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{{Plainlist|1=Where:*''D'' = Duration of design storm in hrs*''i'' = Intensity of design storm in mm/hr*''q''' = Infiltration coefficient in mm/hr (accounting for SCF)*''SCF'' = Safety correction factor*''V<sub>R</sub>'' = Void ratio (porosity), as measured (or default to 0.35 for all aggregates)**''R'' = Ratio of catchment area (''A<sub>c</sub>'') to BMP footprint area (A<sub>p</sub>) syn. I/P ratio. *''A<sub>p</sub>'' = Area of the infiltration practice in m<sup>2</sup>*''A<sub>c</sub>'' = Catchment area in m<sup>2</sup>*''d'' = Depth of infiltration practice in m.}} *Note: For systems that have significant storage in clear open chambers, an effective porosity value (''V<sub>R</sub><nowiki>'</nowiki>'') may be estimated for the whole installation and used in the calculations below. Effective porosity will vary according to the geometry of the storage chambers, so advice should be sought from product manufacturers. Permit applications should include the basis for ''V<sub>R</sub><nowiki>'</nowiki>'' estimates.----
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*''A<sub>c</sub>'' = Catchment area in m<sup>2</sup>
*''A<sub>c</sub>'' = Catchment area in m<sup>2</sup>
*''d'' = Depth of infiltration practice in m.}}
*''d'' = Depth of infiltration practice in m.}}
The following equations assume that infiltration occurs primarily through the base of the facility.
The following equations assume that infiltration occurs primarily through the base of the facility.
They may be easily applied for any shape and size of infiltration facility, in which the reservoir storage is mostly in an aggregate.
They may be easily applied for any shape and size of infiltration facility, in which the reservoir storage is mostly in an aggregate.