Landcom Book 4 Maintenance - WSUD
Landcom Book 4 Maintenance - WSUD
Landcom Book 4 Maintenance - WSUD
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Water Sensitive Urban Design<br />
<strong>Book</strong> 4 | maintenance<br />
Draft
Water Sensitive Urban Design<br />
<strong>Book</strong> 4 | MAINTENANCE<br />
Table of Contents<br />
1 | Introduction 4<br />
2 | Key Operational and <strong>Maintenance</strong> Issues<br />
Identified By Stakeholder Local Councils 6<br />
3 | <strong>WSUD</strong> Elements 8<br />
3.1 Bioretention Basins 8<br />
3.2 Constructed Wetlands and Ponds 9<br />
3.3 Sedimentation Basins 11<br />
4 | Life Cycle Costing 12<br />
4.1 What are the Life Cycle Costs of <strong>WSUD</strong> Elements 13<br />
4.2 How does the LCC of <strong>WSUD</strong> development compare<br />
with that of conventional drainage infrastructure 17<br />
5 | Monitoring and <strong>Maintenance</strong> of <strong>WSUD</strong> Elements 18<br />
5.1 Performance Monitoring Requirements 20<br />
5.2 <strong>Maintenance</strong> Requirements 21<br />
5.2.1 Predictive maintenance 21<br />
5.2.2 Regular inspection and maintenance 22<br />
5.2.3 Bioretention mystems 22<br />
5.2.4 Constructed wetlands and ponds 27<br />
5.2.5 Sedimentation basins 31<br />
5.3 Waste Management and Disposal 35<br />
5.3.1 Dewatered silt 36<br />
5.3.2 Filter media 36<br />
5.3.3 Liquid waste (from dewatering activities) 37<br />
5.3.4 Equipment requirements 37<br />
6 | Construction Requirements 38<br />
6.1 Staging 38<br />
6.1.1 Stage 1: Civil construction (or functional installation) 40<br />
6.1.2 Stage 2: Building phase protection<br />
(or sediment and erosion control) 42<br />
6.1.3 Stage 3: Operational establishment<br />
(civil and/or landscaping) 44<br />
6.2 Construction Tolerances 46<br />
6.3 Construction Certification and Compliance 47<br />
6.4 Filter Media Specifications 48<br />
Appendix A – Construction Inspection and Sign off sheets 49<br />
A.1 Bioretention Systems 50<br />
A.2 Constructed Wetlands 58<br />
A.3 Sedimentation Basins / Ponds 68<br />
Appendix B – Regular <strong>Maintenance</strong> Checklists 75<br />
B.1 Bioretention Basins 76<br />
B.2 Constructed Wetlands 78<br />
B.3 Sedimentation Basin 80<br />
B.4 Ponds 82<br />
Appendix C – Asset handover sheets 84<br />
Appendix D – References 85<br />
<strong>Book</strong> 4 | MAINTENANCE 3
Water Sensitive Urban Design<br />
1 | Introduction<br />
<strong>Landcom</strong> has<br />
implemented a<br />
range of innovative<br />
Water Sensitive<br />
Urban Design<br />
(<strong>WSUD</strong>) initiatives<br />
since 2003.<br />
Since 2003 <strong>Landcom</strong> has embarked on<br />
ensuring that all its projects have a strong<br />
sustainability underpinning, as reflected<br />
in its annual Triple Bottom Line reporting.<br />
<strong>Landcom</strong> prepared a Water Sensitive<br />
Urban Design Policy in 2003 and published<br />
its Water Sensitive Urban Design Strategy<br />
in 2004. Since that time <strong>Landcom</strong> have<br />
progressed steadily towards attaining the<br />
best practice objectives of urban water<br />
management in all its projects. <strong>Landcom</strong><br />
has implemented a range of innovative<br />
Water Sensitive Urban Design (<strong>WSUD</strong>)<br />
initiatives since 2003, which build upon<br />
and extend elements of the original<br />
<strong>WSUD</strong> strategy.<br />
This document forms part of a 4-book set<br />
that updates and revises the <strong>Landcom</strong><br />
Water Sensitive Urban Design Strategy<br />
of 2004 as published. Recent advances<br />
in integrated water cycle management<br />
and <strong>WSUD</strong>, such as the release of<br />
Australian Runoff Quality 1 , the BASIX<br />
scheme, MUSIC (v3) and wider<br />
implementation have seen the stormwater<br />
industry evolve over the last three<br />
years. During this period the NSW<br />
Government has also revised its statewide<br />
water management objectives for new<br />
developments.<br />
1<br />
Engineers Australia (2006), Australian Runoff<br />
Quality: A Guide to Water Sensitive Urban Design,<br />
Wong, T H F (ed), ISBN 0 85825 852 8, Engineers<br />
Australia, Canberra, Australia, 2006<br />
4 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
<strong>Landcom</strong>’s Water Sensitive Urban Design Strategy (2009) is contained in the<br />
following 4 books:<br />
<strong>Book</strong> 1 | <strong>Landcom</strong>’s <strong>WSUD</strong> Policy and Urban Water Management Objectives consisting of:<br />
••<br />
an overview of Water Sensitive Urban Design<br />
••<br />
a revision of the <strong>WSUD</strong> Targets and Mandatory <strong>WSUD</strong> Requirements to ensure appropriateness<br />
and relevance, including proposed realistic and appropriate “Stretch Targets” which <strong>Landcom</strong> may<br />
consistently apply in projects where warranted, and linkages to TBL reporting criteria<br />
••<br />
key components of a project-specific <strong>WSUD</strong> strategy<br />
<strong>Book</strong> 2 | Attaining <strong>Landcom</strong> <strong>WSUD</strong> Objectives consisting of descriptions and discussions on urban water best<br />
planning and management practices applicable to <strong>Landcom</strong> projects including information on:<br />
••<br />
how to meet the water conservation targets, including information on BASIX and information on<br />
wastewater and greywater technologies<br />
••<br />
how to meet the stormwater quality targets, including proposed changes to ensure consistency with<br />
<strong>Landcom</strong>’s Street Design Guide<br />
••<br />
how to meet the flow management targets<br />
<strong>Book</strong> 3 | Case studies and discussions on how water sensitive urban design could be integrated into <strong>Landcom</strong><br />
Development Projects, including examples of:<br />
••<br />
<strong>WSUD</strong> in the planning phase – Renwick<br />
••<br />
<strong>WSUD</strong> in the implementation phase - Prince Henry Hospital and The Ponds<br />
••<br />
<strong>WSUD</strong> after years of operation – Victoria Park<br />
<strong>Book</strong> 4 | Operation and maintenance guidelines of key <strong>WSUD</strong> elements including:<br />
••<br />
life cycle costing of bioretention systems, constructed wetlands and ponds<br />
••<br />
monitoring and maintenance practice and associated checklist<br />
••<br />
construction considerations and associated checklist for construction inspection and asset handover<br />
This document (<strong>Book</strong> 4) describes operational and maintenance practices of a number of key <strong>WSUD</strong> elements<br />
commonly adopted in <strong>Landcom</strong> projects. <strong>Book</strong> 4 was prepared in response to a recurring set of enquiries from<br />
local government on the topics of construction, and ongoing operation and maintenance of <strong>WSUD</strong> elements.<br />
There was a clear desire to have a common set of understanding of the various considerations on these issues.<br />
<strong>Book</strong> 4 | MAINTENANCE 5
Water Sensitive Urban Design<br />
2 | Key Operational And <strong>Maintenance</strong> Issues<br />
Identified By Stakeholder Local Councils<br />
Bioretention system in the public domain | Prince Henry<br />
6 <strong>Book</strong> 4 | MAINTENANCE<br />
In preparing the booklet on <strong>WSUD</strong><br />
Operation and <strong>Maintenance</strong>, two half-day<br />
workshops with invited Local Government<br />
representatives were organised. The<br />
first of these half-day workshops was<br />
held in December 2008. That workshop<br />
served as a platform for Council’s to<br />
present their considerations in approving<br />
<strong>WSUD</strong> elements in land development<br />
projects, concerns with the maintenance<br />
and operation of <strong>WSUD</strong> elements and<br />
information gaps in maintaining and<br />
operating <strong>WSUD</strong> elements.<br />
Representatives from the following<br />
Councils were present at one or both<br />
workshops:<br />
••<br />
Auburn Council<br />
••<br />
Bankstown City Council<br />
••<br />
Blacktown City Council<br />
••<br />
Camden Council<br />
••<br />
Campbelltown City Council<br />
••<br />
City of Sydney<br />
••<br />
Fairfield City Council<br />
••<br />
Hills Shire Council<br />
••<br />
Hunters Hill Council<br />
••<br />
Ku-ring-gai Council<br />
••<br />
Liverpool City Council<br />
••<br />
Penrith City Council<br />
••<br />
Pittwater Council<br />
••<br />
Sydney Metropolitan Catchment<br />
Authority<br />
••<br />
Western Sydney Regional Organisation<br />
of Councils<br />
••<br />
Wingecarribee Shire Council<br />
••<br />
Wollongong City Council<br />
Following this first workshop, the issues<br />
identified were grouped into three<br />
categories:<br />
1) Life cycle cost considerations of <strong>WSUD</strong><br />
strategies<br />
2) Monitoring and maintenance of <strong>WSUD</strong><br />
elements<br />
3) Construction considerations of <strong>WSUD</strong><br />
elements
Water Sensitive Urban Design<br />
Woolwash Park Biofiltration | Victoria Park<br />
The booklet is<br />
structured to<br />
address frequently<br />
asked questions<br />
regarding<br />
construction,<br />
maintenance and<br />
operational issues<br />
of <strong>WSUD</strong> elements.<br />
A draft response was compiled for<br />
specific issues within the three categories<br />
identified. The responses reference<br />
current best practice guidelines and<br />
industry experience. These were then<br />
discussed and reviewed in a second<br />
half-day workshop held in March 2009<br />
involving participants on the first<br />
workshop. This second workshop was<br />
also attended by representatives from a<br />
wider group of local councils.<br />
The 4 th booklet in the <strong>Landcom</strong> <strong>WSUD</strong><br />
booklet series addresses operation and<br />
maintenance concerns of select <strong>WSUD</strong><br />
elements. The booklet is structured<br />
to address frequently asked questions<br />
regarding construction, maintenance and<br />
operational issues of <strong>WSUD</strong> elements as<br />
identified from a focus group of Councils.<br />
The booklet does not aim to recreate or<br />
reiterated current best practice guidelines<br />
for the purpose of Councils. Rather the<br />
booklet provides a consolidated response<br />
to the issues raised, with information<br />
supported by appropriate references/<br />
links to where additional information can<br />
be sourced.<br />
The responses compiled have been<br />
limited to the following <strong>WSUD</strong> elements:<br />
••<br />
Constructed wetlands<br />
••<br />
Bioretention basins<br />
••<br />
Sedimentation basin / ponds<br />
The responses, in particular to monitoring<br />
and maintenance requirements, assume<br />
that the <strong>WSUD</strong> strategy has been<br />
designed and constructed to meet best<br />
management practice objectives and<br />
design guidelines.<br />
<strong>Book</strong> 4 | MAINTENANCE 7
Water Sensitive Urban Design<br />
3 | <strong>WSUD</strong> Elements<br />
Examples of bioretention systems in streetscapes<br />
3.1 Bioretention Basins<br />
Bioretention<br />
systems can<br />
provide a degree<br />
of flow attenuation<br />
and hence reduce<br />
the volume and<br />
frequency of<br />
runoff delivered<br />
to downstream<br />
waterways.<br />
Bioretention systems are vegetated filter<br />
systems designed to allow water to pool<br />
temporarily before percolating through<br />
the filter media. The filter media controls<br />
the flowrate of water through the system,<br />
as well as providing a growing media for<br />
the plants. The filtered water is directed<br />
via perforated pipes to the existing<br />
stormwater system, natural waterways or<br />
a detention basin for reuse. Bioretention<br />
systems can provide a degree of flow<br />
attenuation and hence reduce the volume<br />
and frequency of runoff delivered to<br />
downstream waterways (ARQ, 2006).<br />
Critical to the performance of a<br />
bioretention system is the filter media<br />
and vegetation. The filter media needs<br />
to provide a hydraulic conductivity that<br />
ensures sufficient contact time is available<br />
for pollutants to be taken up by biofilms.<br />
Vegetation root systems provide the<br />
surfaces for the epiphytic biofilms that<br />
take up dissolved pollutants. Vegetation is<br />
also critical in maintaining the porosity of<br />
the soil media of the bioretention system.<br />
Bioretention systems can be integrated<br />
into open space areas and streetscapes<br />
(for example, parking stations and traffic<br />
calming devices). The systems can take<br />
the form of a basin or a swale. A basin is<br />
typically employed for relatively flat areas.<br />
Swales provide a stormwater treatment<br />
and flow conveyance role and are suitable<br />
for long linear sites with a grade ranging<br />
between one and four percent. For some<br />
sites, a combined bioretention basin and<br />
a conventional swale may be required.<br />
8 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Examples of constructed wetlands<br />
3.2 Constructed Wetlands<br />
and Ponds<br />
The deep open<br />
water bodies<br />
typical of ponds<br />
provide larger<br />
detention volumes<br />
as compared<br />
to constructed<br />
wetlands.<br />
Constructed wetlands use enhanced<br />
sedimentation, fine filtration and biological<br />
uptake processes to remove pollutants<br />
from stormwater. The wetland processes<br />
are engaged by slowly passing runoff<br />
through heavily vegetated areas where<br />
plants filter sediments and pollutants from<br />
the water. Biofilms that grow on the plants<br />
can absorb nutrients and other associated<br />
contaminants.<br />
Ponds also provide physical, biological<br />
and chemical mechanisms for pollutant<br />
uptake. The main physical difference<br />
between a pond and a constructed<br />
wetland is the ratio of surface area to<br />
volume and the coverage by vegetation<br />
(ARQ, 2006). Typically ponds have a depth<br />
exceeding 1.5 meters as compared to<br />
constructed wetlands, which have an<br />
average depth in the macrophyte zone of<br />
0.3 metres. Furthermore, a regular water<br />
level fluctuation regime is promoted in a<br />
constructed wetland through the design<br />
of the outlet structures. Combined, the<br />
high surface area to volume ratio and<br />
the promotion of regular water level<br />
fluctuation through the design of the<br />
outlet structure in a constructed wetland,<br />
supports a densely vegetated system<br />
and hence a greater biological uptake of<br />
pollutants as compared to a pond.<br />
The deep open water bodies typical of<br />
ponds provide larger detention volumes<br />
as compared to constructed wetlands.<br />
Higher detention times promote improved<br />
sedimentation; however the risk of large<br />
open water bodies is short circuiting,<br />
redox potential conditions and elevated<br />
levels of nutrients. These processes can<br />
have a reverse effect on stormwater<br />
treatment causing release of pollutants<br />
from the sediment into the water. High<br />
nutrient concentrations can also lead to<br />
nuisance macrophyte growth or algal<br />
blooms that can be toxic and aesthetically<br />
unpleasant.<br />
For these reasons, ponds are commonly<br />
designed in combination with constructed<br />
wetlands, providing polishing of<br />
stormwater quality, attenuation of flows<br />
and protection of downstream waterways,<br />
and storage for reuse applications.<br />
<strong>Book</strong> 4 | MAINTENANCE 9
Water Sensitive Urban Design<br />
Wetland | Koala Bay<br />
Table 1 | Stormwater treatment processes of constructed wetlands and ponds<br />
Constructed Wetlands<br />
Physical – Sedimentation<br />
••<br />
Traps suspended solids – vegetation in the<br />
wetland facilitates enhanced sedimentation of<br />
particles down to the fine fractions<br />
••<br />
Traps adsorbed pollutants – traps a higher<br />
proportion of adsorbed pollutants through<br />
higher capture of fine particles<br />
Biological and Chemical Uptake<br />
••<br />
Traps dissolved pollutants – vegetation<br />
provides surfaces for epiphytic biofilms, which<br />
take up dissolved pollutants<br />
••<br />
Chemical adsorption of pollutants to fine<br />
suspended particles which are trapped through<br />
enhanced sedimentation and surface filtration<br />
facilitated by macrophytes and biofilms<br />
••<br />
Promotes rapid biodegradation of organic<br />
material<br />
Pollutant transformation<br />
••<br />
The regular wetting and drying cycle<br />
progressively leads to less reversible sediment<br />
fixation of contaminants in the substratum<br />
Ponds<br />
Physical – Sedimentation<br />
••<br />
Traps ‘readily settleable solids’ – settling of<br />
solids down to coarse and medium sized silt<br />
fractions<br />
••<br />
Traps adsorbed pollutants – silt particles<br />
trapped in the pond system may also retain<br />
adsorbed pollutants<br />
••<br />
Promotes flocculation of smaller particles<br />
Biological and Chemical Uptake<br />
••<br />
Biological uptake of soluble pollutants<br />
predominately by phytoplankton, which remains<br />
in the water column and is susceptible to washoff<br />
during the next storm event<br />
••<br />
Chemical adsorption of pollutant to fine<br />
suspended sediment which remains in the water<br />
column for extended periods and is susceptible<br />
to washoff during the next storm event<br />
••<br />
UV disinfection of waterbody by sunlight<br />
Pollutant transformation<br />
••<br />
Pollutants adsorbed to deposited sediment are<br />
susceptible to release under conditions of low<br />
redox potential caused by high organic loading<br />
and pond stratification<br />
Table taken from Australian Runoff Quality (Engineers Australia, 2006)<br />
10 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Examples of sedimentation basins and ponds<br />
3.3 Sedimentation Basins<br />
Due to the nature<br />
of a sedimentation<br />
basin, regular clean<br />
out and removal<br />
of accumulated<br />
sediment is<br />
required.<br />
Sedimentation basins are stormwater<br />
detention systems that promote the<br />
settling of coarse sediment (defined<br />
as particles greater than 125 microns<br />
in diameter). A sedimentation basin<br />
can be an integral part of a treatment<br />
train, providing primary removal of<br />
coarse sediment. Removal of coarse<br />
sediment is particularly important in<br />
protecting downstream systems from<br />
high sediment loading, which can reduce<br />
the effectiveness of the system. The<br />
treatment performance of a bioretention<br />
system is particularly susceptible to high<br />
sediment loadings: sediment can smother<br />
