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Crushed rock, gravel base, etc., shall be added as required to maintain a stable driving surface and <br />to stabilize any areas that have eroded. <br />Following construction, these areas shall be restored to pre -construction condition or better to pre- <br />vent future erosion. <br />Perform street cleaning at the end of each day or more often if necessary. <br />BMP C120: Temporary and Permanent Seeding <br />Purpose <br />Seeding reduces erosion by stabilizing exposed soils. A well -established vegetative cover is one of <br />the most effective methods of reducing erosion. <br />Conditions of Use <br />Use seeding throughout the project on disturbed areas that have reached final grade or that will <br />remain unworked for more than 30 days. <br />The optimum seeding windows for western Washington are April 1 through June 30 and September <br />1 through October 1. <br />Between July 1 and August 30 seeding requires irrigation until 75 percent grass cover is established. <br />Between October 1 and March 30 seeding requires a cover of mulch or an erosion control blanket <br />until 75 percent grass cover is established. <br />Review all disturbed areas in late August to early September and complete all seeding by the end of <br />September. Otherwise, vegetation will not establish itself enough to provide more than average pro- <br />tection. <br />Mulch is required at all times for seeding because it protects seeds from heat, moisture loss, and <br />transport due to runoff. Mulch can be applied on top of the seed or simultaneously by hydroseeding. <br />See BMP C121: Mulching for specifications. <br />Seed and mulch all disturbed areas not otherwise vegetated at final site stabilization. Final sta- <br />bilization means the completion of all soil disturbing activities at the site and the establishment of a <br />permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement, <br />riprap, gabions, or geotextiles) which will prevent erosion. See BMP T5.13: Post -Construction Soil <br />Qualitv and Depth. <br />Design and Installation Specifications <br />General <br />. Install channels intended for vegetation before starting major earthwork and hydroseed with a <br />Bonded Fiber Matrix. For vegetated channels that will have high flows, install erosion control <br />blankets over the top of hydroseed. Before allowing water to flow in vegetated channels, <br />establish 75 percent vegetation cover. If vegetated channels cannot be established by seed <br />2019 Stormwater Management Manual for Western Washington <br />Volume ll - Chapter 3 - Page 284 <br />