Changes

#The ''maximum'' total depth will be limited by construction practices i.e. usually ≤ 2 m.

#The ''maximum'' total depth will be limited by construction practices i.e. usually ≤ 2 m.

#The ''maximum'' total depth may be limited by the [[Infiltration| conditions underground]] e.g. the groundwater or underlying geology/infrastructure.

#The ''maximum'' total depth may be limited by the [[Infiltration| conditions underground]] e.g. the groundwater or underlying geology/infrastructure.

#[[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]] have a maximum recommended I/P ratio of 20.

#[[Infiltration trenches]], [[Infiltration chambers| chambers]] and [[bioretention]] have a maximum recommended I/P ratio of 20.

|''i''||mm/hr||Intensity of design storm (for MOECC volume based calculations use whole storm depth (link to map))

|''i''||mm/hr||Intensity of design storm (for MOECC volume based calculations use whole storm depth (link to map))

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|''f'''||mm/hr||Design infiltration rate of the underlying native soil, calculated from measured [[Infiltration: Testing| infiltration rate]] and applied [[Infiltration|safety factor]]

|''q''||mm/hr||Infiltration coefficient of the underlying native soil, calculated from measured [[Infiltration: Testing| infiltration rate]] and applied [[Infiltration|safety factor]]

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|''n''||n/a||Porosity of the aggregate or other fill material (e.g. 0.4 for clear stone).<br> *Note: For systems that have significant storage in clear open chambers or other void producing structures, 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.

|''n''||-||Porosity, 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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|''I''||m²||Impermeable area within the catchment

|''I''||m²||Impermeable area i.e. catchment

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|''d''||m||Depth of infiltration BMP

|''d''||m||depth of infiltration facility or BMP

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|''A<sub>p''||m²||Permeable area (i.e. footprint area of the infiltration BMP)

|''P''||m²||Permeable area i.e. footprint area of the facility or BMP

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|''K''||mm/hr||Infiltration coefficient of the filter media or fill used in the infiltration facility  

|''K''||mm/hr||Saturated hydraulic conductivity of the filter media or granular fill (i.e. aggregate) used in the infiltration BMP  

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:<math>d=a[e^{\left ( -bD \right )} -1]</math>

:<math>d=a[e^{\left ( -bD \right )} -1]</math>

Where

Where

<math>a=\frac{A_p}{x}-\frac{i I}{P f'}</math>

<math>a=\frac{P}{x}-\frac{i I}{P q}</math>

and  

and  

<math>b=\frac{xf'}{nA_p}</math>

<math>b=\frac{xq}{nP}</math>

(The rearrangement to calculate the required footprint area of the facility for a given depth using three dimensions of underground infiltration is not available at this time. Elegant submissions are invited.)

(The rearrangement to calculate the required footprint area of the facility for a given depth using three dimensions of underground infiltration is not available at this time. Elegant submissions are invited.)

==To calculate the required depth, where the area of the facility is constrained (1D)==

==To calculate the required depth, where the area of the facility is constrained (1D)==

In some very constrained sites, the surface area of the BMP may be limited, in this case the required depth of the cell or trench can be calculated.

In some very constrained sites, the surface area of the BMP may be limited, in this case the required depth of cell or trench can be calculated.

Note that in most cases the results of this calculation will be very similar to those of the above equation using 3D infiltration.  

Note that in most cases the results of this calculation will be very similar to those of the above equation using 3D infiltration.  

:<math>d=\frac{D\left[\left( \frac{I}{P} \right )i-f' \right]}{n}</math>

:<math>d=\frac{D\left[\left( \frac{I}{P} \right )i-q \right]}{n}</math>

==To calculate the require facility area or footprint where the depth is constrained (1D)==

==To calculate the require facility area or footprint where the depth is constrained (1D)==

In many locations throughout Ontario, there may be limited depth of soil available into which stormwater may be infiltrated. In this case the required storage needs to be distributed more widely across the landscape. The overall are of BMP required can be calculated:

In many locations throughout Ontario, there may be limited depth of soil available into which stormwater may be infiltrated. In this case the required storage needs to be distributed more widely across the landscape. The overall are of BMP required can be calculated:

<math>P=\frac{IiD}{nd+f'D}</math>

<math>P=\frac{IiD}{nd+qD}</math>

==Time for infiltration of surface ponded water==

==Time for infiltration of surface ponded water==

'''Maximizing the perimeter of the facility directs designers towards longer, linear shapes such as [[infiltration trenches]] and [[bioswales]].'''   

'''Maximizing the perimeter of the facility directs designers towards longer, linear shapes such as [[infiltration trenches]] and [[bioswales]].'''   

To calculate the time (''t'') to fully drain the facility:  

To calculate the time (''t'') to fully drain the facility:  

<math>t=\frac{nP}{f'x}ln\left [ \frac{\left (d+ \frac{P}{x} \right )}{\left(\frac{P}{x}\right)}\right]</math>

<math>t=\frac{nP}{qx}ln\left [ \frac{\left (d+ \frac{P}{x} \right )}{\left(\frac{P}{x}\right)}\right]</math>

[[category: modeling]]

[[category: modeling]]

[[category: infiltration]]

[[category: infiltration]]