1710 W MARINE VIEW DR 2024-01-03

Nets (commonly called matting) are strands of material woven into an open, but high -tensile strength net (for example, coconut fiber matting). Blankets are strands of material that are not tightly woven, but instead form a layer of interlocking fibers, typically held together by a biodegradable or pho- todegradable netting (for example, excelsior or straw blankets). They generally have lower tensile strength than nets, but cover the ground more completely. Coir (coconut fiber) fabric comes as both nets and blankets. Conditions of Use Erosion control netting and blankets shall be made of natural plant fibers unaltered by synthetic materials. Erosion control nets and blankets should be used: . To aid permanent vegetated stabilization of slopes 2H:1 V or greater and with more than 10 feet of vertical relief. . For drainage ditches and swales (highly recommended). The application of appropriate net- ting or blanket to drainage ditches and swales can protect bare soil from channelized runoff while vegetation is established. Nets and blankets also can capture a great deal of sediment due to their open, porous structure. Nets and blankets can be used to permanently stabilize channels and may provide a cost-effective, environmentally preferable alternative to riprap. Disadvantages of nets and blankets include: . Surface preparation is required. . On slopes steeper than 2.5H:1 V, net and blanket installers may need to be roped and har- nessed for safety. . They cost at least $4,000-6,000 per acre installed. Advantages of nets and blankets include: . Installation without mobilizing special equipment. . Installation by anyone with minimal training . Installation in stages or phases as the project progresses. Installers can hand place seed and fertilizer as they progress down the slope. . Installation in any weather. . There are numerous types of nets and blankets that can be designed with various parameters in mind. Those parameters include: fiber blend, mesh strength, longevity, biodegradability, cost, and availability. An alternative to nets and blankets in some limited conditions is BMP C202: Riprap Channel Lining. Ensure that BMP C202: Riprap Channel Lining is appropriate before using it as a substitute for nets and blankets. 2019 Stormwater Management Manual for Western Washington Volume 11 - Chapter 3 - Page 293