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1 <br /> 1 <br /> BMP C121: Mulching <br /> Purpose The purpose of mulching soils is to provide immediate temporary <br /> protection from erosion. Mulch also enhances plant establishment by <br /> conserving moisture,holding fertilizer, seed, and topsoil in place, and <br /> moderating soil temperatures. There is an enormous variety of mulches <br /> that can be used. Only the most common types are discussed in this <br /> ' section. <br /> Conditions of Use As a temporary cover measure,mulch should be used: <br /> • On disturbed areas that require cover measures for less than 30 days. <br /> • As a cover for seed during the wet season and during the hot summer <br /> months. <br /> • During the wet season on slopes steeper than 3H:1 V with more than 10 <br /> feet of vertical relief. <br /> • Mulch may be applied at any time of the year and must be refreshed <br /> periodically. <br /> ' Design and For mulch materials, application rates,and specifications, see Table 4.7. <br /> Installation Note: Thicknesses may be increased for disturbed areas in or near <br /> Specifications sensitive areas or other areas highly susceptible to erosion. <br /> ' Mulch used within the ordinary high-water mark of surface waters should <br /> be selected to minimize potential flotation of organic matter. Composted <br /> organic materials have higher specific gravities (densities)than straw, <br /> wood, or chipped material. <br /> Maintenance The thickness of the cover must be maintained. <br /> ' Standards • <br /> • Any areas that experience erosion shall be remulched and/or protected <br /> with a net or blanket. lithe erosion problem is drainage related,then <br /> ' the problem shall be fixed and the eroded area remulched. <br /> I <br /> i <br /> 4-20 Volume 11—Construction Stormwater Pollution Prevention February 2005 <br />