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Design and • See Figure 4.4 and Figure 4.5 for typical orientation and installation of <br /> Installation blankets used in channels and as slope protection. Note: these are <br /> Specifications typical only; all blankets must be installed per manufacturer's <br /> installation instructions. <br /> • Installation is critical to the effectiveness of these products. If good <br /> ground contact is not achieved, runoff can concentrate under the <br /> product, resulting in significant erosion. <br /> • Installation of Blankets on Slopes: <br /> 1. Complete final grade and track walk up and down the slope. <br /> 2. Install hydromulch with seed and fertilizer. <br /> 3. Dig a small trench, approximately 12 inches wide by 6 inches deep <br /> along the top of the slope. <br /> 4. Install the leading edge of the blanket into the small trench and <br /> staple approximately every 18 inches. NOTE: Staples are <br /> metal,"U"-shaped, and a minimum of 6 inches long. Longer <br /> staples are used in sandy soils. Biodegradable stakes are also <br /> available. <br /> 5. Roll the blanket slowly down the slope as installer walks <br /> backwards. NOTE: The blanket rests against the installer's legs. <br /> Staples are installed as the blanket is unrolled. It is critical that the <br /> proper staple pattern is used for the blanket being installed. The <br /> blanket is not to be allowed to roll down the slope on its own as <br /> this stretches the blanket making it impossible to maintain soil <br /> contact. In addition, no one is allowed to walk on the blanket after <br /> it is in place. <br /> 6. If the blanket is not long enough to cover the entire slope length, <br /> the trailing edge of the upper blanket should overlap the leading <br /> edge of the lower blanket and be stapled. On steeper slopes, this <br /> overlap should be installed in a small trench, stapled, and covered <br /> with soil. <br /> • With the variety of products available, it is impossible to cover all the <br /> details of appropriate use and installation. Therefore, it is critical that <br /> the design engineer consults the manufacturer's information and that a <br /> site visit takes place in order to insure that the product specified is <br /> appropriate. Information is also available at the following web sites: <br /> 1. WSDOT: http://www.wsdot.wa.gov/eesc/environmental/ <br /> 2. Texas Transportation Institute: <br /> http://www.dot.state.tx.us/insdtdot/orgchart/cmd/erosion/contents. <br /> htm <br /> I <br /> February 2005 Volume II— Construction Stormwater Pollution Prevention 4-23 <br />