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Line 33: ==Step 1 alternative==The whole bioretention is a box of rocks. To calculate the required practice area (''A<sub>p</sub>'') or footprint where the depth is constrained:<math>A_{p}=\frac{V}{V_{R}d}</math>
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#a layer of [[filter media]] to support plant growth, and
#a layer of [[filter media]] to support plant growth, and
#a reservoir of [[stone]] to store and facilitate [[infiltration]] of additional water.
#a reservoir of [[stone]] to store and facilitate [[infiltration]] of additional water.
Firstly, all three zones will be sized together within the limited depth to estimate the footprint area of the whole [[bioretention]] facility. To do this the mean void ratio is estimated to be 0.35.
Firstly, all three zones will be sized together within the limited depth to estimate the footprint area of the whole [[bioretention]] facility. To do this the mean void ratio (''V<sub>R</sub>'') will estimated as ~ 0.35.
To calculate the required facility area or footprint where the depth is constrained:
To calculate the required practice area (''A<sub>p</sub>'') or footprint where the depth is constrained:
:<math>A_{p}=\frac{V}{V_{R}d}</math>
{{Plainlist|1=Where:
*''V'' = Required volume of storage in m<sup>3</sup>
*''V<sub>R</sub>'' = Void ratio (porosity), as measured (or default to 0.35 for all aggregates)
*''A<sub>p</sub>'' = Area of the infiltration practice in m<sup>2</sup>
*''d'' = Depth of infiltration practice in m.}}
==Step 1 alternative==
===Accounts for infiltration during a design storm event===
To calculate the required practice area (''A<sub>p</sub>'') or footprint where the depth is constrained:
<math>A_{p}=\frac{A_{c}iD}{V_{R}d+q'D}</math>
<math>A_{p}=\frac{A_{c}iD}{V_{R}d+q'D}</math>
*''A<sub>c</sub>'' = Area of the catchment in m<sup>2</sup>
*''A<sub>c</sub>'' = Area of the catchment in m<sup>2</sup>
*''d'' = Depth of infiltration practice in m.}}
*''d'' = Depth of infiltration practice in m.}}
==Step 2==
==Step 2==