825 N BROADWAY 2017-01-13 - Laserfiche WebLink

BMP C120: Temporary and Permanent Seeding PuYpose Seeding is intended to reduce erosion by stabilizing exposed soils. A well-established vegetative cover is one of the most effective methods of reducing erosion. Conditions of Use ' Seeding may be used throughout the project on disturbed areas that have reached final grade or that will remain unworked for more than 30 days. Channels that will be vegetated should be installed before major earthwork and hydroseeded with a Bonded Fiber Matrix. The vegetation should be well established (i.e., 75 percent cover) before water is allowed to flow in the ditch. With channels that will have high flows, erosion control blankets should be installed over the hydroseed. If vegetation cannot be established from seed before water is allowed in the ditch, sod should be installed in the bottom of the ditch over hydromulch and blankets. • Retention/detention ponds should be seeded as required. • Mulch is required at all times because it protects seeds from heat, moisture loss, and transport due to runoff. • All disturbed areas shall be reviewed in late August to early September and all seeding should be completed by the end of September. Otherwise, vegetation will not establish itself enough to provide more than average protection. • At final site stabilization, all disturbed areas not otherwise vegetated or stabilized shall be seeded and mulched. Final stabilization means the completion of all soil disturbing activities at the site and the establishment of a permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement, riprap, gabions or geotextiles) which will prevent erosion. Design and ° Seeding should be done during those seasons most conducive to Installation growth and will vary with the climate conditions of the region. Specifications Local experience should be used to determine the appropriate seeding periods. The optimum seeding windows for western Washington are April 1 through June 30 and September 1 through October 1. Seeding that occurs between July 1 and August 30 will require irrigation until 75 percent grass cover is established. Seeding that occurs between October 1 and March 30 will require a mulch or plastic cover until 75 percent grass cover is established. • To prevent seed from being washed away, confirm that all required surface water control measures have been installed. February 2005 Volume Il — Construction Stormwater Pollution Prevention 4-13