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→Time for drainage of surface ponded water
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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<sub>p</sub>}{K<sub>f</sub>}</math>
+<math>t=\frac{dp}{Kf}</math>
−Where d<sub>p</sub>' is the mean or effective surface ponding depth.
+Where
+d<sub>p</sub>' is the mean or effective surface ponding depth.
+K<sub>f</sub> is the minimum saturated hydraulic conductivity of the filter media or planting soil.
==Drainage time to empty facility==
==Drainage time to empty facility==