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− | [[File:Levelspread.jpg|thumb|This clever design incorporates a level spreading device after a [[curb cut]] has concentrated flow. This kind of treatement train approach would provide an opportunity to provide [[pretreatment]] at the point of concentration. Photo credit: [https://www.pca.state.mn.us/featured/when-it-rains-it-flows MPCA]] | + | [[File:Levelspread.jpg|thumb|This clever design incorporates a level spreading device after a [[curb cut]] has narrowed the flow path. This kind of treatment train approach would provide an opportunity to provide [[pretreatment]] at the point of concentration. Photo credit: [https://www.pca.state.mn.us/featured/when-it-rains-it-flows MPCA] |
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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]], [[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 type of filter area and the design flow: |
− | * 1.4 m of level spreader length per every 0.01 cubic meter per second (cms) of inflow for discharges to a filter strip or turf conservation area; | + | * 1.4 m of level spreader length per every 0.01 m³/s of inflow for discharges to a [[filter strip]] or turf conservation area; |
− | * 4.3 m of level spreader length per every 0.01 cms 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 the spreader discharges 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, with a well anchored footer, or other accepted rigid, non-erodible material. | | * The level spreader lip should be concrete, wood or pre-fabricated metal, with a well anchored footer, or other accepted rigid, non-erodible material. |
| * The ends of the level spreader section should be tied back into the slope to avoid [[overflow]] scouring or erosion around the ends of the spreader. | | * The ends of the level spreader section should be tied back into the slope to avoid [[overflow]] scouring or erosion around the ends of the spreader. |
− | * The width of the level spreader channel on the up-stream side of the level lip should be three times the diameter of the inflow pipe, and the depth should be 20 cm or one-half the culvert diameter, whichever is greater. | + | * Where relevant, the width of the level spreader channel on the up-stream side of the level lip should be three times the diameter of the inflow pipe, and the depth should be 20 cm or one-half the culvert diameter, whichever is greater. |
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