Line 10: |
Line 10: |
| :<math>V_{f}=A_{c}\times R\times L_{o} \times F_{c}</math> | | :<math>V_{f}=A_{c}\times R\times L_{o} \times F_{c}</math> |
| {{plainlist| 1=Where: | | {{plainlist| 1=Where: |
− | *''A<sub>c</sub>'' = The area of the catchment (Ha), | + | *''A<sub>c</sub>'' = The area of the catchment (ha), |
| *''R'' = The capture efficiency (default to 0.8), | | *''R'' = The capture efficiency (default to 0.8), |
| *''L<sub>o</sub>'' = The sediment loading rate (m³/ha/yr), and | | *''L<sub>o</sub>'' = The sediment loading rate (m³/ha/yr), and |
Line 31: |
Line 31: |
| | | |
| ===Example calculation=== | | ===Example calculation=== |
− | A parking lot catchment of 1.7 ha is being routed through a small forebay into a bioretention cell. The design flow rate is 0.02 m³/s. The system should be designed to require cleaning no more often than once per year. | + | A parking lot catchment of 1.7 ha is being routed through a small forebay into a bioretention cell. The design flow rate is 0.07 m³/s. The system should be designed to require cleaning no more often than once per year. |
| The volume is calculated as: | | The volume is calculated as: |
| :<math>V_{f}=1.7\times 0.8\times 0.6\times 1=0.816\ m^{3}</math> | | :<math>V_{f}=1.7\times 0.8\times 0.6\times 1=0.816\ m^{3}</math> |
| The area required to keep the maximum head of water within the forebay to 0.15 m is calculated as: | | The area required to keep the maximum head of water within the forebay to 0.15 m is calculated as: |
− | :<math>A_{f}=\frac{0.816}{0.1}=8.16\ m^{2}</math> | + | :<math>A_{f}=\frac{0.816}{0.15}=5.44\ m^{2}</math> |
| The area required to settle the 1 mm particles is calculated as: | | The area required to settle the 1 mm particles is calculated as: |
− | :<math>A_{f}=120\times 0.1 = 12\ m^{2}</math> | + | :<math>A_{f}=120\times 0.07 = 8.4\ m^{2}</math> |
− | So to meet the target particle removal, the forebay will be 12 m² in area. This gives the storage volume of 1.8 m³, which can be returned to the initial equation to determine the minimum cleaning frequency as: | + | So to meet the target particle removal, the forebay will be 8.4 m² in area. This gives the storage volume of 1.26 m³, which can be returned to the initial equation to determine the minimum cleaning frequency as: |
− | :<math>C_{f}=\frac{1.8}{1.7\times 0.8\times 0.6}=2.2\ years</math> | + | :<math>F_{c}=\frac{1.26}{1.7\times 0.8\times 0.6}=1.5\ years</math> |
| | | |
| ==Gallery== | | ==Gallery== |
Line 46: |
Line 46: |
| ==Proprietary products== | | ==Proprietary products== |
| As with underground [[pretreatment]] there are an increasing number of proprietary products available. Some of those listed below are currently only available overseas. | | As with underground [[pretreatment]] there are an increasing number of proprietary products available. Some of those listed below are currently only available overseas. |
− | *[http://www.rainguardian.biz/ rain guardian] | + | *[http://www.rainguardian.biz/ Rain Guardian] |
| *[https://oldcastleprecast.com/oldcastle_product/4-out-swalegard-pre-filter-grassy-swale/101168/ Swalegard] | | *[https://oldcastleprecast.com/oldcastle_product/4-out-swalegard-pre-filter-grassy-swale/101168/ Swalegard] |
| | | |
| ---- | | ---- |
| [[Category:Pretreatment]] | | [[Category:Pretreatment]] |