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: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.
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 time for the ponded water to drain. See [[Bioretention: Sizing#Additional step for system without underdrain|Bioretention]]
Metal grates are recommended (over plastic) in all situations.