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Water Sensitive Urban Design Book 4 | maintenance
Draft
Water Sensitive Urban Design
Book 4 | MAINTENANCE
Table of Contents 1 | Introduction
4
2 | Key Operational and Maintenance Issues Identified By Stakeholder Local Councils
6
3 | WSUD Elements
8
3.1
Bioretention Basins
8
3.2
Constructed Wetlands and Ponds
9
3.3
Sedimentation Basins
11
4 | Life Cycle Costing
12
What are the Life Cycle Costs of WSUD Elements
13
How does the LCC of WSUD development compare with that of conventional drainage infrastructure
17
4.1
4.2
5 | Monitoring and Maintenance of WSUD Elements
18
5.1
Performance Monitoring Requirements
20
5.2
Maintenance Requirements
21
5.2.1 Predictive maintenance
21
5.2.2 Regular inspection and maintenance
22
5.2.3 Bioretention mystems
22
5.2.4 Constructed wetlands and ponds
27
5.3
5.2.5 Sedimentation basins
31
Waste Management and Disposal
35
5.3.1 Dewatered silt
36
5.3.2 Filter media
36
5.3.3 Liquid waste (from dewatering activities)
37
5.3.4 Equipment requirements
37
6 | Construction Requirements
6.1
38
Staging
38
6.1.1
40
Stage 1: Civil construction (or functional installation)
6.1.2 Stage 2: Building phase protection (or sediment and erosion control)
42
6.1.3 Stage 3: Operational establishment (civil and/or landscaping)
44
6.2
Construction Tolerances
46
6.3
Construction Certification and Compliance
47
6.4
Filter Media Specifications
48
Appendix A – Construction Inspection and Sign off sheets
A.1 Bioretention Systems
49 50
A.2 Constructed Wetlands
58
A.3 Sedimentation Basins / Ponds
68
Appendix B – Regular Maintenance Checklists
75
B.1 Bioretention Basins
76
B.2 Constructed Wetlands
78
B.3 Sedimentation Basin
80
B.4 Ponds
82
Appendix C – Asset handover sheets
84
Appendix D – References
85
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Water Sensitive Urban Design
1 | Introduction
Landcom has implemented a range of innovative Water Sensitive Urban Design (WSUD) initiatives since 2003.
Since 2003 Landcom has embarked on ensuring that all its projects have a strong sustainability underpinning, as reflected in its annual Triple Bottom Line reporting. Landcom prepared a Water Sensitive Urban Design Policy in 2003 and published its Water Sensitive Urban Design Strategy in 2004. Since that time Landcom have progressed steadily towards attaining the best practice objectives of urban water management in all its projects. Landcom has implemented a range of innovative Water Sensitive Urban Design (WSUD) initiatives since 2003, which build upon and extend elements of the original WSUD strategy.
This document forms part of a 4-book set that updates and revises the Landcom Water Sensitive Urban Design Strategy of 2004 as published. Recent advances in integrated water cycle management and WSUD, such as the release of Australian Runoff Quality1, the BASIX scheme, MUSIC (v3) and wider implementation have seen the stormwater industry evolve over the last three years. During this period the NSW Government has also revised its statewide water management objectives for new developments.
Engineers Australia (2006), Australian Runoff Quality: A Guide to Water Sensitive Urban Design, Wong, T H F (ed), ISBN 0 85825 852 8, Engineers Australia, Canberra, Australia, 2006
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Water Sensitive Urban Design
Landcom’s Water Sensitive Urban Design Strategy (2009) is contained in the following 4 books: Book 1 | Landcom’s WSUD Policy and Urban Water Management Objectives consisting of: •• an overview of Water Sensitive Urban Design •• a revision of the WSUD Targets and Mandatory WSUD Requirements to ensure appropriateness and relevance, including proposed realistic and appropriate “Stretch Targets” which Landcom may consistently apply in projects where warranted, and linkages to TBL reporting criteria •• key components of a project-specific WSUD strategy Book 2 | Attaining Landcom WSUD Objectives consisting of descriptions and discussions on urban water best planning and management practices applicable to Landcom projects including information on: •• how to meet the water conservation targets, including information on BASIX and information on wastewater and greywater technologies •• how to meet the stormwater quality targets, including proposed changes to ensure consistency with Landcom’s Street Design Guide •• how to meet the flow management targets Book 3 | Case studies and discussions on how water sensitive urban design could be integrated into Landcom Development Projects, including examples of: •• WSUD in the planning phase – Renwick •• WSUD in the implementation phase - Prince Henry Hospital and The Ponds •• WSUD after years of operation – Victoria Park Book 4 | Operation and maintenance guidelines of key WSUD elements including: •• life cycle costing of bioretention systems, constructed wetlands and ponds •• monitoring and maintenance practice and associated checklist •• construction considerations and associated checklist for construction inspection and asset handover This document (Book 4) describes operational and maintenance practices of a number of key WSUD elements commonly adopted in Landcom projects. Book 4 was prepared in response to a recurring set of enquiries from local government on the topics of construction, and ongoing operation and maintenance of WSUD elements. There was a clear desire to have a common set of understanding of the various considerations on these issues.
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Water Sensitive Urban Design
2 | Key Operational And Maintenance Issues Identified By Stakeholder Local Councils
Bioretention system in the public domain | Prince Henry
In preparing the booklet on WSUD Operation and Maintenance, two half-day workshops with invited Local Government representatives were organised. The first of these half-day workshops was held in December 2008. That workshop served as a platform for Council’s to present their considerations in approving WSUD elements in land development projects, concerns with the maintenance and operation of WSUD elements and information gaps in maintaining and operating WSUD elements.
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Representatives from the following Councils were present at one or both workshops: •• Auburn Council •• Bankstown City Council •• Blacktown City Council •• Camden Council •• Campbelltown City Council •• City of Sydney •• Fairfield City Council •• Hills Shire Council •• Hunters Hill Council •• Ku-ring-gai Council •• Liverpool City Council •• Penrith City Council •• Pittwater Council •• Sydney Metropolitan Catchment Authority •• Western Sydney Regional Organisation of Councils •• Wingecarribee Shire Council •• Wollongong City Council Following this first workshop, the issues identified were grouped into three categories: 1) Life cycle cost considerations of WSUD strategies 2) Monitoring and maintenance of WSUD elements 3) Construction considerations of WSUD elements
Water Sensitive Urban Design
Woolwash Park Biofiltration | Victoria Park
The booklet is structured to address frequently asked questions regarding construction, maintenance and operational issues of WSUD elements.
A draft response was compiled for specific issues within the three categories identified. The responses reference current best practice guidelines and industry experience. These were then discussed and reviewed in a second half-day workshop held in March 2009 involving participants on the first workshop. This second workshop was also attended by representatives from a wider group of local councils. The 4th booklet in the Landcom WSUD booklet series addresses operation and maintenance concerns of select WSUD elements. The booklet is structured to address frequently asked questions regarding construction, maintenance and operational issues of WSUD elements as identified from a focus group of Councils. The booklet does not aim to recreate or
reiterated current best practice guidelines for the purpose of Councils. Rather the booklet provides a consolidated response to the issues raised, with information supported by appropriate references/ links to where additional information can be sourced. The responses compiled have been limited to the following WSUD elements: •• Constructed wetlands •• Bioretention basins •• Sedimentation basin / ponds The responses, in particular to monitoring and maintenance requirements, assume that the WSUD strategy has been designed and constructed to meet best management practice objectives and design guidelines.
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Water Sensitive Urban Design
3 | WSUD Elements
Examples of bioretention systems in streetscapes
3.1 Bioretention Basins Bioretention systems can provide a degree of flow attenuation and hence reduce the volume and frequency of runoff delivered to downstream waterways.
Bioretention systems are vegetated filter systems designed to allow water to pool temporarily before percolating through the filter media. The filter media controls the flowrate of water through the system, as well as providing a growing media for the plants. The filtered water is directed via perforated pipes to the existing stormwater system, natural waterways or a detention basin for reuse. Bioretention systems can provide a degree of flow attenuation and hence reduce the volume and frequency of runoff delivered to downstream waterways (ARQ, 2006). Critical to the performance of a bioretention system is the filter media and vegetation. The filter media needs to provide a hydraulic conductivity that ensures sufficient contact time is available for pollutants to be taken up by biofilms.
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Vegetation root systems provide the surfaces for the epiphytic biofilms that take up dissolved pollutants. Vegetation is also critical in maintaining the porosity of the soil media of the bioretention system. Bioretention systems can be integrated into open space areas and streetscapes (for example, parking stations and traffic calming devices). The systems can take the form of a basin or a swale. A basin is typically employed for relatively flat areas. Swales provide a stormwater treatment and flow conveyance role and are suitable for long linear sites with a grade ranging between one and four percent. For some sites, a combined bioretention basin and a conventional swale may be required.
Water Sensitive Urban Design
Examples of constructed wetlands
3.2 Constructed Wetlands and Ponds The deep open water bodies typical of ponds provide larger detention volumes as compared to constructed wetlands.
Constructed wetlands use enhanced sedimentation, fine filtration and biological uptake processes to remove pollutants from stormwater. The wetland processes are engaged by slowly passing runoff through heavily vegetated areas where plants filter sediments and pollutants from the water. Biofilms that grow on the plants can absorb nutrients and other associated contaminants. Ponds also provide physical, biological and chemical mechanisms for pollutant uptake. The main physical difference between a pond and a constructed wetland is the ratio of surface area to volume and the coverage by vegetation (ARQ, 2006). Typically ponds have a depth exceeding 1.5 meters as compared to constructed wetlands, which have an average depth in the macrophyte zone of 0.3 metres. Furthermore, a regular water level fluctuation regime is promoted in a constructed wetland through the design of the outlet structures. Combined, the high surface area to volume ratio and the promotion of regular water level fluctuation through the design of the
outlet structure in a constructed wetland, supports a densely vegetated system and hence a greater biological uptake of pollutants as compared to a pond. The deep open water bodies typical of ponds provide larger detention volumes as compared to constructed wetlands. Higher detention times promote improved sedimentation; however the risk of large open water bodies is short circuiting, redox potential conditions and elevated levels of nutrients. These processes can have a reverse effect on stormwater treatment causing release of pollutants from the sediment into the water. High nutrient concentrations can also lead to nuisance macrophyte growth or algal blooms that can be toxic and aesthetically unpleasant. For these reasons, ponds are commonly designed in combination with constructed wetlands, providing polishing of stormwater quality, attenuation of flows and protection of downstream waterways, and storage for reuse applications.
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Water Sensitive Urban Design
Wetland | Koala Bay
Table 1 | Stormwater treatment processes of constructed wetlands and ponds Constructed Wetlands
Ponds
Physical – Sedimentation
Physical – Sedimentation
•• Traps suspended solids – vegetation in the wetland facilitates enhanced sedimentation of particles down to the fine fractions
•• Traps ‘readily settleable solids’ – settling of solids down to coarse and medium sized silt fractions
•• Traps adsorbed pollutants – traps a higher proportion of adsorbed pollutants through higher capture of fine particles
•• Traps adsorbed pollutants – silt particles trapped in the pond system may also retain adsorbed pollutants •• Promotes flocculation of smaller particles
Biological and Chemical Uptake
Biological and Chemical Uptake
•• Traps dissolved pollutants – vegetation provides surfaces for epiphytic biofilms, which take up dissolved pollutants
•• Biological uptake of soluble pollutants predominately by phytoplankton, which remains in the water column and is susceptible to washoff during the next storm event
•• Chemical adsorption of pollutants to fine suspended particles which are trapped through enhanced sedimentation and surface filtration facilitated by macrophytes and biofilms •• Promotes rapid biodegradation of organic material
•• Chemical adsorption of pollutant to fine suspended sediment which remains in the water column for extended periods and is susceptible to washoff during the next storm event •• UV disinfection of waterbody by sunlight
Pollutant transformation
Pollutant transformation
•• The regular wetting and drying cycle progressively leads to less reversible sediment fixation of contaminants in the substratum
•• Pollutants adsorbed to deposited sediment are susceptible to release under conditions of low redox potential caused by high organic loading and pond stratification
Table taken from Australian Runoff Quality (Engineers Australia, 2006)
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Water Sensitive Urban Design
Examples of sedimentation basins and ponds
3.3 Sedimentation Basins Due to the nature of a sedimentation basin, regular clean out and removal of accumulated sediment is required.
Sedimentation basins are stormwater detention systems that promote the settling of coarse sediment (defined as particles greater than 125 microns in diameter). A sedimentation basin can be an integral part of a treatment train, providing primary removal of coarse sediment. Removal of coarse sediment is particularly important in protecting downstream systems from high sediment loading, which can reduce the effectiveness of the system. The treatment performance of a bioretention system is particularly susceptible to high sediment loadings: sediment can smother vegetation and clog the filter media affecting the percolation of stormwater through the media. Sediment basins can also be employed for temporary sediment and erosion control during construction activities.
