Summary of recommended bioretention filter media mixes from worldwide sources
Link to this table.

Guideline Aggregate Organic Note
Auckland Regional Council (2003), Waitakere City Council (2004) Sandy loam, loamy sand, loam, loam/sand mix (35 - 60% v/v sand) Not specified Clay content < 25% v/v1
Prince George’s County, Maryland (2007) 50 - 60% v/v sand 20 - 30% v/v well aged leaf compost, 20 - 30% v/v topsoil2 Clay content < 5% v/v
The SUDS manual (Woods-Ballard et al. 2007) 35 - 60% v/v sand, 30 - 50% v/v silt 0 - 4% v/v organic matter 10 - 25% v/v clay content
Facility for Advanced Water Biofiltration (FAWB, 2009a) Washed, well graded sand with specified PSD band 3% w/w organic material Clay content < 3% w/w, top 100 mm to be ameliorated with organic matter and fertilizer
Seattle Public Utilities (2008) 60 - 65% v/v mineral aggregate, PSD limit (“clean sand” with 2 - 5% passing #200 sieve), U3 ≥ 4 35 - 40% v/v fine compost which has > 40% w/w organic matter content
Puget Sound Partnership (2009) 40% v/v compost, or 8 - 10% w/w organic matter
North Carolina Cooperative Extension Service (Hunt & Lord 2006) 85 - 88% v/v washed medium sand4 3 - 5% v/v organic matter 8 - 12% v/v silt and clay
City of Austin (2011) 70 - 80% v/v concrete sand5 20 - 30% v/v screened bulk topsoil2 70 - 90% sand content, 3 - 10% clay content, silt and clay content < 27% w/w. Warning not to use sandy loam (“red death”).6

1 % v/v is percent by volume; % w/w is percent by weight (mass)
2“Topsoil” is a non-technical term for the upper or outmost layer of soil, however there is no technical standard for topsoil.
3U, Coefficient of Uniformity = D60/D10, where D60 is particle diameter at 60% passing and D10 is particle diameter at 10% passing.
4A specific definition for “medium sand” was not identified. ASTM D2487-10 classifies coarse-grained sandsas those with > 50% retained on the (USA) No. 200 sieve (75 m) and > 50% of coarse fraction passing the No. 4 sieve (4.76 mm). Clean sands contain < 5% fines. Fine-grained soils are silts and clays whereby > 50% passes the No. 200 sieve.
5Concrete sand is described by ASTMD2487-10 as coarse sand that is retained by a (USA) No. 10 sieve (2.00mm)
6“Red death” is commercially available fill material in Austin marketed as sandy loam.

This page was last edited on 15 April 2020, at 17:23.

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