vegetation and clog the filter media<br />
affecting the percolation of stormwater<br />
through the media. Sediment basins can<br />
also be employed for temporary sediment<br />
and erosion control during construction<br />
activities.<br />
Due to the operation of a sedimentation<br />
basin, regular clean out and removal<br />
of accumulated sediment is required.<br />
Sedimentation basins are generally<br />
designed for a clean out frequency of<br />
five years, which equates to a volume<br />
half that of the permanent pool (defined<br />
by the invert of the outlet structure).<br />
The sedimentation basin design should<br />
include an access ramp to allow entry for<br />
a clean-out truck.<br />
<strong>Book</strong> 4 | MAINTENANCE 11
Water Sensitive Urban Design<br />
4 | Life Cycle Costing<br />
Bioswale | Victoria Park<br />
Indirect tangible<br />
benefits associated<br />
with well designed<br />
and constructed<br />
<strong>WSUD</strong> elements are<br />
the environmental<br />
outcomes such<br />
as reductions<br />
in potable<br />
water demands,<br />
downstream<br />
pollution and<br />
waterway<br />
rehabilitation<br />
works.<br />
An important part of implementing<br />
<strong>WSUD</strong> strategies is the cost the systems<br />
pose to Councils. There are many<br />
approaches to computing and accounting<br />
the cost of infrastructure. In the case of<br />
land development, the capital cost is<br />
often borne by the developer with the<br />
asset subsequently assumed by local<br />
government with associated maintenance<br />
and renewal responsibilities.<br />
The life cycle cost of an asset is made up of<br />
its capital cost, operational and<br />
maintenance cost, renewal cost and<br />
decommissioning cost. Often not<br />
included in a life cycle cost/benefit<br />
analysis are the benefits both directly<br />
accrued to the development, and<br />
indirectly attributed to the works within<br />
the development. The benefits directly<br />
accrued to the development are reflected<br />
in the increased demand for properties in<br />
the development as reflected in the sale<br />
price. Indirect tangible benefits associated<br />
with well designed and constructed<br />
<strong>WSUD</strong> elements are the environmental<br />
outcomes such as reductions in potable<br />
water demands, downstream pollution<br />
and waterway rehabilitation works.<br />
Organisations are now considering the<br />
total community costs in evaluating water<br />
management strategies.<br />
12 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
The impact of<br />
maintenance and<br />
renewal costs is<br />
dependent on the<br />
expected life span<br />
of the asset.<br />
4.1 What are the Life<br />
Cycle Costs of<br />
<strong>WSUD</strong> Elements<br />
Life cycle costing is a process to determine<br />
the sum of all expenses associated with a<br />
product or project, including acquisition,<br />
installation, operation, maintenance,<br />
refurbishment, discarding and disposal<br />
costs (Standards Australia, 1999). The life<br />
cycle costs (LCC) for <strong>WSUD</strong> elements<br />
include the total acquisition cost (TAC),<br />
the total annual maintenance (TAM),<br />
renewal, and decommissioning costs. The<br />
impact of maintenance and renewal costs<br />
is dependent on the expected life span<br />
of the asset. The decommissioning cost<br />
in some <strong>WSUD</strong> systems, such as<br />
constructed wetlands, may be irrelevant as<br />
they are designed to operate in perpetuity.<br />
All life cycle costs are discounted back to<br />
a base date (date of installation).<br />
How is the Life Cycle Costs Calculated?<br />
The supporting user manual for the Model<br />
for Urban Stormwater Improvement<br />
Conceptualisation (MUSIC, version 3)<br />
developed by the Cooperative Research<br />
Centre for Catchment Hydrology (CRCCH)<br />
provides a summary of the life cycle costs<br />
associated with bioretention systems,<br />
wetlands, ponds and sedimentation<br />
basins. A summary of the parameters<br />
affecting the LCC of these elements is<br />
given in Table 2.<br />
In many cases, MUSIC uses an algorithm to<br />
define a particular life cycle cost element<br />
in terms of the treatment area. These<br />
algorithms have been developed based<br />
on real data collected between 2002 and<br />
2004.<br />
<strong>Book</strong> 4 | MAINTENANCE 13
Water Sensitive Urban Design<br />
Table 2 | Life cycle cost parameters for specified <strong>WSUD</strong> elements.<br />
Life Cycle Cost<br />
element<br />
Bioretention<br />
Wetlands<br />
Ponds &<br />
Sedimentation Basins<br />
Life cycle 25 to 50 years 15 to 80 years (with 50<br />
years used as the default in<br />
MUSIC)<br />
Wetlands are designed to<br />
have an infinite life span.<br />
However, to determine<br />
a life cycle cost, a finite<br />
number needs to be set<br />
5 year (sedimentation<br />
basins)<br />
50 years (ponds)<br />
Total acquisition<br />
cost (TAC)<br />
(per m 2 )<br />
387.4 x (A) 0.7673<br />
$1000/m 2 for first 20 m 2<br />
($200/m 2 for remaining<br />
area)<br />
1911 x (A) 0.6435<br />
The treatment area<br />
used in defining the<br />
total acquisition cost is<br />
the combined inlet and<br />
macrophyte zone area<br />
685.1 x (A) 0.7893<br />
Total annual<br />
maintenance (TAM)<br />
(%TAC)<br />
48.87 x (TAC) 0.4410 6.831 x (A) 0.8634 185.4 x (A) 0.4780<br />
The annual maintenance<br />
cost considers the volume<br />
of material likely to be<br />
removed from the basin<br />
per year (referred in MUSIC<br />
as the size attribute, V).<br />
The size attribute is the<br />
sum of gross pollutants,<br />
coarse sediment and total<br />
suspended solids (TSS)<br />
that are trapped in the<br />
basin / pond per year<br />
Renewal period<br />
(years)<br />
25 20<br />
Renewal considerations<br />
include replanting and<br />
recontouring of the<br />
macrophyte zone<br />
1 year (default in MUSIC<br />
due to lack of evidence).<br />
10 years based on<br />
available data<br />
Renewal costs<br />
(%TAC p.a.)<br />
2.0% 0.52% 1.4%<br />
Costs associated with<br />
access ramps and<br />
contouring<br />
Limited data available<br />
Decommisioning costs<br />
(% TAC)<br />
38% - only applicable to<br />
sedimentation basins<br />
14 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
What is the Annualised Life<br />
Cycle Cost with respect to<br />
pollutant removal?<br />
The annualised life cycle cost is simply the<br />
Net Present Value (NPV) of the life cycle<br />
cost divided by the life cycle (years) of the<br />
asset.<br />
In developing an example of annualised<br />
life cycle cost, a series of analyses were<br />
undertaken for an asset life cycle period of<br />
50 years. Three different <strong>WSUD</strong> elements<br />
were assessed: bioretention basins,<br />
constructed wetlands, and sedimentation<br />
basins.<br />
Bioretention basins and constructed<br />
wetlands were sized to meet best<br />
management practice pollutant load<br />
reductions for total nitrogen (TN) removal<br />
(that is, 45 percent). The sedimentation<br />
basin was sized to remove 80 percent of<br />
coarse sediment (greater than 125 microns),<br />
while also ensuring the associated clean<br />
out frequency of the basin was a minimum<br />
of 5 years. The life cycle costs are shown in<br />
Figure 1 to Figure 3.<br />
The results are useful in showing the<br />
relative cost of maintenance to upfront<br />
capital cost and in particular the relatively<br />
low cost of maintaining these systems. For<br />
example, the annual maintenance cost of<br />
a bioretention basin sized for a 1 hectare<br />
impervious catchment is approximately 3<br />
percent of the capital cost.<br />
In the life cycle cost figures for each<br />
<strong>WSUD</strong> element (Figure 1 to Figure 3), the<br />
annualised cost in terms of pollutant load<br />
reductions are also reported. Such data is<br />
useful in:<br />
••<br />
assessing the efficiency of one <strong>WSUD</strong><br />
element against another in removing a<br />
specific pollutant<br />
••<br />
comparing the cost of <strong>WSUD</strong> elements<br />
against other pollutant abatement<br />
technology<br />
The annualised cost in terms of pollutant removal for a 1 hectare completely<br />
impervious catchment are:<br />
Bioretention Basin:<br />
− $70 per kg TN removed (45% reduction)<br />
− $320 per kg TP removed (67% reduction)<br />
− $1 per kg TSS removed (81% reduction)<br />
Constructed Wetland:<br />
− $440 per kg TN removed (45% reduction)<br />
− $2,300 per kg TP removed (70% reduction)<br />
− $3 per kg TSS removed (86% reduction)<br />
Sedimentation Basin:<br />
− $500 per kg TN removed (4% reduction)<br />
− $800 per kg TP removed (17% reduction)<br />
− $1 per kg TSS removed (30% reduction)<br />
<strong>Book</strong> 4 | MAINTENANCE 15
Water Sensitive Urban Design<br />
$18,000<br />
$16,000<br />
$14,000<br />
$12,000<br />
Bioretention basin sized to remove 45 percent of TN pollutant<br />
loads generated from a 1 hectare, 100 percent impervious<br />
catchment (road)<br />
Annualised cost of system in terms of pollutant load reductions<br />
are:<br />
/ $70 per kg TN removed<br />
/ $320 per kg TP removed<br />
/ $1 per kg TSS removed<br />
Cost ($)<br />
$10,000<br />
$8,000<br />
Decomissioning Cost<br />
Renewal Cost<br />
<strong>Maintenance</strong> Cost<br />
Capital Cost<br />
$6,000<br />
$4,000<br />
$2,000<br />
$-<br />
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49<br />
Time (years)<br />
Figure 1: LCC for bioretention basins<br />
$140,000.00<br />
$120,000.00<br />
$100,000.00<br />
Constructed wetland sized to remove 45 percent of TN pollutant<br />
loads generated from a 1 hectare, 100 percent impervious<br />
catchment (road)<br />
Annualised cost of system in terms of pollutant load reductions<br />
are:<br />
/ $440 per kg TN removed<br />
/ $2300 per kg TP removed<br />
/ $3 per kg TSS removed<br />
Cost ($)<br />
$80,000.00<br />
$60,000.00<br />
Decomissioning Cost<br />
Renewal Cost<br />
<strong>Maintenance</strong> Cost<br />
Capital Cost<br />
$40,000.00<br />
$20,000.00<br />
$-<br />
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49<br />
Time (years)<br />
Figure 2: LCC for constructed wetlands<br />
16 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
$6,000.00<br />
$5,000.00<br />
$4,000.00<br />
Sediment basin sized to remove 80 percent of course sediment<br />
(defined as particles greater than 125 microns) for a 1 hectare,<br />
100 percent impervious catchment (road)<br />
Annualised cost of system in terms of pollutant load reductions<br />
are:<br />
/ $500 per kg TN removed<br />
/ $800 per kg TP removed<br />
/ $1 per kg TSS removed<br />
Cost ($)<br />
$3,000.00<br />
$2,000.00<br />
Decomissioning Cost<br />
Renewal Cost<br />
<strong>Maintenance</strong> Cost<br />
Capital Cost<br />
$1,000.00<br />
$-<br />
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49<br />
Time (years)<br />
Figure 3: LCC for sedimentation basins<br />
4.2 How does the LCC of <strong>WSUD</strong> development compare<br />
with that of conventional drainage infrastructure<br />
The life cycle costs of water sensitive urban design measures were assessed by Lloyd et al.<br />
(2002) for one of the original <strong>WSUD</strong> strategies implemented in Victoria (that is, Lynbrook<br />
Estate). The assessment considered three stormwater management scenarios:<br />
Conventional Approach:<br />
Downstream<br />
Stormwater Treatment:<br />
Distributed Stormwater<br />
Treatment:<br />
Stormwater is piped to the downstream waterway. No treatment of<br />
stormwater is considered.<br />
An end-of-pipe treatment system is employed to ensure the<br />
quality of discharged stormwater meets best management<br />
practice (BMP) objectives for pollutant load reductions.<br />
A series of <strong>WSUD</strong> elements are employed to remove pollutants at<br />
source, such that a greater volume of stormwater can be treated to<br />
BMP objectives.<br />
The assessment found the capital cost of a distributed system to be 22 percent greater<br />
than the conventional approach, while a downstream stormwater treatment cost an<br />
additional 47 percent. It should be noted that the cost of drainage infrustructure represents<br />
approximately 10% of the total cost of development.<br />
The range of annualised maintenance cost from the study was reported as:<br />
Approach<br />
Annualised <strong>Maintenance</strong><br />
Cost<br />
Annualised <strong>Maintenance</strong><br />
Cost per hectare<br />
Conventional Approach: $737 to $1,672 $27 to $62<br />
Downstream Stormwater Treatment: $2,336 to $6,371 $87 to $236<br />
Distributed Stormwater Treatment: $1,723 to $6,512 $64 to $241<br />
<strong>Book</strong> 4 | MAINTENANCE 17
Water Sensitive Urban Design<br />
5 | Monitoring and <strong>Maintenance</strong><br />
of <strong>WSUD</strong> Elements<br />
Watersteps | Victoria Park<br />
The information provided in this section will help Councils understand the<br />
monitoring and maintenance requirements of <strong>WSUD</strong> elements and assist<br />
in generating and/or assessing maintenance plans such that the associated<br />
monitoring and maintenance plan addresses:<br />
••<br />
inspection frequency<br />
••<br />
maintenance frequency<br />
••<br />
data collection/ storage requirements (i.e. during inspections)<br />
••<br />
detailed cleanout procedures (main element of the plans) including:<br />
––<br />
equipment needs<br />
––<br />
maintenance techniques<br />
––<br />
occupational health and safety<br />
––<br />
public safety<br />
––<br />
environmental management considerations<br />
––<br />
disposal requirements (of material removed)<br />
––<br />
access issues<br />
––<br />
stakeholder notification requirements<br />
––<br />
data collection requirements (if any)<br />
••<br />
design details<br />
The performance of <strong>WSUD</strong> elements<br />
is dependent on the maintenance<br />
considerations incorporated during their<br />
design. <strong>Maintenance</strong> personnel need<br />
to be involved during the design to<br />
ensure their requirements (for example,<br />
access) are addressed, they understand<br />
the functionality of the systems and the<br />
role of maintenance in ensuring design<br />
performance criteria are met, and to<br />
ensure appropriate maintenance budget<br />
is allocated.<br />
18 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Watersteps | Victoria Park<br />
Routine monitoring<br />
checks the status<br />
of key functional<br />
elements to<br />
ensure they meet<br />
specified design<br />
requirements and<br />
include ensuring<br />
that inlet and outlet<br />
structures are free<br />
of debris, and that<br />
well distributed<br />
vegetative cover<br />
of the system is<br />
maintained.<br />
Unlike traditional engineered structures,<br />
<strong>WSUD</strong> elements will only require minimal<br />
routine maintenance and these are<br />
generally of a landscape maintenance<br />
nature. For example, regular weeding<br />
should only be required during the<br />
establishment phase of a well designed<br />
and constructed system with appropriate<br />
planting density limiting the ‘free’ area<br />
available for weed growth. Removal of<br />
debris and siltation is the most common<br />
activity. <strong>Maintenance</strong> activities should<br />
primarily be prompted through predictive<br />
and routine monitoring. Predictive<br />
monitoring activities occur following<br />
significant storm events and are directed<br />
at assessing the performance of the<br />
system (for example, flow distribution<br />
and ponding duration). These activities<br />
help identify potential deviations in<br />
performance and initiate corrective<br />
maintenance actions.<br />
Routine monitoring checks the status of<br />
key functional elements to ensure they<br />
meet specified design requirements and<br />
include ensuring that inlet and outlet<br />
structures are free of debris, and that well<br />
distributed vegetative cover of the system<br />
is maintained.<br />
It is recommended that vegetated <strong>WSUD</strong><br />
elements are monitored by personnel<br />
with bush regeneration qualifications (as<br />
approved by Australian Association of<br />
Bush Regenerators). Bush regenerators<br />
are well equipped at identifying evasive<br />
species within a native landscape<br />
typical of vegetated <strong>WSUD</strong> systems.<br />
Furthermore, personnel in charge of<br />
monitoring should have a good idea and<br />
understanding of the layout and functional<br />
design of the treatment system. The<br />
maintenance activities prompted through<br />
monitoring activities will generally require<br />
coordination between landscape and civil<br />
services.<br />
The following section documents<br />
the monitoring and maintenance<br />
requirements for bioretention basins,<br />
constructed wetlands and sedimentation<br />
basins/ponds. The information given can<br />
be used to guide development of site<br />
specific maintenance plans for <strong>WSUD</strong><br />
developments. The plans will be used<br />
by maintenance personnel and asset<br />
managers to ensure the bioretention<br />
system functions as designed for its entire<br />
life cycle.<br />
<strong>Book</strong> 4 | MAINTENANCE 19
Water Sensitive Urban Design<br />
5.1 Performance Monitoring<br />
Requirements<br />
Surrogate methods<br />
can often be<br />
equally effective<br />
in evaluating the<br />
adequacies of the<br />
operation, and thus<br />
performance, of<br />
<strong>WSUD</strong> elements.<br />
Performance monitoring of <strong>WSUD</strong><br />
elements can be undertaken through<br />
detailed water sampling and laboratory<br />
analyses for contaminant concentrations or<br />
through the use of surrogate performance<br />
indicators. With the former, it will be<br />
necessary to set up field monitoring sites<br />
to undertake the water quality sampling at<br />
inlet and outlet of systems. The following<br />
points should be considered when setting<br />
up a sampling program:<br />
••<br />
Auto-sampling with partial or full<br />
composite samples is most cost<br />
effective<br />
••<br />
Monitoring should be accompanied by<br />
continuous flow and depth observations<br />
••<br />
Design of monitoring set up and<br />
sampling intervals is site dependent<br />
••<br />
20 events should be monitored as a<br />
minimum to obtain typical performance<br />
••<br />
The following key water quality<br />
parameters should be analysed in<br />
registered laboratories:-<br />
––<br />
TSS analysis should be<br />
undertaken<br />
––<br />
TP (with occasional filter of<br />
sample on-site with 0.45um filter<br />
to test for Orthophosphate)<br />
––<br />
TN (with occasional speciation to<br />
