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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 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. See [[Design infiltration rate]] for guidance on field instruments, methods and number of measurements to be collected.<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. See [[Design infiltration rate]] for guidance on field tests, methods and number of test locations and tests (i.e. measurements) to be performed.<br>
If the median measured or field estimated infiltration rate of the underlying native soil (f<sub>f</sub>) is less than 15 mm/h, include an underdrain.
If the median measured or field estimated infiltration rate of the underlying native soil (f<sub>f</sub>) is less than 15 mm/h, include an underdrain.