Changes

*Where flow comes off an impervious surface, a drop of 75 mm or more to the surface level of the diaphragm is recommended,

*Where flow comes off an impervious surface, a drop of 75 mm or more to the surface level of the diaphragm is recommended,

*Typical dimensions for the trench excavation are 300 mm deep and 600 mm wide. The trench may be any length,  

*Typical dimensions for the trench excavation are 300 mm deep and 600 mm wide. The trench may be any length,  

*The trench should be lined with before filling with gravel,   

*The trench should be lined with geotextile before filling with gravel,   

*River rock or decorative aggregate may be included in a layer at the top of the gravel fill, for aesthetic value.  

*River rock or decorative aggregate may be included in a layer at the top of the gravel fill, for aesthetic value.  

===Materials===

===Materials===

<h4>Geotextile</h4>

<h4>Geotextile</h4>

{{:geotextiles}}

{{:geotextiles}}