Due to the operation of a sedimentation basin, regular clean out and removal of accumulated sediment is required. Sedimentation basins are generally designed for a clean out frequency of five years, which equates to a volume half that of the permanent pool (defined by the invert of the outlet structure). The sedimentation basin design should include an access ramp to allow entry for a clean-out truck.
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Water Sensitive Urban Design
4 | Life Cycle Costing
Bioswale | Victoria Park
Indirect tangible benefits associated with well designed and constructed WSUD elements are the environmental outcomes such as reductions in potable water demands, downstream pollution and waterway rehabilitation works.
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An important part of implementing WSUD strategies is the cost the systems pose to Councils. There are many approaches to computing and accounting the cost of infrastructure. In the case of land development, the capital cost is often borne by the developer with the asset subsequently assumed by local government with associated maintenance and renewal responsibilities. The life cycle cost of an asset is made up of its capital cost, operational and maintenance cost, renewal cost and decommissioning cost. Often not included in a life cycle cost/benefit analysis are the benefits both directly accrued to the development, and indirectly attributed to the works within the development. The benefits directly
accrued to the development are reflected in the increased demand for properties in the development as reflected in the sale price. Indirect tangible benefits associated with well designed and constructed WSUD elements are the environmental outcomes such as reductions in potable water demands, downstream pollution and waterway rehabilitation works. Organisations are now considering the total community costs in evaluating water management strategies.
Water Sensitive Urban Design
The impact of maintenance and renewal costs is dependent on the expected life span of the asset.
4.1 What are the Life Cycle Costs of WSUD Elements Life cycle costing is a process to determine the sum of all expenses associated with a product or project, including acquisition, installation, operation, maintenance, refurbishment, discarding and disposal costs (Standards Australia, 1999). The life cycle costs (LCC) for WSUD elements include the total acquisition cost (TAC), the total annual maintenance (TAM), renewal, and decommissioning costs. The impact of maintenance and renewal costs is dependent on the expected life span of the asset. The decommissioning cost in some WSUD systems, such as constructed wetlands, may be irrelevant as they are designed to operate in perpetuity. All life cycle costs are discounted back to a base date (date of installation).
How is the Life Cycle Costs Calculated? The supporting user manual for the Model for Urban Stormwater Improvement Conceptualisation (MUSIC, version 3) developed by the Cooperative Research Centre for Catchment Hydrology (CRCCH) provides a summary of the life cycle costs associated with bioretention systems, wetlands, ponds and sedimentation basins. A summary of the parameters affecting the LCC of these elements is given in Table 2. In many cases, MUSIC uses an algorithm to define a particular life cycle cost element in terms of the treatment area. These algorithms have been developed based on real data collected between 2002 and 2004.
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Water Sensitive Urban Design
Table 2 | Life cycle cost parameters for specified WSUD elements. Life Cycle Cost element Life cycle
Bioretention
25 to 50 years
Wetlands
15 to 80 years (with 50 years used as the default in MUSIC)
Ponds & Sedimentation Basins 5 year (sedimentation basins) 50 years (ponds)
Wetlands are designed to have an infinite life span. However, to determine a life cycle cost, a finite number needs to be set Total acquisition cost (TAC)
387.4 x (A) 0.7673 $1000/m2 for first 20 m2
(per m2)
Total annual maintenance (TAM)
($200/m2 for remaining area)
48.87 x (TAC) 0.4410
1911 x (A) 0.6435 The treatment area used in defining the total acquisition cost is the combined inlet and macrophyte zone area 6.831 x (A) 0.8634
Renewal costs (%TAC p.a.)
185.4 x (A) 0.4780 The annual maintenance cost considers the volume of material likely to be removed from the basin per year (referred in MUSIC as the size attribute, V). The size attribute is the sum of gross pollutants, coarse sediment and total suspended solids (TSS) that are trapped in the basin / pond per year
(%TAC)
Renewal period (years)
685.1 x (A) 0.7893
25
20 Renewal considerations include replanting and recontouring of the macrophyte zone
2.0%
0.52%
1 year (default in MUSIC due to lack of evidence). 10 years based on available data
1.4% Costs associated with access ramps and contouring Limited data available
Decommisioning costs (% TAC)
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38% - only applicable to sedimentation basins
Water Sensitive Urban Design
What is the Annualised Life Cycle Cost with respect to pollutant removal? The annualised life cycle cost is simply the Net Present Value (NPV) of the life cycle cost divided by the life cycle (years) of the asset. In developing an example of annualised life cycle cost, a series of analyses were undertaken for an asset life cycle period of 50 years. Three different WSUD elements were assessed: bioretention basins, constructed wetlands, and sedimentation basins. Bioretention basins and constructed wetlands were sized to meet best management practice pollutant load reductions for total nitrogen (TN) removal (that is, 45 percent). The sedimentation basin was sized to remove 80 percent of coarse sediment (greater than 125 microns), while also ensuring the associated clean out frequency of the basin was a minimum of 5 years. The life cycle costs are shown in Figure 1 to Figure 3.
The results are useful in showing the relative cost of maintenance to upfront capital cost and in particular the relatively low cost of maintaining these systems. For example, the annual maintenance cost of a bioretention basin sized for a 1 hectare impervious catchment is approximately 3 percent of the capital cost. In the life cycle cost figures for each WSUD element (Figure 1 to Figure 3), the annualised cost in terms of pollutant load reductions are also reported. Such data is useful in: •• assessing the efficiency of one WSUD element against another in removing a specific pollutant •• comparing the cost of WSUD elements against other pollutant abatement technology
The annualised cost in terms of pollutant removal for a 1 hectare completely impervious catchment are: Bioretention Basin:
− $70 per kg TN removed (45% reduction) − $320 per kg TP removed (67% reduction) − $1 per kg TSS removed (81% reduction)
Constructed Wetland:
− $440 per kg TN removed (45% reduction) − $2,300 per kg TP removed (70% reduction) − $3 per kg TSS removed (86% reduction)
Sedimentation Basin:
− $500 per kg TN removed (4% reduction) − $800 per kg TP removed (17% reduction) − $1 per kg TSS removed (30% reduction)
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Water Sensitive Urban Design
$18,000
Bioretention basin sized to remove 45 percent of TN pollutant loads generated from a 1 hectare, 100 percent impervious catchment (road)
$16,000
Annualised cost of system in terms of pollutant load reductions are: / $70 per kg TN removed / $320 per kg TP removed / $1 per kg TSS removed
$14,000
Cost ($)
$12,000
$10,000 Decomissioning Cost Renewal Cost $8,000
Maintenance Cost Capital Cost
$6,000
$4,000
$2,000
$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
Time (years)
Figure 1: LCC for bioretention basins
$140,000.00
Constructed wetland sized to remove 45 percent of TN pollutant loads generated from a 1 hectare, 100 percent impervious catchment (road) $120,000.00
Annualised cost of system in terms of pollutant load reductions are: / $440 per kg TN removed / $2300 per kg TP removed / $3 per kg TSS removed
$100,000.00
Cost ($)
$80,000.00 Decomissioning Cost Renewal Cost Maintenance Cost
$60,000.00
Capital Cost
$40,000.00
$20,000.00
$1
3
5
7
9
11
13
15
17
19
21
23
25
27
Time (years)
Figure 2: LCC for constructed wetlands
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29
31
33
35
37
39
41
43
45
47
49
Water Sensitive Urban Design
$6,000.00
Sediment basin sized to remove 80 percent of course sediment (defined as particles greater than 125 microns) for a 1 hectare, 100 percent impervious catchment (road) Annualised cost of system in terms of pollutant load reductions are:
$5,000.00
/ $500 per kg TN removed / $800 per kg TP removed / $1 per kg TSS removed
Cost ($)
$4,000.00
Decomissioning Cost
$3,000.00
Renewal Cost Maintenance Cost Capital Cost
$2,000.00
$1,000.00
$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
Time (years)
Figure 3: LCC for sedimentation basins
4.2 How does the LCC of WSUD development compare with that of conventional drainage infrastructure The life cycle costs of water sensitive urban design measures were assessed by Lloyd et al. (2002) for one of the original WSUD strategies implemented in Victoria (that is, Lynbrook Estate). The assessment considered three stormwater management scenarios: Conventional Approach:
Stormwater is piped to the downstream waterway. No treatment of stormwater is considered.
Downstream Stormwater Treatment:
An end-of-pipe treatment system is employed to ensure the quality of discharged stormwater meets best management practice (BMP) objectives for pollutant load reductions.
Distributed Stormwater Treatment:
A series of WSUD elements are employed to remove pollutants at source, such that a greater volume of stormwater can be treated to BMP objectives.
The assessment found the capital cost of a distributed system to be 22 percent greater than the conventional approach, while a downstream stormwater treatment cost an additional 47 percent. It should be noted that the cost of drainage infrustructure represents approximately 10% of the total cost of development. The range of annualised maintenance cost from the study was reported as: Approach
Annualised Maintenance Cost
Annualised Maintenance Cost per hectare
$737 to $1,672
$27 to $62
Downstream Stormwater Treatment:
$2,336 to $6,371
$87 to $236
Distributed Stormwater Treatment:
$1,723 to $6,512
$64 to $241
Conventional Approach:
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Water Sensitive Urban Design
5 | Monitoring and Maintenance of WSUD Elements
Watersteps | Victoria Park
The information provided in this section will help Councils understand the monitoring and maintenance requirements of WSUD elements and assist in generating and/or assessing maintenance plans such that the associated monitoring and maintenance plan addresses: •• inspection frequency •• maintenance frequency •• data collection/ storage requirements (i.e. during inspections) •• detailed cleanout procedures (main element of the plans) including: –– equipment needs –– maintenance techniques –– occupational health and safety –– public safety –– environmental management considerations –– disposal requirements (of material removed) –– access issues –– stakeholder notification requirements –– data collection requirements (if any) •• design details
The performance of WSUD elements is dependent on the maintenance considerations incorporated during their design. Maintenance personnel need to be involved during the design to ensure their requirements (for example, 18 Book 4 | MAINTENANCE
access) are addressed, they understand the functionality of the systems and the role of maintenance in ensuring design performance criteria are met, and to ensure appropriate maintenance budget is allocated.
Water Sensitive Urban Design
Watersteps | Victoria Park
Routine monitoring checks the status of key functional elements to ensure they meet specified design requirements and include ensuring that inlet and outlet structures are free of debris, and that well distributed vegetative cover of the system is maintained.
Unlike traditional engineered structures, WSUD elements will only require minimal routine maintenance and these are generally of a landscape maintenance nature. For example, regular weeding should only be required during the establishment phase of a well designed and constructed system with appropriate planting density limiting the ‘free’ area available for weed growth. Removal of debris and siltation is the most common activity. Maintenance activities should primarily be prompted through predictive and routine monitoring. Predictive monitoring activities occur following significant storm events and are directed at assessing the performance of the system (for example, flow distribution and ponding duration). These activities help identify potential deviations in performance and initiate corrective maintenance actions. Routine monitoring checks the status of key functional elements to ensure they meet specified design requirements and include ensuring that inlet and outlet structures are free of debris, and that well distributed vegetative cover of the system is maintained.
It is recommended that vegetated WSUD elements are monitored by personnel with bush regeneration qualifications (as approved by Australian Association of Bush Regenerators). Bush regenerators are well equipped at identifying evasive species within a native landscape typical of vegetated WSUD systems. Furthermore, personnel in charge of monitoring should have a good idea and understanding of the layout and functional design of the treatment system. The maintenance activities prompted through monitoring activities will generally require coordination between landscape and civil services. The following section documents the monitoring and maintenance requirements for bioretention basins, constructed wetlands and sedimentation basins/ponds. The information given can be used to guide development of site specific maintenance plans for WSUD developments. The plans will be used by maintenance personnel and asset managers to ensure the bioretention system functions as designed for its entire life cycle.
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Water Sensitive Urban Design
5.1 Performance Monitoring Requirements Surrogate methods can often be equally effective in evaluating the adequacies of the operation, and thus performance, of WSUD elements.
