2018-11-19_PERMIT FILE - C2010089A (3)

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Unsuitable Bench 1 Backfill Mitigation Plan If the results of the sampling indicate that one or more of the unsuitable levels are reached, the Division will be contacted. Also at that juncture, NHN will resample the area to determine the extent of the unsuitable Bench 1. If the problem area is greater than one acre in size it will be necessary to remove or cap the area. If only the lower sample Bench 1 failed, then only two feet of Bench 1 will be added to the area and resampled. If both samples (0-2' & 2'-4') failed where the postmining land use is Dryland Pasture, any area over one acre will be capped with four feet of suitable material. For areas that have a postmining land use of Irrigated Pasture/Cropland the problem area will be excavated to a depth of four feet, and four feet of suitable Bench 1 will be placed within the excavated area. Topsoil Management Plan The NHN Mine topsoil management plan is based upon the detailed topsoil survey contained in Section 2.04.9 and has been developed to ensure the most suitable topsoil materials within the disturbance area are salvaged. The topsoil management plan evaluates the topsoil resources and describes salvage depths and techniques, storage, redistribution and maintenance or testing procedures necessary to restore the disturbed areas to the desired postmining land use. Evaluation of Topsoil Resources The topsoil resources found in the NHN Mine permit area are shown on Map 2.04.9-3: Topsoil Salvage Map and are typical of topsoil found in the semi -arid Colorado Plateau Physiographic Province, Canyon Land Section. A total of eleven different topsoil mapping units were delineated in the survey performed on the NHN Mine Area. Five of these topsoil mapping units lack salvageable topsoil and include livestock ponds, roads, drainage channel, soils mapping unit 78UT (5 to 30 percent slopes), and soils mapping unit RO (40 to 90 percent slopes). These areas lack salvageable topsoil either because the topsoil has already been removed or they contain coarse fragment contents which are too high for use as a plant growth medium. The area of these five topsoil mapping units which lack salvageable topsoil is 5.39 acres. The average stripping thickness for the combined horizons is depicted in the table found on Map 2.04.9-3: Topsoil Salvage Map. The table on this map shows the average areas and volumes obtained from each soil mapping unit sampled. See Map 2.05.4(2)(d)-2: Topsoil and Overburden Stockpile Locations for locations of the Progresso and mixed topsoil piles. The volumes of each stockpile are included in the Annual Reclamation Report and will be updated on an annual basis. As shown on Map 2.04.9-3: Topsoil Salvage Map, there are a total of six topsoil mapping units containing salvageable topsoil. These include topsoil mapping unit 81 PRO, containing 97.96 acres; topsoil mapping unit 77PIN, containing 79.98 acres; topsoil mapping unit REC, containing 74.67 acres; 82 PRO, containing 11.02 acres; soils mapping unit 78PIN, containing 8.06 acres; and topsoil mapping unit Aquolls, containing 3.76 acres. Section 2.05.4(2)(d) Page 3 January 2018 (PR -02)