2008-05-28_REVISION - C1981019 (2)

Home Browse Search

will be to not leave preferential pathways for erosion and to avoid development of surface features that will overly compromise proper seed placement by seeding equipment (e.g., steep and narrow ridges). Another topsoil distribution technique that may be used in areas targeting Sagebrush Steppe would be the development of low berms using emplaced topsoil with the aid of equipment such as a road grader (see Figure 2.05-6 below). For ease of discussion, such berms could be termed "soil fences". These berms would act as natural snowfences trapping wind blown snow to aid sagebrush emergence and development. In this circumstance, a designed amount of topsoil (e.g. 9 inches) would be redistributed over a target area, however, berms would be developed utilizing only the topsoil resource. Where upper layers of topsoil have been pushed aside, a depth of remaining topsoil may be in the 2-4 inch range that should then help to encourage sagebrush emergence while discouraging vigorous grass growth. Where topsoil is bermed, a peak depth up to 30 inches may result. In these thicker topsoil areas, other taxa within the seed mix (or alternate mix) should provide additional competitive advantage. It is critical that berms be constructed on the contour to preclude development of preferential erosion pathways. It is also necessary that berms only be constructed where they will be approximately perpendicular to the prevailing winds, otherwise there is little benefit to be gained. Furthermore, berms would have to exhibit low and rounded shoulders to allow seeding equipment to operate properly. Implementation of techniques such as this must necessarily occur as a result of site-specific opportunity (as opposed to plan) given a variety of factors, not the least of which is availability of equipment and personnel. As indicated in Figure 2.05-6 below, the dimensions (in cross-section) would need to be based on the width of seeding equipment to facilitate proper seeding operations, although the widths indicated may be changed in the field, especially given aspect differences. In this regard, sagebrush conducive seed mixes would be applied to the shallow soil areas as well as the uphill- facing side of the berm (west-facing slopes). This is the area that will receive maximum benefit from entrapped snow. The downhill-facing side of the berm would ideally receive the grassland conducive mix owing to the steeper slope (4:1). For easterly aspects, the grassland conducive mix would still need to be applied to the downhill 4:1 slope. As this technique is developed and "proven", modifications to seed mix placement can and should be made as necessary. Figure 2.05-6 SOIL FENCE CONSTRUCTION DIAGRAM (EXAMPLE) - 6 seeder widths (10:1 Slope) Overburden 2.05-48 1 2 seeder seeder width widths / \ (4:1 slop Revision Date: 3/14/08 Revision No.: TR-72