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Line 1: − [[File:BeehiveGrate.jpeg|thumb|Domed, metal overflow/outlet grate<br> Photo credit:Aaron Volkening]]+ − + − − − :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). + + − + + + + + + + + + − + + Line 25:
Line 33: − | − |- − | Plastic grate − | − | x − | − |- − | Metal grate − | x − | Line 47:
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→Overflow elevation
[[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===
*Infiltration facilities can be designed to be inline or offline from the drainage system. See [[Inlets]]
==Routing==
*Infiltration facilities can be designed to be inline or offline from the drainage system.
*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 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.
===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|time for the ponded water to drain.
See [[Bioretention: Sizing#Additional step for system without underdrain|Bioretention]] and [[Stormwater planters]]
===Freeboard===
{{:freeboard}}
==Options==
===Options===
Metal grates are recommended (over plastic) in all situations.
{| class="wikitable sortable"
{| class="wikitable sortable"
|
|
| x
| x
|
|
|-
|-
| x
| x
|-
|-
| Curb cut
| [[Curb cut]]
| x
| x
| x
| x
| x
| x
|}
|}
===Gallery===
{{:Overflow:Gallery}}