Difference between revisions of "Level spreaders"
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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 m³/s of inflow for discharges to a [[vegetated filter strips|vegetated filter strip]] or grassed area; | + | * 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; |
* 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 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 | + | * The level spreader lip should be concrete, wood or pre-fabricated metal. |
| − | * The ends of the level spreader section should be tied back into the slope to avoid [[overflow]] scouring or erosion around the ends | + | * The ends of the level spreader section should be tied back into the slope to avoid [[overflow]] scouring or erosion around the ends. |
| − | * | + | * 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. | ||
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Revision as of 01:42, 15 July 2020
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: MPCA
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[1].
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 m³/s of inflow for discharges to a vegetated filter strip, bioretention, 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.
- 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 ends of the level spreader section should be tied back into the slope to avoid overflow scouring or erosion around the ends.
- 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.
- ↑ Hathaway, J. M., & Hunt, W. F. (2006). Level Spreaders : Overview , Design , and Maintenance.