8,255
edits
Changes
Jump to navigation
Jump to search
Line 7:
Line 7: − − − − {{Plainlist|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. − *''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. − Line 32:
Line 16: − Line 46:
Line 29: − +
no edit summary
#[[Green roofs]], [[absorbent landscapes]] and [[permeable paving]] often receive very little flow from other surfaces, so that the I/P ratio is close to 1.
#[[Green roofs]], [[absorbent landscapes]] and [[permeable paving]] often receive very little flow from other surfaces, so that the I/P ratio is close to 1.
#[[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.
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 require facility area or footprint where the depth is constrained:
To calculate the require facility area or footprint where the depth is constrained:
<math>A_{p}=\frac{IiD}{V_{R}d+\left ( \frac{q}{SCF} \right )D}</math>
<math>A_{p}=\frac{IiD}{V_{R}d+\left ( \frac{q}{SCF} \right )D}</math>
{{Plainlist|1=Where:
{{Plainlist|1=Where:
*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.
*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.
----