171.1 General Description
This work includes furnishing, installing, and removing a water permeable filter fabric fence to remove suspended particles from drainage water.
171.1.01 Definitions
General Provisions 101 through 150.
171.1.02 Related References
A. Standard Specifications Section 163—Miscellaneous Erosion Control Items S ection 700—Grassing S ection 862—Wood Posts and Bracing S ection 881—Fabrics S ection 894—Fencing B. Referenced Documents ASTM D 3786 ASTM D 4355 ASTM D 4632 ASTM D 4751 GDT 87 QPL 36
171.1.03 Submittals
General Provisions 101 through 150.
171.2 Materials
Materials shall meet the requirements of the following Specifications: Material Section Fabrics 881 Fencing 894 Wood Posts and Bracing 862 C onditions during Project construction will affect the quantity of the silt fence to be installed. The Engineer may increase, decrease, or eliminate the quantity at his or her direction. Variations in quantity are not changes in details of construction or in the character of the work. For Type A, B, and C fences, use fabric as specified in Subsection 881.2.07, Silt Fence Filter Fabric.
171.2.01 Delivery, Storage, and Handling
During shipment and storage, wrap the fabric in a heavy-duty covering protecting the cloth from sunlight, mud, dust, dirt, and debris. Do not expose the fabric to temperatures greater than 140 °F (60 °C). When installed, the Engineer will reject the fabric if it has defects, rips, holes, flaws, deterioration, or damage incurred during manufacture, transportation, or storage.
171.3 Construction Requirements
171.3.01 Personnel
General Provisions 101 through 150.
171.3.02 Equipment
General Provisions 101 through 150.
171.3.03 Preparation
General Provisions 101 through 150.
171.3.04 Fabrication
General Provisions 101 through 150.
171.3.05 Construction
Install the silt fence according to this Specification, as shown on the plans, or as directed by the Engineer A. Install Silt Fence 1. I nstall silt fence by either of the following methods: a. Excavated Trench Method Excavate a trench 4 to 6 in. (100 to 150 mm) deep using equipment such as a trenching machine or motor grader. If equipment cannot be operated on the site, excavate the trench by hand. b. Soil Slicing Method Create a mechanical slice in the soil 8 to 12 in. (200 to 300 mm) deep to receive the silt fence. Ensure the wi dth of the slice is not more than 3 in. (75 mm). Mechanically insert the silt fence fabric into the slice in a s imultaneous operation with the slicing ensuring consistent depth and placement. 2. I nstall the first post at the center of the low point (if applicable). Space the remaining posts a maximum of 6 ft. ( 1.8 m) apart for Types A and B fence and 4 ft. (1.2 m) apart for Type C fence. 3. B ury the posts at least 18 in. (450 mm) into the ground. If this depth cannot be attained, secure the posts enough to prevent the fence from overturning from sediment loading. 4. Attach the filter fabric to the post using wire, cord, staples, nails, pockets, or other acceptable means. a. Staples and Nails (Wood Posts): Evenly space staples or nails with at least five per post for Type A fence a nd four per post for Type B fence. b. Pockets: If using pockets and they are not closed at the top, attach the fabric to a wood post using at least one additional staple or nail, or to a steel post using wire. Ensure the additional attachment is within t he top 6 in. (150 mm) of the fabric. c . Install the filter fabric so 6 to 8 in. (150 to 200 mm) of fabric is left at the bottom to be buried. Provide a minimum overlap of 18 in. (450 mm) at all splice joints. d. For Type C fence: 1) Woven Wire Supported • S teel Post: Use wire to attach the fabric to the top of the woven wire support fence at the midpoint between posts. Also, use wire to attach the fabric to the post. 2) Polypropylene Mesh Supported • Wood Post: Use at least six staples per post. Use two staples in a crisscross or parallel pattern to secure the top portion of the fence. Evenly space the remaining staples down the post. • Steel Post: Use wire to attach the fabric and polypropylene mesh to the post. 5. I nstall the fabric in the trench so 4 to 6 in. (100 to 150 mm) of fabric is against the side of the trench with to 4 in. (50 to 100 mm) of fabric across the bottom in the upstream direction. 6. Backfill and compact the trench to ensure flow cannot pass under the barrier. When the slice method is used, compact the soil disturbed by the slice on the upstream side of the silt fence first, and then compact the d ownstream side. 7. When installing a silt fence across a waterway producing significant runoff, place a settling basin in front of the fence to handle the sediment load, if required. Construct a suitable sump hole or storage area according to Section 163. B. Remove the Silt Fence 1. Keep all silt fence in place unless or until the Engineer directs it to be removed. A removed silt fence may be us ed at other locations if the Engineer approves of its condition. 2. After removing the silt fence, dress the area to natural ground, grass and mulch the area according to Section 700. 3. The silt fence shall remain until the Project is accepted or until the fence is removed. Also, remove and dispose of the silt accumulations at the silt fence. 4. Remove and replace any deteriorated filter fabric reducing the effectiveness of the silt fence.
171.3.06 Quality Acceptance
Approved silt fence is listed in QPL 36. Approved fabrics must consistently exceed the minimum requirements of this Specification as verified by the Office of Materials and Research. The Office of Materials and Research will remove fabric failing to meet the minimum requirements of this specification from the QPL until the products’ acceptability has been reestablished to the Department’s satisfaction. At the time of installation, the Engineer will reject the fabric if it has defects, rips, holes, flaws, deterioration, or damage incurred during manufacture, transportation, or storage.
171.4 Measurement
The quantity of silt fence to be paid for is the actual number of linear feet (meters) of silt fence, measured in place from end post to end post of each separate installation. The silt fence must be complete and accepted.
171.4.01 Limits
General Provisions 101 through 150.
171.5 Payment
Silt fence Type A, B, or C measured as defined in Subsection 171.4, Measurement, is paid for at the Contract Unit Price bid per linear foot (meter). Payment is full compensation for the following: • Furnishing materials • Erecting the fence • Dressing and grassing, when required • Removing the fence, when required Payment for this Item is made as follows: • Seventy-five percent of the Contract Price bid per linear foot (meter) is paid when each fence is • complete in place. • Twenty-five percent is paid at removal or acceptance. If the silt fence must be repaired or removed, as the result of neglect or damage, perform the work at no additional cost to the Department. Payment will be made under: Item No. 171 Silt fence, type__ Per linear foot (meter)
171.5.01 Adjustments
General Provisions 101 through 150.
Silt Fence in other states
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