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