organic and inorganic nitrogen<br />
An implicit assumption made when water<br />
quality improvements are measured by<br />
comparing observed water quality at the<br />
inlet and outlet of the system, is that these<br />
water qualities represent the same ‘parcel’<br />
of water. Occasionally, especially with<br />
wetlands and ponds, negative or very low<br />
pollutant removal results for a system are<br />
observed. These results are common when<br />
the volume of an inflow event is less than<br />
the permanent pool volume of the wetland<br />
or pond. In the case of bioretention<br />
systems, accurately accounting for the<br />
volumetric balance of inflow, outflow,<br />
and soil moisture replenishment, is the<br />
main analytical problem that may lead to<br />
erroneous performance assessment.<br />
Surrogate methods can often be equally<br />
effective in evaluating the adequacies of<br />
the operation, and thus performance, of<br />
<strong>WSUD</strong> elements. They are often more cost<br />
effective and involve the monitoring of the<br />
hydrologic and hydraulic performance of<br />
these systems. The implicit assumption<br />
with surrogate methods is the premise<br />
that if the <strong>WSUD</strong> elements operate in<br />
accordance to the design hydrologic and<br />
hydraulic characteristics, it follows that<br />
these systems can be reasonably expected<br />
to deliver the pollutant reduction as<br />
determined from laboratory and field<br />
experiments.<br />
Key hydrologic and hydraulic operation<br />
characteristics define the detention<br />
time of <strong>WSUD</strong> elements. Monitoring of<br />
the following operation of bioretention<br />
systems, wetlands and ponds, can<br />
provide important insights on the likely<br />
performance of these <strong>WSUD</strong> elements in<br />
pollution reduction:<br />
••<br />
Flow pattern (most relevant to wetlands<br />
and ponds), to identify the presences<br />
of short-circuiting that may inhibit the<br />
uniform distribution of inflow to this<br />
system<br />
••<br />
Duration of inundation (most relevant<br />
to wetlands and bioretention systems)<br />
to assess the operating detention<br />
time of these systems and to highlight<br />
potential clogging of soil media<br />
(bioretention systems) or the outlet<br />
structure (wetlands) that would have<br />
a direct impact on its performance in<br />
water treatment<br />
••<br />
Turbidity of inflow and outflow which<br />
are good surrogates for suspended<br />
solids, total phosphorus, and metal in<br />
urban stormwater<br />
20 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
<strong>WSUD</strong><br />
infrastructure<br />
requires ongoing<br />
inspection and<br />
maintenance<br />
to ensure they<br />
establish and<br />
operate in<br />
accordance with the<br />
design intent.<br />
5.2 <strong>Maintenance</strong><br />
Requirements<br />
<strong>WSUD</strong> infrastructure requires ongoing<br />
inspection and maintenance to ensure<br />
they establish and operate in accordance<br />
with the design intent. Potential problems<br />
associated with <strong>WSUD</strong> infrastructure as a<br />
result of poor maintenance include:<br />
••<br />
Decreased aesthetic amenity<br />
••<br />
Reduced functional performance<br />
••<br />
Public health and safety risks<br />
••<br />
Decreased habitat diversity (dominance<br />
of exotic weeds)<br />
The most time-intensive period of<br />
maintenance for a vegetated system<br />
is during plant establishment (which<br />
typically includes two growing seasons),<br />
when supplementary watering, plant<br />
replacement and weeding may be<br />
required. Generally, <strong>WSUD</strong> elements are<br />
brought online through stages such that<br />
the functional elements are protected from<br />
elevated pollutant loads generated from a<br />
developing catchment. More information<br />
regarding staged construction is given in<br />
the next section of this booklet.<br />
Once <strong>WSUD</strong> elements are established<br />
and operational, on-going inspection,<br />
monitoring and maintenance will be<br />
required. <strong>Maintenance</strong> activities fall<br />
into one of two categories; predictive<br />
maintenance or regular maintenance.<br />
5.2.1 Predictive <strong>Maintenance</strong><br />
Predictive maintenance is scheduled<br />
based on inspections conducted after<br />
a significant storm event (defined<br />
qualitatively as an event likely to mobilise<br />
sediment and coarse material). Predictive<br />
inspections are critical to assessing the<br />
performance of the treatment system,<br />
in particular the hydraulic function and<br />
flow distribution of the system. Items<br />
that should be considered during the<br />
inspection are included over the page.<br />
<strong>Book</strong> 4 | MAINTENANCE 21
Water Sensitive Urban Design<br />
Ponding time<br />
Detention of flows above the design intent could indicate a blockage<br />
in the outlet structures. Typical drainage times for treatment systems<br />
are:<br />
••<br />
72 hours for a constructed wetland<br />
••<br />
6 to 24 hours for a bioretention basin<br />
••<br />
24 hours for a sedimentation basin<br />
Surface<br />
distribution<br />
of flows<br />
Flow should pond evenly within the treatment system<br />
Additionally, the absence of ponding after a significant storm event<br />
may indicate a blocked inlet (that is, flows are being prevented from<br />
entering the treatment system)<br />
Scouring<br />
Scouring can be indicative of a blocked inlet<br />
5.2.2 Regular Inspection and<br />
<strong>Maintenance</strong><br />
Generally, <strong>WSUD</strong> elements should be<br />
inspected every three months, with<br />
particular reference to:<br />
••<br />
Structures, such as overflow weirs,<br />
bypass and inlets<br />
••<br />
Erosion<br />
••<br />
Sediment build-up<br />
••<br />
Weeds<br />
••<br />
Algal blooms<br />
••<br />
Litter (anthropogenic and nonanthropogenic)<br />
••<br />
Oil slicks<br />
The following tables in the next three<br />
sections further explore the above issues<br />
as related to constructed wetlands,<br />
bioretention systems or sedimentation<br />
basins / ponds. In particular, the tables:<br />
••<br />
articulate monitoring requirements<br />
••<br />
suggest graded targets for optimal<br />
performance<br />
••<br />
suggest scheduling of maintenance<br />
and immediate action<br />
••<br />
propose a general approach to<br />
maintenance activities<br />
5.2.3 Bioretention<br />
Systems<br />
The routine maintenance of a bioretention<br />
basin is required to ensure diverted storm<br />
water:<br />
••<br />
Ponds evenly across the basin surface<br />
••<br />
Percolates through the filter media such<br />
that the ponding time does not exceed<br />
the design specifications (typically 6 to<br />
24 hours)<br />
To ensure the functionality of<br />
the bioretention basin is retained,<br />
maintenance activities will typically<br />
involve:<br />
••<br />
Routine inspection of the bioretention<br />
profile to identify any areas of obvious<br />
increased sediment deposition,<br />
scouring of the basin or swale invert<br />
from storm flows, rill erosion of the<br />
batters from lateral inflows, damage<br />
to the swale profile from vehicles and<br />
clogging of the bioretention trench<br />
(evident by a ‘boggy’ swale invert)<br />
••<br />
Routine inspection of inlet points,<br />
surcharge pits and field inlet pits to<br />
identify any areas of scour, litter build<br />
up and blockages<br />
22 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Boardwalk | Victoria Park<br />
••<br />
Removal of sediment, especially where<br />
it is impeding the conveyance of the<br />
bioretention swale and/or smothering<br />
the vegetation, and if necessary, reprofiling<br />
of the system and re-vegetating<br />
to original design specification<br />
••<br />
Repairing any damage to the system<br />
profile, especially in the case of a<br />
bioretention swale, resulting from<br />
scour, rill erosion or vehicle damage<br />
••<br />
Tilling of the bioretention trench surface<br />
if there is evidence of clogging<br />
••<br />
Clearing of blockages to inlet or outlets.<br />
••<br />
Regular watering/irrigation of<br />
vegetation until plants are established<br />
and actively growing<br />
••<br />
Mowing of turf or slashing of vegetation<br />
(if required) to preserve the optimal<br />
design height for the vegetation<br />
••<br />
Removal and management of invasive<br />
weeds<br />
••<br />
Removal of plants that have died and<br />
replacement with plants of equivalent<br />
size and species as detailed in the plant<br />
schedule<br />
••<br />
Pruning to remove dead or diseased<br />
vegetation material and to stimulate<br />
new growth<br />
••<br />
Litter and debris removal<br />
••<br />
Vegetation pest monitoring and control<br />
Resetting (i.e. complete reconstruction)<br />
of bioretention elements will be required<br />
if the available flow area of the overlying<br />
basin is reduced by 25 percent (due<br />
to accumulation of sediment) or if<br />
the bioretention trench fails to drain<br />
adequately after tilling of the surface.<br />
<strong>Book</strong> 4 | MAINTENANCE 23
Water Sensitive Urban Design<br />
Table 3 | Routine monitoring requirement for bioretention basins.<br />
Item to be<br />
Monitored<br />
Purpose of<br />
Monitoring<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
Immediate<br />
Action Required<br />
<strong>Maintenance</strong><br />
Action Required<br />
Structures<br />
The inlet and outlet structures of a<br />
bioretention system should be free of<br />
debris, litter and sediment to ensure<br />
flow is not impeded. Large storms (or<br />
flood) events and vehicles can also<br />
damage or block these structures<br />
and prevent the system working<br />
as designed. The main structural<br />
elements of a bioretention system are:<br />
- GPT / trash rack/s GPT clear of litter GPT 10 percent full greater than 30<br />
percent full<br />
Contact cleaning service.<br />
Generally a GPT will require clean-out<br />
four times per year. For proprietary<br />
GPTs it is recommended that a vacuum<br />
based cleaner be used on at least one<br />
occasion per year, or when frequent<br />
overflow of litter from the GPT is<br />
evident. For all other clean-outs, a<br />
mechanical grab is sufficient.<br />
- Inlet structures Clear and undamaged Partially Blocked<br />
Observed damage<br />
Mostly blocked<br />
Severe damage<br />
Schedule removal of debris or contact<br />
relevant authority within Council for<br />
structural damage.<br />
- Overflow pits<br />
- Underdrains Free flowing Trickle flow while<br />
basin ponding is<br />
observed<br />
No outflow while<br />
basin ponding is<br />
observed<br />
Inspect the bioretention system for<br />
scour or erosion damage and fix<br />
accordingly (refer to maintenance line<br />
item “bioretention system profile” for<br />
advise).<br />
- Sediment Forebay Sediment absent Sediment<br />
accumulation appears<br />
excessive<br />
Sediment<br />
accumulated to half<br />
the basin depth<br />
Schedule removal of sediment from<br />
forebay area.<br />
Erosion<br />
Erosion impairs bioretention systems<br />
by changing the bed profile and<br />
preventing uniform distribution of flow<br />
across the system.<br />
If left untreated, small sites of erosion<br />
can quickly spread over large areas<br />
becoming costly to repair.<br />
Erosion absent<br />
Erosion damage<br />
visible, but function<br />
not impaired<br />
Severe erosion.<br />
Damage impairing<br />
function of device<br />
Schedule investigation to identify<br />
cause of profile damage.<br />
Once source of damage is rectified,<br />
scour holes should be replaced with<br />
appropriate filter media.<br />
Lightly spread and compact replaced<br />
filter media using either hand tools, an<br />
excavator bucket or a pozitrack bobcat<br />
(DO NOT drive over the media with any<br />
vehicle but a pozitrack bobcat).<br />
Replace any damaged plants to meet<br />
the design plant schedule.<br />
24 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Item to be<br />
Monitored<br />
Purpose of<br />
Monitoring<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
Immediate<br />
Action Required<br />
<strong>Maintenance</strong><br />
Action Required<br />
Sediment<br />
build up<br />
The accumulation of sediment in the<br />
sediment forebay of the bioretention<br />
system is a prescribed function of<br />
this zone. However, sediment must be<br />
regularly removed to ensure that the<br />
sediment trapping performance of this<br />
zone is sustained.<br />
If sediment accumulates on the<br />
bioretention surface, percolation<br />
of water into the media may be<br />
reduced, resulting in poor treatment<br />
performance.<br />
Sediment absent<br />
Sediment<br />
accumulation<br />
appears excessive in<br />
sediment forebay<br />
Fine sediment<br />
accumulation<br />
apparent on<br />
bioretention media<br />
surface<br />
Sediment<br />
accumulated to half<br />
the forebay depth<br />
Coarse sediment<br />
or large volumes<br />
of sediment<br />
accumulation<br />
apparent on the<br />
bioretention media<br />
surface<br />
Schedule investigation to identify<br />
sediment source.<br />
Once sediment source is stabilised,<br />
remove accumulated sediment and<br />
replace the top 100 mm of filter media<br />
from the bioretention system. The filter<br />
media specifications should be as per<br />
the design intent.<br />
Common sense should be exercised<br />
in deciding if plantings need to be<br />
replaced as part of maintenance work.<br />
If the sediment build-up is extensive<br />
and smothering vegetation, it may be<br />
easier and less costly to remove the<br />
plantings and replant once the filter<br />
media has been replaced. Conversely,<br />
if the sediment build-up is small and<br />
isolated or the system is planted<br />
with trees, it may only be necessary<br />
to scrape away the accumulated<br />
sediment and the top 100mm of filter<br />
media and replace without disturbing<br />
the plants within the bioretention<br />
system.<br />
Lightly spread and compact replaced<br />
filter media using either hand tools, an<br />
excavator bucket or a pozitrack bobcat<br />
(DO NOT drive over the media with any<br />
vehicle but a pozitrack bobcat).<br />
Replace any damaged plants to meet<br />
the design plant schedule.<br />
Compaction<br />
Percolation into the media may be<br />
reduced if the media surface has been<br />
compacted, i.e. by pedestrian traffic,<br />
poor construction methods.<br />
No compaction<br />
evident<br />
Localised compaction<br />
or subsidence<br />
evident. Localised<br />
ponding longer than<br />
24 hours after storm<br />
event<br />
Water remains<br />
ponding longer than<br />
24hours after storm<br />
event<br />
Schedule investigation to identify<br />
cause of compaction.<br />
If compaction is localised, remove top<br />
500 mm of filter media with auger.<br />
- Break-up removed filter media so<br />
that it is no longer compacted.<br />
- Refill hole with uncompacted filter<br />
media (that is, there is no need to<br />
replace with new filter media).<br />
If compaction is extensive, seek expert<br />
advice.<br />
Weeds and<br />
invasive<br />
plants<br />
The growth of weeds can impair a<br />
bioretention system’s performance by<br />
- Changing flow paths across the<br />
bioretention system<br />
- Shading and out-competing plant<br />
species that are important for water<br />
treatment, or filter media stability.<br />
Weeds can spread to downstream<br />
environments, compromising<br />
ecosystem health.<br />
No weeds present Weeds present Noxious or<br />
environmental weeds<br />
present, or weed<br />
cover more than 25<br />
percent<br />
Hand removal or targeted herbicide<br />
treatment (herbicides registered for<br />
use around waterways).<br />
Note: Herbicides should not be<br />
routinely used to maintain edges and<br />
batter slopes. General spraying of<br />
batter slopes should not be undertaken<br />
without follow up revegetation with<br />
native species.<br />
Weeds compromise the visual amenity<br />
of the bioretention system.<br />
<strong>Book</strong> 4 | MAINTENANCE 25
Water Sensitive Urban Design<br />
Item to be<br />
Monitored<br />
Purpose of<br />
Monitoring<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
Immediate<br />
Action Required<br />
<strong>Maintenance</strong><br />
Action Required<br />
Plant<br />
Condition<br />
Plants are crucial to the performance<br />
of a bioretention system.<br />
Healthy vegetation<br />
Poorly growing or<br />
visibly stressed<br />
Die back / dead<br />
plants<br />
Schedule an investigation into the<br />
cause of plant die-back or poor health.<br />
During dry periods: Plants help<br />
maintain the structure and porosity of<br />
the filter media.<br />
During rainfall events: Vegetation<br />
aboveground acts to retard and<br />
distribute flows, and provides scour<br />
protection if the bioretention system<br />
is designed as a swale. Below ground<br />
the roots provide an important media<br />
for trapping or absorbing pollutants as<br />
they percolate through the media.<br />
<strong>Maintenance</strong> action will depend on the<br />
cause of die-back or poor plant health.<br />
Once the problem is rectified, infill<br />
planting may be required, especially if<br />
more than 1 square meter of plantings<br />
has died. Infill planting must be as per<br />
the original planting schedule.<br />
The accumulation of dead plant<br />
material can detract from the visual<br />
amenity of the bioretention system.<br />
Litter<br />
(organic)<br />
Organic litter can provide an additional<br />
source of nutrients to the bioretention<br />
system, introduce non-native species,<br />
which out-compete native plants and<br />
block the filter media.<br />
Accumulated organic matter / litter<br />
can also cause offensive odours<br />
(such as methane gas and hydrogen<br />
sulphide, i.e. rotten egg gas) and can<br />
reduce percolation of water into the<br />
filter media.<br />
No litter visible Litter visible Litter thickly covers<br />
filter media surface or<br />
detracting from visual<br />
amenity<br />
Identify source of organic litter and<br />
address with appropriate response<br />
action: e.g. change of landscape<br />
maintenance practices; community<br />
education re: litter dumping<br />
(appropriate for repeat incidences).<br />
In the interim, all litter must be<br />
removed by maintenance crews.<br />
Litter<br />
(anthropogenic)<br />
Litter can potentially block the<br />
inlet and outlet structures of the<br />
bioretention system resulting in<br />
flooding, as well as detract from the<br />