Performance monitoring of WSUD elements can be undertaken through detailed water sampling and laboratory analyses for contaminant concentrations or through the use of surrogate performance indicators. With the former, it will be necessary to set up field monitoring sites to undertake the water quality sampling at inlet and outlet of systems. The following points should be considered when setting up a sampling program: •• Auto-sampling with partial or full composite samples is most cost effective •• Monitoring should be accompanied by continuous flow and depth observations •• Design of monitoring set up and sampling intervals is site dependent •• 20 events should be monitored as a minimum to obtain typical performance •• The following key water quality parameters should be analysed in registered laboratories:–– TSS analysis undertaken
should
be
–– TP (with occasional filter of sample on-site with 0.45um filter to test for Orthophosphate) –– TN (with occasional speciation to organic and inorganic nitrogen An implicit assumption made when water quality improvements are measured by comparing observed water quality at the inlet and outlet of the system, is that these water qualities represent the same ‘parcel’ of water. Occasionally, especially with wetlands and ponds, negative or very low pollutant removal results for a system are observed. These results are common when the volume of an inflow event is less than the permanent pool volume of the wetland or pond. In the case of bioretention systems, accurately accounting for the volumetric balance of inflow, outflow, and soil moisture replenishment, is the
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main analytical problem that may lead to erroneous performance assessment. Surrogate methods can often be equally effective in evaluating the adequacies of the operation, and thus performance, of WSUD elements. They are often more cost effective and involve the monitoring of the hydrologic and hydraulic performance of these systems. The implicit assumption with surrogate methods is the premise that if the WSUD elements operate in accordance to the design hydrologic and hydraulic characteristics, it follows that these systems can be reasonably expected to deliver the pollutant reduction as determined from laboratory and field experiments. Key hydrologic and hydraulic operation characteristics define the detention time of WSUD elements. Monitoring of the following operation of bioretention systems, wetlands and ponds, can provide important insights on the likely performance of these WSUD elements in pollution reduction: •• Flow pattern (most relevant to wetlands and ponds), to identify the presences of short-circuiting that may inhibit the uniform distribution of inflow to this system •• Duration of inundation (most relevant to wetlands and bioretention systems) to assess the operating detention time of these systems and to highlight potential clogging of soil media (bioretention systems) or the outlet structure (wetlands) that would have a direct impact on its performance in water treatment •• Turbidity of inflow and outflow which are good surrogates for suspended solids, total phosphorus, and metal in urban stormwater
Water Sensitive Urban Design
5.2 Maintenance Requirements WSUD infrastructure requires ongoing inspection and maintenance to ensure they establish and operate in accordance with the design intent.
WSUD infrastructure requires ongoing inspection and maintenance to ensure they establish and operate in accordance with the design intent. Potential problems associated with WSUD infrastructure as a result of poor maintenance include: •• Decreased aesthetic amenity •• Reduced functional performance •• Public health and safety risks •• Decreased habitat diversity (dominance of exotic weeds) The most time-intensive period of maintenance for a vegetated system is during plant establishment (which typically includes two growing seasons), when supplementary watering, plant replacement and weeding may be required. Generally, WSUD elements are brought online through stages such that the functional elements are protected from elevated pollutant loads generated from a developing catchment. More information regarding staged construction is given in the next section of this booklet.
Once WSUD elements are established and operational, on-going inspection, monitoring and maintenance will be required. Maintenance activities fall into one of two categories; predictive maintenance or regular maintenance.
5.2.1 Predictive Maintenance Predictive maintenance is scheduled based on inspections conducted after a significant storm event (defined qualitatively as an event likely to mobilise sediment and coarse material). Predictive inspections are critical to assessing the performance of the treatment system, in particular the hydraulic function and flow distribution of the system. Items that should be considered during the inspection are included over the page.
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Water Sensitive Urban Design
Ponding time
Detention of flows above the design intent could indicate a blockage in the outlet structures. Typical drainage times for treatment systems are:
•• 72 hours for a constructed wetland •• 6 to 24 hours for a bioretention basin •• 24 hours for a sedimentation basin Surface distribution of flows
Flow should pond evenly within the treatment system
Scouring
Scouring can be indicative of a blocked inlet
Additionally, the absence of ponding after a significant storm event may indicate a blocked inlet (that is, flows are being prevented from entering the treatment system)
5.2.2 Regular Inspection and Maintenance
5.2.3 Bioretention Systems
Generally, WSUD elements should be inspected every three months, with particular reference to:
The routine maintenance of a bioretention basin is required to ensure diverted storm water:
•• Structures, such as overflow weirs, bypass and inlets
•• Ponds evenly across the basin surface •• Percolates through the filter media such that the ponding time does not exceed the design specifications (typically 6 to 24 hours)
•• Erosion •• Sediment build-up •• Weeds
To ensure the functionality of the bioretention basin is retained, maintenance activities will typically involve:
•• Algal blooms •• Litter (anthropogenic and nonanthropogenic) •• Oil slicks The following tables in the next three sections further explore the above issues as related to constructed wetlands, bioretention systems or sedimentation basins / ponds. In particular, the tables: •• articulate monitoring requirements •• suggest graded targets for optimal performance •• suggest scheduling of maintenance and immediate action •• propose a general maintenance activities
22 Book 4 | MAINTENANCE
approach
to
•• Routine inspection of the bioretention profile to identify any areas of obvious increased sediment deposition, scouring of the basin or swale invert from storm flows, rill erosion of the batters from lateral inflows, damage to the swale profile from vehicles and clogging of the bioretention trench (evident by a ‘boggy’ swale invert) •• Routine inspection of inlet points, surcharge pits and field inlet pits to identify any areas of scour, litter build up and blockages
Water Sensitive Urban Design
Boardwalk | Victoria Park
•• Removal of sediment, especially where it is impeding the conveyance of the bioretention swale and/or smothering the vegetation, and if necessary, reprofiling of the system and re-vegetating to original design specification •• Repairing any damage to the system profile, especially in the case of a bioretention swale, resulting from scour, rill erosion or vehicle damage •• Tilling of the bioretention trench surface if there is evidence of clogging •• Clearing of blockages to inlet or outlets. •• Regular watering/irrigation of vegetation until plants are established and actively growing •• Mowing of turf or slashing of vegetation (if required) to preserve the optimal design height for the vegetation
•• Removal and management of invasive weeds •• Removal of plants that have died and replacement with plants of equivalent size and species as detailed in the plant schedule •• Pruning to remove dead or diseased vegetation material and to stimulate new growth •• Litter and debris removal •• Vegetation pest monitoring and control Resetting (i.e. complete reconstruction) of bioretention elements will be required if the available flow area of the overlying basin is reduced by 25 percent (due to accumulation of sediment) or if the bioretention trench fails to drain adequately after tilling of the surface.
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Water Sensitive Urban Design
Table 3 | Routine monitoring requirement for bioretention basins. Item to be Monitored
Purpose of Monitoring
Performance Target
Schedule Maintenance or Investigation
Immediate Action Required
Maintenance Action Required
Structures
The inlet and outlet structures of a bioretention system should be free of debris, litter and sediment to ensure flow is not impeded. Large storms (or flood) events and vehicles can also damage or block these structures and prevent the system working as designed. The main structural elements of a bioretention system are:
- GPT / trash rack/s
GPT clear of litter
GPT 10 percent full
greater than 30 percent full
Contact cleaning service. Generally a GPT will require clean-out four times per year. For proprietary GPTs it is recommended that a vacuum based cleaner be used on at least one occasion per year, or when frequent overflow of litter from the GPT is evident. For all other clean-outs, a mechanical grab is sufficient.
- Inlet structures
- Overflow pits
- Underdrains
Free flowing
Trickle flow while basin ponding is observed
No outflow while basin ponding is observed
- Sediment Forebay
Sediment absent
Sediment accumulation appears excessive
Sediment accumulated to half the basin depth
Schedule removal of sediment from forebay area.
Erosion
Erosion impairs bioretention systems by changing the bed profile and preventing uniform distribution of flow across the system.
Erosion absent
Erosion damage visible, but function not impaired
Severe erosion. Damage impairing function of device
Schedule investigation to identify cause of profile damage.
If left untreated, small sites of erosion can quickly spread over large areas becoming costly to repair.
Clear and undamaged
Partially Blocked Observed damage
Mostly blocked Severe damage
Schedule removal of debris or contact relevant authority within Council for structural damage. Inspect the bioretention system for scour or erosion damage and fix accordingly (refer to maintenance line item “bioretention system profile” for advise).
Once source of damage is rectified, scour holes should be replaced with appropriate filter media. Lightly spread and compact replaced filter media using either hand tools, an excavator bucket or a pozitrack bobcat (DO NOT drive over the media with any vehicle but a pozitrack bobcat). Replace any damaged plants to meet the design plant schedule.
24 Book 4 | MAINTENANCE
Water Sensitive Urban Design
Item to be Monitored
Purpose of Monitoring
Performance Target
Schedule Maintenance or Investigation
Immediate Action Required
Maintenance Action Required
Sediment build up
The accumulation of sediment in the sediment forebay of the bioretention system is a prescribed function of this zone. However, sediment must be regularly removed to ensure that the sediment trapping performance of this zone is sustained.
Sediment absent
Sediment accumulation appears excessive in sediment forebay
Sediment accumulated to half the forebay depth
Schedule investigation to identify sediment source.
Coarse sediment or large volumes of sediment accumulation apparent on the bioretention media surface
Once sediment source is stabilised, remove accumulated sediment and replace the top 100 mm of filter media from the bioretention system. The filter media specifications should be as per the design intent.
Fine sediment accumulation apparent on bioretention media surface
If sediment accumulates on the bioretention surface, percolation of water into the media may be reduced, resulting in poor treatment performance.
Common sense should be exercised in deciding if plantings need to be replaced as part of maintenance work. If the sediment build-up is extensive and smothering vegetation, it may be easier and less costly to remove the plantings and replant once the filter media has been replaced. Conversely, if the sediment build-up is small and isolated or the system is planted with trees, it may only be necessary to scrape away the accumulated sediment and the top 100mm of filter media and replace without disturbing the plants within the bioretention system. Lightly spread and compact replaced filter media using either hand tools, an excavator bucket or a pozitrack bobcat (DO NOT drive over the media with any vehicle but a pozitrack bobcat). Replace any damaged plants to meet the design plant schedule.
Compaction
Percolation into the media may be reduced if the media surface has been compacted, i.e. by pedestrian traffic, poor construction methods.
No compaction evident
Localised compaction or subsidence evident. Localised ponding longer than 24 hours after storm event
Water remains ponding longer than 24hours after storm event
Schedule investigation to identify cause of compaction. If compaction is localised, remove top 500 mm of filter media with auger. - Break-up removed filter media so that it is no longer compacted. - Refill hole with uncompacted filter media (that is, there is no need to replace with new filter media). If compaction is extensive, seek expert advice.
Weeds and invasive plants
The growth of weeds can impair a bioretention system’s performance by - Changing flow paths across the bioretention system - Shading and out-competing plant species that are important for water treatment, or filter media stability. Weeds can spread to downstream environments, compromising ecosystem health.
No weeds present
Weeds present
Noxious or environmental weeds present, or weed cover more than 25 percent
Hand removal or targeted herbicide treatment (herbicides registered for use around waterways). Note: Herbicides should not be routinely used to maintain edges and batter slopes. General spraying of batter slopes should not be undertaken without follow up revegetation with native species.
Weeds compromise the visual amenity of the bioretention system.
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Water Sensitive Urban Design
Item to be Monitored
Purpose of Monitoring
Performance Target
Schedule Maintenance or Investigation
Immediate Action Required
Maintenance Action Required
Plant Condition
Plants are crucial to the performance of a bioretention system.
Healthy vegetation
Poorly growing or visibly stressed
Die back / dead plants
Schedule an investigation into the cause of plant die-back or poor health. Maintenance action will depend on the cause of die-back or poor plant health. Once the problem is rectified, infill planting may be required, especially if more than 1 square meter of plantings has died. Infill planting must be as per the original planting schedule.
During dry periods: Plants help maintain the structure and porosity of the filter media. During rainfall events: Vegetation aboveground acts to retard and distribute flows, and provides scour protection if the bioretention system is designed as a swale. Below ground the roots provide an important media for trapping or absorbing pollutants as they percolate through the media. The accumulation of dead plant material can detract from the visual amenity of the bioretention system. Litter (organic)
Organic litter can provide an additional source of nutrients to the bioretention system, introduce non-native species, which out-compete native plants and block the filter media.
No litter visible
Litter visible
Litter thickly covers filter media surface or detracting from visual amenity
Accumulated organic matter / litter can also cause offensive odours (such as methane gas and hydrogen sulphide, i.e. rotten egg gas) and can reduce percolation of water into the filter media. Litter
(anthropogenic)
Litter can potentially block the inlet and outlet structures of the bioretention system resulting in flooding, as well as detract from the system’s visual amenity.
Identify source of organic litter and address with appropriate response action: e.g. change of landscape maintenance practices; community education re: litter dumping (appropriate for repeat incidences). In the interim, all litter must be removed by maintenance crews.
No litter visible
Litter visible
Litter blocking structures or detracting from visual amenity
Identify source of rubbish: e.g. from catchment (commercial precinct); overflow of rubbish bins; accumulation in backwater area and schedule general maintenance to remove rubbish. Where required address source of rubbish (e.g. increase in frequency of rubbish bin emptying; gross pollutant traps in high load generation land uses). In the interim, all litter must be removed by maintenance crews. WARNING: Contact with sharp objects, including hypodermic needles is a risk when removing litter. All workers must be made aware of this risk, wear appropriate protective gear and use caution.
Oil slicks
Oil spills / inflows are not necessarily an impedance to bioretention system function. Bioretention systems are designed to remove oils from stormwater; hydrocarbons decompose relatively quickly in the presence of soil microbes and water. It is expected that fuel or oil trapped in the bioretention basin would decompose within two to three weeks, depending on the size of the oil spill.
