Laserfiche WebLink
Design and Installation Specifications <br />. Use in combination with other construction stormwater BMPs. <br />. Maximum slope steepness (perpendicular to the silt fence line) 1 H :1 V. <br />. Maximum sheet or overland flow path length to the silt fence of 100 feet. <br />. Do not allow flows greater than 0.5 cfs. <br />Use geotextile fabric that meets the following standards. All geotextile properties listed below <br />are minimum average roll values (i.e., the test result for any sampled roll in a lot shall meet or <br />exceed the values shown in Table II-3.11: Geotextile Fabric Standards for Silt Fence): <br />Table II-3.11: Geotextile Fabric Standards for Silt Fence <br />Geotextile Property <br />Minimum Average Roll Value <br />0.60 mm maximum for slit film woven (#30 sieve). <br />Polymeric Mesh AOS <br />0.30 mm maximum for all other geotextile types (#50 sieve). <br />(ASTM D4751) <br />0.15 mm minimum for all fabric types (#100 sieve). <br />Water Permittivity <br />0.02 sec-1 minimum <br />(ASTM D4491) <br />Grab Tensile Strength <br />180 lbs. Minimum for extra strength fabric. <br />(ASTM D4632) <br />100 Ibs minimum for standard strength fabric. <br />Grab Tensile Strength <br />30% maximum <br />(ASTM D4632) <br />Ultraviolet Resistance <br />70% minimum <br />(ASTM D4355) <br />. Support standard strength geotextiles with wire mesh, chicken wire, 2-inch x 2-inch wire, <br />safety fence, orjute mesh to increase the strength of the geotextile. Silt fence materials are <br />available that have synthetic mesh backing attached. <br />Silt fence material shall contain ultraviolet ray inhibitors and stabilizers to provide a minimum <br />of six months of expected usable construction life at a temperature range of 0°F to 120°F. <br />One -hundred percent biodegradable silt fence is available that is strong, long lasting, and can <br />be left in place after the project is completed, if permitted by the local jurisdiction. <br />Refer to Figure 11-3.22: Silt Fence for standard silt fence details. Include the following Stand- <br />ard Notes for silt fence on construction plans and specifications: <br />1. The Contractor shall install and maintain temporary silt fences at the locations shown in <br />the Plans. <br />2. Construct silt fences in areas of clearing, grading, or drainage prior to starting those <br />activities. <br />2019 Stormwater Management Manual for Western Washington <br />Volume 11 - Chapter 3 - Page 372 <br />