system’s visual amenity.<br />
No litter visible Litter visible Litter blocking<br />
structures or<br />
detracting from visual<br />
amenity<br />
Identify source of rubbish: e.g. from<br />
catchment (commercial precinct);<br />
overflow of rubbish bins; accumulation<br />
in backwater area and schedule<br />
general maintenance to remove<br />
rubbish. Where required address<br />
source of rubbish (e.g. increase in<br />
frequency of rubbish bin emptying;<br />
gross pollutant traps in high load<br />
generation land uses). In the<br />
interim, all litter must be removed by<br />
maintenance crews.<br />
WARNING: Contact with sharp objects,<br />
including hypodermic needles is a<br />
risk when removing litter. All workers<br />
must be made aware of this risk, wear<br />
appropriate protective gear and use<br />
caution.<br />
Oil slicks<br />
Oil spills / inflows are not necessarily<br />
an impedance to bioretention system<br />
function. Bioretention systems<br />
are designed to remove oils from<br />
stormwater; hydrocarbons decompose<br />
relatively quickly in the presence<br />
of soil microbes and water. It is<br />
expected that fuel or oil trapped in the<br />
bioretention basin would decompose<br />
within two to three weeks, depending<br />
on the size of the oil spill.<br />
No visible oil<br />
Persistent but limited<br />
visible oil<br />
Extensive or localised<br />
thick layer of oil<br />
visible<br />
Do not isolate bioretention system<br />
in the case of an oil spill - it is better<br />
that the oil is contained within the<br />
system than allowed to flow to the<br />
downstream water course.<br />
Notify the EPA of the spill and clean-up<br />
requirements<br />
NOTE: do not add any fertiliser, or<br />
other nitrogen based product to the<br />
system. The microbes within the filter<br />
media are capable of decomposing<br />
hydrocarbons.<br />
26 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
5.2.4 Constructed Wetlands<br />
and Ponds<br />
A pond treats<br />
runoff by providing<br />
extended detention<br />
and allowing<br />
sedimentation to<br />
occur.<br />
NOTE:-<br />
A separate<br />
maintenance<br />
checksheet has<br />
been developed<br />
for ponds as<br />
provided in the<br />
appendix to this<br />
booklet.<br />
Wetlands treat runoff by filtering it through<br />
vegetation and providing extended<br />
detention to allow sedimentation to occur.<br />
In addition, they have a flow management<br />
role that needs to be maintained to<br />
ensure adequate flood protection for<br />
local properties and protection of the<br />
wetland ecosystem. Ponds are frequently<br />
designed downstream of a wetland to<br />
provide further polishing of stormwater<br />
as well as detention (either to meet reuse<br />
requirements or attenuation of flows). A<br />
pond treats runoff by providing extended<br />
detention and allowing sedimentation<br />
to occur. This same principle applies for<br />
ponds designed for primary treatment.<br />
To ensure the functionality of the system,<br />
routine monitoring and maintenance of<br />
constructed wetlands will require:<br />
••<br />
Checking flow paths in and out of the<br />
system are unobstructed<br />
••<br />
Ensuring vegetation is healthy and is<br />
sufficiently dense<br />
••<br />
Preventing undesired vegetation from<br />
taking over the desirable vegetation<br />
••<br />
Removal of noxious plants or weeds<br />
••<br />
Re-establishment of plants that die<br />
••<br />
Removal of accumulated sediments<br />
••<br />
Litter and debris removal<br />
Of the above items, debris removal<br />
should be the only action requiring<br />
ongoing attention. Debris, if not removed,<br />
can block inlets or outlets, and can be<br />
unsightly if located in a visible location.<br />
Inspection and removal of debris should<br />
be done regularly, but debris should be<br />
removed whenever it is observed.<br />
The monitoring and maintenance<br />
requirements of ponds are similar to<br />
constructed wetlands in maintaining<br />
flow into and through the system,<br />
ensuring healthy vegetation, minimising<br />
establishment of evasive and noxious<br />
plants and removal of accumulated<br />
sediment, litter and debris. The guidance<br />
given for monitoring and maintaining<br />
constructed wetlands can in general be<br />
adopted for ponds, (refer to note) noting<br />
the following:<br />
••<br />
Artificial turnover of the lake may be<br />
required (because of long residence<br />
times). A mechanical system will need<br />
to be employed and will require specific<br />
maintenance<br />
••<br />
Ponds designed to provide primary<br />
treatment will typically be more<br />
maintenance intensive due to the<br />
higher loads of nutrients delivered and<br />
captured<br />
<strong>Book</strong> 4 | MAINTENANCE 27
Water Sensitive Urban Design<br />
Table 4 | Routine monitoring requirement for constructed wetlands.<br />
Item to be<br />
Monitored<br />
Purpose of Monitoring<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
Immediate<br />
Action Required<br />
<strong>Maintenance</strong> Action Required<br />
The purpose of the inspection is to<br />
check that the structures associated<br />
with the constructed wetland<br />
(macrophyte zone cells and inlet<br />
zone) are not damaged and function<br />
as designed. Examples of causes of<br />
structural damage include sediment<br />
and/or litter accumulation and large<br />
storms (flood events).<br />
Structures<br />
- GPT / trash rack GPT clear of litter GPT 10 percent full GPT / trash rack<br />
for than 30 percent<br />
full<br />
Notify Cleaning Services<br />
NOTE: If the wetland substrate has<br />
been disturbed during maintenance<br />
activities, ensure bed profile<br />
re-established as designed.<br />
Irregularities in bed profile may have<br />
the potential to act as mosquito<br />
breeding habitats.<br />
- Inlet pipe Clear and<br />
undamaged<br />
- Pipes connecting macrophyte<br />
cells<br />
- Outlet pit<br />
Partially Blocked<br />
Observed damage<br />
Mostly blocked<br />
Severe damage<br />
Schedule removal of debris, or notify<br />
relevant authority within Council for<br />
structural damage.<br />
Inspect for associated erosion and<br />
scour damage within the wetland<br />
and associated structure, and<br />
schedule repair work as required by<br />
Council.<br />
Erosion<br />
Erosion impairs wetland function by<br />
- Changing flow paths through the<br />
wetland<br />
- Smothering wetland vegetation<br />
and biota<br />
- Creation of mosquito habitat<br />
- Contributing to poor water quality<br />
by adding additional sediment<br />
If left untreated, small sites of<br />
erosion can quickly spread over<br />
large areas becoming costly to<br />
repair.<br />
Erosion absent<br />
Erosion damage<br />
visible, but structure<br />
functional<br />
Severe erosion.<br />
Damage impairing<br />
function of device<br />
Schedule investigation into cause<br />
of erosion. Action appropriate<br />
stabilisation response.<br />
Any erosion damage of the<br />
macrophyte zone batters, berms,<br />
and around the inlet and outlet<br />
structures should be noted on the<br />
Inspection Form and remediation<br />
measures undertaken immediately.<br />
Remediation measures may include<br />
surface reinforcement and revegetation.<br />
Sediment<br />
build up<br />
The accumulation of sediment<br />
in the inlet pond of the wetland<br />
is a prescribed function of this<br />
zone. However, sediment must be<br />
regularly removed to ensure that the<br />
sediment trapping performance of<br />
this zone is sustained.<br />
Sediment absent<br />
Sediment<br />
accumulation<br />
appears excessive<br />
Sediment<br />
accumulated to<br />
half the basin<br />
depth<br />
Schedule an investigation into<br />
source of sediment: e.g. localised<br />
erosion or catchment based runoff.<br />
Sediment build up can affect<br />
the hydraulics of the wetland,<br />
and smother aquatic plants,<br />
compromising plant growth.<br />
28 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Item to be<br />
Monitored<br />
Purpose of Monitoring<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
Immediate<br />
Action Required<br />
<strong>Maintenance</strong> Action Required<br />
The growth of weeds can impair a<br />
wetlands performance by<br />
- Changing flow paths through the<br />
wetland<br />
- Shading and out-competing plant<br />
species that are important for water<br />
treatment, or bed / bank stability.<br />
Weeds can spread to downstream<br />
environments, compromising<br />
ecosystem health.<br />
Weeds compromise the visual<br />
amenity of the wetland.<br />
Invasive plants in constructed<br />
wetlands take the following forms:<br />
Weeds<br />
- Aquatic weeds (submerged,<br />
emergent and floating)<br />
No weeds present Weeds present Noxious or<br />
environmental<br />
weeds present<br />
Emergent Plants (e.g. Typha):<br />
schedule hand weed removal or<br />
herbicide treatment.<br />
Floating Plants (e.g. Salvinia) with<br />
30% cover: removal with harvester<br />
- Terrestrial weeds (e.g. within the<br />
batter slopes)<br />
No weeds present Weeds present Noxious or<br />
environmental<br />
weeds present<br />
Hand removal or targeted herbicide<br />
treatment (herbicide registered for<br />
use around waterways).<br />
Note: Herbicides should not be<br />
routinely used to maintain edges<br />
and banks. General spraying of<br />
banks should not be undertaken<br />
without follow up revegetation with<br />
native species.<br />
Algal<br />
blooms<br />
Algal blooms are easily detected:<br />
the water colour becomes green,<br />
the water clarity is poor and there<br />
is an offensive odour. Although an<br />
algal bloom can be a sign that the<br />
wetland is working as intended (as<br />
wetland organisms such as algae<br />
remove nutrients from the water<br />
column), algal blooms can be toxic<br />
to aquatic organisms and humans.<br />
Algal shading can kill macrophytes.<br />
No algae apparent Algae visible Algal growth<br />
prominent or<br />
extensive<br />
Schedule water quality testing:<br />
e.g. cyanobacterial community<br />
composition and cell count. When a<br />
potentially toxic bloom is identified,<br />
notify residents to avoid contact<br />
with the water and continue<br />
monitoring until the bloom subsides.<br />
Notify the Environment Branch<br />
Waterways Project Officer so the<br />
lakes priority for management/<br />
retrofit works can be reviewed.<br />
<strong>Book</strong> 4 | MAINTENANCE 29
Water Sensitive Urban Design<br />
Item to be<br />
Monitored<br />
Purpose of Monitoring<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
Immediate<br />
Action Required<br />
<strong>Maintenance</strong> Action Required<br />
Plant<br />
Condition<br />
Vigorous plant growth is important<br />
in ensuring good water treatment.<br />
The plants take up nutrients and<br />
provide surface area for biofilms to<br />
form (another important mode of<br />
nutrient removal).<br />
The accumulation of decaying<br />
vegetation can create mosquito<br />
breeding habitats and inhibit<br />
seasonal growth of plants.<br />
Healthy vegetation<br />
Poorly growing or<br />
visibly stressed<br />
Die back / dead<br />
plants<br />
Schedule an investigation of<br />
cause: e.g. is the observed<br />
changes in health and cover due to<br />
inappropriate water level or water<br />
level variation; disease; competition<br />
by weeds; damage (e.g. by birds or<br />
flood) or poison contaminant.<br />
<strong>Maintenance</strong> action will depend<br />
on the cause of die-back or poor<br />
plant health. Once the problem<br />
is rectified, infill planting may be<br />
required, especially if more than 3<br />
square meters of plantings has died.<br />
Infill planting must be as per the<br />
original design planting schedule.<br />
Dead vegetation may need to be<br />
removed as part of ensuring good<br />
plant condition.<br />
Litter<br />
(organic)<br />
Organic litter can provide an<br />
additional source of nutrients to<br />
the constructed wetland, and<br />
introduce non-native species, which<br />
out-compete native plants (both<br />
terrestrial and aquatic).<br />
Accumulated organic matter / litter<br />
can also cause offensive odours<br />
(such as methane gas and hydrogen<br />
sulphide, i.e. rotten egg gas).<br />
No litter visible Litter visible Litter blocking<br />
structures or<br />
detracting from<br />
visual amenity<br />
Identify source of organic litter and<br />
address with appropriate response<br />
action: e.g. change of landscape<br />
maintenance practices; community<br />
education re: litter dumping<br />
(appropriate for repeat incidences).<br />
In the interim, all litter must be<br />
removed by maintenance crews.<br />
Litter can potentially block the<br />
inlet and outlet structures of the<br />
constructed wetland resulting in<br />
flooding, as well as detract from the<br />
wetland’s visual amenity.<br />
No litter visible Litter visible Litter blocking<br />
structures or<br />
detracting from<br />
visual amenity<br />
Identify source of rubbish from<br />
catchment, for example, overflow<br />
of rubbish bins. Target areas of<br />
litter accumulation, for example,<br />
backwater areas. Schedule general<br />
maintenance to remove rubbish.<br />
Litter<br />
(anthropogenic)<br />
Where required, address source<br />
of rubbish (e.g. increase in<br />
frequency of rubbish bin emptying;<br />
gross pollutant traps in high load<br />
generation land uses). In the<br />
interim, all litter must be removed by<br />
maintenance crews.<br />
WARNING: Contact with sharp<br />
objects, including hypodermic<br />
needles is a risk when removing<br />
litter. All workers must be made<br />
aware of this risk, wear appropriate<br />
protective gear and use caution.<br />
30 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
The frequency of<br />
litter and debris<br />
removal may be<br />
high, but will<br />
depend on the<br />
land use within the<br />
systems catchment.<br />
5.2.5 Sedimentation Basins<br />
Sedimentation basins are designed to<br />
retain coarse sediment by providing<br />
sufficient extended detention (and hence<br />
settling time). Furthermore, sedimentation<br />
basins are designed to allow sediment<br />
to accumulate to half the basin depth<br />
before clean out is necessary. The design<br />
of sedimentation basins is critical in<br />
preventing coarse sediment to carry over<br />
and smother vegetation in downstream<br />
treatment systems such as bioretention<br />
basins and constructed wetlands.<br />
The majority of maintenance associated<br />
with sedimentation basins concerns the<br />
inlet zone (and GPT if installed). Inlets can<br />
be prone to scour and build up of litter.<br />
Litter removal and potential replanting<br />
may be required as part of maintaining<br />
an inlet zone. The frequency of litter<br />
and debris removal may be high, but will<br />
depend on the land use within the systems<br />
catchment.<br />
Weed removal and replanting of edge<br />
vegetation will also be required.<br />
<strong>Book</strong> 4 | MAINTENANCE 31
Water Sensitive Urban Design<br />
Table 5 | Routine monitoring requirement for sedimentation basins.<br />
Item to be<br />
Monitored<br />
Purpose of Monitoring<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
Immediate<br />
Action Required<br />
<strong>Maintenance</strong> Action Required<br />
Structures<br />
The inlet and outlet structures of<br />
a sedimentation basin should be<br />
free of debris, litter and sediment<br />
to ensure flow is not impeded.<br />
Large storms (or flood) events<br />
and vehicles can also damage or<br />
block these structures and prevent<br />
the system working as designed.<br />
The main structural elements of a<br />
sedimentation basin are:<br />
- GPT / trash rack/s GPT clear of litter GPT 10 percent full greater than 30<br />
percent full<br />
Contact cleaning service.<br />
Generally a GPT will require<br />
clean-out four times per year. For<br />
proprietary GPTs it is recommended<br />
that a vacuum cleaner be used on<br />
at least one occasion per year, or<br />
when frequent overflow of litter<br />
from the GPT is evident. For all other<br />
clean-outs, a mechanical grab is<br />
sufficient.<br />
- Inlet structures Clear and<br />
undamaged<br />
Partially Blocked<br />
Observed damage<br />
Mostly blocked<br />
Severe damage<br />
Schedule removal of debris or<br />
contact relevant authority within<br />
Council for structural damage.<br />
- Overflow pits<br />
Inspect the sedimentation basin for<br />
scour or erosion damage and fix<br />
accordingly.<br />
Erosion<br />
Erosion will affect the distribution of<br />
flow across the sedimentation basin.<br />
If left untreated, small sites of<br />
erosion can quickly spread over<br />
large areas becoming costly to<br />
repair.<br />
Erosion absent<br />
Erosion damage<br />
visible, but function<br />
not impaired<br />
Severe erosion.<br />
Damage impairing<br />
function of device<br />
Schedule investigation to identify<br />
cause of profile damage.<br />
Once source of damage is rectified,<br />
scour holes should be replaced with<br />
appropriate filter media.<br />
Replace any damaged plants to<br />
meet the design plant schedule.<br />
Sediment<br />
build up<br />
The accumulation of sediment<br />
is a prescribed function of a<br />
sedimentation basin. However,<br />
sediment must be regularly removed<br />
to ensure that the sediment trapping<br />
performance of this system is<br />
sustained.<br />
Sediment absent<br />
Sediment<br />
accumulation<br />
appears excessive<br />
Sediment<br />
accumulated to half<br />
the sediment basin<br />
depth<br />
Schedule investigation to identify<br />
sediment source.<br />
Once sediment source is stabilised,<br />
remove accumulated sediment.<br />
Replace any damaged plants to<br />
meet the design plant schedule.<br />
32 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Item to be<br />
Monitored<br />
Purpose of Monitoring<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
Immediate<br />
Action Required<br />
<strong>Maintenance</strong> Action Required<br />
Weeds and<br />
invasive<br />
plants<br />
Weeds should be removed from the<br />
sedimentation basin:<br />
- Weeds can spread to downstream<br />
environments, compromising<br />
ecosystem health.<br />
- Weeds compromise the visual<br />
amenity of the sedimentation basin.<br />
No weeds present Weeds present Noxious or<br />
environmental<br />
weeds present, or<br />
weed cover more<br />
than 25 percent<br />
Hand removal or targeted herbicide<br />
treatment (herbicides registered for<br />
use around waterways).<br />
Note: Herbicides should not be<br />
routinely used to maintain edges<br />
