Changes

==Underdrains for exfiltrating practices==

==Underdrains for exfiltrating practices==

The pipe within the drain should be elevated from the base to promote infiltration of the water stored beneath. The depth of this [[Bioretention: Internal_water_storage| internal water storage reservoir]] should be sized according to the desired [[drainage time]] and the infiltration rate of the native soils below. An alternative design configuration permits the head of water to be stored by using an upturned outflow pipe.  

The pipe within the drain should be elevated from the base to promote infiltration of the water stored beneath. The depth of this [[Bioretention: Internal_water_storage| internal water storage reservoir]] should be sized according to the desired [[drainage time]] and the [[design infiltration rate]] of the native soils below. An alternative design configuration permits the head of water to be stored by using an upturned outflow pipe.  

*At least one pair of vertical cleanout pipes/wells should be included in the design, for inspection and periodic flushing of accumulated sediment. As most hydro-jetting apparatus used for this has some trouble accommodating narrow 90 deg bends, it is important that both ends of a perforated pipe be connected with a pair of 45 deg elbows/Y connectors instead.  

*At least one pair of vertical cleanout pipes/wells should be included in the design, for inspection and periodic flushing of accumulated sediment. As most hydro-jetting apparatus used for this has some trouble accommodating narrow 90 deg bends, it is important that both ends of a perforated pipe be connected with a pair of 45 deg elbows/Y connectors instead.  

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