Landcom Book 4 Maintenance - WSUD

Water Sensitive Urban Design
Item to be
Monitored
Purpose of
Monitoring
Performance
Target
Schedule
Maintenance or
Investigation
Immediate
Action Required
Maintenance
Action Required
Plant
Condition
Plants are crucial to the performance
of a bioretention system.
Healthy vegetation
Poorly growing or
visibly stressed
Die back / dead
plants
Schedule an investigation into the
cause of plant die-back or poor health.
During dry periods: Plants help
maintain the structure and porosity of
the filter media.
During rainfall events: Vegetation
aboveground acts to retard and
distribute flows, and provides scour
protection if the bioretention system
is designed as a swale. Below ground
the roots provide an important media
for trapping or absorbing pollutants as
they percolate through the media.
Maintenance action will depend on the
cause of die-back or poor plant health.
Once the problem is rectified, infill
planting may be required, especially if
more than 1 square meter of plantings
has died. Infill planting must be as per
the original planting schedule.
The accumulation of dead plant
material can detract from the visual
amenity of the bioretention system.
Litter
(organic)
Organic litter can provide an additional
source of nutrients to the bioretention
system, introduce non-native species,
which out-compete native plants and
block the filter media.
Accumulated organic matter / litter
can also cause offensive odours
(such as methane gas and hydrogen
sulphide, i.e. rotten egg gas) and can
reduce percolation of water into the
filter media.
No litter visible Litter visible Litter thickly covers
filter media surface or
detracting from visual
amenity
Identify source of organic litter and
address with appropriate response
action: e.g. change of landscape
maintenance practices; community
education re: litter dumping
(appropriate for repeat incidences).
In the interim, all litter must be
removed by maintenance crews.
Litter
(anthropogenic)
Litter can potentially block the
inlet and outlet structures of the
bioretention system resulting in
flooding, as well as detract from the
system’s visual amenity.
No litter visible Litter visible Litter blocking
structures or
detracting from visual
amenity
Identify source of rubbish: e.g. from
catchment (commercial precinct);
overflow of rubbish bins; accumulation
in backwater area and schedule
general maintenance to remove
rubbish. Where required address
source of rubbish (e.g. increase in
frequency of rubbish bin emptying;
gross pollutant traps in high load
generation land uses). In the
interim, all litter must be removed by
maintenance crews.
WARNING: Contact with sharp objects,
including hypodermic needles is a
risk when removing litter. All workers
must be made aware of this risk, wear
appropriate protective gear and use
caution.
Oil slicks
Oil spills / inflows are not necessarily
an impedance to bioretention system
function. Bioretention systems
are designed to remove oils from
stormwater; hydrocarbons decompose
relatively quickly in the presence
of soil microbes and water. It is
expected that fuel or oil trapped in the
bioretention basin would decompose
within two to three weeks, depending
on the size of the oil spill.
No visible oil
Persistent but limited
visible oil
Extensive or localised
thick layer of oil
visible
Do not isolate bioretention system
in the case of an oil spill - it is better
that the oil is contained within the
system than allowed to flow to the
downstream water course.
Notify the EPA of the spill and clean-up
requirements
NOTE: do not add any fertiliser, or
other nitrogen based product to the
system. The microbes within the filter
media are capable of decomposing
hydrocarbons.
26 Book 4 | MAINTENANCE