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Chapter 4 ='Besf;Nana - ement Pzactices:fof:.Erosion and Sediment Control . . . <br /> In addition, a curtain installed in such a manner can "billow up" toward the surface <br /> under the pressure of the moving water, which will result in an effective depth which <br /> is significantly less than the skirt depth. <br /> 7 , Turbidity curtains should be located parallel to the direction of flow of a moving body <br /> of water. Turbiditycurtains should not be laced across. the main flow of a <br /> significant body of moving water. <br /> g , When sizing the length of the floating cuitain, allow an additional 10 - 20% variance <br /> in the straight - line measurements. This will allow for measuring errors, make <br /> _ installing easier and reduce stress from potential wave action during high winds . <br /> g , An attempt should .be made to avoid an excessive number of joints in the curtain ; a <br /> minimum continuous span of 50 feet (15 m) between joints is a good "rule of <br /> thumb ." <br /> tta <br /> .. <br /> lo . orn' axe to span of 100 feet (30 m) between anchor or at <br /> locations s also a goad <br /> 11. . The ends of the curtain , both floating upper and weighted lower, should extend well <br /> up into the shoreline, especially if high water conditions are expected . The ends <br /> should be secured firmly to the shoreline to fully enclose the area where sediment <br /> may enter the water. <br /> 12. When there is a specific need to extend the curtain to thebottomvious <br /> offiltt e watercourse <br /> bric may be <br /> in tidal or moving water conditions, a heavy <br /> wo�fen"p substituted for the normally reco1.mmended impervious geotextile. This creates a <br /> "flow-through" the norr which significantly reduces pressure ,on the curtain and <br /> will help to keep it in the same relative location and shape during the rise and fall <br /> Ow of tidal waters . <br /> 13 . Typical- alignments-of turbidity curtains can be- seen in Plate 4.45c: The number <br /> and spacing of external anchors may vary depending on current velocities and <br /> potential wind and wave. action ; manufacturer' s recommendations should ' be <br /> followed . <br /> 14. Be certain- that-the type, location ; and. installation of the barrier is as shown on the <br /> approved plan and permit Additional permits may be required in navigable <br /> waterways , especially when the barrier creates an obstruction . <br /> w <br /> r <br /> 4-117 <br />