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1 • <br /> • Mulch is always required for seeding. Mulch can be applied on top of <br /> the seed or simultaneously by hydroseeding. <br /> • On steep slopes,Bonded Fiber Matrix(BFM) or Mechanically Bonded <br /> Fiber Matrix (MBFM)products should be used. BFM/MBFM <br /> products are applied at a minimum rate of 3,000 pounds per acre of <br /> mulch with approximately 10 percent tackifier. Application is made <br /> so that a minimum of 95 percent soil coverage is achieved. Numerous <br /> products are available commercially and should be installed per <br /> manufacturer's instructions. Most products require 24-36 hours to <br /> cure before a rainfall and cannot be installed on wet or saturated soils. <br /> Generally,these products come in 40-50 pound bags and include all <br /> necessary ingredients except for seed and fertilizer. <br /> BFMs and MBFMs have some advantages over blankets: <br /> • No surface preparation required; <br /> • Can be installed via helicopter in remote areas; <br /> • On slopes steeper than 2.5:1,blanket installers may need to be roped <br /> and harnessed for safety; <br /> • They are at least$1,000 per acre cheaper installed. <br /> In most cases,the shear strength of blankets is not a factor when used on <br /> slopes, only when used in channels. BFMs and MBFMs are good <br /> alternatives to blankets in most situations where vegetation establishment <br /> is the goal. <br /> • When installing seed via hydroseeding operations,only about 1/3 of <br /> the seed actually ends up in contact with the soil surface. This reduces <br /> the ability to establish a good stand of grass quickly. One way to <br /> overcome this is to increase seed quantities by up to 50 percent. <br /> • Vegetation establishment can also be enhanced by dividing the <br /> hydromulch operation into two phases: <br /> 1. Phase 1-Install all seed and fertilizer with 25-30 percent mulch <br /> and tackifier onto soil in the first lift; <br /> • 2. Phase 2-Install the rest of the mulch and tackifier over the first lift. <br /> An alternative is to install the mulch, seed,fertilizer, and tackifier in one <br /> lift. Then, spread or blow straw over the top of the hydromulch at a rate of <br /> about 800-1000 pounds per acre. Hold straw in place with a standard <br /> tackifier. Both of these approaches will increase cost moderately but will <br /> greatly improve and enhance vegetative establishment. The increased cost <br /> may be offset by the reduced need for: <br /> 1. Irrigation <br /> 2. Reapplication of mulch <br /> 3. Repair of failed slope surfaces <br /> February 2005 Volume lI—Construction Stormwater Pollution Prevention 4-15 <br />