SE 1 Silt Fence Rev0 Stanislaus County California

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Silt Fence SE 1,Limitations, Do not use in streams channels drain inlets or anywhere flow is concentrated. Do not use in locations where ponded water may cause a flooding hazard Runoff typically. ponds temporarily on the upstream side of silt fence. Do not use silt fence to divert water flows or place across any contour line Fences not. constructed on a level contour or fences used to divert flow will concentrate flows resulting. in additional erosion and possibly overtopping or failure of the silt fence. Improperly installed fences are subject to failure from undercutting overtopping or. collapsing,Not effective unless trenched and keyed in. Not intended for use as mid slope protection on slopes greater than 4 1 H V. Do not use on slopes subject to creeping slumping or landslides. Implementation, A silt fence is a temporary sediment barrier consisting of woven geotextile stretched across and. attached to supporting posts trenched in and depending upon the strength of fabric used. supported with plastic or wire mesh fence Silt fences trap sediment by intercepting and. detaining small amounts of sediment laden runoff from disturbed areas in order to promote. sedimentation behind the fence, The following layout and installation guidance can improve performance and should be. Use principally in areas where sheet flow occurs, Install along a level contour so water does not pond more than 1 5 ft at any point along the.
silt fence, The maximum length of slope draining to any point along the silt fence should be 200 ft or. The maximum slope perpendicular to the fence line should be 1 1. Provide sufficient room for runoff to pond behind the fence and to allow sediment removal. equipment to pass between the silt fence and toes of slopes or other obstructions About. 1200 ft2 of ponding area should be provided for every acre draining to the fence. Turn the ends of the filter fence uphill to prevent stormwater from flowing around the fence. Leave an undisturbed or stabilized area immediately down slope from the fence where. November 2009 California Stormwater BMP Handbook 2 of 8. Construction,www casqa org,Silt Fence SE 1, Silt fences should remain in place until the disturbed area is permanently stabilized after. which the silt fence should be removed and properly disposed. Silt fence should be used in combination with erosion source controls up slope in order to. provide the most effective sediment control, Be aware of local regulations regarding the type and installation requirements of silt fence. which may differ from those presented in this fact sheet. Design and Layout, The fence should be supported by a plastic or wire mesh if the fabric selected does not have. sufficient strength and bursting strength characteristics for the planned application as. recommended by the fabric manufacturer Woven geotextile material should contain ultraviolet. 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,Layout in accordance with attached figures.
For slopes steeper than 2 1 H V and that contain a high number of rocks or large dirt clods. that tend to dislodge it may be necessary to install additional protection immediately. adjacent to the bottom of the slope prior to installing silt fence Additional protection may. be a chain link fence or a cable fence, For slopes adjacent to sensitive receiving waters or Environmentally Sensitive Areas ESAs. silt fence should be used in conjunction with erosion control BMPs. Standard vs Heavy Duty Silt Fence,Standard Silt Fence. Generally applicable in cases where the slope of area draining to the silt fence is 4 1. H V or less, Used for shorter durations typically 5 months or less. Area draining to fence produces moderate sediment loads. Heavy Duty Silt Fence,Use is generally limited to 8 months or less. Area draining to fence produces moderate sediment loads. Heavy duty silt fence usually has 1 or more of the following characteristics not. possessed by standard silt fence,o Fence fabric has higher tensile strength.
o Fabric is reinforced with wire backing or additional support. o Posts are spaced closer than pre manufactured standard silt fence products. o Posts are metal steel or aluminum,Standard Silt Fence. Silt fence material should be woven geotextile with a minimum width of 36 in and a. minimum tensile strength of 100 lb force The fabric should conform to the requirements in. ASTM designation D4632 and should have an integral reinforcement layer The. November 2009 California Stormwater BMP Handbook 3 of 8. Construction,www casqa org,Silt Fence SE 1, reinforcement layer should be a polypropylene or equivalent net provided by the. manufacturer The permittivity of the fabric should be between 0 1 sec 1 and 0 15 sec 1 in. conformance with the requirements in ASTM designation D4491. Wood stakes should be commercial quality lumber of the size and shape shown on the plans. Each stake should be free from decay splits or cracks longer than the thickness of the stake. or other defects that would weaken the stakes and cause the stakes to be structurally. unsuitable, Staples used to fasten the fence fabric to the stakes should be not less than 1 75 in long and. should be fabricated from 15 gauge or heavier wire The wire used to fasten the tops of the. stakes together when joining two sections of fence should be 9 gauge or heavier wire. Galvanizing of the fastening wire will not be required. Heavy Duty Silt Fence, Some silt fence has a wire backing to provide additional support and there are products that. may use prefabricated plastic holders for the silt fence and use metal posts or bar. reinforcement instead of wood stakes If bar reinforcement is used in lieu of wood stakes. use number four or greater bar Provide end protection for any exposed bar reinforcement. for health and safety purposes,Installation Guidelines Traditional Method.
