[[File:Gravel.jpg|thumb|medium sized granular, free from fines]]
[[File:Gravel.jpg|thumb|medium sized granular, free from fines]]
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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]].
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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]].
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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]].
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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]].