Changes

:<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_c'' = The area of the catchment (Ha),   

*''A_c'' = The area of the catchment (ha),   

*''R'' = The capture efficiency (default to 0.8),

*''R'' = The capture efficiency (default to 0.8),

*''L_o'' = The sediment loading rate (m³/ha/yr), and

*''L_o'' = The sediment loading rate (m³/ha/yr), and

===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==

==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]

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[[Category:Pretreatment]]

[[Category:Pretreatment]]