9Structural Controls - Department of Water - The Western Australian ...

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used for residential development. Urban development is a significant factor that has caused an increase in peak stormwater flows and runoff volumes, and the deterioration of stormwater quality and environmental amenity. These issues have been ongoing for several years and whilst the City has adopted a policy for new developments to prevent direct stormwater discharge into wetlands, the existing stormwater systems need to be addressed. Lake Goollelal is part of Bush Forever Site Number 299 and is a Conservation category wetland that is protected under the Environmental Protection (Swan Coastal Plain Lakes) Policy 1992. The groundwater Millimetres (mm) 140 120 100 80 60 40 20 0 January February March Annual rainfall pattern: Swanbourne 3 Stormwater Management Manual for Western Australia: Structural Controls April May June July August September October Decile 5 (median) monthly rainfall (mm) Mean number of days of rain >= 1 mm November December Figure 1. Annual rainfall pattern, Swanbourne. (Source: Bureau of Meteorology 2007.) flow is in a westerly direction and the soil type is highly permeable Spearwood Sands. Lake Goollelal is located within an area with a high risk of acid sulphate soil disturbance. A review of the environmental and engineering aspects of the various stormwater outfalls associated with the Yellagonga Regional Park was undertaken in 2003. From these investigations, an overall strategy was prepared with the community and other stakeholders. The strategy proposed retrofitting the various outfalls entering the Regional Park lake system with inline stormwater treatment measures. Outfall Number 21 is located on the southern extreme of Lake Goollelal, near the arterial road of Hepburn Avenue. The catchment area of Outfall Number 21 is approximately 38 hectares with a mixture of land uses, including natural bushland, parks and reserves, commercial uses, a petrol station and residential development. Stormwater pollutant characteristics are largely determined by the land uses within the catchment. Due to its catchment characteristics, this outfall was selected to be studied in the development of a strategy to improve the water quality of the Yellagonga Regional Park Lake System. A conventional stormwater pipe system that was constructed when the subdivision was developed in the 1970s discharged directly into the lake. The principal source of stormwater discharge and associated pollutants is the impervious surfaces, namely the road reserves and commercial developments, which account for 14% of the catchment area. Approximately 86% of the catchment consists of residential housing and vegetated areas. The highly permeable sands allow the majority of lot stormwater runoff to be infiltrated. Residential roofed and paved areas drain into on-site soakwells. 16 14 12 10 8 6 4 2 0 Raindays
Approaches implemented In order to protect the receiving waters of Lake Goollelal, the following structural and non-structural stormwater management measures have been implemented in the catchment area of Outfall Number 21 (Figure 2): Figure 2. Drainage schematic of the Lake Goollelal area, Joondalup. (Source: Department of Water.) Structural controls: The structural treatment measures implemented in this project are: • gross pollutant traps • soakwells and infiltration areas • bioretention basins • disconnection of the stormwater system, i.e. isolation of receiving waters from sections of the catchment Non-structural source controls: Non-structural controls are important to minimise the source of pollutants, however it can be difficult to enforce these controls or to engage the community in their implementation. For this reason, a combination of structural and non-structural controls is highly recommended to achieve best practice stormwater management. The following three non-structural controls are considered essential to this project: • community education and awareness for stormwater management (see BMPs 2.3.2, 2.3.3 and 2.3.5 of Chapter 7, and Chapter 8) • best management practices on construction and land development sites (see BMP 2.1.1 in Chapter 7) Stormwater Management Manual for Western Australia: Structural Controls 39
Page 1 and 2: 9 Structural Controls
Page 3 and 4: Stormwater Management Manual for We
Page 5 and 6: Department of Water Ms Lisa Chalmer
Page 7 and 8: Preface A growing public awareness
Page 9 and 10: Contents Summary ..................
