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→Determine the required surface area of the practice
<math>d_{p}'=d_{p, max}</math>
<math>d_{p}'=d_{p, max}</math>
==Determine the required surface area of the practice==
==Determine the required surface area of the practice==
* Step 4: Calculate the surface (i.e footprint) area of the practice (A<sub>p</sub>) needed to capture the runoff volume produced from the catchment during the design storm event:<br>
* Step 4: Calculate the surface (i.e footprint) area of the practice (A<sub>p</sub>) needed to capture the runoff volume produced from the catchment during the design storm event<br>
For practices where flow is delivered to the filter media bed:
For practices where flow is delivered to the filter media bed:
<math>A_{p}=i\times D\times A_{i}/[(d_{p}' + (f_{m, min} \times D)]</math>
<math>A_{p}=i\times D\times A_{i}/[(d_{p}' + (f_{m, min} \times D)]</math>
{{Plainlist|1=Where:
{{Plainlist|1=Where:
*i = Design storm intensity (mm/h)
*i = Design storm intensity (m/h)
*D = Design storm duration (h)
*D = Design storm duration (h)
*A<sub>i</sub> = Catchment impervious area (m<sup>2</sup>)
*A<sub>i</sub> = Catchment impervious area (m<sup>2</sup>)
*d<sub>p</sub>' = Design surface ponding depth (m)
*d<sub>p</sub>' = Design surface ponding depth (m)
*f<sub>m, min</sub> = minimum infiltration rate of the filter media (mm/h), see [[Bioretention: Filter media|Filter media]] for guidance}}
*f<sub>m, min</sub> = minimum infiltration rate of the filter media (m/h), see [[Bioretention: Filter media|Filter media]] for guidance}}<br>
For practices where flow is delivered to the storage reservoir:
<math>A_{p}=i\times D\times A_{i}/[(d_{a} + (f' \times D)]</math>
{{Plainlist|1=Where:
*d<sub>a</sub> = Active storage depth (m)
*f' = design infiltration rate of the underlying native soil (m/h)
*D = Design storm duration (h)}}<br>
==Determine the active storage depth of the practice==
==Determine the active storage depth of the practice==