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The first two considerations listed above were among those used for establishing the grading <br />system for texture. Unsuitable clay textures were identified within two thin lenses of the upper <br />overburden in the western half of the study area (Section 2.04.6). These clay lenses occur only <br />near overburden Drill Site 870E (see Map 2.04.6-1, Geologic Cross Section and Sample <br />Locations for New Horizon 2 Study Area). These clay lenses are in the projected mining <br />disturbance area and when they are being excavated, they will be thoroughly mixed with non clay <br />type overburden. The mixing and dillution process will be accomplished by: 1) blasting, which will <br />start the mixing of clay lenses with non clay formations above and below the clay seam 2) the <br />overburden shovel wit be digging a full face through the clay tense from top to bottom to load each <br />truck for transportation to the backfill, 3) and finally, the trucks with the diluted clay lenses on <br />board will dump their load along a several hundred foot dump face. After this process, the <br />concentration in any one spot of clay like material will be minimal and compatibility of the backfill <br />will be negligible. <br />The New Horizon 2 postmine spoil textures will typically be loamy with an approximate particle <br />size distribution of 65 percent sand, 25 percent silt, and 10 percent clay (Section 2.04.6, Geology <br />Description). Surface crusting, which is critical to seedling emergence, is discussed in the Soil <br />i Survey (Section 2.04.9), Revegetation Plan (Section 2.05.4(2)(e)), and Topsoil Management of <br />this Section. Since clay percentages and shrink-swell potentials are low, stability and trafficability <br />problems are not anticipated. <br />Prior to topsoil replacement, the regraded spoil within mined areas will be scarified by deep ripping <br />or chisel plowing on the contour to a depth of 12 to 24 inches to reduce excessive compaction, <br />prevent potential slippage zones, reduce erosion, and improve water and air movement and root <br />growth across the topsoil/spoil interface. Abandoned roads shall also be ripped and/or chisel <br />plowed prior to topsoil replacement. Spoil erodibility is discussed in the Backfilling and Grading <br />(Section 2.05.4(2)(c)) and Facilities (Section 2.05.3) sections. Soil and topsoil erodibility is <br />discussed in the Soil Survey (Section 2.04.9) and the Revegetation (Section 2.05.4(2)(e)) <br />sections. <br />The resultant loamy textured spoil will possess suitable physical qualities which are conducive to <br />plant growth. The available water holding capacity will likely be moderately low to moderate <br />(approximately 0.07 to 0.11 inches of water per inch of soil), permeability moderate to moderately <br />. cae..iaaa is xov oz~ 2.05.4(2)(d) - 6 <br />