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===Design===

====Design====

<p>An underdrain comprises a length of perforated pipe embedded into a reservoir gravel layer.  A pair of small wells are recommended to inspect and periodically flush accumulated sediment from the underdrain pipe.</p>

<p>An underdrain comprises a length of perforated pipe embedded into a reservoir gravel layer.  A pair of small wells are recommended to inspect and periodically flush accumulated sediment from the underdrain pipe.</p>

*To promote infiltration the base of the gravel reservoir and the underdrain pipe should be horizontal to optimize distribution of the water within.  

*To promote infiltration the base of the gravel reservoir and the underdrain pipe should be horizontal to optimize distribution of the water within.  

*A layer of geotextile is usually then used to prevent migration of fines into the underdrain/reservoir space.

*A layer of geotextile is usually then used to prevent migration of fines into the underdrain/reservoir space.

===Materials===

====Materials====

<h4>Geotextile</h4>

<h5>Geotextile</h5>

{{:Geotextiles}}

{{:Geotextiles}}

<h4>Pipes</h4>

<h5>Pipes</h5>

{{:Pipes}}

{{:Pipes}}

<h4>Reservoir gravel</h4>

<h5>Reservoir gravel</h5>

{{:Reservoir gravel}}

{{:Reservoir gravel}}

<h4>Pea gravel</h4>

<h5>Pea gravel</h5>

{{:Pea gravel}}

{{:Pea gravel}}