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