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→Select a surface ponding depth to begin sizing with
*48 = Maximum permissible drainage time for ponded water (h)
*48 = Maximum permissible drainage time for ponded water (h)
*Note that in designs without underdrains, conceptually the drainage of ponded water is limited by infiltration through the base of the practice.}}<br>
*Note that in designs without underdrains, conceptually the drainage of ponded water is limited by infiltration through the base of the practice.}}<br>
For practices with underdrains elevated in the storage reservoir profile:
For practices with underdrains elevated off the bottom of the storage reservoir profile:
<math>d_{p, max}= depth of storage reservoir below invert of the underdrain perforated pipe.<br>
d<sub>p, max</sub>= depth of storage reservoir below invert of the underdrain perforated pipe.<br>
For practices with underdrain on base of the storage reservoir and connected to a riser (e.g., standpipe and 90 degree coupling):
For practices with underdrain on base of the storage reservoir and connected to a riser (e.g., standpipe and 90 degree coupling):
d<sub>p, max</sub>= Difference between elevation of reservoir bottom and invert of the riser (i.e 90 degree coupling).<br>
d<sub>p, max</sub>= Difference between elevation of reservoir bottom and invert of the riser (i.e 90 degree coupling).<br>
For practices with soft (i.e. landscaped) edges and bowl-shaped ponding areas calculate the mean ponding depth:
For practices with soft (i.e. landscaped) edges and bowl-shaped ponding areas calculate the mean ponding depth:
<math>d_{p}'=d_{p, max}\divide 2
<math>d_{p}'=d_{p, max}\divide 2
==Calculate the total depth of the practice, d<sub>T</sub>==
==Calculate the total depth of the practice, d<sub>T</sub>==