TECHNICAL

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Installation:

Installation should be in accordance with ASTM D 6462, Standard Practice for Silt Fence Installation, or local council specifications. The sediment can be contained and channelled into lined holding ponds. Install using a silt fence trenching machine, if available.

The marker lines are 150 mm from the edge and are designed as guides for proper burial depth during trenching process. In absence of the proper machinery several other methods are used, as follows.

Method 1: This procedure is primarily based upon Auckland Regional Council Sediment Control Guidelines (TP90): A trench is constructed, to a width of 100 mm x 200 mm depth, minimum. Proper installation requires the Silt Fence be anchored in the trench preferably with the fabric covering the bottom of the trench. Backfill using earth moving equipment.

Stakes should be either tantalised timber of 50 mm square or steel waratahs of 1.5 m length. Drive the stakes into the ground to a minimum depth of 400 mm, or 600 mm on a slope of 3:1 or greater. Spacing of stakes or waratahs is at a minimum distance of 2 m apart. Always install the silt fence with the stakes behind the flow.

Support fence is recommended to be installed along the entire length along the upslope side of the fence from the top to the bottom of the silt fence. A support wire (2.5 mm galvanised) is attached along the top of the fence.

Method 2: A faster (less effective) method is to drive the stakes into the ground and fasten the silt fence with the guideline at ground level allowing a 200 mm flap which is covered with earth.

As this method may not totally prevent sediment flow under the fence it may not be allowed under the District Plan, therefore check for compliance.