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→Time required to drain surface ponded water (1D drainage)
K<sub>f</sub> is the minimum acceptable saturated hydraulic conductivity of the filter media and growing medium when compacted to 85% maximum dry density (mm/h); minimum of 25 mm/hr is recommended for bioretention filter media; minimum of 15 mm/hr is recommended for enhanced grass swale and stormwater tree trench growing medium.<br>
K<sub>f</sub> is the minimum acceptable saturated hydraulic conductivity of the filter media and growing medium when compacted to 85% maximum dry density (mm/h); minimum of 25 mm/hr is recommended for bioretention filter media; minimum of 15 mm/hr is recommended for enhanced grass swale and stormwater tree trench growing medium.<br>
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For full infiltration design practices that do not feature an underdrain, once the internal water storage capacity has been filled, the length of time required to fully drain surface ponded water is limited by the saturated hydraulic conductivity of the underlying in-situ (native) subsoil.<br>
For full infiltration design practices that do not feature an underdrain, once the internal water storage capacity has been filled, the length of time required to fully drain surface ponded water is limited by the saturated hydraulic conductivity of the underlying in-situ (native) subsoil. To calculate the time (''t'') to fully drain surface ponded water once filled to capacity:
To calculate the time (''t'') to fully drain surface ponded water once filled to capacity:
<math>t=\frac{d_{p}'}{f'}</math> <br>
<math>t=\frac{d_{p}'}{f'}</math> <br>
Where <br>
Where <br>