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Chapter4`- Rest Mana ement Practices for Erosion and. Sediment .Contro Construction Sgecificatlons Materials 1 . Barriers should be a bright color (yellow or "international" orange are recommended) that will attract the attention of nearby boaters . 2 . The curtain fabric must meet the minimum requirements noted in Table 3 .27-A. 3 . Seams in the fabric shall be either vulcanized welded or sewn ;. and shall develop the full strength of the fabric. r ividual 4. Floatation devices shall be flexibie , buoyant units contained in an inaby the r floatation sleeve or collar attached; to the curtain. Buoyancy p. floatation units shall be sufficient to support:the weight of the curtain and maintain a freeboard of at least 3 inches (8 cm) above the.water surface level. (See Plate 4.45c) 5 • Load _ line.a must be fabricated into the bottom of all floating turbidity curtains . Type II and Type III must have load lines also fabricated into the top o€`the fabric. The top ` load line shall consist of woven webbing or vinyl-sheathed steel cable and shall have a break strength in excess of 1o , 000 pounds (4.5 t) . The supplemental ` (bottom) load-line shall consist of a chain incorporated into the bottom hem of the curtain of sufficient weight to serve `as ballast to hold the curtain in a vertical position . Additional anchorage shall be• proVided`as necessary. . The load lines shall have suitable connecting devices which develop the full breaking strength for connecting to load lines in adjacent sections (See Plates 4.45a and. 4.45b which portray this orientation) . . 6, Externatanchors may consist of 2 x 4 inch (5 x 10 cm) or 2-1/2 in6h (6 dm) minimum diameter wooden stakes , or 1 .33 pound sllinearfoot (2 kd1m) steel posts when Type CinstMidtfon is. used when Type It orrType 11F.Installations are used , bottom anchors. should be used . 7 _ Bolton► anchors must be sufficient to hold the curtain. in the same position relafive to the bottom of the watercourse without interfering with the action oethoe may be The anchor may dia into the bottom (grappling hook, plow or fluke-typ ) weighted (mushroom type) and should be attached to a floating anchor buoy via an anchor line. The anchor line would then run from the buoy to the top load line of the curtain . When used with Type Ill installations , these lines must contain enough slack to allow the buoy and curtain to float freely.with tidal changes without pulling VW the buoy or curtain down and must be checked regularly to make sure they do not become entangied with debris . As previously noted , anchor spacing will vary with current velocity and expected wind and wave action ; manufacturer's recommendations should be followed . See orientation of external anchors and anchor buoys for tidal installation in Plate 4 .45b. ,w 4-119