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CITY OF EVERETT STORMWATER MANAGEMENT MANUAL <br /> i <br /> � 3.3.16 BMP C235: Straw Wattles <br /> Purpose <br /> Straw wattles aze TESC barriers consisting oCstraw that is wrapped�n biodegradablc tubular plastic or <br /> similar encasing material. They reduce the velociry and can spread the i'1o�H of nll and shat runoff;and <br /> can capture and retain sediment. Straw wattles are rypically 8 to ]0 inches in diameter and 25 to 30 (eet <br /> in length. The wattles are placed in shellow trenches and staked along thc contour of disturbed or ncwly <br /> constructed slopes. See Figure 3.4 for typical construcdon detaiL=. <br /> CondiUons o/Use <br /> • Disturbed azeas that requirc immediate erosion protection <br /> • Exposed soils duting the period of shoR conshvction delays,or over winter months <br /> • On slopes rcquiring stabilization until permanent vegetation can be established <br /> • Straw wattles are effective for one to two wet seasons <br /> • If conditions aze appropriate,wattles can be staked to the ground using willow cuttings for added <br /> mvegetation <br /> • Rilling can occur bencath wattles if not properly entrenched and water can pass bctween wattles <br /> if not tig6tly abutted together. <br /> Design Criteria <br /> � I. It is critical that wattics are installed pecpendicular to the tlow direclion and parallel to the slope <br /> contour. <br /> i <br /> 2. Nazrow trenches s6ould be dug across the slope on contour to a depth o(3 to 5 inc6es on ciay <br /> soils and soils with gradual slopes. On loosc soils,steep slopes,and areas with high rainfall, thc <br /> trenches should ba dug ta a depth of 5 to 7 inches,or one-half to two-thirds of the thiclmess of thc <br /> wattic. <br /> 3. Start building trenches and installing wattles from the base of the slope and work up. Excavated <br /> material should be spread evenly along the uphill slope and compacted using hand tamping or <br /> othcr methods. <br /> 4. Construct trenches on conrours at intervals of l0 to 25 fec�apart depending on thc stcepncss of . <br /> t6e slape,soil rypc,and rain(all. Thc stccper the slopc,tl�c closcr rogelhcr the trenches. <br /> 5. Install the watdes snugly into the trcnches and abut tightly cud to end. Do not ovcrlap thc cnds. <br /> 6. Instal!stakes at each end of lhe u•atlle,and at 4-foot centcrs along entite Icngth of wanlc. <br /> 7. If required,install pilot holes for thc stakes using a straighl bar to drive holes through the wattle <br /> end into the soil. <br /> B. At a minimum,wooden stakes should be approximately 0.75 x 0.75 x 24 inches. Willow cuttings <br /> or threc-cighlhs-inch rcinforoemcnt bar can elso be uscd For stakes. <br /> Mainte»ance Standards <br /> 1. Stakes should be driven through the middle of the wattle,teaving 2 to 3 inches of the stake <br /> prowding above the wanle. <br /> 2. Wattles may require maintenance to ensurc thcy aze in contact with soil and thoroughly <br /> entrcnchcd, especially after signiGcant rainfall on steep sandy soils. <br /> Volume II—Construcfion Sformwater Pollution P2vention <br /> 3-58 <br />