26 Book 4 | MAINTENANCE
No visible oil
Persistent but limited visible oil
Extensive or localised thick layer of oil visible
Do not isolate bioretention system in the case of an oil spill - it is better that the oil is contained within the system than allowed to flow to the downstream water course. Notify the EPA of the spill and clean-up requirements NOTE: do not add any fertiliser, or other nitrogen based product to the system. The microbes within the filter media are capable of decomposing hydrocarbons.
Water Sensitive Urban Design
5.2.4 Constructed Wetlands and Ponds A pond treats runoff by providing extended detention and allowing sedimentation to occur.
Wetlands treat runoff by filtering it through vegetation and providing extended detention to allow sedimentation to occur. In addition, they have a flow management role that needs to be maintained to ensure adequate flood protection for local properties and protection of the wetland ecosystem. Ponds are frequently designed downstream of a wetland to provide further polishing of stormwater as well as detention (either to meet reuse requirements or attenuation of flows). A pond treats runoff by providing extended detention and allowing sedimentation to occur. This same principle applies for ponds designed for primary treatment. To ensure the functionality of the system, routine monitoring and maintenance of constructed wetlands will require: •• Checking flow paths in and out of the system are unobstructed •• Ensuring vegetation is healthy and is sufficiently dense
NOTE:A separate maintenance checksheet has been developed for ponds as provided in the appendix to this booklet.
•• Preventing undesired vegetation from taking over the desirable vegetation •• Removal of noxious plants or weeds •• Re-establishment of plants that die •• Removal of accumulated sediments
Of the above items, debris removal should be the only action requiring ongoing attention. Debris, if not removed, can block inlets or outlets, and can be unsightly if located in a visible location. Inspection and removal of debris should be done regularly, but debris should be removed whenever it is observed. The monitoring and maintenance requirements of ponds are similar to constructed wetlands in maintaining flow into and through the system, ensuring healthy vegetation, minimising establishment of evasive and noxious plants and removal of accumulated sediment, litter and debris. The guidance given for monitoring and maintaining constructed wetlands can in general be adopted for ponds, (refer to note) noting the following: •• Artificial turnover of the lake may be required (because of long residence times). A mechanical system will need to be employed and will require specific maintenance •• Ponds designed to provide primary treatment will typically be more maintenance intensive due to the higher loads of nutrients delivered and captured
•• Litter and debris removal Book 4 | MAINTENANCE
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Water Sensitive Urban Design
Table 4 | Routine monitoring requirement for constructed wetlands. Item to be Monitored
Performance Target
Schedule Maintenance or Investigation
Immediate Action Required
Maintenance Action Required
The purpose of the inspection is to check that the structures associated with the constructed wetland (macrophyte zone cells and inlet zone) are not damaged and function as designed. Examples of causes of structural damage include sediment and/or litter accumulation and large storms (flood events).
- GPT / trash rack
GPT clear of litter
GPT 10 percent full
GPT / trash rack for than 30 percent full
Notify Cleaning Services
Schedule removal of debris, or notify relevant authority within Council for structural damage.
Purpose of Monitoring
Structures
- Inlet pipe
Clear and undamaged
Partially Blocked Observed damage
Mostly blocked Severe damage
- Pipes connecting macrophyte cells
- Outlet pit
NOTE: If the wetland substrate has been disturbed during maintenance activities, ensure bed profile re-established as designed. Irregularities in bed profile may have the potential to act as mosquito breeding habitats.
Inspect for associated erosion and scour damage within the wetland and associated structure, and schedule repair work as required by Council.
Erosion
Erosion impairs wetland function by - Changing flow paths through the wetland - Smothering wetland vegetation and biota - Creation of mosquito habitat - Contributing to poor water quality by adding additional sediment
Erosion absent
Erosion damage visible, but structure functional
Severe erosion. Damage impairing function of device
Any erosion damage of the macrophyte zone batters, berms, and around the inlet and outlet structures should be noted on the Inspection Form and remediation measures undertaken immediately. Remediation measures may include surface reinforcement and revegetation.
If left untreated, small sites of erosion can quickly spread over large areas becoming costly to repair.
Sediment build up
The accumulation of sediment in the inlet pond of the wetland is a prescribed function of this zone. However, sediment must be regularly removed to ensure that the sediment trapping performance of this zone is sustained. Sediment build up can affect the hydraulics of the wetland, and smother aquatic plants, compromising plant growth.
28 Book 4 | MAINTENANCE
Schedule investigation into cause of erosion. Action appropriate stabilisation response.
Sediment absent
Sediment accumulation appears excessive
Sediment accumulated to half the basin depth
Schedule an investigation into source of sediment: e.g. localised erosion or catchment based runoff.
Water Sensitive Urban Design
Item to be Monitored
Performance Target
Schedule Maintenance or Investigation
Immediate Action Required
Maintenance Action Required
- Aquatic weeds (submerged, emergent and floating)
No weeds present
Weeds present
Noxious or environmental weeds present
Emergent Plants (e.g. Typha): schedule hand weed removal or herbicide treatment. Floating Plants (e.g. Salvinia) with 30% cover: removal with harvester
- Terrestrial weeds (e.g. within the batter slopes)
No weeds present
Weeds present
Noxious or environmental weeds present
Hand removal or targeted herbicide treatment (herbicide registered for use around waterways).
Purpose of Monitoring The growth of weeds can impair a wetlands performance by - Changing flow paths through the wetland - Shading and out-competing plant species that are important for water treatment, or bed / bank stability. Weeds can spread to downstream environments, compromising ecosystem health. Weeds compromise the visual amenity of the wetland. Invasive plants in constructed wetlands take the following forms:
Weeds
Note: Herbicides should not be routinely used to maintain edges and banks. General spraying of banks should not be undertaken without follow up revegetation with native species.
Algal blooms
Algal blooms are easily detected: the water colour becomes green, the water clarity is poor and there is an offensive odour. Although an algal bloom can be a sign that the wetland is working as intended (as wetland organisms such as algae remove nutrients from the water column), algal blooms can be toxic to aquatic organisms and humans. Algal shading can kill macrophytes.
No algae apparent
Algae visible
Algal growth prominent or extensive
Schedule water quality testing: e.g. cyanobacterial community composition and cell count. When a potentially toxic bloom is identified, notify residents to avoid contact with the water and continue monitoring until the bloom subsides. Notify the Environment Branch Waterways Project Officer so the lakes priority for management/ retrofit works can be reviewed.
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Water Sensitive Urban Design
Item to be Monitored
Purpose of Monitoring Vigorous plant growth is important in ensuring good water treatment. The plants take up nutrients and provide surface area for biofilms to form (another important mode of nutrient removal).
Plant Condition
Litter (organic)
Performance Target Healthy vegetation
Schedule Maintenance or Investigation
Immediate Action Required
Poorly growing or visibly stressed
Die back / dead plants
The accumulation of decaying vegetation can create mosquito breeding habitats and inhibit seasonal growth of plants.
Organic litter can provide an additional source of nutrients to the constructed wetland, and introduce non-native species, which out-compete native plants (both terrestrial and aquatic).
Litter
(anthropogenic)
Schedule an investigation of cause: e.g. is the observed changes in health and cover due to inappropriate water level or water level variation; disease; competition by weeds; damage (e.g. by birds or flood) or poison contaminant. Maintenance action will depend on the cause of die-back or poor plant health. Once the problem is rectified, infill planting may be required, especially if more than 3 square meters of plantings has died. Infill planting must be as per the original design planting schedule. Dead vegetation may need to be removed as part of ensuring good plant condition.
No litter visible
Litter visible
Litter blocking structures or detracting from visual amenity
Accumulated organic matter / litter can also cause offensive odours (such as methane gas and hydrogen sulphide, i.e. rotten egg gas). Litter can potentially block the inlet and outlet structures of the constructed wetland resulting in flooding, as well as detract from the wetland’s visual amenity.
Maintenance Action Required
Identify source of organic litter and address with appropriate response action: e.g. change of landscape maintenance practices; community education re: litter dumping (appropriate for repeat incidences). In the interim, all litter must be removed by maintenance crews.
No litter visible
Litter visible
Litter blocking structures or detracting from visual amenity
Identify source of rubbish from catchment, for example, overflow of rubbish bins. Target areas of litter accumulation, for example, backwater areas. Schedule general maintenance to remove rubbish. Where required, address source of rubbish (e.g. increase in frequency of rubbish bin emptying; gross pollutant traps in high load generation land uses). In the interim, all litter must be removed by maintenance crews. WARNING: Contact with sharp objects, including hypodermic needles is a risk when removing litter. All workers must be made aware of this risk, wear appropriate protective gear and use caution.
30 Book 4 | MAINTENANCE
Water Sensitive Urban Design
5.2.5 Sedimentation Basins The frequency of litter and debris removal may be high, but will depend on the land use within the systems catchment.
Sedimentation basins are designed to retain coarse sediment by providing sufficient extended detention (and hence settling time). Furthermore, sedimentation basins are designed to allow sediment to accumulate to half the basin depth before clean out is necessary. The design of sedimentation basins is critical in preventing coarse sediment to carry over and smother vegetation in downstream treatment systems such as bioretention basins and constructed wetlands.
The majority of maintenance associated with sedimentation basins concerns the inlet zone (and GPT if installed). Inlets can be prone to scour and build up of litter. Litter removal and potential replanting may be required as part of maintaining an inlet zone. The frequency of litter and debris removal may be high, but will depend on the land use within the systems catchment. Weed removal and replanting of edge vegetation will also be required.
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Water Sensitive Urban Design
Table 5 | Routine monitoring requirement for sedimentation basins. Performance Target
Schedule Maintenance or Investigation
Immediate Action Required
Maintenance Action Required
The inlet and outlet structures of a sedimentation basin should be free of debris, litter and sediment to ensure flow is not impeded. Large storms (or flood) events and vehicles can also damage or block these structures and prevent the system working as designed. The main structural elements of a sedimentation basin are:
- GPT / trash rack/s
GPT clear of litter
GPT 10 percent full
greater than 30 percent full
Contact cleaning service.
Item to be Monitored
Purpose of Monitoring
Structures
Generally a GPT will require clean-out four times per year. For proprietary GPTs it is recommended that a vacuum cleaner be used on at least one occasion per year, or when frequent overflow of litter from the GPT is evident. For all other clean-outs, a mechanical grab is sufficient.
- Inlet structures
Clear and undamaged
Partially Blocked Observed damage
Mostly blocked Severe damage
Inspect the sedimentation basin for scour or erosion damage and fix accordingly.
- Overflow pits
Erosion will affect the distribution of flow across the sedimentation basin.
Erosion
Schedule removal of debris or contact relevant authority within Council for structural damage.
Erosion absent
Erosion damage visible, but function not impaired
Severe erosion. Damage impairing function of device
If left untreated, small sites of erosion can quickly spread over large areas becoming costly to repair.
Schedule investigation to identify cause of profile damage. Once source of damage is rectified, scour holes should be replaced with appropriate filter media.
Replace any damaged plants to meet the design plant schedule.
Sediment build up
The accumulation of sediment is a prescribed function of a sedimentation basin. However, sediment must be regularly removed to ensure that the sediment trapping performance of this system is sustained.
32 Book 4 | MAINTENANCE
Sediment absent
Sediment accumulation appears excessive
Sediment accumulated to half the sediment basin depth
Schedule investigation to identify sediment source. Once sediment source is stabilised, remove accumulated sediment. Replace any damaged plants to meet the design plant schedule.
Water Sensitive Urban Design
Item to be Monitored
Weeds and invasive plants
Plant Condition
Performance Target
Schedule Maintenance or Investigation
Weeds should be removed from the sedimentation basin: - Weeds can spread to downstream environments, compromising ecosystem health. - Weeds compromise the visual amenity of the sedimentation basin.
No weeds present
Weeds present
Plants are crucial to bank stability and visual amenity
Healthy vegetation
Purpose of Monitoring
Poorly growing or visibly stressed
Immediate Action Required
Maintenance Action Required
Noxious or environmental weeds present, or weed cover more than 25 percent
Hand removal or targeted herbicide treatment (herbicides registered for use around waterways).
Die back / dead plants
Schedule an investigation into the cause of plant die-back or poor health.
Note: Herbicides should not be routinely used to maintain edges and batter slopes. General spraying of batter slopes should not be undertaken without follow up revegetation with native species.
Maintenance action will depend on the cause of die-back or poor plant health. Once the problem is rectified, infill planting may be required, especially if more than 1 square meter of plantings has died. Infill planting must be as per the original planting schedule. Litter (organic)
Organic litter can provide an additional source of nutrients and on-native species which have a high likelihood of being transferred to downstream treatment systems and waterways.
No litter visible
Litter visible
Litter thickly covers filter media surface or detracting from visual amenity
Accumulated organic matter / litter can also cause offensive odours (such as methane gas and hydrogen sulphide, i.e. rotten egg gas). Litter
(anthropogenic)
Litter can potentially block the inlet and outlet structures resulting in flooding, as well as detract from the system’s visual amenity.