and batter slopes. General spraying<br />
of batter slopes should not be<br />
undertaken without follow up<br />
revegetation with native species.<br />
Plant<br />
Condition<br />
Plants are crucial to bank stability<br />
and visual amenity<br />
Healthy vegetation<br />
Poorly growing or<br />
visibly stressed<br />
Die back / dead<br />
plants<br />
Schedule an investigation into the<br />
cause of plant die-back or poor<br />
health.<br />
<strong>Maintenance</strong> action will depend<br />
on the cause of die-back or poor<br />
plant health. Once the problem<br />
is rectified, infill planting may be<br />
required, especially if more than 1<br />
square meter of plantings has died.<br />
Infill planting must be as per the<br />
original planting schedule.<br />
Litter<br />
(organic)<br />
Organic litter can provide an<br />
additional source of nutrients and<br />
on-native species which have a high<br />
likelihood of being transferred to<br />
downstream treatment systems and<br />
waterways.<br />
No litter visible Litter visible Litter thickly covers<br />
filter media surface<br />
or detracting from<br />
visual amenity<br />
Identify source of organic litter and<br />
address with appropriate response<br />
action: e.g. change of landscape<br />
maintenance practices; community<br />
education re: litter dumping<br />
(appropriate for repeat incidences).<br />
Accumulated organic matter / litter<br />
can also cause offensive odours<br />
(such as methane gas and hydrogen<br />
sulphide, i.e. rotten egg gas).<br />
In the interim, all litter must be<br />
removed by maintenance crews.<br />
Litter<br />
(anthropogenic)<br />
Litter can potentially block the inlet<br />
and outlet structures resulting in<br />
flooding, as well as detract from the<br />
system’s visual amenity.<br />
No litter visible Litter visible Litter blocking<br />
structures or<br />
detracting from<br />
visual amenity<br />
Identify source of rubbish: e.g.<br />
from catchment (commercial<br />
precinct); overflow of rubbish bins;<br />
accumulation in backwater area<br />
and schedule general maintenance<br />
to remove rubbish. Where required<br />
address source of rubbish (e.g.<br />
increase in frequency of rubbish<br />
bin emptying; gross pollutant traps<br />
in high load generation land uses).<br />
In the interim, all litter must be<br />
removed by maintenance crews.<br />
WARNING: Contact with sharp<br />
objects, including hypodermic<br />
needles is a risk when removing<br />
litter. All workers must be made<br />
aware of this risk, wear appropriate<br />
protective gear and use caution.<br />
<strong>Book</strong> 4 | MAINTENANCE 33
Water Sensitive Urban Design<br />
Item to be<br />
Monitored<br />
Purpose of Monitoring<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
Immediate<br />
Action Required<br />
<strong>Maintenance</strong> Action Required<br />
Oil slicks<br />
Oil spills / inflows are better<br />
trapped and isolated within<br />
a sedimentation basin<br />
than allowed to flow to the<br />
downstream waterway.<br />
No visible oil<br />
Persistent but<br />
limited visible oil<br />
Extensive or<br />
localised thick<br />
layer of oil<br />
visible<br />
Do not isolate sedimentation<br />
basin in the case of an oil<br />
spill - it is better that the oil is<br />
contained within the system<br />
than allowed to flow to the<br />
downstream water course.<br />
Notify the EPA of the spill and<br />
clean-up requirements<br />
NOTE: do not add any fertiliser,<br />
or other nitrogen based product<br />
to the system. The microbes<br />
within the filter media are<br />
capable of decomposing<br />
hydrocarbons.<br />
34 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Water sensitive<br />
urban design<br />
elements are<br />
designed to detain<br />
pollutants from<br />
being discharged<br />
to the downstream<br />
watercourse.<br />
5.3 Waste Management<br />
and Disposal<br />
Water sensitive urban design elements<br />
are designed to detain pollutants from<br />
being discharged to the downstream<br />
watercourse. Vegetated <strong>WSUD</strong> elements<br />
such as constructed wetlands and<br />
bioretention basins use pollutants such as<br />
nitrogen and phosphorus in plant growth,<br />
minimising the build up of nutrients in<br />
the system. Conversely, suspended solids<br />
and gross pollutants cannot be used by a<br />
vegetated treatment system and hence<br />
accumulate and will eventually require the<br />
intervention of maintenance crews.<br />
Three types of waste are associated with<br />
<strong>WSUD</strong> elements:<br />
••<br />
Contaminated silt (sedimentation<br />
basins, constructed wetlands and<br />
ponds)<br />
••<br />
Spoiled filter media (bioretention<br />
basins)<br />
••<br />
Liquid waste from dewatering activities<br />
<strong>Book</strong> 4 | MAINTENANCE 35
Water Sensitive Urban Design<br />
5.3.1 Dewatered silt<br />
The NSW Department of Environment<br />
and Climate Change (DECC) has recently<br />
amended the rules governing waste<br />
disposal. Silt collected from sediment<br />
basins is now defined as general waste<br />
(non-putrescibles). For general waste<br />
(non-putrescibles), there is no requirement<br />
for the silt to be tested, unless the Council<br />
(or owner of the asset) believes that the<br />
nature of the catchment could cause the<br />
silt to have:<br />
••<br />
A Specific Contaminant Concentration<br />
(SCC) higher than the guideline values<br />
given by DECC; and/or<br />
••<br />
A leachable concentration of any<br />
chemical contaminant (as determined<br />
through the Toxicity Characteristics<br />
Leaching Procedure (TCLP)) higher than<br />
the guideline values given by DECC<br />
Guideline values for General Solid<br />
Waste for both measures are given in<br />
the following document http://www.<br />
environment.nsw.gov.au/resources/<br />
waste/08202classifyingwaste.pdf<br />
Disposal of dewatered silt is accepted<br />
by WSN Environmental solutions, but<br />
only at their Eastern Creek and Lucas<br />
Heights locations. WSN Environmental<br />
solutions classify General Solid Waste as<br />
Special Waste, which has a disposal cost<br />
of $220 per tonne. The waste service<br />
facility at Belrose will also accept General<br />
Solid Waste; however due to a limited<br />
capacity, it will only accept waste from the<br />
surrounding LGA (Ku-ring-gai).<br />
Although in theory general waste (nonputrescibles)<br />
can be accepted by private<br />
waste disposal operators, very few facilities<br />
within the Sydney Metropolitan actually<br />
have the capacity to accept sludge / silt<br />
type material. One of the few exceptions<br />
is Blacktown Waste Service who accepts<br />
general solid waste (non-putrescibles) at a<br />
cost between $75 and $110 per tonne.<br />
5.3.2 Filter media<br />
The filter media for bioretention basins<br />
may need replacing in the following<br />
situations:<br />
1) Filter media has reached full capacity<br />
for retaining metals as identified<br />
through pollutant breakthrough.<br />
2) Surface of filter media is clogged.<br />
Recent research conducted by FAWB has<br />
shown for a bioretention basin sized at two<br />
percent of the impervious catchment area<br />
and a filter media depth of 0.5 metres,<br />
pollutant breakthrough will occur within<br />
15 years. The results were considered<br />
conservative (ie lower estimate) as the<br />
soils had a low pH. Soils with a neutral<br />
pH will have a greater capacity to attract<br />
metal pollutants, hence further delaying<br />
breakthrough from occuring. When<br />
breakthrough occurs, the entire filter<br />
media will need replacing.<br />
Surface clogging can be observed<br />
through poor plant growth, or when<br />
ponding times exceed the design<br />
specifications. The replacement of filter<br />
media is not required if plant growth is<br />
poor. The clogging of the surface media<br />
could be remedied by re-establishing<br />
plants to ensure density is sufficient in<br />
maintaining surface porosity. If, however,<br />
plant growth is adequate, clogging<br />
is related to failure of the filter media<br />
and the top 200 to 300 millimetres of<br />
filter media will require replacing.<br />
Removed filter media may be<br />
contaminated and should be tested<br />
accordingly. Filter media classified as<br />
contaminated should be disposed of<br />
at a certified waste disposal centre.<br />
Alternatively, there may be options to<br />
bio-remediate the soil and reuse it.<br />
36 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Detention pond | Garden Gates<br />
Open space | Victoria Park<br />
The location of the<br />
dewatering facility<br />
should consider<br />
existing site<br />
constraints.<br />
5.3.3 Liquid waste<br />
(from dewatering activities)<br />
Prior to discharge, the silt removed must<br />
be dewatered such that it does not<br />
contain any free liquid (that is, the density<br />
is 1.5 to 3 times the density of the material<br />
if completely dry (Collins, 2006)).<br />
The dewatering of collected silt can<br />
be accommodated in the design of<br />
the sedimentation basin, whereby free<br />
liquid is directed back into the treatment<br />
train. Alternatively, collected silt can be<br />
stockpiled within designated bunded<br />
areas offsite or stored in skip trucks<br />
brought into the site. The location of<br />
the dewatering facility should consider<br />
existing site constraints, DECC regulatory<br />
requirements, health and safety issues,<br />
odours and other community concerns<br />
(WBM and Ecological Engineering, 2005).<br />
Liquid removed during dewatering is likely<br />
to be classified as either Group A liquid<br />
waste or non-controlled aqueous liquid<br />
waste, depending on the concentration<br />
of suspended or dissolved chemicals<br />
(WBM and Ecological Engineering,<br />
2005). The level of contamination should<br />
be confirmed by laboratory testing;<br />
however it is likely that dewatered water<br />
will classified as non-controlled aqueous<br />
liquid waste.<br />
The decantered water must be treated<br />
prior to discharge to a receiving<br />
waterbody. Treatment can be achieved<br />
through many mechanisms, including:<br />
••<br />
Pumping decantered water to a settling<br />
tank to remove elevated levels of<br />
suspended solids. This may require the<br />
addition of a flocculent such as gypsum.<br />
••<br />
Decanting liquids to pervious areas,<br />
ensuring liquids are appropriately<br />
treated to meet reuse requirements.<br />
Potential implications of reusing<br />
decanted water from stormwater<br />
treatment measures include high<br />
pollutant (in particular heavy metal)<br />
concentrations and health risks posed<br />
by trapped pathogens.<br />
••<br />
Decanting liquids back into the<br />
stormwater treatment system.<br />
5.3.4 Equipment requirements<br />
For a sediment basin, wetland or pond,<br />
cleaning will generally require a backhoe,<br />
excavator or eductor / vacuum truck,<br />
requiring service from one to two vehicle<br />
operators and one to three labourers<br />
(HSC, 2001).<br />
The removal of waste from a bioretention<br />
basin must be done by hand to protect<br />
the bathymetry and compaction of the<br />
filter media.<br />
<strong>Book</strong> 4 | MAINTENANCE 37
Water Sensitive Urban Design<br />
6 | Construction Requirements<br />
Watersteps | Victoria Park<br />
The ultimate aim<br />
of each option<br />
is to protect the<br />
functional elements<br />
of the <strong>WSUD</strong><br />
element.<br />
This section provides advice on the<br />
construction of <strong>WSUD</strong> elements. In<br />
particular, the advice concentrates on<br />
the staging of construction in association<br />
with other development in the catchment.<br />
The construction advice is supported by<br />
a series of checklists, which have been<br />
developed to ensure critical design<br />
elements are checked and signed off<br />
as completed; hence minimising the<br />
potential for expensive re-work.<br />
6.1 Staging<br />
The construction of <strong>WSUD</strong> elements<br />
should be coordinated with other<br />
construction activities within the<br />
catchment. Construction activities<br />
will generate greater loads of coarse<br />
sediment and gross pollutants, for which<br />
the <strong>WSUD</strong> treatment element is unlikely<br />
to be designed for. High loadings of<br />
coarse sediment and gross pollutants<br />
can be particularly detrimental during<br />
plant establishment for a vegetated<br />
system, smothering infant vegetation and<br />
changing the bathymetry of the element<br />
(which in turns affects the hydraulic<br />
function and the distribution of flow within<br />
the treatment element).<br />
The Water Sensitive Urban Design<br />
Construction and Establishment<br />
Guidelines (version 1) developed by Water<br />
by Design (2009) a program of the South<br />
East Queensland provides guidance<br />
on the staged construction of <strong>WSUD</strong><br />
elements. Multiple options are presented<br />
for each <strong>WSUD</strong> element, which assess:<br />
1) The location of the <strong>WSUD</strong> element<br />
(that is, streetscape, parkland);<br />
2) The level of environmental protection<br />
the system provides during staged<br />
construction; and<br />
3) The landscape amenity of the system<br />
during staged construction.<br />
The ultimate aim of each option is to<br />
protect the functional elements of the<br />
<strong>WSUD</strong> element. This is achieved by either<br />
isolating the functional elements by<br />
diverting stormwater flows or increasing<br />
the capacity for sediment capture either<br />
upstream or within the <strong>WSUD</strong> element.<br />
For each option, construction and<br />
establishment of <strong>WSUD</strong> elements is<br />
divided into three stages:<br />
Stage 1: Civil construction<br />
(or functional installation)<br />
Stage 2: Building phase protection<br />
(or sediment and erosion<br />
control)<br />
Stage 3: Operational establishment<br />
(civil and/or landscaping)<br />
These are illustrated in Figure 7 together<br />
with a list of corresponding management<br />
forms contained in Appendix A.<br />
38 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Stage 1: Civil Construction<br />
Pre start construction meeting<br />
Subdivision<br />
Construction<br />
FORM A<br />
Earthworks and hydraulic /<br />
Functional Structures<br />
FORM C (bioretention basin)<br />
Filter media and finished levels<br />
Stage 2: Building phase protection<br />
FORM B<br />
Erosion and Sediment Control<br />
Allotment<br />
Building<br />
(up to 30 percent<br />
completion)<br />
Stage 3: Operational establishment<br />
FORM C<br />
(wetland and sedimentation)<br />
Top soil and finished levels<br />
FORM D<br />
Landscape Planting<br />
Allotment<br />
Building<br />
(greater than<br />
80 percent<br />
completion)<br />
Asset handover<br />
Asset handover checklist<br />
Completion<br />
of construction<br />
activities<br />
Figure 7: Staged construction of <strong>WSUD</strong> elements and the timing of relevant forms<br />
<strong>Book</strong> 4 | MAINTENANCE 39
Water Sensitive Urban Design<br />
6.1.1 Stage 1: Civil construction (or functional installation)<br />
Stage 1 requires the construction of the functional components for the <strong>WSUD</strong> element.<br />
The functional components for the <strong>WSUD</strong> elements addressed in the booklet are:<br />
Bioretention basin Constructed wetland Sedimentation basin<br />
Bulk earthworks to<br />
establish bunds and system<br />
batter slopes<br />
Detailed profiling of bunds,<br />
batters, sides and base<br />
of system to meet design<br />
requirements (given<br />
allowed tolerances)<br />
Construct all hydraulic<br />
structures, for example,<br />
inlet pipes and headwalls,<br />
bypass weir, outlet riser and<br />
rock protection*<br />
Install system lining,<br />
underdrainage, clean out<br />
points and various layers<br />
(that is, drainage layer,<br />
transition layer and filter<br />
media)<br />
Survey wetland layout in<br />
accordance with the design<br />
Remove ground cover and topsoil<br />
as indicated from the survey<br />
Stockpile topsoil designated for<br />
reuse in construction, noting<br />
that the soil must be tested<br />
and screened to remove coarse<br />
sediment and weed seeds<br />
Bulk earthworks to establish the<br />
inlet and macrophyte zone, high<br />
flow bypass and surrounding<br />
bunds and batters<br />
Detailed profiling of bunds,<br />
batters, sides and base of system<br />
to meet design requirements<br />
(given allowed tolerances as<br />
well as 300 mm of topsoil and<br />
impervious liner, if specified)<br />
Install impervious liner (if required)<br />
Construct bunding between the<br />
inlet and outlet zone, as well as<br />
between the wetland and lake (if a<br />
lake is included in the design)<br />
Construct all hydraulic structures,<br />
for example, inlet pipes and<br />
headwalls, bypass weir, outlet riser<br />
and rock protection*<br />
Topsoil placement and profiling to<br />
within accepted tolerances<br />
Bulk earthworks to<br />
establish bunds and system<br />
batter slopes, as well as<br />
maintenance access (e.g.<br />
ramp)<br />
Installation of outlet<br />
structures (for example,<br />
overflow pit / weir and<br />
spillway)<br />
Installation of inlet<br />
structures including inlet<br />
pipe and headwall.<br />
For a sedimentation basin,<br />
install the inlet energy<br />
dissipater and primary<br />
treatment measure (for<br />
example, gross pollutant<br />
trap)<br />
Detailed profiling of<br />
bunds, batters, system<br />
base, access points and<br />
spillway to meet design<br />
requirements (given<br />
allowed tolerances)<br />
Install system lining<br />
Stabilise system batters<br />
and base with sterile grass<br />
NOTE:<br />
* This is not a complete list of hydraulic, functional and structural elements of a constructed wetland – the<br />
reader is referred to the Water by Design documents for complete details.<br />
Immediately following completion of stage 1, sediment fences should be installed at the<br />
top of the system batter. Bioretention basins will also require sediment fences installed<br />
around the filter media.<br />
40 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Stage 1 – Functional Installation<br />
Civil construction<br />
<strong>Book</strong> 4 | MAINTENANCE 41
Water Sensitive Urban Design<br />
6.1.2 Stage 2: Building phase protection (or sediment and erosion control)<br />
Stage 2 involves the construction of temporary measures to protect the functional elements<br />
of the system. As stated, two options are typically considered, either diversion of flows<br />
