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Mulch <br />Mulching means covering a disturbed soil surface with plant residue or other <br />suitable material, such as rock, for the purpose of stabilizing the soil surface, slowing <br />erosion, and preserving soil moisture. This is an immediate, effective, and economical <br />erosion-control practice, although it is not permanent unless the material is rock. Mulching <br />with organic material is generally suitable for one to two years. <br />Mulch is used to reduce raindrop impact, water runoff, or wind erosion. In addition <br />to this, mulch may aid in soil water infiltration and to hold seed in place. Bare soils can be <br />protected by mulch until vegetation is established. Mulches are most suitable for flat or <br />gently sloping areas, but may be anchored to steep slope areas by means of nets, mats, or <br />tacifiers. <br />Basic Design and Construction Criteria <br />Material Selection <br />The selection of mulching materials will depend primarily on site conditions and <br />availability. Organic mulches such as straw, hay, wood fiber, organic debris, wood chips, or <br />inorganic rock are usually preferred because they are effective and compatible with the <br />environment. <br />Rock <br />Rock is used on and site reclamation as a permanent mulch to stabilize the soil <br />surface and reduce evaporation in areas with less than 40% vegetative cover. The use of <br />rock as surface mulch is an attempt to copy the <br />desert pavement, or rock veneer found occurring <br />naturally in Utah deserts. Armoring soil with rock <br />nprap or thick gravel mulch is a common practice on <br />radioactive waste burial sites in and environments. <br />This rock armoring breaks up raindrop energy, <br />reduces flow velocity, and increases water movement <br />into the soil. Rock mulch consisting of various sizes <br />r of gravel (1/10 to 3 inches) is more effective in <br />reducing sediment loss from overland flow or wind <br />Figure 3.1: Desert pavement armors the erosion than cobbles (>3 inches) (Waugh 1994). <br />soil surface and controls erosion in Large-sized cobbles, rocks, and boulders provide <br />Utah's and deserts. Emery County. shading, trap wind-blown snow, and help create <br />microclimates within reclaimed sites. It is <br />recommended that rock used as mulch consist of interlocking angular shapes, ranging in <br />size from small gravel to large boulders. <br />Rock mulch can either be applied as a surface layer treatment or mixed with <br />existing surface soils. Rock or rocky soils can be salvaged during operations and <br />stockpiled for reclamation use. Optimum rock coverage means that 60% to 70% of the <br />111