, no greater than moderate wind and water erosion hazards as determined by U.S. natural resources conservation service procedures; and
(iv) levels of electrical conductivity, sodium adsorption ratio, and plant available water-holding capacity meeting the criteria for class III soils according to the "Land Capability Guide for Montana, U.S. Soil Conservation Service, June 1988", which is incorporated by reference into this rule. A copy of this document may be obtained from the Natural Resources Conservation Service, 10 E. Babcock St., Bozeman, MT 59715;
(c) soil materials must be capable of selection and handling in such a way, and redistribution to such a thickness, and the underlying regraded spoil properties must be of sufficient quality, that the postmining productivity of the root zone will be sufficient to support cropland as the postmining land use;
(d) slope gradients must not exceed 8%;
(e) the area must receive a minimum of 12 inches average annual precipitation, or there must be sufficient irrigation water available and committed to maintain crop production;
(f) the area must not be subject to flooding that would impair its suitability as cropland due to flood effects including, but not limited to, erosion, siltation, and inundation;
(g) the area must have a minimum of 90 frost-free days per year; and
(h) the department must determine that:
(i) saline seep on the proposed cropland area will not occur; and
(ii) the reclaimed area will not function as a saline seep recharge area for lands downgradient.
(2) The operator shall comply with the following requirements in reclaiming to cropland:
(a) (i) soil materials must be selected and handled in such a way and redistributed to such a thickness, and the underlying regraded spoil properties must be of sufficient quality such that the postmining productivity of the root zone will be sufficient to support cropland as the postmining land use.
(ii) the following minimum requirements must be met:
(A) soils must be replaced to a minimum thickness of 24 inches; and
(B) the root zone thickness must be consistent with the requirements of ARM 17.24.501(2) ;
(b) if necessary to protect replaced soil materials from wind and water erosion, or if necessary to enhance soil productivity, stability or the capacity for root penetration, a grass-legume mixture must be planted and maintained as determined by the department; and
(c) soil amendments must be added in accordance with ARM 17.24.718.