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− | 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 [[Reservoir gravel|coarse aggregate]]. | + | [[File:Gravel.jpg|thumb|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 gravel|storage reservoir 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 pavements]]. |
| + | |
| 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 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]] |