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Line 54: − [[file:Hydraulic radius.png|thumb|Three footprint areas of 9 m<sup>2</sup>.<br>+ − From left to right x = 12 m, x = 14 m, and x = 16 m]] − For some geometries (e.g. particularly deep facilities or linear facilities), it may be preferred to also account for lateral infiltration. − The 3 dimensional equations make use of the hydraulic radius (''P''/''x''), where ''x'' is the perimeter (m) of the facility. <br> − Maximizing the perimeter of the facility directs designers towards longer, linear shapes such as [[infiltration trenches]] and [[bioswales]]. − To calculate the required depth: Line 55:
Line 60: + + + − + + + + − − (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.) Line 67:
Line 76: − + − The design of infiltration facilities should be checked for [[drawdown time]]. The target drawdown time for the internal storage of an infiltration facility is between 48-72 hours. <br>+ + + + + +
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__NOTOC__
__NOTOC__
<imagemap>
Image:Infiltration.png|thumb|700 px|This is an image map; clicking on components will load the appropriate article.
poly 315 507 208 555 317 605 423 555 [[Drainage time]]
rect 210 658 426 730 [[Details]]
rect 568 522 728 594 [[Underdrain]]
poly 73 27 39 75 75 126 179 126 215 78 181 27 [[Infiltration]]
poly 268 25 235 75 270 123 364 124 395 76 365 25 [[Infiltration: Testing]]
rect 237 185 397 225 [[Select BMP type]]
rect 238 266 397 329 [[Bioretention: Sizing]]
</imagemap>
{{textbox|
{{textbox|
{{plainlist|
{{plainlist|
#The minimum total depth may be limited by the need to support vegetation i.e. not < 0.6 m.
#The minimum total depth may be limited by the need to support vegetation i.e. not < 0.6 m.
#[[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]] have a maximum recommended I/P ratio of 20.
{|class="wikitable"
{|class="wikitable"
==To calculate the required depth, where the area of the facility is constrained (3D)==
==To calculate the required depth, where the area of the facility is constrained (3D)==
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:
:<math>d=a[e^{\left ( -bD \right )} -1]</math>
:<math>d=a[e^{\left ( -bD \right )} -1]</math>
Where
Where
and
and
<math>b=\frac{xq}{nP}</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.)
==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)==
<math>d=\frac{D\left[\left( \frac{I}{P} \right )i-q \right]}{n}</math>
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.
:<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:
<math>P=\frac{IiD}{nd+qD}</math>
<math>P=\frac{IiD}{nd+qD}</math>
==Time for infiltration of surface ponded water==
==Time for infiltration of surface ponded water==
It is best applied to calculate the limited duration ponding on the surface of [[bioretention cells]], [[bioswales]] and [[enhanced grass swales]].
It is best applied to calculate the limited duration ponding on the surface of [[bioretention cells]], [[bioswales]] and [[enhanced grass swales]].
To calculate the time (''t'') to fully drain the facility through the footprint area only:
To calculate the time (''t'') to fully drain the facility through the footprint area only:
<math>t=\frac{nd}{K}</math>
<math>t=\frac{d}{K}</math>
==Drawdown time to empty facility==
==Drawdown time to empty facility==
[[file:Hydraulic radius.png|thumb|Three footprint areas of 9 m<sup>2</sup>.<br>
From left to right x = 12 m, x = 14 m, and x = 16 m]]
The target [[drawdown time]] for the internal storage of an infiltration facility is between 48-72 hours. <br>
For some geometries (e.g. particularly deep facilities or linear facilities), it preferable to account for lateral infiltration.
The 3D equation make use of the hydraulic radius (''P''/''x''), where ''x'' is the perimeter (m) of the facility. <br>
'''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}{qx}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>