Identify source of organic litter and address with appropriate response action: e.g. change of landscape maintenance practices; community education re: litter dumping (appropriate for repeat incidences). In the interim, all litter must be removed by maintenance crews.
No litter visible
Litter visible
Litter blocking structures or detracting from visual amenity
Identify source of rubbish: e.g. from catchment (commercial precinct); overflow of rubbish bins; accumulation in backwater area and schedule general maintenance to remove rubbish. Where required address source of rubbish (e.g. increase in frequency of rubbish bin emptying; gross pollutant traps in high load generation land uses). In the interim, all litter must be removed by maintenance crews. WARNING: Contact with sharp objects, including hypodermic needles is a risk when removing litter. All workers must be made aware of this risk, wear appropriate protective gear and use caution.
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Water Sensitive Urban Design
Item to be Monitored Oil slicks
Purpose of Monitoring
Oil spills / inflows are better trapped and isolated within a sedimentation basin than allowed to flow to the downstream waterway.
Performance Target No visible oil
Schedule Maintenance or Investigation Persistent but limited visible oil
Immediate Action Required Extensive or localised thick layer of oil visible
Maintenance Action Required
Do not isolate sedimentation basin in the case of an oil spill - it is better that the oil is contained within the system than allowed to flow to the downstream water course. Notify the EPA of the spill and clean-up requirements NOTE: do not add any fertiliser, or other nitrogen based product to the system. The microbes within the filter media are capable of decomposing hydrocarbons.
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Water Sensitive Urban Design
5.3 Waste Management and Disposal Water sensitive urban design elements are designed to detain pollutants from being discharged to the downstream watercourse.
Water sensitive urban design elements are designed to detain pollutants from being discharged to the downstream watercourse. Vegetated WSUD elements such as constructed wetlands and bioretention basins use pollutants such as nitrogen and phosphorus in plant growth, minimising the build up of nutrients in the system. Conversely, suspended solids and gross pollutants cannot be used by a vegetated treatment system and hence accumulate and will eventually require the intervention of maintenance crews.
Three types of waste are associated with WSUD elements: •• Contaminated silt basins, constructed ponds) •• Spoiled basins)
filter
media
(sedimentation wetlands and (bioretention
•• Liquid waste from dewatering activities
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Water Sensitive Urban Design
5.3.1 Dewatered silt
5.3.2 Filter media
The NSW Department of Environment and Climate Change (DECC) has recently amended the rules governing waste disposal. Silt collected from sediment basins is now defined as general waste (non-putrescibles). For general waste (non-putrescibles), there is no requirement for the silt to be tested, unless the Council (or owner of the asset) believes that the nature of the catchment could cause the silt to have:
The filter media for bioretention basins may need replacing in the following situations:
•• A Specific Contaminant Concentration (SCC) higher than the guideline values given by DECC; and/or •• A leachable concentration of any chemical contaminant (as determined through the Toxicity Characteristics Leaching Procedure (TCLP)) higher than the guideline values given by DECC Guideline values for General Solid Waste for both measures are given in the following document http://www. environment.nsw.gov.au/resources/ waste/08202classifyingwaste.pdf Disposal of dewatered silt is accepted by WSN Environmental solutions, but only at their Eastern Creek and Lucas Heights locations. WSN Environmental solutions classify General Solid Waste as Special Waste, which has a disposal cost of $220 per tonne. The waste service facility at Belrose will also accept General Solid Waste; however due to a limited capacity, it will only accept waste from the surrounding LGA (Ku-ring-gai). Although in theory general waste (nonputrescibles) can be accepted by private waste disposal operators, very few facilities within the Sydney Metropolitan actually have the capacity to accept sludge / silt type material. One of the few exceptions is Blacktown Waste Service who accepts general solid waste (non-putrescibles) at a cost between $75 and $110 per tonne.
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1) Filter media has reached full capacity for retaining metals as identified through pollutant breakthrough. 2) Surface of filter media is clogged. Recent research conducted by FAWB has shown for a bioretention basin sized at two percent of the impervious catchment area and a filter media depth of 0.5 metres, pollutant breakthrough will occur within 15 years. The results were considered conservative (ie lower estimate) as the soils had a low pH. Soils with a neutral pH will have a greater capacity to attract metal pollutants, hence further delaying breakthrough from occuring. When breakthrough occurs, the entire filter media will need replacing. Surface clogging can be observed through poor plant growth, or when ponding times exceed the design specifications. The replacement of filter media is not required if plant growth is poor. The clogging of the surface media could be remedied by re-establishing plants to ensure density is sufficient in maintaining surface porosity. If, however, plant growth is adequate, clogging is related to failure of the filter media and the top 200 to 300 millimetres of filter media will require replacing. Removed filter media may be contaminated and should be tested accordingly. Filter media classified as contaminated should be disposed of at a certified waste disposal centre. Alternatively, there may be options to bio-remediate the soil and reuse it.
Water Sensitive Urban Design
Detention pond | Garden Gates
5.3.3 Liquid waste (from dewatering activities) The location of the dewatering facility should consider existing site constraints.
Prior to discharge, the silt removed must be dewatered such that it does not contain any free liquid (that is, the density is 1.5 to 3 times the density of the material if completely dry (Collins, 2006)). The dewatering of collected silt can be accommodated in the design of the sedimentation basin, whereby free liquid is directed back into the treatment train. Alternatively, collected silt can be stockpiled within designated bunded areas offsite or stored in skip trucks brought into the site. The location of the dewatering facility should consider existing site constraints, DECC regulatory requirements, health and safety issues, odours and other community concerns (WBM and Ecological Engineering, 2005). Liquid removed during dewatering is likely to be classified as either Group A liquid waste or non-controlled aqueous liquid waste, depending on the concentration of suspended or dissolved chemicals (WBM and Ecological Engineering, 2005). The level of contamination should be confirmed by laboratory testing; however it is likely that dewatered water will classified as non-controlled aqueous liquid waste.
Open space | Victoria Park
The decantered water must be treated prior to discharge to a receiving waterbody. Treatment can be achieved through many mechanisms, including: •• Pumping decantered water to a settling tank to remove elevated levels of suspended solids. This may require the addition of a flocculent such as gypsum. •• Decanting liquids to pervious areas, ensuring liquids are appropriately treated to meet reuse requirements. Potential implications of reusing decanted water from stormwater treatment measures include high pollutant (in particular heavy metal) concentrations and health risks posed by trapped pathogens. •• Decanting liquids back into stormwater treatment system.
the
5.3.4 Equipment requirements For a sediment basin, wetland or pond, cleaning will generally require a backhoe, excavator or eductor / vacuum truck, requiring service from one to two vehicle operators and one to three labourers (HSC, 2001). The removal of waste from a bioretention basin must be done by hand to protect the bathymetry and compaction of the filter media. Book 4 | MAINTENANCE
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Water Sensitive Urban Design
6 | Construction Requirements
Watersteps | Victoria Park
The ultimate aim of each option is to protect the functional elements of the WSUD element.
This section provides advice on the construction of WSUD elements. In particular, the advice concentrates on the staging of construction in association with other development in the catchment. The construction advice is supported by a series of checklists, which have been developed to ensure critical design elements are checked and signed off as completed; hence minimising the potential for expensive re-work.
by Design (2009) a program of the South East Queensland provides guidance on the staged construction of WSUD elements. Multiple options are presented for each WSUD element, which assess: 1) The location of the WSUD element (that is, streetscape, parkland); 2) The level of environmental protection the system provides during staged construction; and 3) The landscape amenity of the system during staged construction.
6.1 Staging The construction of WSUD elements should be coordinated with other construction activities within the catchment. Construction activities will generate greater loads of coarse sediment and gross pollutants, for which the WSUD treatment element is unlikely to be designed for. High loadings of coarse sediment and gross pollutants can be particularly detrimental during plant establishment for a vegetated system, smothering infant vegetation and changing the bathymetry of the element (which in turns affects the hydraulic function and the distribution of flow within the treatment element). The Water Sensitive Urban Design Construction and Establishment Guidelines (version 1) developed by Water
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The ultimate aim of each option is to protect the functional elements of the WSUD element. This is achieved by either isolating the functional elements by diverting stormwater flows or increasing the capacity for sediment capture either upstream or within the WSUD element. For each option, construction and establishment of WSUD elements is divided into three stages: Stage 1: Civil construction (or functional installation) Stage 2: Building phase protection (or sediment and erosion control) Stage 3: Operational establishment (civil and/or landscaping) These are illustrated in Figure 7 together with a list of corresponding management forms contained in Appendix A.
Water Sensitive Urban Design
Stage 1: Civil Construction Pre start construction meeting
Subdivision Construction
FORM A Earthworks and hydraulic /
Functional Structures FORM C (bioretention basin) Filter media and finished levels
Stage 2: Building phase protection FORM B Erosion and Sediment Control
Stage 3: Operational establishment FORM C (wetland and sedimentation) Top soil and finished levels
FORM D Landscape Planting
Asset handover
Allotment Building (up to 30 percent completion)
Allotment Building (greater than 80 percent completion)
Completion of construction activities
Asset handover checklist
Figure 7: Staged construction of WSUD elements and the timing of relevant forms
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6.1.1 Stage 1: Civil construction (or functional installation) Stage 1 requires the construction of the functional components for the WSUD element. The functional components for the WSUD elements addressed in the booklet are: Bioretention basin Bulk earthworks to establish bunds and system batter slopes Detailed profiling of bunds, batters, sides and base of system to meet design requirements (given allowed tolerances) Construct all hydraulic structures, for example, inlet pipes and headwalls, bypass weir, outlet riser and rock protection* Install system lining, underdrainage, clean out points and various layers (that is, drainage layer, transition layer and filter media)
Constructed wetland Survey wetland layout in accordance with the design Remove ground cover and topsoil as indicated from the survey Stockpile topsoil designated for reuse in construction, noting that the soil must be tested and screened to remove coarse sediment and weed seeds Bulk earthworks to establish the inlet and macrophyte zone, high flow bypass and surrounding bunds and batters Detailed profiling of bunds, batters, sides and base of system to meet design requirements (given allowed tolerances as well as 300 mm of topsoil and impervious liner, if specified) Install impervious liner (if required) Construct bunding between the inlet and outlet zone, as well as between the wetland and lake (if a lake is included in the design) Construct all hydraulic structures, for example, inlet pipes and headwalls, bypass weir, outlet riser and rock protection*
Sedimentation basin Bulk earthworks to establish bunds and system batter slopes, as well as maintenance access (e.g. ramp) Installation of outlet structures (for example, overflow pit / weir and spillway) Installation of inlet structures including inlet pipe and headwall. For a sedimentation basin, install the inlet energy dissipater and primary treatment measure (for example, gross pollutant trap) Detailed profiling of bunds, batters, system base, access points and spillway to meet design requirements (given allowed tolerances) Install system lining Stabilise system batters and base with sterile grass
Topsoil placement and profiling to within accepted tolerances NOTE: * This is not a complete list of hydraulic, functional and structural elements of a constructed wetland – the reader is referred to the Water by Design documents for complete details.
Immediately following completion of stage 1, sediment fences should be installed at the top of the system batter. Bioretention basins will also require sediment fences installed around the filter media.
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Water Sensitive Urban Design
Stage 1 – Functional Installation
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41
Water Sensitive Urban Design
6.1.2 Stage 2: Building phase protection (or sediment and erosion control) Stage 2 involves the construction of temporary measures to protect the functional elements of the system. As stated, two options are typically considered, either diversion of flows away from the functional elements to allow plant establishment, or the establishment of temporary sedimentation basins (within or upstream of the main functional part of the WSUD element). The main activities required as part of stage 2 are: Bioretention basin
Constructed wetland
Sedimentation basin / pond
Bypass of stormwater flows / isolation of functional design Install bypass structure. The system will typically involve one of the following: 1) Completely bypassing the inlet pipe around the filter media area 2) Partitioning the systems such that the inlet and outlet only are engaged
Isolate macrophyte zone from the inlet zone by blocking the connection pipe between the two zones Stabilise the high flow bypass either with turf or reinforced turf Ensure the entire perimeter of the wetland is protected by sediment fences Construct non-wetland related hardscapes, such as boardwalks and pathways
Sedimentation Basins Generally not considered for sedimentation basins
Ponds Isolate pond from downstream treatment devices by blocking connecting pipework Ensure the entire perimeter of the pond is protected by sediment fences
Establishment of temporary sediment protection devices Protect the filter media with a filter cloth or 25 to 50 mm of course sand plus 25 mm of topsoil and turf
The entire constructed wetland footprint is allowed to operate as a sediment basin
Sedimentation Basins Ensure earthworks are stabilised immediately post construction (basin profile should be stabilised through sterile grasses, while terrestrial planting established around the basin perimeter) Ensure overflow from basin disconnected from any downstream treatment devices (such as wetlands)
The protective measures identified above should be removed only when 80 to 90 percent of construction works in the catchment have been completed. If a distributed water sensitive design process has been implemented, treatment systems can be brought online gradually without having to wait for all development to cease. Landscaping can be established in areas isolated from stormwater flow. For constructed wetlands, special attention is required in manipulating the water level during plant establishment within the macrophyte zone such that plants are not ‘drowned’. The specific plant establishment requirements for constructed wetlands are detailed in the Water by Design documentation.
