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→Determine the required surface area of the practice
*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>f, min</sub> = minimum infiltration rate (i.e. saturated hydraulic conductivity) of the filter media (m/h), see [[Bioretention: Filter media|Filter media]] for guidance}}<br>
*f<sub>f, min</sub> = minimum acceptable infiltration rate (i.e. saturated hydraulic conductivity) of the filter media (m/h), see [[Bioretention: Filter media|Filter media]] for guidance}}<br>
For practices where flow is delivered directly to the storage reservoir:
For practices where flow is delivered directly to the storage reservoir:
<math>A_{p}=i\times D\times A_{i}/[d_{i} + (f' \times D)]</math>
<math>A_{p}=i\times D\times A_{i}/[d_{i} + (f' \times D)]</math>
* Step 7: Calculate catchment impervious area to practice permeable (footprint) area ratio, R, also referred to as I/P ratio:
* Step 7: Calculate catchment impervious area to practice permeable (footprint) area ratio, R, also referred to as I/P ratio:
<math>R=A_{i}/A_{p}</math><br>
<math>R=A_{i}/A_{p}</math><br>
Adjust A<sub>p</sub> or A<sub>i</sub> to keep R between 5 and 20.
Adjust *d<sub>p</sub>', d<sub>i</sub>, A<sub>p</sub> or A<sub>i</sub> to keep R between 5 and 20.
==Determine the required surface area of the storage reservoir==
==Determine the required surface area of the storage reservoir==