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RULE 2 PERMITS <br />The potential for wind erosion is based on the soil surface layer's texture, organic matter content, <br />carbonate reaction, mineralogy, and coarse fragment content are factors affecting soil loss due to wind <br />erosion (USDA 2003). Clay content, organic matter, and coarse fragment content decrease wind erodibility, <br />whereas silty and fine sandy surface materials are the most prone to wind erosion. While many of the soils in <br />the Soils Survey Area are in a fine textural family, many have much more loamy surface textures. This is <br />primarily a result of the notable loess influence on soils throughout the Soils Survey Area. Those soils with <br />the most notable loess influence, including Shawa, Maudlin, Weed, Skyway, and Lamphier, are all highly <br />erodible by wind. In the absence of moisture, these soils may begin to erode and may be difficult to <br />stabilize once exposed. The deep blowouts created in areas of intense traffic on ridges in the southwestern <br />portion of the Soils Survey Area are evidence of this erodibility. Care should be taken when salvaging and <br />replacing these soils to limit their exposure to wind. <br />The fine sand and silt fractions of soil are most susceptible to water erosion while organic matter and <br />coarse fragments reduce susceptibility to erosion. Water erosion hazard is based on a soil - crodibility factor <br />(K- factor) which is determined by the percentage of silt, clay, very fine sand, and organic matter of the <br />surface horizon, soil structure, and profile permeability class. K- factors commonly range from less than <br />0.05 to over 0.5. If the K- factor is below 0.3, susceptibility to water erosion is low and the soil is "good" <br />for use in reclamation without limits. However, when the K- factor approaches or exceeds 0.4, there is <br />notable potential for water erosion from overland flow when it occurs. <br />While the surface soil is the material initially at risk from runoff and water erosion when a soil is exposed, <br />soils within the top 12 inches of each site were evaluated to consider the effects of mixing during salvage <br />operations. Textural and organic matter values used in the calculation of the K- factor for the soils of the <br />Soils Survey Area were determined through review of laboratory results. Soil structure and permeability <br />class were based on field observations. The K- factors were calculated using the soil erodibility equation <br />presented in the NSSH (NRCS, 2003a). The results of these calculations (Kf) are shown with other soil <br />physical properties in Table 2.04.9.18. <br />None of the soils tested in the Soils Survey Area had K- factors in excess of 0.4, but several did have <br />values greater than 0.25, indicating a moderate susceptibility to water erosion. Sites with K- factors in <br />excess of 0.25 were residual and colluvial soils located on ridge crests and steep slopes in the extreme <br />southern end of the Soils Survey Area, or soils developed on alluvial fans, terraces, and other gentle <br />sloping sites in the northern portion of the Soils Survey Area. These locations correlate closely to <br />alluvium and other soils formed in materials weathered from hard sandstones and siltstones in the lower <br />portion of the Williams Fork Formation and the upper portion of the Iles Formation. In light of these <br />moderately high K- factors, it is advisable to avoid placement of these materials on steep slopes in the <br />post -mine landscape, or ensure that they are mixed with other less erosive soils. <br />Soil Acidity and Alkalinity <br />The acidity and alkalinity of soils in the Soils Survey Area are closely tied to the parent materials, <br />topographic position, and moisture regime. Soils developed in alluvial parent materials in frigid aridic and <br />ustic regimes (e.g.., Adderton, Havre, and Battlement) all had average pH levels above neutral (neutral <br />pH = 7). Other soils developed primarily from residuum, slope colluvium and loess in cryic and ustic <br />regimes (e.g., Waybe, Rhone, Maudlin, Thornburgh) all had average pH values below neutral. Soils <br />developed from alkaline bedrock (carbonate cemented sedimentary materials) under an ustic regime in the <br />central portion of the Soils Survey Area generally have the most neutral of all soils. <br />This correlation is reflective of three factors: <br />1) soils at higher elevations likely experience more leaching, which removes carbonates from the <br />soil and lowers pH; <br />Collom — Rule 2, Page 53 Revision Date: 9/28/11 <br />Revision No.: PR -03 <br />