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| [[File:Routing.png|thumb|Conceptual diagram of the excess routing alternatives: On the left, excess flow leaves the cell via an overflow; on the right, excess flow is diverted so that only the design volume enters the cell.]] | | [[File:Routing.png|thumb|Conceptual diagram of the excess routing alternatives: On the left, excess flow leaves the cell via an overflow; on the right, excess flow is diverted so that only the design volume enters the cell.]] |
− | ==Routing== | + | ===Routing=== |
| *Infiltration facilities can be designed to be inline or offline from the drainage system. See [[Inlets]] | | *Infiltration facilities can be designed to be inline or offline from the drainage system. See [[Inlets]] |
| *Inline facilities accept all of the flow from a drainage area and convey larger event flows through an overflow outlet. The overflow must be sized to safely convey larger storm events out of the facility. | | *Inline facilities accept all of the flow from a drainage area and convey larger event flows through an overflow outlet. The overflow must be sized to safely convey larger storm events out of the facility. |
− | :The invert of the overflow should be placed at the maximum water surface elevation of the bioretention area, (typically 150 - 250 mm above the surface).
| + | |
| + | *The overflow must be situated at the far end of the facility to prevent any localised ponding to cause bypassing of the infiltration facility. |
| *Offline facilities use flow splitters or bypass channels that only allow the required water quality storage volume to enter the facility. | | *Offline facilities use flow splitters or bypass channels that only allow the required water quality storage volume to enter the facility. |
− | :Higher flows are diverted and do not enter the infiltration practice. A pipe can by used for this, but a weir or [[curb cuts|curb cut]] minimizes clogging and reduces the maintenance frequency. | + | :Higher flows are diverted and do not enter the infiltration practice. A pipe can by used for this, but a [[weir]] or [[curb cuts|curb cut]] minimizes clogging and reduces the maintenance frequency. |
| | | |
− | ==Options== | + | ===Overflow elevation=== |
| + | The invert of the overflow should be placed at the maximum water surface elevation of the practice. i.e. the maximum ponding depth. |
| + | A good starting point is around 300 mm over the surface of the practice. However, consideration should be given to public safety and drainage time for the ponded water to drain. |
| + | See [[Bioretention: Sizing#Additional step for system without underdrain|Bioretention]] and [[Stormwater planters]] |
| + | |
| + | ===Freeboard=== |
| + | {{:freeboard}} |
| + | |
| + | ===Options=== |
| Metal grates are recommended (over plastic) in all situations. | | Metal grates are recommended (over plastic) in all situations. |
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| |- | | |- |
− | | [[Catch basin]] | + | | Catch basin |
| | x | | | x |
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| |} | | |} |
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− | ==Gallery== | + | ===Gallery=== |
| {{:Overflow:Gallery}} | | {{:Overflow:Gallery}} |