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Water Sensitive Urban Design
Stage 2 – Sediment Control Measures
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Water Sensitive Urban Design
6.1.3 Stage 3: Operational establishment (civil and/or landscaping) Stage 3 involves reconnecting the functional elements of the WSUD element to meet design specifications. In general, this involves decommissioning erosion and sediment control protection devices and replanting of landscape areas. Specific tasks within stage 3 as they relate the WSUD elements addressed in the Operations and Maintenance booklet are: Bioretention basin
Constructed wetland
Desilt basin if converted to a temporary sediment basin.
Remove accumulated sediment and gross pollutants from inlet zone (and macrophyte zone if the wetland has been used as a sedimentation basin during stage 2)
Remove measures protecting filter media, for example bunds, filter cloth, topsoil and turf. Flush out under-drainage using potable (mains) water Flatten filter media surface to within given tolerance (additional media may be required to fill in over-excavated areas) Mulch filter media, allowing for planting holes Dig holes for planting Plant nominated species Maintain landscaping to ensure healthy plant establishment
Assess the condition of the impervious liner and hydraulic structures (if the wetland has been operated as a temporary sediment basin in stage 2) and amend accordingly
Sedimentation basin / pond Desilt basin Remove sterile grass from basin and establish marsh zone and embankment planting as per the design specifications Install topsoil to a depth of 300 mm on batters and 500 mm below the normal water level Landscape basin as per the planting specifications***
Install topsoil in basin to a depth of 300 mm on batters and 500 mm below the normal water level (this will be required for the macrophyte zone only if zone used as a sediment basin during stage 2) Remove disconnection between inlet and macrophyte zone (only if macrophyte plantings have been established during stage 2)* Landscape macrophyte zone if zone not yet established** Landscape inlet zone according to the design specifications**
NOTE: * If the wetland has been used as a temporary sedimentation basin during stage 2, establish macrophyte plantings prior to bringing the macrophyte zone online. Specific requirements for plant establishment in the macrophyte zone of a constructed wetland are detailed in the Water by Design documentation. ** Water levels will need to be manipulated during landscape establishment *** Water level manipulation is not required for ponds. The plants specified for the base of ponds will be suitable for an environment starved of oxygen. Typically plant establishment in ponds is through anchoring the plants / seedlings to the pond base with rocks. This task is required regardless of what sediment control measures are instigated as part of stage 2.
Specific plant establishment requirements including fertiliser application and recommended watering schedule (including frequency of watering for terrestrial and marsh plantings, and the requirements for water level manipulation in constructed wetlands and ponds) are not detailed in this booklet. The reader is directed to the Water by Design (2009) documentation for further information.
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Water Sensitive Urban Design
Stage 3 – Operational Establishment
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Water Sensitive Urban Design
6.2 Construction Tolerances The distribution of flow within a WSUD element affects the treatment efficiency.
Important to the design of bioretention basins, constructed wetlands, and sedimentation basins/ponds is the hydraulic function of the system (that is, how water is delivered from one part of a system to another) and the distribution of flow within the system. The distribution of flow within a WSUD element affects the treatment efficiency. Poor distribution of flow and the creation of localised water pools can also cause adverse affects such as mosquito breeding.
or flow distribution. The revised technical guidelines for bioretention systems and constructed wetlands produced through Water by Design (2009) have seen the relaxing of these tolerances. A summary of the tolerances stipulated in the revised Water by Design documentation are given in the following table. The tolerances for sedimentation basins and ponds have also been updated to ensure consistency between similar design elements (for example, hydraulic structures).
The WSUD Technical Design Guidelines for South-East Queensland (SEQ) (Moreton Bay Waterways and Catchments Partnership, 2006) identifies key construction tolerances for typical WSUD elements as related to system hydraulics
Further details on construction details can be found in the WSUD Technical Design Guidelines for South-East Queensland, which can be downloaded online from the Healthy Waterways website http://www/waterbydesign.com.
CONSTRUCTION TOLERANCES Bioretention Basins
Constructed Wetlands
Sedimentation basins / ponds
Profiling of base
Relative levels of flow control structures*
Relative levels of flow control structures
(+25 mm)
(+25 mm)
Bathymetry of macrophyte zone topsoil levels
Bathymetry of basin
(+50 mm) Profiling of surface grades (i.e. drainage, transition and filter layer) (+25mm) Relative levels of hydraulic structures (+25 mm)
(+50 mm)
(+50 mm)
Surface levels (+50 mm)
Minimum slope of drainage system (0.5 %)
* NOTE: Control structures are described as inlet connections, bypass weir and outlet structures
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Water Sensitive Urban Design
6.3 Construction Certification and Compliance The construction of a vegetated WSUD strategy requires coordination between the civil and landscaping contractors. Civil contractors are responsible for the construction of the functional elements of a treatment system, while landscape contractors are responsible for the initial plantings and management of the treatment system to ensure plant establishment is successful and meets the design brief. Consequently, construction certification is required from both civil and landscaping contractors as documented in the revised Water by Design (2009) documentation. The suggested construction certificates for constructed wetlands, bioretention systems and sediment basins/ponds are described in the table below. Additionally for bioretention basins, certification is required from the soil supplier to ensure the soil specifications of the filter media meet the requirements documented by the Facility for Advancing Water Biofiltration (FAWB) (refer to section 4.04). The certification outlined above should form the basis of compliance for WSUD elements. However, to minimise rework due to non-compliance issues, it is suggested that inspections/meetings be scheduled as follows (refer column over): Civil Certification
1) Pre-start meeting: Ensure all contractors are aware of the key issues for each stage of construction. For example, compaction requirements for filter media. 2) Inspection of all functional elements (as completed) of the treatment system (for example, the under-drainage for a bioretention should be inspected prior to the gravel being inserted around the pipes). 3) Inspection of sediment control structures to ensure vulnerable elements within the treatment system are isolated from storm flows as dictated in the design documentation. 4) Inspection of plant establishment (if required) to ensure species and densities are as per the design. Continual inspections should be scheduled to check plant establishment. 5) Final inspection of plant establishment and civil works. The scheduling of the above inspections within the three main construction stages is given below. Example inspection and sign off sheets for WSUD elements are given in Appendix A.
Designers certification of functional elements Civil certification that functional elements have been constructed as per the designers certification As constructed survey, drawings and photos
Landscape Certification
Designers or ecologist sign off of plant species As constructed drawings identifying species and plant density
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Water Sensitive Urban Design
6.4 Filter Media Specifications The Facility for Advancing Water Biofiltration (FAWB), a joint collaboration between Monash University and Ecological Engineering Holdings recently updated the original filter media specifications produced in 2006. Specifications are given for the three main layers defined for a bioretention basin as described in the table below. Further details relating to the testing of hydraulic conductivity, the specific filter media specifications (for example, organic matter content, pH, electrical conductivity and phosphorus content), and particle size distribution can be found in the FAWB document Guidelines For Soil Filter Media In Bioretention Systems (version 2.01). http://www.clearwater.asn. au/resources/658_1.FAWB%20Filter%20 media%20guidelines_revised_March%20 2008.pdf
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Recently, bioretention basin design has evolved to include an anoxic zone. In 2008, FAWB conducted a series of workshops on biofiltration systems, which included the design requirements and performance of biofiltration systems with submerged zones. The workshop material made the following specifications: 1. Depth of submerged zone – approximately 450 mm. 2. Media specifications – sand or gravel, containing a carbon source such as hardwood chips or sugar cane. The carbon source is to account for 5 percent of the volume of the submerged zone media. The workshop manual produced by FAWB can be downloaded from the following url: h t t p : // w w w . m o n a s h . e d u . a u / f a w b / products/index.html
Filter Media (typically 400 to 600 millimetres in depth)
Loamy sand, with an appropriate hydraulic conductivity (100 to 300 millimetres per hour) and soil properties given in AS4419 – 2003 (Soils for Landscaping and Garden Use)
Drainage Layer (typically 150 millimetres in depth)
Clean, well graded sand / coarse sand material (containing no/little fines)
Transition Layer (typically 100 millimetres in depth, or sufficient to provide 50 millimetres of cover to drainage network)
Clean fine gravel
Water Sensitive Urban Design
Appendix A – Construction Inspection and Sign off sheets A.1. Bioretention Systems
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Water Sensitive Urban Design
Bioretention Basin Sign-Off Forms Development stage: Bioretention basin ID:
Pre-Start Construction Meeting Location: Date:
List of Attendees Name
Discipline (suggested)
Company
1
Developer
2
Site superintendent (civil)
3
Site superintendent (landscape)
4
Civil Contractor
5
Landscape Contractor
6
WSUD - Design Engineer
7
Civil Engineer
8
Landscape Architect
9
Checklist of Sign-Off Forms Sign-Off Form Form A
Earthworks and Hydraulic / Functional Structures
Form B
Erosion and Sediment Control
Form C
Filter Material and Finished Levels
Form D
Landscape Planting (Macrophyte and Inlet Zone)
Date Completed
Construction Tolerances: The construction tolerances on the bioretention systems are to be: •• plus or minus 50 mm on earth works and filter media levels. •• plus or minus 25 mm on hydraulic structures (e.g. pit and weir crests/ bund heights, pipe and pit invert levels) Deviations to be approved only at the discretion of superintendent.
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Water Sensitive Urban Design
Form A - Earthworks and Hydraulic / Functional Structures Purpose: 1) To ensure bulking out, trimming and profiling is in accordance with design specifications (including allowance for 300 mm topsoil and a minimum 300 mm of impervious liner where required). 2) To ensure hydraulic structures associated with the bioretention basin are constructed in accordance with the design specifications.
Actions addressed (initial)
Action/s (if required)
Satisfactory
Items
Checked
Checklist:
Bulking out & hard structures
As constructed survey of basin base and surrounding bunds, pit crests, inlet and outlet pipes
Base levels are at correct elevation, given the minimum allowances for topsoil and impervious liner (where required)
Base at correct grading (0.5 percent)
Hold Point - Sign off is required from superintendent and bioretention basin designer before proceeding Bunds and impervious liner
Laboratory test results of liner material submitted and adequate
Delivery docket of liner material submitted and adequate
Delivery docket of liner material supplied
Geotechnical engineer certification of in-situ compaction or liner placement
Geotechnical engineer certification / sign off of key bunds
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Water Sensitive Urban Design
Hold Point - Sign off is required from superintendent and bioretention basin designer before proceeding Functional and hydraulic functions
Inlet and outlet pipes and headwalls correctly set out and at correct level (upstream and downstream ends)
Bypass weir correct width and level
Overflow pit is correct size and crest is at correct level
Maintenance pipe and valve installed at correct location and level
Maintenance access installed to inlet zone
Rock or concrete base constructed at inlet to bioretention basin
Rock protection provided at correct locations and rock size consistent with design
Hold Point - Sign off is required from superintendent and bioretention basin designer before proceeding Under-drainage
Base of system free from debris
Under-drainage pipes laid at required grade (verified using level or string line)
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Water Sensitive Urban Design
All junctions and connections have been appropriately sealed using sealant
Underdrain pipes correctly connected and sealed into overflow pit
Top of clean out points at design level (i.e. approximately 100mm above filter media surface level)
Extension of under-drains out of the basin are NOT perforated
Clean out points capped
Hold Point - Sign off is required from superintendent and bioretention basin designer before proceeding
Comments:
Signed by Superintendent(s): Print Name: Date:
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Form B – Erosion and Sediment Control Purpose: To ensure sediment and erosion control measures are correctly installed to protect the bioretention basin filter media.
Continuous silt fences installed around all elements of constructed wetlands
If silt fences are deemed inadequate, other sediment and erosion control measures installed to ensure sediment does not enter basin
High flow bypass channel protective measures in place (that is, turf installed and where required reinforced turf)
If basin to be used as a sedimentation basin during lot development Filter media surface protected, either by installing a filter cloth or 25 to 50 mm of course sand plus 25 mm of topsoil and turf If basin is to be isolated during lot development
Stormwater diverted away from functional elements of bioretention basin
Hold Point - Sign off is required from superintendent and bioretention basin designer before proceeding
Comments
Signed by Superintendent(s): Print Name: Date:
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Actions addressed (initial)
Action/s (if required)
Satisfactory
Items
Checked
Checklist:
Water Sensitive Urban Design
Form C – Filter Material and Finished Levels Purpose: To ensure that the soils to be placed in the basin match the soils that were specified and ordered. To ensure soil layers are placed according to specifications prior to any landscape works.