away from the functional elements to allow plant establishment, or the establishment of<br />
temporary sedimentation basins (within or upstream of the main functional part of the<br />
<strong>WSUD</strong> element).<br />
The main activities required as part of stage 2 are:<br />
Bioretention basin Constructed wetland Sedimentation basin / pond<br />
Bypass of stormwater flows / isolation of functional design<br />
Install bypass structure. The<br />
system will typically involve<br />
one of the following:<br />
1) Completely bypassing<br />
the inlet pipe around the<br />
filter media area<br />
2) Partitioning the systems<br />
such that the inlet and<br />
outlet only are engaged<br />
Isolate macrophyte zone<br />
from the inlet zone by<br />
blocking the connection<br />
pipe between the two zones<br />
Stabilise the high flow<br />
bypass either with turf or<br />
reinforced turf<br />
Ensure the entire perimeter<br />
of the wetland is protected<br />
by sediment fences<br />
Construct non-wetland<br />
related hardscapes, such as<br />
boardwalks and pathways<br />
Sedimentation Basins<br />
Generally not considered for<br />
sedimentation basins<br />
Ponds<br />
Isolate pond from downstream<br />
treatment devices by blocking<br />
connecting pipework<br />
Ensure the entire perimeter of the<br />
pond is protected by sediment<br />
fences<br />
Establishment of temporary sediment protection devices<br />
Protect the filter media with<br />
a filter cloth or 25 to 50 mm<br />
of course sand plus 25 mm<br />
of topsoil and turf<br />
The entire constructed<br />
wetland footprint is allowed<br />
to operate as a sediment<br />
basin<br />
Sedimentation Basins<br />
Ensure earthworks are stabilised<br />
immediately post construction<br />
(basin profile should be stabilised<br />
through sterile grasses, while<br />
terrestrial planting established<br />
around the basin perimeter)<br />
Ensure overflow from basin<br />
disconnected from any<br />
downstream treatment devices<br />
(such as wetlands)<br />
The protective measures identified above should be removed only when 80 to 90 percent of<br />
construction works in the catchment have been completed. If a distributed water sensitive<br />
design process has been implemented, treatment systems can be brought online gradually<br />
without having to wait for all development to cease.<br />
Landscaping can be established in areas isolated from stormwater flow. For constructed<br />
wetlands, special attention is required in manipulating the water level during plant<br />
establishment within the macrophyte zone such that plants are not ‘drowned’. The specific<br />
plant establishment requirements for constructed wetlands are detailed in the Water by<br />
Design documentation.<br />
42 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Stage 2 – Sediment Control Measures<br />
Sediment Control<br />
<strong>Book</strong> 4 | MAINTENANCE 43
Water Sensitive Urban Design<br />
6.1.3 Stage 3: Operational establishment (civil and/or landscaping)<br />
Stage 3 involves reconnecting the functional elements of the <strong>WSUD</strong> element to meet<br />
design specifications. In general, this involves decommissioning erosion and sediment<br />
control protection devices and replanting of landscape areas. Specific tasks within stage 3<br />
as they relate the <strong>WSUD</strong> elements addressed in the Operations and <strong>Maintenance</strong> booklet<br />
are:<br />
Bioretention basin<br />
Desilt basin if converted<br />
to a temporary sediment<br />
basin.<br />
Remove measures<br />
protecting filter media,<br />
for example bunds, filter<br />
cloth, topsoil and turf.<br />
Flush out under-drainage<br />
using potable (mains)<br />
water<br />
Flatten filter media<br />
surface to within given<br />
tolerance (additional<br />
media may be required<br />
to fill in over-excavated<br />
areas)<br />
Mulch filter media,<br />
allowing for planting<br />
holes<br />
Dig holes for planting<br />
Plant nominated species<br />
Maintain landscaping<br />
to ensure healthy plant<br />
establishment<br />
Constructed wetland<br />
Remove accumulated sediment<br />
and gross pollutants from inlet<br />
zone (and macrophyte zone if<br />
the wetland has been used as a<br />
sedimentation basin during stage<br />
2)<br />
Assess the condition of the<br />
impervious liner and hydraulic<br />
structures (if the wetland has<br />
been operated as a temporary<br />
sediment basin in stage 2) and<br />
amend accordingly<br />
Install topsoil in basin to a depth<br />
of 300 mm on batters and 500<br />
mm below the normal water<br />
level (this will be required for the<br />
macrophyte zone only if zone<br />
used as a sediment basin during<br />
stage 2)<br />
Remove disconnection between<br />
inlet and macrophyte zone (only if<br />
macrophyte plantings have been<br />
established during stage 2)*<br />
Landscape macrophyte zone if<br />
zone not yet established**<br />
Landscape inlet zone according<br />
to the design specifications**<br />
Sedimentation basin /<br />
pond<br />
Desilt basin<br />
Remove sterile grass from basin<br />
and establish marsh zone and<br />
embankment planting as per<br />
the design specifications<br />
Install topsoil to a depth of 300<br />
mm on batters and 500 mm<br />
below the normal water level<br />
Landscape basin as per the<br />
planting specifications***<br />
NOTE:<br />
* If the wetland has been used as a temporary sedimentation basin during stage 2, establish macrophyte<br />
plantings prior to bringing the macrophyte zone online. Specific requirements for plant establishment in the<br />
macrophyte zone of a constructed wetland are detailed in the Water by Design documentation.<br />
** Water levels will need to be manipulated during landscape establishment<br />
*** Water level manipulation is not required for ponds. The plants specified for the base of ponds will be suitable<br />
for an environment starved of oxygen. Typically plant establishment in ponds is through anchoring the plants /<br />
seedlings to the pond base with rocks.<br />
This task is required regardless of what sediment control measures are instigated as part of stage 2.<br />
Specific plant establishment requirements including fertiliser application and<br />
recommended watering schedule (including frequency of watering for terrestrial and<br />
marsh plantings, and the requirements for water level manipulation in constructed wetlands<br />
and ponds) are not detailed in this booklet. The reader is directed to the Water by Design<br />
(2009) documentation for further information.<br />
44 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Stage 3 – Operational Establishment<br />
Operational Establishment<br />
<strong>Book</strong> 4 | MAINTENANCE 45
Water Sensitive Urban Design<br />
6.2 Construction Tolerances<br />
The distribution of<br />
flow within a <strong>WSUD</strong><br />
element affects<br />
the treatment<br />
efficiency.<br />
Important to the design of bioretention<br />
basins, constructed wetlands, and<br />
sedimentation basins/ponds is the<br />
hydraulic function of the system (that is,<br />
how water is delivered from one part of a<br />
system to another) and the distribution of<br />
flow within the system. The distribution of<br />
flow within a <strong>WSUD</strong> element affects the<br />
treatment efficiency. Poor distribution of<br />
flow and the creation of localised water<br />
pools can also cause adverse affects such<br />
as mosquito breeding.<br />
The <strong>WSUD</strong> Technical Design Guidelines<br />
for South-East Queensland (SEQ)<br />
(Moreton Bay Waterways and Catchments<br />
Partnership, 2006) identifies key<br />
construction tolerances for typical <strong>WSUD</strong><br />
elements as related to system hydraulics<br />
or flow distribution. The revised technical<br />
guidelines for bioretention systems and<br />
constructed wetlands produced through<br />
Water by Design (2009) have seen the<br />
relaxing of these tolerances. A summary<br />
of the tolerances stipulated in the revised<br />
Water by Design documentation are given<br />
in the following table. The tolerances for<br />
sedimentation basins and ponds have<br />
also been updated to ensure consistency<br />
between similar design elements (for<br />
example, hydraulic structures).<br />
Further details on construction details can<br />
be found in the <strong>WSUD</strong> Technical Design<br />
Guidelines for South-East Queensland,<br />
which can be downloaded online<br />
from the Healthy Waterways website<br />
http://www/waterbydesign.com.<br />
CONSTRUCTION TOLERANCES<br />
Bioretention Basins Constructed Wetlands Sedimentation basins / ponds<br />
Profiling of base<br />
(+50 mm)<br />
Profiling of surface grades<br />
(i.e. drainage, transition and<br />
filter layer)<br />
(+25mm)<br />
Relative levels of flow<br />
control structures*<br />
(+25 mm)<br />
Bathymetry of macrophyte<br />
zone topsoil levels<br />
(+50 mm)<br />
Relative levels of flow control<br />
structures<br />
(+25 mm)<br />
Bathymetry of basin<br />
(+50 mm)<br />
Relative levels of hydraulic<br />
structures<br />
(+25 mm)<br />
Surface levels<br />
(+50 mm)<br />
Minimum slope of drainage<br />
system<br />
(0.5 %)<br />
* NOTE: Control structures are described as inlet connections, bypass weir and outlet structures<br />
46 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
6.3 Construction<br />
Certification and<br />
Compliance<br />
The construction of a vegetated <strong>WSUD</strong><br />
strategy requires coordination between<br />
the civil and landscaping contractors.<br />
Civil contractors are responsible for the<br />
construction of the functional elements<br />
of a treatment system, while landscape<br />
contractors are responsible for the<br />
initial plantings and management of<br />
the treatment system to ensure plant<br />
establishment is successful and meets the<br />
design brief.<br />
Consequently, construction certification is<br />
required from both civil and landscaping<br />
contractors as documented in the revised<br />
Water by Design (2009) documentation.<br />
The suggested construction certificates<br />
for constructed wetlands, bioretention<br />
systems and sediment basins/ponds are<br />
described in the table below.<br />
Additionally for bioretention basins,<br />
certification is required from the soil<br />
supplier to ensure the soil specifications<br />
of the filter media meet the requirements<br />
documented by the Facility for Advancing<br />
Water Biofiltration (FAWB) (refer to section<br />
4.04).<br />
The certification outlined above should<br />
form the basis of compliance for <strong>WSUD</strong><br />
elements. However, to minimise rework<br />
due to non-compliance issues, it is<br />
suggested that inspections/meetings be<br />
scheduled as follows (refer column over):<br />
1) Pre-start meeting: Ensure all<br />
contractors are aware of the key issues<br />
for each stage of construction. For<br />
example, compaction requirements<br />
for filter media.<br />
2) Inspection of all functional elements<br />
(as completed) of the treatment system<br />
(for example, the under-drainage for a<br />
bioretention should be inspected prior<br />
to the gravel being inserted around<br />
the pipes).<br />
3) Inspection of sediment control<br />
structures to ensure vulnerable<br />
elements within the treatment system<br />
are isolated from storm flows as<br />
dictated in the design documentation.<br />
4) Inspection of plant establishment<br />
(if required) to ensure species and<br />
densities are as per the design.<br />
Continual inspections should<br />
be scheduled to check plant<br />
establishment.<br />
5) Final inspection of plant establishment<br />
and civil works.<br />
The scheduling of the above inspections<br />
within the three main construction stages<br />
is given below. Example inspection and<br />
sign off sheets for <strong>WSUD</strong> elements are<br />
given in Appendix A.<br />
Civil Certification<br />
Designers certification of functional elements<br />
Civil certification that functional elements have been constructed as<br />
per the designers certification<br />
As constructed survey, drawings and photos<br />
Landscape Certification<br />
Designers or ecologist sign off of plant species<br />
As constructed drawings identifying species and plant density<br />
<strong>Book</strong> 4 | MAINTENANCE 47
Water Sensitive Urban Design<br />
6.4 Filter Media<br />
Specifications<br />
The Facility for Advancing Water<br />
Biofiltration (FAWB), a joint collaboration<br />
between Monash University and Ecological<br />
Engineering Holdings recently updated<br />
the original filter media specifications<br />
produced in 2006. Specifications are<br />
given for the three main layers defined for<br />
a bioretention basin as described in the<br />
table below.<br />
Further details relating to the testing<br />
of hydraulic conductivity, the specific<br />
filter media specifications (for example,<br />
organic matter content, pH, electrical<br />
conductivity and phosphorus content),<br />
and particle size distribution can be found<br />
in the FAWB document Guidelines For<br />
Soil Filter Media In Bioretention Systems<br />
(version 2.01). http://www.clearwater.asn.<br />
au/resources/658_1.FAWB%20Filter%20<br />
media%20guidelines_revised_March%20<br />
2008.pdf<br />
Recently, bioretention basin design has<br />
evolved to include an anoxic zone. In 2008,<br />
FAWB conducted a series of workshops on<br />
biofiltration systems, which included the<br />
design requirements and performance<br />
of biofiltration systems with submerged<br />
zones. The workshop material made the<br />
following specifications:<br />
1. Depth of submerged zone –<br />
approximately 450 mm.<br />
2. Media specifications – sand<br />
or gravel, containing a carbon<br />
source such as hardwood chips<br />
or sugar cane. The carbon source<br />
is to account for 5 percent of the<br />
volume of the submerged zone<br />
media.<br />
The workshop manual produced by FAWB<br />
can be downloaded from the following url:<br />
h t t p: // w w w.m o n a s h.e d u.au/ f a w b/<br />
products/index.html<br />
Filter Media (typically 400 to<br />
600 millimetres in depth)<br />
Loamy sand, with an appropriate hydraulic<br />
conductivity (100 to 300 millimetres per hour)<br />
and soil properties given in AS4419 – 2003 (Soils<br />
for Landscaping and Garden Use)<br />
Drainage Layer (typically 150<br />
millimetres in depth)<br />
Clean, well graded sand / coarse sand material<br />
(containing no/little fines)<br />
Transition Layer (typically<br />
100 millimetres in depth,<br />
or sufficient to provide<br />
50 millimetres of cover to<br />
drainage network)<br />
Clean fine gravel<br />
48 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Appendix A – Construction Inspection<br />
and Sign off sheets<br />
A.1. Bioretention Systems<br />
<strong>Book</strong> 4 | MAINTENANCE 49
Water Sensitive Urban Design<br />
Bioretention Basin Sign-Off Forms<br />
Development stage:<br />
Bioretention basin ID:<br />
Pre-Start Construction Meeting<br />
Location:<br />
Date:<br />
List of Attendees<br />
Name Discipline (suggested) Company<br />
1 Developer<br />
2 Site superintendent (civil)<br />
3 Site superintendent (landscape)<br />
4 Civil Contractor<br />
5 Landscape Contractor<br />
6 <strong>WSUD</strong> - Design Engineer<br />
7 Civil Engineer<br />
8 Landscape Architect<br />
9<br />
Checklist of Sign-Off Forms<br />
Sign-Off Form<br />
Date Completed<br />
Form A<br />
Form B<br />
Form C<br />
Form D<br />
Earthworks and Hydraulic / Functional Structures<br />
Erosion and Sediment Control<br />
Filter Material and Finished Levels<br />
Landscape Planting (Macrophyte and Inlet Zone)<br />
Construction Tolerances:<br />
The construction tolerances on the bioretention systems are to be:<br />
••<br />
plus or minus 50 mm on earth works and filter media levels.<br />
••<br />
plus or minus 25 mm on hydraulic structures (e.g. pit and weir<br />
crests/ bund heights, pipe and pit invert levels)<br />
Deviations to be approved only at the discretion of superintendent.<br />
50 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Form A - Earthworks and Hydraulic / Functional Structures<br />
Purpose:<br />
1) To ensure bulking out, trimming and profiling is in accordance with design specifications<br />
(including allowance for 300 mm topsoil and a minimum 300 mm of impervious liner where required).<br />
2) To ensure hydraulic structures associated with the bioretention basin are constructed in accordance<br />
with the design specifications.<br />
Checklist:<br />
Items<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Bulking out & hard structures<br />
As constructed survey of basin base and surrounding<br />
bunds, pit crests, inlet and outlet pipes<br />
Base levels are at correct elevation, given the<br />
minimum allowances for topsoil and impervious liner<br />
(where required)<br />
Base at correct grading (0.5 percent)<br />
Hold Point - Sign off is required from superintendent and bioretention basin designer before proceeding<br />
Bunds and impervious liner<br />
Laboratory test results of liner material submitted<br />
and adequate<br />
Delivery docket of liner material submitted and<br />
adequate<br />
Delivery docket of liner material supplied<br />
Geotechnical engineer certification of in-situ<br />
compaction or liner placement<br />
Geotechnical engineer certification / sign off of key<br />
bunds<br />
<strong>Book</strong> 4 | MAINTENANCE 51
Water Sensitive Urban Design<br />
Hold Point - Sign off is required from superintendent and bioretention basin designer before proceeding<br />
Functional and hydraulic functions<br />
Inlet and outlet pipes and headwalls correctly set<br />
out and at correct level (upstream and downstream<br />
ends)<br />
Bypass weir correct width and level<br />
Overflow pit is correct size and crest is at correct<br />
level<br />
<strong>Maintenance</strong> pipe and valve installed at<br />
correct location and level<br />
<strong>Maintenance</strong> access installed to inlet zone<br />
Rock or concrete base constructed at<br />
inlet to bioretention basin<br />
Rock protection provided at correct locations<br />
and rock size consistent with design<br />
Hold Point - Sign off is required from superintendent and bioretention basin designer before proceeding<br />
Under-drainage<br />
Base of system free from debris<br />
Under-drainage pipes laid at required grade<br />
(verified using level or string line)<br />
52 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
All junctions and connections have<br />
been appropriately sealed using sealant<br />
Underdrain pipes correctly connected and<br />
sealed into overflow pit<br />
Top of clean out points at design level (i.e.<br />
