Difference between revisions of "Choker layer"

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Revision as of 20:30, 6 March 2018

medium sized granular, free from fines

In bioretention systems a choking layer of ≥ 100 mm is the recommended method to prevent migration of finer filter media into an underlying reservoir of coarse aggregate. Suitable materials include:

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.
HL 6
Is a clean, angular aggregate screened between 10 - 20 mm. Free from fines by definition.
Pea Gravel
Rounded natural aggregate, screened between 5 - 15 mm, and washed free from fines.

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