Actions addressed (initial)
Action/s (if required)
Satisfactory
Item
Checked
Checklist:
Filter Material Drainage layer (fine gravel): Supply docket matches gravel specification NOTE: Attach Supply Docket
Transition layer (coarse sand): Supply docket matches sand specification NOTE: Attach Supply Docket
Filter layer (sandy loam): Supply docket matches media specification NOTE: Attach Supply Docket
Filter material testing completed and approved in accordance with design report
Drainage layer (fine gravel) installed to correct depth (photo and survey)
Transition layer (coarse sand) installed to correct depth (photo and survey)
Filter media installed to correct depth (photo and survey)
Light, even compaction applied to remove air gaps
Even flat surface of filter media
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Water Sensitive Urban Design
Finished levels
As constructed survey of basin surface and surrounding bunds completed
Final constructed levels are consistent with design levels
Under-drainage pipes flushed to remove initial ingress of material
All civil construction items are complete and basin is ready for planting by landscape contractor
Geofabric layer + 50mm topsoil (top layer of supplied filter material) and turf applied to basin surface.
Suitable batter protection in place (e.g. sediment fence or landscape netting)
HOLD POINT - Sign off is required from superintendent and bioretention basin designer before proceeding
Comments
Signed by Superintendent(s): Print Name: Date:
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Water Sensitive Urban Design
Form D – Landscape Planting Purpose: To ensure correct plants are supplied and installed. To be used in conjunction with other landscape sign off requirements.
Actions addressed (initial)
Action/s (if required)
Satisfactory
Item
Checked
Checklist:
Basin desilted and filter media levels reinstated to meet design specifications NOTE: This action is applicable if bioretention basin was converted to a sediment basin during lot development Supplied plants are correct species Changes to species planted must be approved by wetland designer/ecologist and marked up on asconstructed drawings
Supplied plants are in correct pot sizes, maturity (minimum 300 mm in height) and hardened
Plants have been installed at correct planting density
Correct mulch has been supplied and installed to batters and bunds above the extended detention and secured in place
As constructed drawings marked up with final plant species and densities
HOLD POINT - Sign off is required from superintendent and bioretention basin designer before proceeding
Comments
Signed by Superintendent(s): Print Name: Date:
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Appendix A – Construction Inspection and Sign off sheets A.2. Constructed Wetlands
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Water Sensitive Urban Design
Constructed Wetland Sign-Off Forms Development stage: Wetland ID::
Pre-Start Construction Meeting Location: Date:
List of Attendees Name
Discipline (suggested)
Company
1
Developer
2
Site superintendent (civil)
3
Site superintendent (landscape)
4
Civil Contractor
5
Landscape Contractor
6
WSUD - Design Engineer
7
Civil Engineer
8
Landscape Architect
9
Checklist of Sign-Off Forms Sign-Off Form Form A
Earthworks and Hydraulic / Functional Structures
Form B
Erosion and Sediment Control
Form C
Topsoil and Finished Levels
Form D
Landscape Planting (Macrophyte and Inlet Zone)
Date Completed
Construction Tolerances: The construction tolerances on the constructed wetland systems are to be: •• plus or minus 25 mm on hydraulic structures (e.g. pit and weir crests/ bund heights, pipe and pit invert levels) •• plus or minus 50 mm on earthworks (base of wetland, as measured from the surface of the topsoil). •• plus or minus 50 mm on embankments and bunds (that is, crest level of the embankment). Deviations to be approved only at the discretion of the superintendent.
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Form A – Earthworks and Hydraulic/Functional Structures Purpose: 3) To ensure bulking out, trimming and profiling is in accordance with design specifications (including allowance for 300 mm topsoil and a minimum 300 mm of impervious liner where required). 4) To ensure hydraulic structures associated with the wetland are constructed in accordance with the design specifications.
Bulking out & hard structures
As constructed survey of basin base and surrounding bunds, pit crests, inlet and outlet pipes
Set out of wetlands is correct (including inlet zone, macrophyte zone, high flow bypass)
Base levels are at correct elevation, given the minimum allowances for topsoil and impervious liner (where required)
Hold Point - Sign off is required from superintendent and wetland designer before proceeding Bunds and impervious liner
Laboratory test results of liner material submitted and adequate
Delivery docket of liner material submitted and adequate
Delivery docket of liner material supplied
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Actions addressed (initial)
Action/s (if required)
Satisfactory
Items
Checked
Checklist:
Water Sensitive Urban Design
Geotechnical engineer certification of in-situ compaction or liner placement
Geotechnical engineer certification / sign off of key bunds
Hold Point - Sign off is required from superintendent and wetland designer before proceeding Functional and hydraulic functions
Inlet and outlet pipes and headwalls correctly set out and at correct level (upstream and downstream ends)
Inlet zone connection pit or pipe correct size, location and level
Outlet riser connection, location, size and levels correct
Bypass weir correct width and level
Overflow pit is correct size and crest is at correct level
Maintenance pipe and valve installed at correct location and level
Maintenance access installed to inlet zone
Rock or concrete base constructed to inlet zone
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Water Sensitive Urban Design
Rock protection provided at correct locations and rock size consistent with design
Seepage collar(s) installed to all pipe outlets from wetland
Hold Point - Sign off is required from superintendent and wetland designer before proceeding
Comments
Signed by Superintendent(s): Print Name: Date:
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Water Sensitive Urban Design
Form B – Sediment and Erosion Control Purpose: To ensure sediment and erosion control measures are correctly installed to protect the macrophyte zone of the constructed wetland.
Actions addressed (initial)
Action/s (if required)
Satisfactory
Items
Checked
Checklist:
Continuous silt fences installed around all elements of constructed wetlands
If silt fences are deemed inadequate, other sediment and erosion control measures installed to ensure sediment does not enter basin
High flow bypass channel protective measures in place (that is, turf installed and where required reinforced turf)
Inlet zone disconnected from macrophyte zone (that is, plates placed on overflow pit and secured)
If inlet zone not disconnected, macrophyte zone converted into a sedimentation basin (base and batters of macrophyte Hold Point - Sign off is required from superintendent and wetland designer before proceeding
Comments
Signed by Superintendent(s): Print Name: Date:
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Form C – Topsoil and Finished Levels Purpose: To ensure the topsoil is installed to the correct depth and finished levels of wetland are correct and meet the design.
Topsoil meets the requirements of AS4419 and laboratory tests provided
Topsoil has been screened and is free of large debris
Topsoil applied to wetland (minimum 300 mm depth)
Final topsoil levels are consistent with design levels (CRITICAL in the macrophyte zone)
Surface is smooth and free of local depressions and debris
Hold Point - Sign off is required from superintendent and wetland designer before proceeding
Comments
Signed by Superintendent(s): Print Name: Date:
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Actions addressed (initial)
Action/s (if required)
Satisfactory
Item
Checked
Checklist:
Water Sensitive Urban Design
Form D – Landscape Planting Purpose: To ensure correct plants are supplied and installed.
Actions addressed (initial)
Action/s (if required)
Satisfactory
Item
Checked
Checklist:
Macrophyte zone landscape installation Supplied plants are correct species Changes to species planted must be approved by wetland designer/ecologist and marked up on as-constructed drawings
Supplied plants are in correct pot sizes, maturity (minimum 300 mm in height) and hardened
Plants have been installed at correct planting density
Water level control is operating appropriately
Correct mulch has been supplied and installed to batters and bunds above the extended detention and secured in place
As constructed drawings marked up with final plant species and densities
HOLD POINT - Sign off is required from superintendent and wetland designer before proceeding Macrophyte zone landscape establishment
Weeds removed as required
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Watering occurring as required
Macrophyte plants established such that the water level in the macrophyte zone can be allowed to reach design level (typically 500 mm above the normal water level)
HOLD POINT - Sign off is required from superintendent and wetland designer before proceeding
Comments
Signed by Superintendent(s): Print Name: Date:
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Form D – Landscape Planting (inlet zone) Purpose: To ensure correct plants are supplied and installed.
Actions addressed (initial)
Action/s (if required)
Satisfactory
Item
Checked
Checklist:
Inlet zone landscape installation Supplied plants are correct species Changes to species planted must be approved by wetland designer/ecologist and marked up on as-constructed drawings Supplied plants are in correct pot sizes, maturity (minimum 300 mm in height) and hardened
Plants have been installed at correct planting density
Correct mulch has been supplied and installed to batters and bunds above the normal water level and secured in place As constructed drawings marked up with final plant species and densities HOLD POINT - Sign off is required from superintendent and wetland designer before proceeding Inlet zone landscape establishment Weeds removed as required
Watering occurring as required
Inlet zone plantings established such that the water level in the macrophyte zone can be allowed to reach design level (typically 500 mm above the normal water level) HOLD POINT - Sign off is required from superintendent and wetland designer before proceeding
Comments
Signed by Superintendent(s): Print Name: Date:
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Appendix A – Construction Inspection and Sign off sheets A.3 Sedimentation Basins / Ponds
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Sedimentation Basin Sign-Off Forms Development stage: Sediment basin / pond ID:
Pre-Start Construction Meeting Location: Date:
List of Attendees Name
Discipline (suggested)
Company
1
Developer
2
Site superintendent (civil)
3
Site superintendent (landscape)
4
Civil Contractor
5
Landscape Contractor
6
WSUD - Design Engineer
7
Civil Engineer
8
Landscape Architect
9
Checklist of Sign-Off Forms Sign-Off Form Form A
Earthworks and Hydraulic / Functional Structures
Form B
Sediment and Erosion Control
Form C
Topsoil and Finished Levels
Form D
Landscape Planting (Macrophyte and Inlet Zone)
Date Completed
Construction Tolerances: The construction tolerances on the constructed wetland systems are to be: •• plus or minus 25 mm on hydraulic structures (e.g. pit and weir crests/ bund heights, pipe and pit invert levels) •• plus or minus 50 mm on earthworks (base of wetland, as measured from the surface of the topsoil). •• plus or minus 50 mm on embankments and bunds (that is, crest level of the embankment). Deviations to be approved only at the discretion of superintendent.
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Form A – Earthworks and Hydraulic/Functional Structures Purpose: 5) To ensure bulking out and key levels of hard structures are in accordance with design specifications. 6) To ensure hydraulic structures associated with the sedimentation basin or pond is constructed in accordance with the design specifications.
Bulking out & hard structures
As constructed survey of basin base and surrounding bunds, pit crests, inlet and outlet pipes
Base levels are at correct elevation, given the minimumallowances for topsoil and impervious liner (where required)
Hold Point - Sign off is required from superintendent and wetland designer before proceeding Bunds and impervious liner
Laboratory test results of liner material submitted and adequate
Delivery docket of liner material submitted and adequate
Delivery docket of liner material supplied
Geotechnical engineer certification / sign off of key bunds
Hold Point - Sign off is required from superintendent and wetland designer before proceeding
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Actions addressed (initial)
Action/s (if required)
Satisfactory
Items
Checked
Checklist:
Water Sensitive Urban Design
Functional and hydraulic functions
Inlet and outlet pipes and headwalls correctly set out and at correct level (upstream and downstream ends)
Bypass weir correct width and level
Overflow pit is correct size and crest is at correct level
Bypass weir correct width and level
Maintenance pipe and valve installed at correct location and level
Maintenance access installed to basin
Rock protection provided at correct locations and rock size consistent with design (applicable to sediment basin, only)
Hold Point - Sign off is required from superintendent and wetland designer before proceeding
Comments
Signed by Superintendent(s): Print Name: Date:
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Form B – Sediment and Erosion Control Purpose: To ensure sediment and erosion control measures are correctly installed to protect either downstream treatment systems (in the case of sedimentation basins) or minimise clean-out post construction (in the case of an ornamental pond).
Continuous silt fences installed around all elements of basin / pond
If silt fences are deemed inadequate, other sediment and erosion control measures installed to ensure sediment does not enter basin
High flow bypass channel protective measures in place (that is, turf installed and where required reinforced turf)
Basin profile stabilised through sterile grasses, while terrestrial planting established around the basin perimeter
SEDIMENT BASIN, ONLY Ensure overflow from sediment basin disconnected from any downstream treatment devices (such as wetlands) POND, ONLY Ensure inlet to pond is isolated from any upstream sediment control measures Hold Point - Sign off is required from superintendent and basin/pond designer before proceeding
Comments
Signed by Superintendent(s): Print Name: Date:
72 Book 4 | MAINTENANCE
Actions addressed (initial)
Action/s (if required)
Satisfactory
Items
Checked
Checklist:
Water Sensitive Urban Design
Form C – Topsoil and Finished Levels Purpose: To ensure the topsoil is installed to the correct depth and finished levels of wetland are correct and meet the design.
Actions addressed (initial)
Action/s (if required)
Satisfactory
Item
Checked
Checklist:
Sedimentation basin desilted prior to plant establishment
Topsoil meets the requirements of AS4419 and laboratory tests provided
Topsoil has been screened and is free of large debris
Topsoil applied to base (minimum 300 mm depth)
Final topsoil levels are consistent with design levels
Surface is smooth and free of local depressions and debris
Hold Point - Sign off is required from superintendent and basin/pond designer before proceeding
Comments
Signed by Superintendent(s): Print Name: Date:
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Form D – Landscape Planting Purpose: To ensure correct plants are supplied and installed.