Silt fences are to be constructed on a level contour Sufficient area should exist behind the fence. for ponding to occur without flooding or overtopping the fence. A trench should be excavated approximately 6 in wide and 6 in deep along the line of the. proposed silt fence trenches should not be excavated wider or deeper than necessary for. proper silt fence installation, Bottom of the silt fence should be keyed in a minimum of 12 in. Posts should be spaced a maximum of 6 ft apart and driven securely into the ground a. minimum of 18 in or 12 in below the bottom of the trench. When standard strength geotextile is used a plastic or wire mesh support fence should be. fastened securely to the upslope side of posts using heavy duty wire staples at least 1 in. long The mesh should extend into the trench, When extra strength geotextile and closer post spacing are used the mesh support fence. may be eliminated, Woven geotextile should be purchased in a long roll then cut to the length of the barrier. When joints are necessary geotextile should be spliced together only at a support post with. a minimum 6 in overlap and both ends securely fastened to the post. The trench should be backfilled with native material and compacted. Construct silt fences with a setback of at least 3 ft from the toe of a slope Where due to. specific site conditions a 3 ft setback is not available the silt fence may be constructed at the. November 2009 California Stormwater BMP Handbook 4 of 8. Construction,www casqa org,Silt Fence SE 1, toe of the slope but should be constructed as far from the toe of the slope as practicable Silt. fences close to the toe of the slope will be less effective and more difficult to maintain. Construct the length of each reach so that the change in base elevation along the reach does. not exceed 1 3 the height of the barrier in no case should the reach exceed 500 ft. Cross barriers should be a minimum of 1 3 and a maximum of the height of the linear. See typical installation details at the end of this fact sheet. Installation Guidelines Static Slicing Method, Static Slicing is defined as insertion of a narrow blade pulled behind a tractor similar to a.
plow blade at least 10 inches into the soil while at the same time pulling silt geotextile fabric. into the ground through the opening created by the blade to the depth of the blade Once the. gerotextile is installed the soil is compacted using tractor tires. This method will not work with pre fabricated wire backed silt fence. o Ease of installation most often done with a 2 person crew In addition. installation using static slicing has been found to be more efficient on slopes in. rocky soils and in saturated soils,o Minimal soil disturbance. o Greater level of compaction along fence leading to higher performance i e. greater sediment retention,o Uniform installation,o Less susceptible to undercutting undermining. It should be noted that costs vary greatly across regions due to available supplies and labor. Average annual cost for installation using the traditional silt fence installation method. assumes 6 month useful life is 7 per linear foot based on vendor research Range of cost. is 3 50 9 10 per linear foot, In tests the slicing method required 0 33 man hours per 100 linear feet while the trenched. based systems required as much as 1 01 man hours per linear foot. Inspection and Maintenance, BMPs must be inspected in accordance with General Permit requirements for the associated. project type and risk level It is recommended that at a minimum BMPs be inspected. weekly prior to forecasted rain events daily during extended rain events and after the. conclusion of rain events,Repair undercut silt fences.
November 2009 California Stormwater BMP Handbook 5 of 8. Construction,www casqa org,Silt Fence SE 1, Repair or replace split torn slumping or weathered fabric The lifespan of silt fence fabric. is generally 5 to 8 months, Silt fences that are damaged and become unsuitable for the intended purpose should be. removed from the site of work disposed and replaced with new silt fence barriers. Sediment that accumulates in the BMP should be periodically removed in order to maintain. BMP effectiveness Sediment should be removed when the sediment accumulation reaches. one third of the barrier height, Silt fences should be left in place until the upstream area is permanently stabilized Until. then the silt fence should be inspected and maintained regularly. Remove silt fence when upgradient areas are stabilized Fill and compact post holes and. anchor trench remove sediment accumulation grade fence alignment to blend with adjacent. ground and stabilize disturbed area,References, Manual of Standards of Erosion and Sediment Control Measures Association of Bay Area. Governments May 1995, National Management Measures to Control Nonpoint Source Pollution from Urban Areas.
United States Environmental Protection Agency 2002. Proposed Guidance Specifying Management Measures for Sources of Nonpoint Pollution in. Coastal Waters Work Group Working Paper USEPA April 1992. Sedimentation and Erosion Control Practices and Inventory of Current Practices Draft. UESPA 1990, Southeastern Wisconsin Regional Planning Commission SWRPC Costs of Urban Nonpoint. Source Water Pollution Control Measures Technical Report No 31 Southeastern Wisconsin. Regional Planning Commission Waukesha WI 1991, Stormwater Quality Handbooks Construction Site Best Management Practices BMPs Manual. State of California Department of Transportation Caltrans March 2003. Stormwater Management Manual for The Puget Sound Basin Washington State Department of. Ecology Public Review Draft 1991, U S Environmental Protection Agency USEPA Stormwater Management for Industrial. Activities Developing Pollution Prevention Plans and Best Management Practices U S. Environmental Protection Agency Office of Water Washington DC 1992. Water Quality Management Plan for the Lake Tahoe Region Volume II Handbook of. Management Practices Tahoe Regional Planning Agency November 1988 Soil Stabilization. BMP Research for Erosion and Sediment Controls Cost Survey Technical Memorandum State. of California Department of Transportation Caltrans July 2007. Erosion and Sediment Control Manual Oregon Department of Environmental Quality February. November 2009 California Stormwater BMP Handbook 6 of 8. Construction,www casqa org,Silt Fence SE 1, November 2009 California Stormwater BMP Handbook 7 of 8. Construction,www casqa org,Silt Fence SE 1, November 2009 California Stormwater BMP Handbook 8 of 8.
Silt Fence SE 1 November 2009 California Stormwater BMP Handbook 2 of 8 Construction www casqa org Limitations Do not use in streams channels drain inlets or anywhere flow is concentrated Do not use in locations where ponded water may cause a flooding hazard Runoff typically ponds temporarily on the upstream side of silt fence

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