Difference between revisions of "Choker layer"

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[[File:Gravel.jpg|thumb|medium sized granular, free from fines]]
[[File:Gravel.jpg|thumb|medium sized granular, free from fines]]
In [[bioretention]] systems a choking layer of ≥ 100 mm depth is the recommended method to prevent migration of finer [[filter media]] into an underlying reservoir of [[Reservoir gravel|coarse aggregate]].
In [[bioretention]] systems a choker layer of ≥ 100 mm depth is the recommended method to prevent migration of finer [[filter media]] into the underlying reservoir of [[Reservoir gravel|coarse aggregate]].
These same mid sized granular materials are recommended for use in [[Stormwater planter]] underdrains and may be useful in the fine grading of foundations courses for [[permeable paving]].
These same mid sized granular materials are recommended for use in [[Stormwater planter]] underdrains and may be useful in the fine grading of foundations courses for [[permeable paving]].


Suitable materials include:
Suitable materials include:
;High performance bedding (HPB)
;High performance bedding (HPB)
:Clean, angular aggregate screened to between 6 - 10 mm. Widely available and designed specifically for drainage applications. Free from fines by definition.   
:Clean, angular aggregate screened to between 6 and 10 mm. Widely available and designed specifically for drainage applications. Free from fines by definition.   
;HL 6
;HL 6
:Is a clean, angular aggregate screened between 10 - 20 mm. Free from fines by definition.  
:Is a clean, angular aggregate screened between 10 and 20 mm. Free from fines by definition.  
;Pea Gravel
;Pea Gravel
:Rounded natural aggregate, screened between 5 - 15 mm, and washed free from fines.  
:Rounded natural aggregate, screened between 5 and 15 mm, and washed free from fines.  


In most scenarios, a [[geotextiles|geotextile]] layer is unnecessary and have been associated with rapid decline and [[Clogging#Filter fabric|clogging]] in some circumstances.  
In most scenarios, a [[geotextiles|geotextile]] layer is unnecessary and has been associated with rapid decline and [[Clogging#Filter fabric|clogging]] in some circumstances.  
[[category: materials]]
[[category: materials]]

Revision as of 04:12, 10 July 2020

medium sized granular, free from fines

In bioretention systems a choker layer of ≥ 100 mm depth is the recommended method to prevent migration of finer filter media into the underlying reservoir of coarse aggregate. These same mid sized granular materials are recommended for use in Stormwater planter underdrains and may be useful in the fine grading of foundations courses for permeable paving.

Suitable materials include:

High performance bedding (HPB)
Clean, angular aggregate screened to between 6 and 10 mm. Widely available and designed specifically for drainage applications. Free from fines by definition.
HL 6
Is a clean, angular aggregate screened between 10 and 20 mm. Free from fines by definition.
Pea Gravel
Rounded natural aggregate, screened between 5 and 15 mm, and washed free from fines.

In most scenarios, a geotextile layer is unnecessary and has been associated with rapid decline and clogging in some circumstances.