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→Time for infiltration of surface ponded water
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<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==