Article 16
Sec 20.16.012
Silt Fence

A. A Silt Fence as required herein shall consist of furnishing, installing, maintaining, and removing a geotextile barrier-fence designed to remove suspended particles from water passing through the fence.

This Silt Fence may be either a wire-supported geotextile silt fence or a self-supporting geotextile silt fence.

B. Fibers used in the manufacture of geotextiles shall consist of longchain synthetic polymers, composed of at least eighty-five percent (85%) by weight polyolefins, polyesters, or polyamides. They shall be formed into a network such that the filaments or yarns retain dimensional stability relative to each other, including salvages. The geotextile shall be free of any treatment or coating which might adversely alter its physical properties after installation. Unless otherwise specified, geotextile shall be furnished in thirty-six inch (36") width rolls.

C. Geotextile rolls shall be furnished with suitable wrapping for protection against moisture and extended ultraviolet exposure prior to placement. Each roll shall be labeled or tagged to provide product identification sufficient for inventory and quality control purposes. Rolls shall be stored in a manner which protects them from the elements.

D. The Silt Fence shall be supported by either wood, steel, or synthetic posts. Posts shall have a minimum length of thirty-six inches (36") plus embedment depth and be of sufficient strength to resist damage during installation and to support applied loads.

E. Support Fence, as required herein, shall be at least twenty-four inches (24") high and strong enough to support applied loads.

F. Prefabricated fence systems may be used, provided they meet all of the above material requirements.

G. A temporary silt fence shall be installed as shown on the plans, and at other locations as directed by the Engineer. Fence construction shall be adequate to handle the stress from hydraulic and sediment loading. Geotextile at the bottom of the fence shall be buried as indicated on the standard drawings shown in Article 4. The trench shall be backfilled and the soil compacted over the geotextile. The geotextile shall be spliced together as indicated on the standard drawings.

H. Post spacing shall not exceed eight feet (8') for wire support fence installations or five feet (5') for self-supported installations. Posts shall be driven a minimum of twenty-four inches (24") into the ground. Where rock is encountered posts shall be installed in a manner approved by the Engineer. Closer spacing, greater embedment depth and/or wider posts shall be used as necessary in low areas and soft or swampy ground to ensure adequate resistance to applied loads.

I. When support fence is used, the mesh shall be fastened securely to the up-slope side of the post. The mesh shall extend into the trench a minimum of two inches (2") and extend a maximum of thirty-six inches (36") above the original ground surface.

When self-supported fence is used, the geotextile shall be securely fastened to fence posts.

J. The integrity of silt fences shall be maintained to contain sediment runoff. Any deficiencies shall be immediately corrected.

K. Sediment deposits shall be removed when the deposit approaches one-half the height of the fence or as directed by the engineer.

L. The silt fence shall remain in place until the Engineer directs that it be removed. Upon removal, silt shall be removed and disposed of and the area finished to the satisfaction of the Engineer.

Sec 20.16.013
Physical Requirements For Temporary Silt Fence Geotextiles

Property	Test Method	Wire Fence Supported Requirements	Self Supported Requirements
Tensile Minimum2  Strength, Lbs.	ASTM D46 32	90 Minimum2	90
Elongation at 50% Minimum tensile strength. (45 Lbs.)	ASTM D46 32	N/A	50 Maximum
Filtering Efficiency, %	VTM-513	75	75
Flow Rate, gal/ft2/min	VTM-513	0.3	0.3
Ultraviolet Degradation at 500 hrs.	ASTM D43 55	Minimum 70% Strength Retained	Minimum 70% Strength Retained

1. All numerical values represent minimum average roll value.

2. When tested in any principal direction.

3. Virginia DOT test method.

Sec 20.16.014
Permits Required

An erosion control permit is required for all clearing, grubbing, grading and building construction projects, except where land disruption is 1,000 square feet or less. An application for an erosion control permit shall be made to the Public Works Director on forms furnished. The application must be accompanied by an erosion control plan prepared in accordance with applicable provisions contained herein.

Sec 20.16.015
Financial Surety

A performance and maintenance bond, letter of credit, or other financial surety shall be provided by the owner in the amount of $1,000 per acre or fraction thereof, with a maximum not to exceed $10,000, and shall be provided prior to issuance of permit or beginning of any work. Release of the surety shall be two years from installation of Erosion Control measure.

Sec 20.16.016
Permit Fee

No person shall perform any clearing, grubbing, grading, or building construction without first obtaining an erosion control permit and paying the permit fee of $100 per acre or fraction thereof.

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