2018-04-02_PERMIT FILE - C1981019A (7)

Home Browse Search

RULE 2 PERMITS the prominent ridge and high elevations in the extreme southern end of the Soils Survey Area. Transitional moisture zones include aridic ridge tops and south -facing slopes, and ustic valley bottoms and steep north -facing slopes. Entisols were present throughout the Soils Survey Area on steep slopes, in areas of active alluvial deposition, and areas of bedrock exposure or extremely shallow depth -to -bedrock. The Collom permit expansion area contains deep soils in mostly gently to moderately sloping locations on the benches and drainages, shallow soils on steep slopes at the north end of the area and very deep soils on steep slopes at the southern end of the area. Except for the north end of the area, the primary limitation of the soils in the Collom permit expansion area is the high percentage of clay. The other primary concern is a high percentage of coarse fragments and occasionally shallow depths to bedrock restricting salvage depths. Soils on the northern end of the area are very deep loess derived soils with stripping depths of two feet or more over large areas of north facing slopes. The potential for wind erosion is based on the soil surface layer's texture, organic matter content, carbonate reaction, mineralogy, and coarse fragment content are factors affecting soil loss due to wind erosion (USDA 2003). Clay content, organic matter, and coarse fragment content decrease wind erodibility, whereas silty and fine sandy surface materials are the most prone to wind erosion. While many of the soils in the Soils Survey Area are in a fine textural family, many have much more loamy surface textures. This is primarily a result of the notable loess influence on soils throughout the Soils Survey Area. Those soils with the most notable loess influence, including Shawa, Maudlin, Weed, Skyway, and Lamphier, are all highly erodible by wind. In the absence of moisture, these soils may begin to erode and may be difficult to stabilize once exposed. The deep blowouts created in areas of intense traffic on ridges in the southwestern portion of the Soils Survey Area are evidence of this erodibility. Care should be taken when salvaging and replacing these soils to limit their exposure to wind. The fine sand and silt fractions of soil are most susceptible to water erosion while organic matter and coarse fragments reduce susceptibility to erosion. Water erosion hazard is based on a soil-erodibility factor (K -factor) which is determined by the percentage of silt, clay, very fine sand, and organic matter of the surface horizon, soil structure, and profile permeability class. K -factors commonly range from less than 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" for use in reclamation without limits. However, when the K -factor approaches or exceeds 0.4, there is notable potential for water erosion from overland flow when it occurs. While the surface soil is the material initially at risk from runoff and water erosion when a soil is exposed, soils within the top 12 inches of each site were evaluated to consider the effects of mixing during salvage operations. Textural and organic matter values used in the calculation of the K -factor for the soils of the Soils Survey Area were determined through review of laboratory results. Soil structure and permeability class were based on field observations. The K -factors were calculated using the soil erodibility equation presented in the NSSH (MRCS, 2003a). The results of these calculations (Kf) are shown with other soil physical properties in Table 2.04.9.18. None of the soils tested in the Soils Survey Area had K -factors in excess of 0.4, but several did have values greater than 0.25, indicating a moderate susceptibility to water erosion. Sites with K -factors in excess of 0.25 were residual and colluvial soils located on ridge crests and steep slopes in the extreme southern end of the Soils Survey Area, or soils developed on alluvial fans, terraces, and other gentle sloping sites in the northern portion of the Soils Survey Area. These locations correlate closely to alluvium and other soils formed in materials weathered from hard sandstones and siltstones in the lower portion of the Williams Fork Formation and the upper portion of the Iles Formation. In light of these moderately high K -factors, it is advisable to avoid placement of these materials on steep slopes in the post -mine landscape, or ensure that they are mixed with other less erosive soils. Collom — Rule 2, Page 38 Revision Date: 12/30/16 Revision No.: TR -108