819 N BROADWAY WASHINGTON STATE UNIVERSITY 2018-05-11

Table 4.10 Geotextile Standards Polymeric Mesh AOS 0.60 mm maximum for slit film wovens(#30 sieve). 0.30 (ASTM D4751) mm maximum for all other geotextile types(#50 sieve). 0.15 mm minimum for all fabric types(#100 sieve). Water Permittivity 0.02 sec1 minimum (ASTM D4491) Grab Tensile Strength 180 lbs.Minimum for extra strength fabric. (ASTM D4632) 100 lbs minimum for standard strength fabric. Grab Tensile Strength 30%maximum (ASTM D4632) Ultraviolet Resistance 70%minimum (ASTM D4355) • Standard strength fabrics shall be supported with wire mesh, chicken wire, 2-inch x 2-inch wire, safety fence, or jute mesh to increase the strength of the fabric. Silt fence materials are available that have synthetic mesh backing attached. • Filter fabric material shall contain ultraviolet ray inhibitors and stabilizers to provide a minimum of six months of expected usable construction life at a temperature range of 0°F. to 120°F. • 100 percent biodegradable silt fence is available that is strong, long lasting, and can be left in place after the project is completed, if permitted by local regulations. • Standard Notes for construction plans and specifications follow. Refer to Figure 4.19 for standard silt fence details. The contractor shall install and maintain temporary silt fences at the locations shown in the Plans. The silt fences shall be constructed in the areas of clearing, grading, or drainage prior to starting those activities. A silt fence shall not be considered temporary if the silt fence must function beyond the life of the contract. The silt fence shall prevent soil carried by runoff water from going beneath, through, or over the top of the silt fence, but shall allow the water to pass through the fence. The minimum height of the top of silt fence shall be 2 feet and the maximum height shall be 2'/2 feet above the original ground surface. The geotextile shall be sewn together at the point of manufacture, or at an approved location as determined by the Engineer, to form geotextile lengths as required. All sewn seams shall be located at a support post. Alternatively,two sections of silt fence can be overlapped,provided the Contractor can demonstrate, to the satisfaction of the Engineer, that the overlap is long enough and that the adjacent fence sections are close enough together to prevent silt laden water from escaping through the fence at the overlap. February 2005 Volume ll— Construction Stormwater Pollution Prevention 4-95