Page 11 and 12: Summary The aims of this chapter ar
Page 13 and 14: Introduction . Aims of the structur
Page 15 and 16: Table 1 provides a summary of the s
Page 17 and 18: CONSULTATION WITH RELEVANT STATUTOR
Page 19 and 20: Table 2. Structural control BMP sel
Page 21 and 22: Opportunities for retaining natural
Page 23 and 24: Maintain the pre-development water
Page 25 and 26: Different processes are required fo
Page 27 and 28: .7.9 Life cycle costs Consideration
Page 29 and 30: The pollutant removal effectiveness
Page 31 and 32: pervious pavements. Infiltration ca
Page 33 and 34: Detention Systems Liege Street Wetl
Page 35 and 36: Best Management Practices BMP Syste
Page 37 and 38: Non-structural controls: • Proact
Page 39 and 40: Figure 6. Flush kerbing to allow di
Page 41 and 42: • reduced dwelling setback (3 m)
Page 43 and 44: Challenges/lessons learnt Stabilisa
Page 45 and 46: could be applied to this site to so
Page 47 and 48: Figure 7. Central drainage linked t
Page 49: water that does not drain away imme
Page 53 and 54: Disconnection: Much of the upper ca
Page 55 and 56: The City of Joondalup has recognise
Page 57 and 58: . 3 References and further reading
Page 59 and 60: 2 Stormwater Storage and Use 2. Rai
Page 61 and 62: Sydney, Melbourne and Adelaide. Are
Page 63 and 64: Design guidelines The required capa
Page 65 and 66: Below-ground stormwater storage dev
Page 67 and 68: Stormwater Storage and Use 2.2 Mana
Page 69 and 70: Design considerations At the MAR pl
Page 71 and 72: plans should be developed to cater
Page 73 and 74: A recent analysis of a 400-lot MAR
Page 75 and 76: 3 Infiltration Systems 3. Infiltrat
Page 77 and 78: These devices should not be placed
Page 79 and 80: conductivity of clayey soils and ov
Page 81 and 82: Where: C = runoff coefficient i = p
Page 83 and 84: y infiltration or percolation only.
Page 85 and 86: Based on the above, the design rain
Page 87 and 88: Infiltration Systems 3.2 Soakwells
Page 89 and 90: i = probabilistic rainfall intensit
Page 91 and 92: Runoff Volume Inflow Volume ∀ = F
Page 93 and 94: Infiltration Systems 3.3 Pervious P
Page 95 and 96: Pervious pavement systems require r
Page 97 and 98: Figure 6. Example definition of a c
Page 99 and 100: Brattebo, B. O. and Booth, D. B. 20
Page 101 and 102:
4 Conveyance Systems 4. Swales and
Page 103 and 104:
Table 1. Typical annual pollutant l
Page 105 and 106:
Another consideration when locating
Page 107 and 108:
Figure 5. Impact of flow depth on h
Page 109 and 110:
with grass never cut shorter than t
Page 111 and 112:
ƒ = (2125 × 1 +1125 × 0.1)/3250
Page 113 and 114:
Inlet details Flows reach the swale
Page 115 and 116:
Conveyance Systems 4.2 Bioretention
Page 117 and 118:
TP Removal (%) 100 90 80 70 60 50 4
Page 119 and 120:
Bioretention systems can be used in
Page 121 and 122:
media in the long term due to its d
Page 123 and 124:
Flow per perforation is therefore d
Page 125 and 126:
growth, organic decomposition and t
Page 127 and 128:
• Fraction impervious: 0.60 (grav
Page 129 and 130:
A = catchment area (ha) Maximum inf
Page 131 and 132:
Assume orifice flow conditions: Q =
Page 133 and 134:
Impervious liner requirement In thi
Page 135 and 136:
Conveyance Systems 4.3 Living Strea
Page 137 and 138:
Table 1. Indicative costs for water
Page 139 and 140:
flow, which may compromise the surf
Page 141 and 142:
interference with the natural flows
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encourage the growth of biofilms an
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• map the morphology (plan and cr
Page 147 and 148:
Creek Project in the City of Cannin
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5 Detention Systems 5. Dry/Ephemera
Page 151 and 152:
Center for Watershed Protection (19
Page 153 and 154:
Note that in Figure 3, the circles
Page 155 and 156:
A o = Orifice area (m 2 ) Q d = Des
Page 157 and 158:
Detention Systems 5.2 Constructed W
Page 159 and 160:
Table 1. Typical annual pollutant l
Page 161 and 162:
Figure 3. Natural wetlands are clas
Page 163 and 164:
• Vegetate around the wetland’s
Page 165 and 166:
Table 2. Components of a constructe
Page 167 and 168:
Vegetation design Remnant vegetatio
Page 169 and 170:
• Schedule biannual inspections a
Page 171 and 172:
Taylor, A.C. and Wong, T.H.F. 2002,
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6 Pollutant Control 6. Litter and S
Page 175 and 176:
exits the chamber through a riser p
Page 177 and 178:
• In-transit LSM systems are gene
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is lower than the design discharge
Page 181 and 182:
The studies also found that a high
Page 183 and 184:
Victoria Stormwater Committee 1999,
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Pollutant Control 6.2 Hydrocarbon M
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floats to the surface of the separa
Page 189 and 190:
Where: Q d = required design (treat
Page 191 and 192:
• Nuisance problems such as odour
Page 193 and 194:
Melbourne Water 2005, WSUD Engineer
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