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→Spacing drainage pipes
''K<sub>media</sub> is expressed in m/day
''K<sub>media</sub> is expressed in m/day
''D<sub>d</sub>'' is the depth to the drain pipe (m)
''D<sub>d</sub>'' is the depth to the drain pipe (m)
''D<sub>w</sub>'' is the minimum acceptable depth to the water table during infiltration
''D<sub>w</sub>'' is the minimum acceptable depth to the water table during infiltration event
''q'' is the inflow volume expressed as a depth over the entire surface (m)
''q'' is the inflow volume expressed as a depth over the entire surface (m)
===Example===
===Example===
During a 25 mm storm event, a bioretention cell receives concentrated flow from a catchment 20 times larger than its own footprint (25 x 20 = 500 mm = 0.5 m).
During a 25 mm storm event, a bioretention cell receives concentrated flow from a catchment 20 times larger than its own footprint (25 x 20 = 500 mm = 0.5 m).
The bioretention cell comprises 0.6 m filter media laid over 0.6 m clear, coarse reservoir gravel. The pipes are laid within the reservoir, 0.9 m below the surface:
The bioretention cell comprises 0.6 m filter media laid over 0.6 m clear, coarse reservoir gravel. The pipes are laid within the reservoir, 0.9 m below the surface.
<math>Drain\ spacing=\sqrt{\frac{4\times 2.4m\left(0.9m-0.6m\right)^{2}}{0.5}}=3.4 m</math>
The system is designed to fill entirely during the rainstorm event. i.e. Depth to water table = 0 m.
<math>Drain\ spacing=\sqrt{\frac{4\times 2.4m\left(0.9m-0m\right)^{2}}{0.5}}=6 m</math>
==Recommendations for material specifications==
==Recommendations for material specifications==