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before water flow; install sod in the channel bottom — over top of hydromulch and erosion con- <br />trol blankets. <br />. Confirm the installation of all required surface water control measures to prevent seed from <br />washing away. <br />. Hydroseed applications shall include a minimum of 1,500 pounds per acre of mulch with 3 per- <br />cent tackifier. See BMP C 121: Mulching for specifications. <br />. Areas that will have seeding only and not landscaping may need compost or meal -based <br />mulch included in the hydroseed in order to establish vegetation. Re -install native topsoil on <br />the disturbed soil surface before application. See BMP T5.13: Post -Construction Soil Quality <br />and Depth. <br />. When installing seed via hydroseeding operations, only about 1 /3 of the seed actually ends up <br />in contact with the soil surface. This reduces the ability to establish a good stand of grass <br />quickly. To overcome this, consider increasing seed quantities by up to 50 percent. <br />. Enhance vegetation establishment by dividing the hydromulch operation into two phases: <br />o Phase 1- Install all seed and fertilizer with 25-30 percent mulch and tackifier onto soil in <br />the first lift. <br />Phase 2- Install the rest of the mulch and tackifier over the first lift. <br />Or, enhance vegetation by: <br />o Installing the mulch, seed, fertilizer, and tackifier in one lift. <br />Spread or blow straw over the top of the hydromulch at a rate of 800-1000 pounds per <br />acre. <br />Hold straw in place with a standard tackifier. <br />Both of these approaches will increase cost moderately but will greatly improve and enhance <br />vegetative establishment. The increased cost may be offset by the reduced need for: <br />o Irrigation. <br />o Reapplication of mulch. <br />o Repair of failed slope surfaces. <br />This technique works with standard hydromulch (1,500 pounds per acre minimum) and Bon- <br />ded Fiber Matrix/ Mechanically Bonded Fiber Matrix (BFM/MBFMs) (3,000 pounds per acre <br />minimum). <br />. Seed may be installed by hand if: <br />o Temporary and covered by straw, mulch, or topsoil. <br />o Permanent in small areas (usually less than 1 acre) and covered with mulch, topsoil, or <br />erosion blankets. <br />. The seed mixes listed in Table II-3.4: Temporary and Permanent Seed Mixes include <br />2019 Stormwater Management Manual for Western Washington <br />Volume 11 - Chapter 3 - Page 285 <br />