[[File:Clogged drain.jpg|thumb|Drain clogged by 9 squares of 32 = 28 %]]
[[File:Clogged drain.jpg|thumb|Drain clogged by 9 squares of 32 = 28 %]]
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==Grates and orifices==
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Debris in stormwater is often deposited in the narrowest parts of our low impact development systems. Garbage, leaf litter and sediment all contribute towards the clogging of these structures.
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It is often prudent to assume that maintenance will be intermittent and to include a clogging factor into engineering calculations to account for periods in which the debris has not been removed. A suggested value of 0.5 is often adopted.