Landcom Book 4 Maintenance - WSUD

Water Sensitive Urban Design
6.4 Filter Media
Specifications
The Facility for Advancing Water
Biofiltration (FAWB), a joint collaboration
between Monash University and Ecological
Engineering Holdings recently updated
the original filter media specifications
produced in 2006. Specifications are
given for the three main layers defined for
a bioretention basin as described in the
table below.
Further details relating to the testing
of hydraulic conductivity, the specific
filter media specifications (for example,
organic matter content, pH, electrical
conductivity and phosphorus content),
and particle size distribution can be found
in the FAWB document Guidelines For
Soil Filter Media In Bioretention Systems
(version 2.01). http://www.clearwater.asn.
au/resources/658_1.FAWB%20Filter%20
media%20guidelines_revised_March%20
2008.pdf
Recently, bioretention basin design has
evolved to include an anoxic zone. In 2008,
FAWB conducted a series of workshops on
biofiltration systems, which included the
design requirements and performance
of biofiltration systems with submerged
zones. The workshop material made the
following specifications:
1. Depth of submerged zone –
approximately 450 mm.
2. Media specifications – sand
or gravel, containing a carbon
source such as hardwood chips
or sugar cane. The carbon source
is to account for 5 percent of the
volume of the submerged zone
media.
The workshop manual produced by FAWB
can be downloaded from the following url:
h t t p: // w w w.m o n a s h.e d u.au/ f a w b/
products/index.html
Filter Media (typically 400 to
600 millimetres in depth)
Loamy sand, with an appropriate hydraulic
conductivity (100 to 300 millimetres per hour)
and soil properties given in AS4419 – 2003 (Soils
for Landscaping and Garden Use)
Drainage Layer (typically 150
millimetres in depth)
Clean, well graded sand / coarse sand material
(containing no/little fines)
Transition Layer (typically
100 millimetres in depth,
or sufficient to provide
50 millimetres of cover to
drainage network)
Clean fine gravel
48 Book 4 | MAINTENANCE