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| #a reservoir of [[stone]] to store and facilitate [[infiltration]] of additional water. | | #a reservoir of [[stone]] to store and facilitate [[infiltration]] of additional water. |
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− | 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. | + | Firstly, all three zones will be sized together within the limited depth to estimate 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: | + | To calculate the required facility area or footprint where the depth is constrained: |
| <math>A_{p}=\frac{IiD}{V_{R}d+q'D}</math> | | <math>A_{p}=\frac{IiD}{V_{R}d+q'D}</math> |
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| *''A<sub>p</sub>'' = Area of the infiltration practice in m<sup>2</sup> | | *''A<sub>p</sub>'' = Area of the infiltration practice in m<sup>2</sup> |
| *''d'' = Depth of infiltration practice in m.}} | | *''d'' = Depth of infiltration practice in m.}} |
| + | |
| + | ==Step 2== |
| + | <poem> |
| + | The 'bowl' area is simply the depressed elevation of the surface compared to the surrounding areas; a space to permit temporary ponding. |
| + | The depth of the bowl would not typically exceed 0.5 m due to safety concerns. |
| + | {{Infobox|1=Some jurisdictions or particular sites may demand a lower maximum depth of ponding. It is worth bearing in mind that in most cases this ponded water will only occur once or twice per year.}} |
| + | The ponded water within the bowl should drain within 48 hrs. This addresses public concerns about [[mosquitoes]] and reduces the probability of losing vegetation due to saturated growing conditions. |
| + | The drainage of the bowl is not usually constrained by the surface infiltration (filter media should drain > 25 mm/hr). The infiltration of water from the bowl is determined by the drainage of the filter media and reservoir into the soils. |
| + | </poem> |