approximately 100mm above filter media surface<br />
level)<br />
Extension of under-drains out of the<br />
basin are NOT perforated<br />
Clean out points capped<br />
Hold Point - Sign off is required from superintendent and bioretention basin designer before proceeding<br />
Comments:<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
<strong>Book</strong> 4 | MAINTENANCE 53
Water Sensitive Urban Design<br />
Form B – Erosion and Sediment Control<br />
Purpose:<br />
To ensure sediment and erosion control measures are correctly installed to protect the bioretention<br />
basin filter media.<br />
Checklist:<br />
Items<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Continuous silt fences installed around all<br />
elements of constructed wetlands<br />
If silt fences are deemed inadequate, other sediment<br />
and erosion control measures installed to ensure<br />
sediment does not enter basin<br />
High flow bypass channel protective measures in place<br />
(that is, turf installed and where required reinforced turf)<br />
If basin to be used as a sedimentation basin<br />
during lot development<br />
Filter media surface protected, either by installing a<br />
filter cloth or 25 to 50 mm of course sand plus 25 mm<br />
of topsoil and turf<br />
If basin is to be isolated during lot development<br />
Stormwater diverted away from functional elements<br />
of bioretention basin<br />
Hold Point - Sign off is required from superintendent and bioretention basin designer before proceeding<br />
Comments<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
54 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Form C – Filter Material and Finished Levels<br />
Purpose:<br />
To ensure that the soils to be placed in the basin match the soils that were specified and ordered. To ensure<br />
soil layers are placed according to specifications prior to any landscape works.<br />
Checklist:<br />
Item<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Filter Material<br />
Drainage layer (fine gravel):<br />
Supply docket matches gravel specification<br />
NOTE: Attach Supply Docket<br />
Transition layer (coarse sand):<br />
Supply docket matches sand specification<br />
NOTE: Attach Supply Docket<br />
Filter layer (sandy loam):<br />
Supply docket matches media specification<br />
NOTE: Attach Supply Docket<br />
Filter material testing completed and approved<br />
in accordance with design report<br />
Drainage layer (fine gravel) installed to<br />
correct depth (photo and survey)<br />
Transition layer (coarse sand) installed to<br />
correct depth (photo and survey)<br />
Filter media installed to correct depth<br />
(photo and survey)<br />
Light, even compaction applied to remove air gaps<br />
Even flat surface of filter media<br />
<strong>Book</strong> 4 | MAINTENANCE 55
Water Sensitive Urban Design<br />
Finished levels<br />
As constructed survey of basin surface and<br />
surrounding bunds completed<br />
Final constructed levels are consistent with<br />
design levels<br />
Under-drainage pipes flushed to remove initial<br />
ingress of material<br />
All civil construction items are complete and basin is<br />
ready for planting by landscape contractor<br />
Geofabric layer + 50mm topsoil (top layer of<br />
supplied filter material) and turf applied to basin<br />
surface.<br />
Suitable batter protection in place<br />
(e.g. sediment fence or landscape netting)<br />
HOLD POINT - Sign off is required from superintendent and bioretention basin designer before proceeding<br />
Comments<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
56 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Form D – Landscape Planting<br />
Purpose:<br />
To ensure correct plants are supplied and installed. To be used in conjunction with other landscape sign off<br />
requirements.<br />
Checklist:<br />
Item<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Basin desilted and filter media levels reinstated to<br />
meet design specifications<br />
NOTE: This action is applicable if bioretention<br />
basin was converted to a sediment basin during lot<br />
development<br />
Supplied plants are correct species<br />
Changes to species planted must be approved by<br />
wetland designer/ecologist and marked up on asconstructed<br />
drawings<br />
Supplied plants are in correct pot sizes, maturity<br />
(minimum 300 mm in height) and hardened<br />
Plants have been installed at correct planting density<br />
Correct mulch has been supplied and installed to<br />
batters and bunds above the extended detention<br />
and secured in place<br />
As constructed drawings marked up with final plant<br />
species and densities<br />
HOLD POINT - Sign off is required from superintendent and bioretention basin designer before proceeding<br />
Comments<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
<strong>Book</strong> 4 | MAINTENANCE 57
Water Sensitive Urban Design<br />
Appendix A – Construction Inspection<br />
and Sign off sheets<br />
A.2. Constructed Wetlands<br />
58 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Constructed Wetland Sign-Off Forms<br />
Development stage:<br />
Wetland ID::<br />
Pre-Start Construction Meeting<br />
Location:<br />
Date:<br />
List of Attendees<br />
Name Discipline (suggested) Company<br />
1 Developer<br />
2 Site superintendent (civil)<br />
3 Site superintendent (landscape)<br />
4 Civil Contractor<br />
5 Landscape Contractor<br />
6 <strong>WSUD</strong> - Design Engineer<br />
7 Civil Engineer<br />
8 Landscape Architect<br />
9<br />
Checklist of Sign-Off Forms<br />
Sign-Off Form<br />
Date Completed<br />
Form A<br />
Form B<br />
Form C<br />
Form D<br />
Earthworks and Hydraulic / Functional Structures<br />
Erosion and Sediment Control<br />
Topsoil and Finished Levels<br />
Landscape Planting (Macrophyte and Inlet Zone)<br />
Construction Tolerances:<br />
The construction tolerances on the constructed wetland systems are to be:<br />
••<br />
plus or minus 25 mm on hydraulic structures (e.g. pit and weir crests/ bund heights, pipe and pit invert<br />
levels)<br />
••<br />
plus or minus 50 mm on earthworks (base of wetland, as measured from the surface of the topsoil).<br />
••<br />
plus or minus 50 mm on embankments and bunds (that is, crest level of the embankment).<br />
Deviations to be approved only at the discretion of the superintendent.<br />
<strong>Book</strong> 4 | MAINTENANCE 59
Water Sensitive Urban Design<br />
Form A – Earthworks and Hydraulic/Functional Structures<br />
Purpose:<br />
3) To ensure bulking out, trimming and profiling is in accordance with design specifications (including<br />
allowance for 300 mm topsoil and a minimum 300 mm of impervious liner where required).<br />
4) To ensure hydraulic structures associated with the wetland are constructed in accordance with the<br />
design specifications.<br />
Checklist:<br />
Items<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Bulking out & hard structures<br />
As constructed survey of basin base and surrounding<br />
bunds, pit crests, inlet and outlet pipes<br />
Set out of wetlands is correct (including inlet<br />
zone, macrophyte zone, high flow bypass)<br />
Base levels are at correct elevation, given the<br />
minimum allowances for topsoil and impervious<br />
liner (where required)<br />
Hold Point - Sign off is required from superintendent and wetland designer before proceeding<br />
Bunds and impervious liner<br />
Laboratory test results of liner material submitted<br />
and adequate<br />
Delivery docket of liner material submitted<br />
and adequate<br />
Delivery docket of liner material supplied<br />
60 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Geotechnical engineer certification of in-situ<br />
compaction or liner placement<br />
Geotechnical engineer certification / sign off<br />
of key bunds<br />
Hold Point - Sign off is required from superintendent and wetland designer before proceeding<br />
Functional and hydraulic functions<br />
Inlet and outlet pipes and headwalls<br />
correctly set out and at correct level<br />
(upstream and downstream ends)<br />
Inlet zone connection pit or pipe<br />
correct size, location and level<br />
Outlet riser connection, location,<br />
size and levels correct<br />
Bypass weir correct width and level<br />
Overflow pit is correct size and crest<br />
is at correct level<br />
<strong>Maintenance</strong> pipe and valve installed<br />
at correct location and level<br />
<strong>Maintenance</strong> access installed to inlet zone<br />
Rock or concrete base constructed to inlet zone<br />
<strong>Book</strong> 4 | MAINTENANCE 61
Water Sensitive Urban Design<br />
Rock protection provided at correct locations and<br />
rock size consistent with design<br />
Seepage collar(s) installed to all pipe outlets from<br />
wetland<br />
Hold Point - Sign off is required from superintendent and wetland designer before proceeding<br />
Comments<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
62 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Form B – Sediment and Erosion Control<br />
Purpose:<br />
To ensure sediment and erosion control measures are correctly installed to protect the macrophyte zone of<br />
the constructed wetland.<br />
Checklist:<br />
Items<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Continuous silt fences installed around all elements<br />
of constructed wetlands<br />
If silt fences are deemed inadequate, other sediment<br />
and erosion control measures installed to ensure<br />
sediment does not enter basin<br />
High flow bypass channel protective measures in<br />
place (that is, turf installed and where required<br />
reinforced turf)<br />
Inlet zone disconnected from macrophyte zone (that<br />
is, plates placed on overflow pit and secured)<br />
If inlet zone not disconnected, macrophyte zone<br />
converted into a sedimentation basin (base and<br />
batters of macrophyte<br />
Hold Point - Sign off is required from superintendent and wetland designer before proceeding<br />
Comments<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
<strong>Book</strong> 4 | MAINTENANCE 63
Water Sensitive Urban Design<br />
Form C – Topsoil and Finished Levels<br />
Purpose:<br />
To ensure the topsoil is installed to the correct depth and finished levels of wetland are correct and meet the<br />
design.<br />
Checklist:<br />
Item<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Topsoil meets the requirements of AS4419 and<br />
laboratory tests provided<br />
Topsoil has been screened and is free of large debris<br />
Topsoil applied to wetland (minimum 300 mm depth)<br />
Final topsoil levels are consistent with design levels<br />
(CRITICAL in the macrophyte zone)<br />
Surface is smooth and free of local depressions and<br />
debris<br />
Hold Point - Sign off is required from superintendent and wetland designer before proceeding<br />
Comments<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
64 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Form D – Landscape Planting<br />
Purpose:<br />
To ensure correct plants are supplied and installed.<br />
Checklist:<br />
Item<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Macrophyte zone landscape installation<br />
Supplied plants are correct species<br />
Changes to species planted must be approved by<br />
wetland designer/ecologist and marked up on<br />
as-constructed drawings<br />
Supplied plants are in correct pot sizes, maturity<br />
(minimum 300 mm in height) and hardened<br />
Plants have been installed at correct planting density<br />
Water level control is operating appropriately<br />
Correct mulch has been supplied and installed to<br />
batters and bunds above the extended detention<br />
and secured in place<br />
As constructed drawings marked up with final<br />
plant species and densities<br />
HOLD POINT - Sign off is required from superintendent and wetland designer before proceeding<br />
Macrophyte zone landscape establishment<br />
Weeds removed as required<br />
<strong>Book</strong> 4 | MAINTENANCE 65
Water Sensitive Urban Design<br />
Watering occurring as required<br />
Macrophyte plants established such that the water level<br />
in the macrophyte zone can be allowed to reach design<br />
level (typically 500 mm above the normal water level)<br />
HOLD POINT - Sign off is required from superintendent and wetland designer before proceeding<br />
Comments<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
66 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Form D – Landscape Planting (inlet zone)<br />
Purpose:<br />
To ensure correct plants are supplied and installed.<br />
Checklist:<br />
Item<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Inlet zone landscape installation<br />
Supplied plants are correct species<br />
Changes to species planted must be approved by wetland<br />
designer/ecologist and marked up on as-constructed<br />
drawings<br />
Supplied plants are in correct pot sizes, maturity (minimum<br />
300 mm in height) and hardened<br />
Plants have been installed at correct planting density<br />
Correct mulch has been supplied and installed to batters<br />
and bunds above the normal water level and secured in<br />
place<br />
As constructed drawings marked up with final plant species<br />
and densities<br />
HOLD POINT - Sign off is required from superintendent and wetland designer before proceeding<br />
Inlet zone landscape establishment<br />
Weeds removed as required<br />
Watering occurring as required<br />
Inlet zone plantings established such that the water level in<br />
the macrophyte zone can be allowed to reach design level<br />
(typically 500 mm above the normal water level)<br />
HOLD POINT - Sign off is required from superintendent and wetland designer before proceeding<br />
Comments<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
<strong>Book</strong> 4 | MAINTENANCE 67
Water Sensitive Urban Design<br />
Appendix A – Construction Inspection<br />
and Sign off sheets<br />
A.3 Sedimentation Basins / Ponds<br />
68 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Sedimentation Basin Sign-Off Forms<br />
Development stage:<br />
Sediment basin / pond ID:<br />
Pre-Start Construction Meeting<br />
Location:<br />
Date:<br />
List of Attendees<br />
Name Discipline (suggested) Company<br />
1 Developer<br />
2 Site superintendent (civil)<br />
3 Site superintendent (landscape)<br />
4 Civil Contractor<br />
5 Landscape Contractor<br />
6 <strong>WSUD</strong> - Design Engineer<br />
7 Civil Engineer<br />
8 Landscape Architect<br />
9<br />
Checklist of Sign-Off Forms<br />
Sign-Off Form<br />
Date Completed<br />
Form A<br />
Form B<br />
Form C<br />
Form D<br />
Earthworks and Hydraulic / Functional Structures<br />
Sediment and Erosion Control<br />
Topsoil and Finished Levels<br />
Landscape Planting (Macrophyte and Inlet Zone)<br />
Construction Tolerances:<br />
The construction tolerances on the constructed wetland systems are to be:<br />
••<br />
plus or minus 25 mm on hydraulic structures (e.g. pit and weir crests/ bund heights, pipe and pit invert<br />
levels)<br />
••<br />
plus or minus 50 mm on earthworks (base of wetland, as measured from the surface of the topsoil).<br />
••<br />
plus or minus 50 mm on embankments and bunds (that is, crest level of the embankment).<br />
Deviations to be approved only at the discretion of superintendent.<br />
<strong>Book</strong> 4 | MAINTENANCE 69
Water Sensitive Urban Design<br />
Form A – Earthworks and Hydraulic/Functional Structures<br />
Purpose:<br />
5) To ensure bulking out and key levels of hard structures are in accordance with design specifications.<br />
6) To ensure hydraulic structures associated with the sedimentation basin or pond is constructed in<br />
accordance with the design specifications.<br />
Checklist:<br />
Items<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Bulking out & hard structures<br />
As constructed survey of basin base and surrounding<br />
bunds, pit crests, inlet and outlet pipes<br />
Base levels are at correct elevation, given the<br />
minimumallowances for topsoil and impervious<br />
liner (where required)<br />
Hold Point - Sign off is required from superintendent and wetland designer before proceeding<br />
Bunds and impervious liner<br />
Laboratory test results of liner material submitted<br />
and adequate<br />
Delivery docket of liner material submitted<br />
and adequate<br />
Delivery docket of liner material supplied<br />
Geotechnical engineer certification / sign off<br />
of key bunds<br />
Hold Point - Sign off is required from superintendent and wetland designer before proceeding<br />
70 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Functional and hydraulic functions<br />
Inlet and outlet pipes and headwalls<br />
correctly set out and at correct level<br />
(upstream and downstream ends)<br />
Bypass weir correct width and level<br />
Overflow pit is correct size and crest is<br />
at correct level<br />
Bypass weir correct width and level<br />
<strong>Maintenance</strong> pipe and valve installed<br />
at correct location and level<br />
<strong>Maintenance</strong> access installed to basin<br />
Rock protection provided at correct locations and<br />
rock size consistent with design (applicable to<br />
sediment basin, only)<br />
Hold Point - Sign off is required from superintendent and wetland designer before proceeding<br />
Comments<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
<strong>Book</strong> 4 | MAINTENANCE 71
Water Sensitive Urban Design<br />
Form B – Sediment and Erosion Control<br />
Purpose:<br />
To ensure sediment and erosion control measures are correctly installed to protect either downstream<br />
treatment systems (in the case of sedimentation basins) or minimise clean-out post construction (in the case<br />
of an ornamental pond).<br />
Checklist:<br />
Items<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Continuous silt fences installed around all<br />
elements of basin / pond<br />
If silt fences are deemed inadequate, other sediment<br />
and erosion control measures installed to ensure<br />
sediment does not enter basin<br />
High flow bypass channel protective measures in place<br />
(that is, turf installed and where required reinforced turf)<br />
Basin profile stabilised through sterile grasses, while<br />
terrestrial planting established around the basin perimeter<br />
SEDIMENT BASIN, ONLY<br />
Ensure overflow from sediment basin disconnected from<br />
any downstream treatment devices (such as wetlands)<br />
POND, ONLY<br />
Ensure inlet to pond is isolated from any upstream<br />
sediment control measures<br />
Hold Point - Sign off is required from superintendent and basin/pond designer before proceeding<br />
Comments<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
72 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Form C – Topsoil and Finished Levels<br />
Purpose:<br />
