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it blanket and be stapled. On steeper slopes, this overlap should be installed in a small trench, stapled, and covered with soil. With the variety of products available, it is impossible to cover all the details of appropriate use and installation. Therefore, it is critical that the design engineer consult the manufacturer's information and that a site visit takes place in order to ensure that the product specified is appropriate. Information is also available at the following web sites: 1. WSDOT (Section 3.2.4): http://www.wsdot.wa.gov/NR/rdonlyres/3B41 E087-FA86-4717-932D- D7A8556CCD57/0/ErosionTrainingManua l.pdf 2. Texas Transportation Institute: http://www.txdot.gov/business/doing_business/product evaluation/erosion_ control.htm • Use jute matting in conjunction with mulch (BMP C121: Mulching (p.284)). Excel- sior, woven straw blankets and coir (coconut fiber) blankets may be installed without mulch. There are many other types of erosion control nets and blankets on the market that may be appropriate in certain circumstances. In general, most nets (e.g., jute matting) require mulch in order to prevent erosion because they have a fairly open structure. Blankets typically do not require mulch because they usually provide complete protection of the surface. . Extremely steep, unstable, wet, or rocky slopes are often appropriate candidates for use of synthetic blankets, as are riverbanks, beaches and other high-energy environments. If synthetic blankets are used, the soil should be hydromulched first. . 100-percent biodegradable blankets are available for use insensitive areas. These organic blankets are usually held together with a paper or fiber mesh and stitching which may last up to a year. . Most netting used with blankets is photodegradable, meaning they break down under sunlight (not UV stabilized). However, this process can take months or years even under bright sun. Once vegetation is established, sunlight does not reach the mesh. It is not uncommon to find non -degraded netting still in place several years after installation. This can be a problem if maintenance requires the use of mowers or ditch cleaning equipment. In addition, birds and small animals can become trapped in the netting. Maintenance Standards Maintain good contact with the ground. Erosion must not occur beneath the net or blanket. 2014 Stormwater Management Manual for Westem Washington 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Volume 11 - Chapter 4 - Page 290 1