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→Determine the required surface area of the practice
==Determine the required surface area of the practice==
==Determine the required surface area of the practice==
* Step 5: Calculate the surface area of the practice (A<sub>p</sub>) needed to capture the volume of runoff produced from the catchment from the design storm event<br>
* Step 5: Calculate the surface area of the practice (A<sub>p</sub>) needed to capture the volume of runoff produced from the catchment by the design storm event<br>
For practices where flow is delivered to a surface ponding area:
For practices where flow is delivered to a surface ponding area:
<math>A_{p}=i\times D\times A_{i}/[d_{p}' + (f_{f, min} \times D)]</math>
<math>A_{p}=i\times D\times A_{i}/[d_{p}' + (f_{f, min} \times D)]</math>
*D = Design storm duration (h)}}<br>
*D = Design storm duration (h)}}<br>
* Step 6: Compare required surface area of the practice to available space.<br>
* Step 6: Compare required surface area of the practice to available space.<br>
To decrease A<sub>p</sub>, consider increasing ponding depth if feasible and would not create a safety hazard, or decreasing catchment impervious area.
To decrease A<sub>p</sub>, consider increasing ponding depth if feasible and would not create a safety hazard (recommended maximum of 0.45 m), or decreasing the catchment area.
* 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>