819 N BROADWAY WASHINGTON STATE UNIVERSITY 2018-05-11

• Jute matting must be used in conjunction with mulch(BMP C121). Excelsior, 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 in sensitive 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 • Good contact with the ground must be maintained, and erosion must Standards not occur beneath the net or blanket. • Any areas of the net or blanket that are damaged or not in close contact with the ground shall be repaired and stapled. • If erosion occurs due to poorly controlled drainage,the problem shall be fixed and the eroded area protected. I 4-24 Volume ll—Construction Stormwater Pollution Prevention February 2005