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| [[File:Level spreader diagram.jpg|thumb|Diagram from Wikimedia commons. Credit: U.S. Army Corps of Engineers, Construction Engineering Research Laboratory]] | | [[File:Level spreader diagram.jpg|thumb|Diagram from Wikimedia commons. Credit: U.S. Army Corps of Engineers, Construction Engineering Research Laboratory]] |
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− | Level spreaders should conform to the following design criteria in order to ensure non-erosive sheet flow into vegetated areas such as [[vegetated filter strips]], [[swales]] or forested conservation areas<ref>Hathaway, J. M., & Hunt, W. F. (2006). Level Spreaders : Overview , Design , and Maintenance.</ref>. | + | Level spreaders should conform to the following design criteria in order to ensure non-erosive sheet flow into vegetated areas such as [[vegetated filter strips]], [[Bioretention|bioretention]], [[swales]] or forested conservation areas<ref>Hathaway, J. M., & Hunt, W. F. (2006). Level Spreaders : Overview , Design , and Maintenance.</ref>. |
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− | The length of the level spreader should be determined by the type of filter area and the design flow: | + | The length of the level spreader should be determined by the design storm inflow rate and type of landscape downstream: |
− | * 1.4 m of level spreader length per every 0.01 m³/s of inflow for discharges to a [[vegetated filter strips|vegetated filter strip]], [[Bioretention| bioretention]], [[Swale| swale]] or grassed area; | + | * 1.4 m of level spreader length per every 0.01 m³/s of inflow when draining to a [[vegetated filter strips|vegetated filter strip]], [[Bioretention| bioretention]], [[Swale| swale]] or grassed area; |
− | * 4.3 m of level spreader length per every 0.01 m³/s of inflow when the spreader discharges to a forested conservation area. | + | * 4.3 m of level spreader length per every 0.01 m³/s of inflow when draining to a forested conservation area. |
| * The minimum level spreader length is 4 m and the maximum is 40 m. | | * The minimum level spreader length is 4 m and the maximum is 40 m. |
| * The level spreader lip should be concrete, wood or pre-fabricated metal. | | * The level spreader lip should be concrete, wood or pre-fabricated metal. |
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| * The width of the level spreader should be the greater of 300 mm or three times the diameter of the inflow pipe. | | * The width of the level spreader should be the greater of 300 mm or three times the diameter of the inflow pipe. |
| * The depth should be the greater of 200 mm or half the inflow pipe diameter. | | * The depth should be the greater of 200 mm or half the inflow pipe diameter. |
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| + | ==References== |
| + | [[Category:Pretreatment]] |