Supplied plants are correct species Changes to species planted must be approved by wetland designer/ecologist and marked up on as-constructed drawings
Supplied plants are in correct pot sizes, maturity (minimum 300 mm in height) and hardened
Plants have been installed at correct planting density
Correct mulch has been supplied and installed to batters and bunds above the normal water level and secured in place
As constructed drawings marked up with final plant species and densities
HOLD POINT - Sign off is required from superintendent and wetland designer before proceeding
Comments
Signed by Superintendent(s): Print Name: Date:
74 Book 4 | MAINTENANCE
Actions addressed (initial)
Action/s (if required)
Satisfactory
Item
Checked
Checklist:
Water Sensitive Urban Design
Appendix B – Regular Maintenance Checklists
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Water Sensitive Urban Design
Comment
(circle relevant category)
1
GPT / trash rack/s
GPT clear of litter
GPT 10 percent full
greater than 30 percent full
2
Inlet structures
Clear and undamaged
Partially Blocked Observed damage
Mostly blocked Severe damage
3
Overflow pits
Clear and undamaged
Partially Blocked Observed damage
Mostly blocked Severe damage
4
Underdrains
Clear and undamaged
Partially Blocked Observed damage
Mostly blocked Severe damage
5
Sediment Forebay
Sediment absent
Sediment accumulation appears excessive
Sediment accumulated to half the basin depth
Erosion absent
Erosion damage visible, but function not impaired
Severe erosion. Damage impairing function of device
6
7
Erosion
Sediment accumulation (bioretention basin)
76 Book 4 | MAINTENANCE
Sediment absent
Sediment accumulation appears excessive in sediment forebay. Fine sediment accumulation apparent on bioretention media surface.
Location (mark on attached map of bioretention basin)
Sediment accumulated to half the forebay depth Coarse sediment or large volumes of sediment accumulation apparent on the bioretention media surface
Location (mark on attached map of bioretention basin)
Action Processed
Immediate Action Required
Schedule Maintenance or Investigation
Item
Performance Target
B.1 Bioretention Basins
Comment
(circle relevant category)
8
9
10
11
12
13
Compaction of filter media surface
Weeds
Plant condition
Litter (organic)
Litter (anthropogenic)
Oil spills / inflows
No compaction evident
No weeds present
Healthy vegetation
No litter visible
No litter visible
No visible oil
Localised compaction or subsidence evident. Localised ponding longer than 24 hours after storm event
Water remains ponding longer than 24 hours after storm event
Weeds present
Noxious or environmental weeds present, or weed cover more than 25 percent
Die back / dead plants
Litter visible
Litter thickly covers filter media surface or detracting from visual amenity
Persistent but limited visible oil
Location (mark on attached map of bioretention basin)
Location (mark on attached map of bioretention basin)
Identify weed species
Location (mark on attached map of bioretention basin)
Poorly growing or visibly stressed
Litter visible
Action Processed
Immediate Action Required
Schedule Maintenance or Investigation
Item
Performance Target
Water Sensitive Urban Design
Identify species requiring replacement
Litter blocking structures or detracting from visual amenity
Location (mark on attached map of bioretention basin) Note type of litter removed
Location (mark on attached map of bioretention basin) Note type of litter removed
Extensive or localised thick layer of oil visible
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Comments
(circle relevant category)
1
GPT / trash rack
GPT clear of litter
GPT 10 percent full
GPT / trash rack for than 30 percent full
Partially Blocked Observed damage
Mostly blocked Severe damage
2
Inlet pipe
Clear and undamaged
3
Pipes connecting macrophyte cells
Clear and undamaged
Partially Blocked Observed damage
Mostly blocked Severe damage
4
Outlet pit
Clear and undamaged
Partially Blocked Observed damage
Mostly blocked Severe damage
Erosion absent
Erosion damage visible, but structure functional
Severe erosion. Damage impairing function of device
Location (mark on attached map of wetland)
Sediment accumulation appears excessive
Sediment accumulated to half the basin depth
Location (mark on attached map of wetland)
Weeds present
Noxious or environmental weeds present
5
Erosion
6
Sediment build-up
Sediment absent
7
Aquatic weeds (submerged, emergent and floating)
No weeds present
78 Book 4 | MAINTENANCE
Location (mark on attached map of wetland) Identify weed species
Action Processed
Immediate Action Required
Schedule Maintenance or Investigation
Item
Performance Target
B.2 Constructed Wetlands
Action Processed
Immediate Action Required
Schedule Maintenance or Investigation
Item
Performance Target
Water Sensitive Urban Design
Comments
(circle relevant category)
8
Terrestrial weeds (e.g. within the batter slopes)
No weeds present
Weeds present
Noxious or environmental weeds present
Location (mark on attached map of wetland)
Identify weed species
No algae apparent
Algae visible
Algal growth prominent or extensive
Plant condition (aquatic macrophytes)
Healthy vegetation
Poorly growing or visibly stressed
Die back / dead plants
Note species which require replanting
11
Plant condition (terrestrial)
Healthy vegetation
Poorly growing or visibly stressed
Die back / dead plants
Note species which require replanting
12
Litter (organic)
No litter visible
Litter visible
Litter blocking structures or detracting from visual amenity
Location (mark on attached map of wetland)
Litter blocking structures or detracting from visual amenity
Location (mark on attached map of wetland)
9
Algal blooms
10
13
Litter (anthropogenic)
No litter visible
Litter visible
Note type of litter removed
Note type of litter removed
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Comment
(circle relevant category)
1
GPT / trash rack/s
GPT clear of litter
GPT 10 percent full
greater than 30 percent full
2
Inlet structures
Clear and undamaged
Partially Blocked Observed damage
Mostly blocked Severe damage
3
Overflow pits
Clear and undamaged
Partially Blocked Observed damage
Mostly blocked Severe damage
4
Sediment Forebay
Sediment absent
Sediment accumulation appears excessive
Sediment accumulated to half the basin depth
Severe erosion. Damage impairing function of device
Sediment accumulation greater than half the basin depth
5
Erosion
Erosion absent
Erosion damage visible, but function not impaired
6
Sediment accumulation
Sediment accumulated to less than half the basin depth
Sediment accumulated to half basin depth
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Location (mark on attached map of sedimentation basin)
Note timing since last desilting operation
Action Processed
Immediate Action Required
Item
Schedule Maintenance or Investigation
Performance Target
B.3 Sedimentation Basin
Comment
(circle relevant category)
7
8
Weeds
Plant condition
No weeds present
Healthy vegetation
Weeds present
Poorly growing or visibly stressed
Noxious or environmental weeds present, or weed cover more than 25 percent
Die back / dead plants
Action Processed
Immediate Action Required
Item
Schedule Maintenance or Investigation
Performance Target
Water Sensitive Urban Design
Location (mark on attached map of sedimentation basin)
Identify weed species
Location (mark on attached map of sedimentation basin)
Identify species requiring replacement
9
10
11
Litter (organic)
Litter (anthropogenic)
Oil spills / inflows
No litter visible
No litter visible
No visible oil
Litter visible
Litter visible
Persistent but limited visible oil
Litter thickly covers filter media surface or detracting from visual amenity
Litter blocking structures or detracting from visual amenity
Location (mark on attached map of sedimentation basin) Note type of litter removed
Location (mark on attached map of sedimentation basin) Note type of litter removed
Extensive or localised thick layer of oil visible
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Comments
(circle relevant category)
Partially Blocked Observed damage
Mostly blocked Severe damage
1
Inlet pipe
Clear and undamaged
2
Outlet pipe
Clear and undamaged
Partially Blocked Observed damage
Mostly blocked Severe damage
Erosion absent
Erosion damage visible, but structure functional
Severe erosion. Damage impairing function of device
Location (mark on attached map of pond)
Sediment absent
Sediment accumulation appears excessive
Sediment accumulated to half the basin depth
Location (mark on attached map of pond)
Weeds present
Noxious or environmental weeds present
3
Erosion
4
Sediment build-up
5
Aquatic weeds ( s u b m e r g e d , emergent and floating)
No weeds present
Location (mark on attached map of pond)
Identify weed species
6
Terrestrial weeds (e.g. within the batter slopes)
No weeds present
Weeds present
Noxious or environmental weeds present
Location (mark on attached map of pond)
Identify weed species
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Action Processed
Immediate Action Required
Item
Schedule Maintenance or Investigation
Performance Target
B.4 Ponds
Action Processed
Immediate Action Required
Item
Schedule Maintenance or Investigation
Performance Target
Water Sensitive Urban Design
Comments
(circle relevant category)
No algae apparent
Algae visible
Algal growth prominent or extensive
Plant condition (aquatic macrophytes)
Healthy vegetation
Poorly growing or visibly stressed
Die back / dead plants
Note species which require replanting
9
Plant (terrestrial)
Healthy vegetation
Poorly growing or visibly stressed
Die back / dead plants
Note species which require replanting
10
Litter (organic)
No litter visible
Litter visible
Litter blocking structures or detracting from visual amenity
Location attached
Litter blocking structures or detracting from visual amenity
Location attached
7
Algal blooms
8
11
condition
Litter (anthropogenic)
No litter visible
Litter visible
(mark map of
on pond)
Note type of litter removed
(mark map of
on pond)
Note type of litter removed
NOTE: A check for trash racks / nets has not been included, as the pond should not be designed as a water quality treatment system, but rather to provide storage capacity of attenuation of peak flows to downstream waterways.
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Appendix C | Asset handover sheets Asset HANDOVER Checklist* Asset I.D. Asset Location: Construction by: Time since planting established and maintenance required: TREATMENT
Y
N
Y
N
Y
N
Y
N
System appears to be working as designed visually? No obvious signs of under-performance? MAINTENANCE Maintenance plans and indicative maintenance costs provided for each asset? Vegetation establishment period completed (2 years)? Inspection and maintenance undertaken as per maintenance plan? Inspection and maintenance forms provided? Asset inspected for defects and/or maintenance issues at time of asset transfer Sediment accumulation at inflow points? Litter within basin? Erosion at inlet or other key structures? Traffic damage present? Evidence of dumping (e.g. building waste)? Vegetation condition satisfactory (density, weeds etc)? Watering of vegetation required? Replanting required? Mowing/slashing required? Clogging of drainage points (sediment or debris)? Evidence of ponding? Damage/vandalism to structures present? Surface clogging visible? Drainage system inspected? COMMENTS/ACTIONS REQUIRED FOR ASSET TRANSFER
ASSET INFORMATION Design Assessment Checklist provided? As constructed plans provided? Copies of all required permits (both construction and operational) submitted? Proprietary information provided (if applicable)? Digital files (e.g. drawings, survey, models) provided? Asset listed on asset register or database? * Asset handover checklists are generic and can be used for all WSUD elements discussed in this booklet
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Appendix D | References Collins (2006), Destination SQID Waster Stormwater Industry Association available online at :www.wsud.org/downloads/2006_SIA_Papers/Anthony%20Collins%20%20-%20Hornsby%20Council.pdf Facility for Advancing Water Biofiltration (FAWB) (2008), Workshop Advancing the Design of Biofiltration available online at :http://www.monash.edu.au/fawb/products/fawb-advancing-rain-gardens-workshop-booklet.pdf Facility for Advancing Water Biofiltration (FAWB) (2008) Guidelines for Soil Filter Media in Bioretention Systems available online at :http://www.monash.edu.au/fawb/products/obtain.html Water by Design (2009) Chapter 4 – Constructed Wetlands South East Queensland Healthy Waterways Partnership Water by Design (2009) Chapter 3 – Bioretention Systems South East Queensland Healthy Waterways Partnership Water by Design (2009) Construction and Establishment Guidelines Swales, Bioretention Systems and Wetlands South East Queensland Healthy Waterways Partnership WBM Oceanics Australia and Ecological Engineering (2004) Maintenance Guidelines for Stormwater Treatment Measures Hornsby Shire Council (HSC) (2001) Catchment Remediation Capital Works Program Annual report 2000-2001 Water Catchments Team HSC Lloyd, S.D., Wong, T.H.F and Chesterfield, C.J. (2002) Water Sensitive Urban Design A Stormwater Management Perspective Cooperative Research Centre for Catchment Hydrology Facility for Advancing Water Biofiltration (FAWB) (2008) Workshop: Advancing Raingarden Design Filter Media and Landscaping available online at :http://www.wsud.org/downloads/Seminars%20&%20Events/fawb-workshop-vegetation-and-landscaping.pdf Wong, T.H.F (editor in chief) (2006), Australian Runoff Quality, Engineers Australia
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Notes
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Level 2, 330 Church Street Parramatta NSW 2150 PO Box 237 Parramatta NSW 2124 DX 28448 Parramatta Telephone 61 2 9841 8600 Facsimile 61 2 9841 8688 Printed May 2009 on recycled paper.
