REV03713 - Laserfiche WebLink

Home Browse Search

the western half of the study area (Section 2.04.6). These clay lenses occur only in the extreme western part of the New Horizon 2 permit area near overburden Drill Site 870E (see Map 2.05.41, Geologic Cross Section and Sample Locations for New Horizon 2 Study Area]. These increments are not currentty in the projected mining disturbance area (see Map 2.05.3-1, Dperations Plan -New Horizon 2). No sandy clay textures were identified within the New Horizon 2 Study Area. The New Horizon 2 postmine spoil textures will typically be loamy with an approximate particle size distribution of 65 percent sand, 25 peroent silt, and 10 percent clay (Section 2.04.6, Geology Description). Surface crusting, which is critical to seedling emergence, is discussed in the Soil Survey (Section 2.04.9), Revegetation Plan (Section 2.05.4(2](e]], and Topsoil Management of this Section. Since clay percentages and shrink-swell potentials are low, stability and trafficability problems are not anticipated. Prior to topsoil replacement, the regraded spoil within mined areas will be scarified by deep ripping or chisel plowing on the contour to a depth of 12 to 24 inches to reduce excessive compaction, prevent potential slippage zones, reduce erosion, and improve water and air movement and root growth across the topsoil/spoil interfiace. Abandoned roads shall also be ripped and/or chisel plowed prior to topsoil replacement. Spoi! erodibility is discussed in the Backfilling and Grading (Section 2.05.4(2)(c)) and Facilities (Section 2.05.3) sections. Soil and topsoil erodibility is discussed in the Soil Survey (Section 2.04.9) and the Revegetation (Section 2.05.4(2](e]] sections. The resultant loamy textured spoil will possess suitable physics( qualities which are conducive to plant growth. The available water holding capacity will likely be moderately !ow to moderate (approximately 0.07 to 0.11 inches of water per inch of soil), permeability moderate to moderately rapid (about 1.0 to 6.0 inches per hour], and cation exchange capacity low to moderately low (5 to 10 millfequivalents per 100 grams]. Since the overburden contains a mixture of soft, slightly hard, hard, and extremely hard rock fragments, the spoil will generally possess acceptable root growth and water holding characteristics. The chemical properties of the overburden/interburden are also quite favorable. Sodicity and salinity levels are low to moderate in the New Horizon 2 permit area and should pose no severe problem to successful reclamation. Salinity levels in the upper four feet of regraded spoil will likely be comparable to premining values. New HO(4On Mine Topsoil Management Plan The New Horizon Mine topsoil management plan, based predominantly upon the detailed soil survey contained in Section 2.04.9 and secondarily on historic reclamation at New Horizon 1 mining area, was developed to insure that the most suitable topsoil within the disturbance area is salvaged. The