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→Decide if an underdrain will be included
==Decide if an underdrain will be included==
==Decide if an underdrain will be included==
* Step 1: Based on the median infiltration rate of the native soil at 1.5 to 3 metres depth below the practice location, or interpolation from the median grain-size distribution results, decide if an underdrain will be included in the design.<br>
* Step 1: Based on the median measured infiltration rate of the native soil at the estimated location and bottom elevation of the practice, or estimated from the median grain-size distribution results, decide if an underdrain will be included in the design.<br>
If the field estimated infiltration rate of the underlying native soil (f<sub>f</sub>) is less than 15 mm/h, include an underdrain.
If the field estimated infiltration rate of the underlying native soil (f<sub>f</sub>) is less than 15 mm/h, include an underdrain.