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Line 8: − {|class="wikitable"+ − |+ Inputs + − |- − !style="background: darkcyan; color: white"|Symbol − !style="background: darkcyan; color: white"|Units − !style="background: darkcyan; color: white"|Parameter − |- − |''D''||hrs||Duration of design storm (for MOECC volume based caclulations set to 1) − |- − |''i''||mm/hr||Intensity of design storm (for MOECC volume based calculations use whole storm depth (link to map)) − |- − |''q''||mm/hr||Infiltration coefficient, calculated from measured [[Infiltration: Testing| infiltration rate]] and applied [[Infiltration|safety factor]] − |- Line 29:
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#[[Infiltration trenches]], [[Infiltration chambers| chambers]] and [[bioretention cells]] have a maximum recommended I/P ratio of 20.
#[[Infiltration trenches]], [[Infiltration chambers| chambers]] and [[bioretention cells]] have a maximum recommended I/P ratio of 20.
|''V<sub>R</sub>''||-||Porosity (void ratio), as measured (or default to 0.35 for all aggregates).<br> *Note: For systems that have significant storage in clear open chambers, an effective porosity value (''n<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 ''n<nowiki>'</nowiki>'' estimates.
|''V<sub>R</sub>''||-||Porosity (void ratio), as measured (or default to 0.35 for all aggregates).<br> *Note: For systems that have significant storage in clear open chambers, an effective porosity value (''n<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 ''n<nowiki>'</nowiki>'' estimates.
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|''P''||m<sup>2</sup>||Permeable area i.e. footprint area of the facility or BMP
|''P''||m<sup>2</sup>||Permeable area i.e. footprint area of the facility or BMP
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{{Textbox|1=Where:
''D'' = Duration of design storm in hrs
''i'' = Intensity of design storm in mm/hr
''q'' = Infiltration rate of underlying soil in mm/hr
''SF'' = Safety 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.
*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.
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.
To calculate the required depth, where the area of the facility is constrained:
To calculate the required depth, where the area of the facility is constrained:
<math>d=\frac{D\left[Ri-q \right]}{V_{R}}</math>
<math>d=\frac{D\left[Ri-\left ( \frac{q}{SCF} \right ) \right]}{V_{R}}</math>
To calculate the require facility area or footprint where the depth is constrained:
To calculate the require facility area or footprint where the depth is constrained:
<math>P=\frac{IiD}{nd+qD}</math>
<math>A_{p}=\frac{IiD}{V_{R}d+\left ( \frac{q}{SCF} \right )D}</math>
This spreadsheet tool has been set up to perform either of the above calculations.<br>
This spreadsheet tool has been set up to perform either of the above calculations.<br>