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→Time for infiltration of surface ponded water
<math>Ap=\frac{iDAi}{nd+f'D}</math>
<math>Ap=\frac{iDAi}{nd+f'D}</math>
==Time for infiltration of surface ponded water==
==Time for drainage of surface ponded water==
The following equation assumes that infiltration occurs primarily through the footprint of the facility.
The following equation assumes one dimensional drainage over the surface ponding area.
It is best applied to calculate the maximum duration of ponding on the surface of [[bioretention cells]], and upstream of check dams of [[bioswales]] and [[enhanced grass swales]] to ensure all surface ponding drains within 48 hours.
It is best applied to calculate the maximum duration of ponding on the surface of [[bioretention cells]], and upstream of check dams of [[bioswales]] and [[enhanced grass swales]] to ensure all surface ponding drains within 48 hours.
To calculate the time (''t'') to fully drain surface ponded water through the filter media or planting soil:
To calculate the time (''t'') to fully drain surface ponded water through the filter media or planting soil:
<math>t=\frac{d}{K}</math>
<math>t=\frac{d<sub>p</sub>}{K<sub>f</sub>}</math>
Where d is the mean ponding depth
Where d<sub>p</sub>' is the mean or effective surface ponding depth.
==Drainage time to empty facility==
==Drainage time to empty facility==