To ensure the topsoil is installed to the correct depth and finished levels of wetland are correct and meet the<br />
design.<br />
Checklist:<br />
Item<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Sedimentation basin desilted prior to plant establishment<br />
Topsoil meets the requirements of AS4419 and laboratory<br />
tests provided<br />
Topsoil has been screened and is free of large debris<br />
Topsoil applied to base (minimum 300 mm depth)<br />
Final topsoil levels are consistent with design levels<br />
Surface is smooth and free of local depressions and debris<br />
Hold Point - Sign off is required from superintendent and basin/pond designer before proceeding<br />
Comments<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
<strong>Book</strong> 4 | MAINTENANCE 73
Water Sensitive Urban Design<br />
Form D – Landscape Planting<br />
Purpose:<br />
To ensure correct plants are supplied and installed.<br />
Checklist:<br />
Item<br />
Checked<br />
Satisfactory<br />
Action/s<br />
(if required)<br />
Actions<br />
addressed<br />
(initial)<br />
Supplied plants are correct species<br />
Changes to species planted must be approved by<br />
wetland designer/ecologist and marked up on<br />
as-constructed drawings<br />
Supplied plants are in correct pot sizes, maturity<br />
(minimum 300 mm in height) and hardened<br />
Plants have been installed at correct planting density<br />
Correct mulch has been supplied and installed to<br />
batters and bunds above the normal water level<br />
and secured in place<br />
As constructed drawings marked up with final plant<br />
species and densities<br />
HOLD POINT - Sign off is required from superintendent and wetland designer before proceeding<br />
Comments<br />
Signed by Superintendent(s):<br />
Print Name:<br />
Date:<br />
74 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Appendix B – Regular <strong>Maintenance</strong><br />
Checklists<br />
<strong>Book</strong> 4 | MAINTENANCE 75
Water Sensitive Urban Design<br />
B.1 Bioretention Basins<br />
Item<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
(circle relevant category)<br />
Immediate<br />
Action<br />
Required<br />
Comment<br />
Action Processed<br />
1 GPT / trash rack/s<br />
GPT clear of<br />
litter<br />
GPT 10 percent<br />
full<br />
greater than 30<br />
percent full<br />
2 Inlet structures<br />
Clear and<br />
undamaged<br />
Partially<br />
Blocked<br />
Observed<br />
damage<br />
Mostly blocked<br />
Severe damage<br />
3 Overflow pits<br />
Clear and<br />
undamaged<br />
Partially<br />
Blocked<br />
Observed<br />
damage<br />
Mostly blocked<br />
Severe damage<br />
4 Underdrains<br />
Clear and<br />
undamaged<br />
Partially<br />
Blocked<br />
Observed<br />
damage<br />
Mostly blocked<br />
Severe damage<br />
5 Sediment Forebay<br />
Sediment<br />
absent<br />
Sediment<br />
accumulation<br />
appears<br />
excessive<br />
Sediment<br />
accumulated to<br />
half the basin<br />
depth<br />
6 Erosion Erosion absent<br />
Erosion<br />
damage visible,<br />
but function<br />
not impaired<br />
Severe erosion.<br />
Damage<br />
impairing<br />
function of<br />
device<br />
Location (mark on attached<br />
map of bioretention basin)<br />
7<br />
Sediment<br />
accumulation<br />
(bioretention basin)<br />
Sediment<br />
absent<br />
Sediment<br />
accumulation<br />
appears<br />
excessive<br />
in sediment<br />
forebay.<br />
Fine sediment<br />
accumulation<br />
apparent on<br />
bioretention<br />
media surface.<br />
Sediment<br />
accumulated to<br />
half the forebay<br />
depth<br />
Coarse<br />
sediment or<br />
large volumes<br />
of sediment<br />
accumulation<br />
apparent on the<br />
bioretention<br />
media surface<br />
Location (mark on attached<br />
map of bioretention basin)<br />
76 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Item<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
(circle relevant category)<br />
Immediate<br />
Action<br />
Required<br />
Comment<br />
Action Processed<br />
8<br />
Compaction of filter<br />
media surface<br />
No compaction<br />
evident<br />
Localised<br />
compaction<br />
or subsidence<br />
evident.<br />
Localised<br />
ponding longer<br />
than 24 hours<br />
after storm<br />
event<br />
Water remains<br />
ponding longer<br />
than 24 hours<br />
after storm<br />
event<br />
Location (mark on attached<br />
map of bioretention basin)<br />
9 Weeds<br />
No weeds<br />
present<br />
Weeds present<br />
Noxious or<br />
environmental<br />
weeds present,<br />
or weed cover<br />
more than 25<br />
percent<br />
Location (mark on attached<br />
map of bioretention basin)<br />
Identify weed species<br />
10 Plant condition<br />
Healthy<br />
vegetation<br />
Poorly growing<br />
or visibly<br />
stressed<br />
Die back / dead<br />
plants<br />
Location (mark on attached<br />
map of bioretention basin)<br />
Identify species requiring<br />
replacement<br />
11 Litter (organic) No litter visible Litter visible<br />
Litter thickly<br />
covers filter<br />
media surface<br />
or detracting<br />
from visual<br />
amenity<br />
Location (mark on attached<br />
map of bioretention basin)<br />
Note type of litter removed<br />
12<br />
Litter<br />
(anthropogenic)<br />
No litter visible<br />
Litter visible<br />
Litter blocking<br />
structures or<br />
detracting from<br />
visual amenity<br />
Location (mark on attached<br />
map of bioretention basin)<br />
Note type of litter removed<br />
13 Oil spills / inflows No visible oil<br />
Persistent but<br />
limited visible<br />
oil<br />
Extensive or<br />
localised thick<br />
layer of oil<br />
visible<br />
<strong>Book</strong> 4 | MAINTENANCE 77
Water Sensitive Urban Design<br />
B.2 Constructed Wetlands<br />
Item<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
(circle relevant category)<br />
Immediate<br />
Action<br />
Required<br />
Comments<br />
Action Processed<br />
1 GPT / trash rack<br />
GPT clear of<br />
litter<br />
GPT 10 percent<br />
full<br />
GPT / trash<br />
rack for than 30<br />
percent full<br />
2 Inlet pipe<br />
Clear and<br />
undamaged<br />
Partially<br />
Blocked<br />
Observed<br />
damage<br />
Mostly blocked<br />
Severe damage<br />
3<br />
Pipes connecting<br />
macrophyte cells<br />
Clear and<br />
undamaged<br />
Partially<br />
Blocked<br />
Observed<br />
damage<br />
Mostly blocked<br />
Severe damage<br />
4 Outlet pit<br />
Clear and<br />
undamaged<br />
Partially<br />
Blocked<br />
Observed<br />
damage<br />
Mostly blocked<br />
Severe damage<br />
5 Erosion Erosion absent<br />
Erosion<br />
damage visible,<br />
but structure<br />
functional<br />
Severe erosion.<br />
Damage<br />
impairing<br />
function of<br />
device<br />
Location<br />
(mark on attached map of<br />
wetland)<br />
6 Sediment build-up<br />
Sediment<br />
absent<br />
Sediment<br />
accumulation<br />
appears<br />
excessive<br />
Sediment<br />
accumulated to<br />
half the basin<br />
depth<br />
Location<br />
(mark on attached map of<br />
wetland)<br />
7<br />
Aquatic weeds<br />
(submerged,<br />
emergent and floating)<br />
No weeds<br />
present<br />
Weeds present<br />
Noxious or<br />
environmental<br />
weeds present<br />
Location<br />
(mark on attached map of<br />
wetland)<br />
Identify weed species<br />
78 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Item<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
(circle relevant category)<br />
Immediate<br />
Action<br />
Required<br />
Comments<br />
Action Processed<br />
8<br />
Terrestrial weeds<br />
(e.g. within the batter<br />
slopes)<br />
No weeds<br />
present<br />
Weeds present<br />
Noxious or<br />
environmental<br />
weeds present<br />
Location (mark on attached<br />
map of wetland)<br />
Identify weed species<br />
9 Algal blooms<br />
No algae<br />
apparent<br />
Algae visible<br />
Algal growth<br />
prominent or<br />
extensive<br />
10<br />
Plant condition<br />
(aquatic macrophytes)<br />
Healthy<br />
vegetation<br />
Poorly growing<br />
or visibly<br />
stressed<br />
Die back / dead<br />
plants<br />
Note species which require<br />
replanting<br />
11<br />
Plant condition<br />
(terrestrial)<br />
Healthy<br />
vegetation<br />
Poorly growing<br />
or visibly<br />
stressed<br />
Die back / dead<br />
plants<br />
Note species which require<br />
replanting<br />
12 Litter (organic) No litter visible Litter visible<br />
Litter blocking<br />
structures or<br />
detracting from<br />
visual amenity<br />
Location (mark on attached<br />
map of wetland)<br />
Note type of litter removed<br />
13 Litter (anthropogenic) No litter visible Litter visible<br />
Litter blocking<br />
structures or<br />
detracting from<br />
visual amenity<br />
Location (mark on attached<br />
map of wetland)<br />
Note type of litter removed<br />
<strong>Book</strong> 4 | MAINTENANCE 79
Water Sensitive Urban Design<br />
B.3 Sedimentation Basin<br />
Item<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
(circle relevant category)<br />
Immediate<br />
Action<br />
Required<br />
Comment<br />
Action Processed<br />
1 GPT / trash rack/s<br />
GPT clear of<br />
litter<br />
GPT 10 percent<br />
full<br />
greater than 30<br />
percent full<br />
2 Inlet structures<br />
Clear and<br />
undamaged<br />
Partially<br />
Blocked<br />
Observed<br />
damage<br />
Mostly blocked<br />
Severe damage<br />
3 Overflow pits<br />
Clear and<br />
undamaged<br />
Partially<br />
Blocked<br />
Observed<br />
damage<br />
Mostly blocked<br />
Severe damage<br />
4 Sediment Forebay<br />
Sediment<br />
absent<br />
Sediment<br />
accumulation<br />
appears<br />
excessive<br />
Sediment<br />
accumulated to<br />
half the basin<br />
depth<br />
5 Erosion Erosion absent<br />
Erosion<br />
damage visible,<br />
but function<br />
not impaired<br />
Severe erosion.<br />
Damage<br />
impairing<br />
function of<br />
device<br />
Location<br />
(mark on attached map of<br />
sedimentation basin)<br />
6<br />
Sediment<br />
accumulation<br />
Sediment<br />
accumulated to<br />
less than half<br />
the basin depth<br />
Sediment<br />
accumulated to<br />
half basin depth<br />
Sediment<br />
accumulation<br />
greater than<br />
half the basin<br />
depth<br />
Note timing since last desilting<br />
operation<br />
80 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Item<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
(circle relevant category)<br />
Immediate<br />
Action<br />
Required<br />
Comment<br />
Action Processed<br />
7 Weeds<br />
No weeds<br />
present<br />
Weeds present<br />
Noxious or<br />
environmental<br />
weeds present,<br />
or weed cover<br />
more than 25<br />
percent<br />
Location<br />
(mark on attached map of<br />
sedimentation basin)<br />
Identify weed species<br />
8 Plant condition<br />
Healthy<br />
vegetation<br />
Poorly growing<br />
or visibly<br />
stressed<br />
Die back / dead<br />
plants<br />
Location<br />
(mark on attached map of<br />
sedimentation basin)<br />
Identify species requiring<br />
replacement<br />
9 Litter (organic) No litter visible Litter visible<br />
Litter thickly<br />
covers filter<br />
media surface<br />
or detracting<br />
from visual<br />
amenity<br />
Location<br />
(mark on attached map of<br />
sedimentation basin)<br />
Note type of litter removed<br />
10<br />
Litter<br />
(anthropogenic)<br />
No litter visible<br />
Litter visible<br />
Litter blocking<br />
structures or<br />
detracting from<br />
visual amenity<br />
Location<br />
(mark on attached map of<br />
sedimentation basin)<br />
Note type of litter removed<br />
11 Oil spills / inflows No visible oil<br />
Persistent but<br />
limited visible<br />
oil<br />
Extensive or<br />
localised thick<br />
layer of oil<br />
visible<br />
<strong>Book</strong> 4 | MAINTENANCE 81
Water Sensitive Urban Design<br />
B.4 Ponds<br />
Item<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
(circle relevant category)<br />
Immediate Action<br />
Required<br />
Comments<br />
Action Processed<br />
1 Inlet pipe<br />
Clear and<br />
undamaged<br />
Partially<br />
Blocked<br />
Observed<br />
damage<br />
Mostly blocked<br />
Severe damage<br />
2 Outlet pipe<br />
Clear and<br />
undamaged<br />
Partially<br />
Blocked<br />
Observed<br />
damage<br />
Mostly blocked<br />
Severe damage<br />
3 Erosion Erosion absent<br />
Erosion<br />
damage visible,<br />
but structure<br />
functional<br />
Severe erosion.<br />
Damage<br />
impairing<br />
function of<br />
device<br />
Location (mark on attached map<br />
of pond)<br />
4 Sediment build-up<br />
Sediment<br />
absent<br />
Sediment<br />
accumulation<br />
appears<br />
excessive<br />
Sediment<br />
accumulated to<br />
half the basin<br />
depth<br />
Location (mark on attached map<br />
of pond)<br />
5<br />
Aquatic weeds<br />
( s u b m e r g e d ,<br />
emergent and floating)<br />
No weeds<br />
present<br />
Weeds present<br />
Noxious or<br />
environmental<br />
weeds present<br />
Location (mark on attached map<br />
of pond)<br />
Identify weed species<br />
6<br />
Terrestrial weeds<br />
(e.g. within the batter<br />
slopes)<br />
No weeds<br />
present<br />
Weeds present<br />
Noxious or<br />
environmental<br />
weeds present<br />
Location (mark on attached map<br />
of pond)<br />
Identify weed species<br />
82 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Item<br />
Performance<br />
Target<br />
Schedule<br />
<strong>Maintenance</strong> or<br />
Investigation<br />
(circle relevant category)<br />
Immediate Action<br />
Required<br />
Comments<br />
Action Processed<br />
7 Algal blooms<br />
No algae<br />
apparent<br />
Algae visible<br />
Algal growth<br />
prominent or<br />
extensive<br />
8<br />
Plant condition<br />
(aquatic macrophytes)<br />
Healthy<br />
vegetation<br />
Poorly growing<br />
or visibly<br />
stressed<br />
Die back / dead<br />
plants<br />
Note species which require<br />
replanting<br />
9<br />
Plant<br />
(terrestrial)<br />
condition<br />
Healthy<br />
vegetation<br />
Poorly growing<br />
or visibly<br />
stressed<br />
Die back / dead<br />
plants<br />
Note species which require<br />
replanting<br />
10 Litter (organic) No litter visible Litter visible<br />
Litter blocking<br />
structures or<br />
detracting from<br />
visual amenity<br />
Location (mark on<br />
attached map of pond)<br />
Note type of litter removed<br />
11 Litter (anthropogenic) No litter visible Litter visible<br />
Litter blocking<br />
structures or<br />
detracting from<br />
visual amenity<br />
Location (mark on<br />
attached map of pond)<br />
Note type of litter removed<br />
NOTE: A check for trash racks / nets has not been included, as the pond should not be designed as a water quality treatment<br />
system, but rather to provide storage capacity of attenuation of peak flows to downstream waterways.<br />
<strong>Book</strong> 4 | MAINTENANCE 83
Water Sensitive Urban Design<br />
Appendix C | Asset handover sheets<br />
Asset HANDOVER Checklist*<br />
Asset I.D.<br />
Asset Location:<br />
Construction by:<br />
Time since planting established and maintenance required:<br />
TREATMENT Y N<br />
System appears to be working as designed visually?<br />
No obvious signs of under-performance?<br />
MAINTENANCE Y N<br />
<strong>Maintenance</strong> plans and indicative maintenance costs provided for each asset?<br />
Vegetation establishment period completed (2 years)?<br />
Inspection and maintenance undertaken as per maintenance plan?<br />
Inspection and maintenance forms provided?<br />
Asset inspected for defects and/or maintenance issues at time of asset transfer Y N<br />
Sediment accumulation at inflow points?<br />
Litter within basin?<br />
Erosion at inlet or other key structures?<br />
Traffic damage present?<br />
Evidence of dumping (e.g. building waste)?<br />
Vegetation condition satisfactory (density, weeds etc)?<br />
Watering of vegetation required?<br />
Replanting required?<br />
Mowing/slashing required?<br />
Clogging of drainage points (sediment or debris)?<br />
Evidence of ponding?<br />
Damage/vandalism to structures present?<br />
Surface clogging visible?<br />
Drainage system inspected?<br />
COMMENTS/ACTIONS REQUIRED FOR ASSET TRANSFER<br />
ASSET INFORMATION Y N<br />
Design Assessment Checklist provided?<br />
As constructed plans provided?<br />
Copies of all required permits (both construction and operational) submitted?<br />
Proprietary information provided (if applicable)?<br />
Digital files (e.g. drawings, survey, models) provided?<br />
Asset listed on asset register or database?<br />
* Asset handover checklists are generic and can be used for all <strong>WSUD</strong> elements discussed in this booklet<br />
84 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
Appendix D | References<br />
Collins (2006), Destination SQID Waster<br />
Stormwater Industry Association<br />
available online at :-<br />
www.wsud.org/downloads/2006_SIA_Papers/Anthony%20Collins%20%20-%20Hornsby%20Council.pdf<br />
Facility for Advancing Water Biofiltration (FAWB) (2008), Workshop<br />
Advancing the Design of Biofiltration<br />
available online at :-<br />
http://www.monash.edu.au/fawb/products/fawb-advancing-rain-gardens-workshop-booklet.pdf<br />
Facility for Advancing Water Biofiltration (FAWB) (2008)<br />
Guidelines for Soil Filter Media in Bioretention Systems<br />
available online at :-<br />
http://www.monash.edu.au/fawb/products/obtain.html<br />
Water by Design (2009)<br />
Chapter 4 – Constructed Wetlands<br />
South East Queensland Healthy Waterways Partnership<br />
Water by Design (2009)<br />
Chapter 3 – Bioretention Systems<br />
South East Queensland Healthy Waterways Partnership<br />
Water by Design (2009)<br />
Construction and Establishment Guidelines<br />
Swales, Bioretention Systems and Wetlands<br />
South East Queensland Healthy Waterways Partnership<br />
WBM Oceanics Australia and Ecological Engineering (2004)<br />
<strong>Maintenance</strong> Guidelines for Stormwater Treatment Measures<br />
Hornsby Shire Council (HSC) (2001)<br />
Catchment Remediation Capital Works Program Annual report 2000-2001<br />
Water Catchments Team HSC<br />
Lloyd, S.D., Wong, T.H.F and Chesterfield, C.J. (2002)<br />
Water Sensitive Urban Design<br />
A Stormwater Management Perspective<br />
Cooperative Research Centre for Catchment Hydrology<br />
Facility for Advancing Water Biofiltration (FAWB) (2008)<br />
Workshop: Advancing Raingarden Design Filter Media and Landscaping<br />
available online at :-<br />
http://www.wsud.org/downloads/Seminars%20&%20Events/fawb-workshop-vegetation-and-landscaping.pdf<br />
Wong, T.H.F (editor in chief) (2006), Australian Runoff Quality, Engineers Australia<br />
<strong>Book</strong> 4 | MAINTENANCE 85
Water Sensitive Urban Design<br />
Notes<br />
86 <strong>Book</strong> 4 | MAINTENANCE
Water Sensitive Urban Design<br />
<strong>Book</strong> 4 | MAINTENANCE 87
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