Changes

If the median field infiltration rate of the underlying native soil is less than 15 mm/h, include an underdrain.

If the median field infiltration rate of the underlying native soil is less than 15 mm/h, include an underdrain.

==Select a surface ponding depth to begin sizing with==

==Select a surface ponding depth to begin sizing with:==

* Step 2: Determine a maximum surface ponding depth (''d_{p, max}'')

* Step 2: Determine a maximum surface ponding depth (''d_{p, max}'')

For practices without underdrains:<br>

For practices without underdrains:<br>

*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 off the bottom of the storage reservoir profile:

 

d_{p, max}= depth of storage reservoir below invert of the underdrain perforated pipe.<br>

For practices with underdrain perforated pipe elevated off the bottom of the storage reservoir:

d_{p, max}= depth of storage reservoir below the 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_{p, max}= Difference between elevation of reservoir bottom and invert of the riser (i.e 90 degree coupling).<br>  

d_{p, max}= Difference between elevation of reservoir bottom and invert of the riser (i.e 90 degree coupling).<br>