8,255
edits
Changes
Jump to navigation
Jump to search
Created page with "To size a bioretention facility using this page, the design infiltration rate (q' in mm/hr, after correction) of the native underlying soils must estimated, and the maxi..."
To size a bioretention facility using this page, the [[design infiltration rate]] (q' in mm/hr, after correction) of the native underlying soils must estimated, and the [[maximum available excavation depth]] (d in m) is the primary constraint to sizing. <br>
If the space on the ground is the tighter constraint to design, try this article on [[sizing bioretention for space]].
===Step 1===
The bioretention facility will comprise three vertical zones:
#a 'bowl' permitting water to pond occasionally,
#a layer of [[filter media]] to support plant growth, and
#a reservoir of [[stone]] to store and facilitate [[infiltration]] of additional water.
Firstly, all three zones will be sized together within the limited depth to find the footprint area of the whole [[bioretention]] facility. To do this the mean void ratio is estimated to be 0.35.
To calculate the require facility area or footprint where the depth is constrained:
<math>A_{p}=\frac{IiD}{V_{R}d+q'D}</math>
{{Plainlist|1=Where:
*''D'' = Duration of design storm in hrs
*''i'' = Intensity of design storm in mm/hr
*''q''' = Design infiltration rate in mm/hr
*''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>
*''d'' = Depth of infiltration practice in m.}}
If the space on the ground is the tighter constraint to design, try this article on [[sizing bioretention for space]].
===Step 1===
The bioretention facility will comprise three vertical zones:
#a 'bowl' permitting water to pond occasionally,
#a layer of [[filter media]] to support plant growth, and
#a reservoir of [[stone]] to store and facilitate [[infiltration]] of additional water.
Firstly, all three zones will be sized together within the limited depth to find the footprint area of the whole [[bioretention]] facility. To do this the mean void ratio is estimated to be 0.35.
To calculate the require facility area or footprint where the depth is constrained:
<math>A_{p}=\frac{IiD}{V_{R}d+q'D}</math>
{{Plainlist|1=Where:
*''D'' = Duration of design storm in hrs
*''i'' = Intensity of design storm in mm/hr
*''q''' = Design infiltration rate in mm/hr
*''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>
*''d'' = Depth of infiltration practice in m.}}