Changes

==Size a bioretention cell for constrained depth==

==Size a bioretention cell for constrained depth==

If there is a constraint to the depth (''d_T'', m) of the practice, calculate the required footprint area (''A_p'', m²), as:

If there is a constraint to the depth (''d_T'', m) of the practice, calculate the required footprint area (''A_p'', m²), as:

<math>A_{p}=\frac{A_c\times i\times D}{(V_{R}\times d_{T})+(f'\times D)}</math>

<math>A_{p}=\frac{A_c\times i\times D}{(n\times d_{T})+(f'\times D)}</math>

{{Plainlist|1=Where:

{{Plainlist|1=Where:

*''A_p'' = Area of the infiltration practice in m²

*''A_p'' = Area of the infiltration practice in m²

*''i'' = Intensity of design storm in mm/hr

*''i'' = Intensity of design storm in mm/hr

*''f''' = [[design infiltration rate]] in mm/hr

*''f''' = [[design infiltration rate]] in mm/hr

*''V_R'' = Mean void ratio of the fill within the practice

*''n'' = Mean porosity of the fill within the practice

*''d_T'' = Total depth of the infiltration practice in m.}}

*''d_T'' = Total depth of the infiltration practice in m.}}

Then calculate the required depth (''d_T''), as:

Then calculate the required depth (''d_T''), as:

<math>d_{T}=\frac{D \left[ (R\times i)-f'\right]}{V_{R}}</math>

<math>d_{T}=\frac{D \left[ (R\times i)-f'\right]}{n}</math>

{{Plainlist|1=Where:

{{Plainlist|1=Where:

*''i'' = Intensity of design storm in mm/hr

*''i'' = Intensity of design storm in mm/hr

*''f''' = Design infiltration rate in mm/hr  

*''f''' = Design infiltration rate in mm/hr  

*''V_R'' = Void ratio

*''n'' = Porosity

*''d_T'' = Depth of infiltration practice in m.}}

*''d_T'' = 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.  

*Begin the drainage time calculation by dividing the area of the practice (''A_p'') by the perimeter (''P'').

*Begin the drainage time calculation by dividing the area of the practice (''A_p'') by the perimeter (''P'').

*Use the following equation to estimate the time (''t'') to fully drain the facility:  

*Use the following equation to estimate the time (''t'') to fully drain the facility:  

:<math>t=\frac{V_{R}A_{p}}{f'P}ln\left [ \frac{\left (d_{T}+ \frac{A_{p}}{P} \right )}{\left(\frac{A_{p}}{P}\right)}\right]</math>

:<math>t=\frac{nA_{p}}{f'P}ln\left [ \frac{\left (d_{T}+ \frac{A_{p}}{P} \right )}{\left(\frac{A_{p}}{P}\right)}\right]</math>

{{Plainlist|1=Where:

{{Plainlist|1=Where:

*''V_R'' is the void ratio of the media,  

*''n'' is the porosity of the media,  

*''A_p'' is the area of the practice (m²),

*''A_p'' is the area of the practice (m²),

*''f''' is the design infiltration rate (mm/hr),  

*''f''' is the design infiltration rate (mm/hr),