Hobsons Bay Neighbourhood Green Infrastructure

NEIGHBOUHOOD GREEN INFRASTRUCTURE GREEN INFRASTRUCTURE STRATEGY Green Infrastructure for Liveable Cities HORT900039 Post-Intensive Assessment Alistair Nancarrow - 299805

CONTENTS 1.0 - Introduction 1.1 - Foreword 1.2 - Altona 1.3 - Neighbourhood Selection 1.4 - Target Ecosystem Service

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2.0 - Existing Green Infrastructure 2.1 - Assessment of Existing GI

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3.0 - Green Infrastructures 3.1 - Identifying Necessary GIs 3.2 - Shorefront Swales 3.3 - Residential Raingardens 3.4 - Retail Rooftops

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4.0 - Locating Green Infrastructure 4.1 - A Distributed System 4.2 - Locating Shorefront Swales 4.3 - Locating Residential Raingardens 4.4 - Locating Retail Rooftops

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5.0 - Costing Green Infrastructure 5.1 - Costing Shorefront Swales 5.2 - Costing Residential Raingardens 5.3 - Costing Retail Rooftops 5.4 - Providing a Funding Model

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6.0 - Green Infrastructure Benefits 6.1 - Anticipating Ecosystem Service Benefits

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7.0 - Success 7.1 - Monitoring & Measuring Success

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8.0 - Conclusion

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9.0 - References 9.1 - Body 9.2 - Figures 9.3 - Images

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1.0 INTRODUCTION 1.1 Foreword

1.2 Altona

Green Infrastructure seeks to replace traditional grey infrastructural systems for the provision of essential services to urbanised areas. Traditional approaches to the development and management of urban infrastructures are struggling to accommodate growing urban populations and adapt to climate variability, and as the realities of these systems (which are typically costly, energy intensive and environmentally detrimental) become more apparent, urban management authorities are seeking to substitute them with Green Infrastructure. This report investigates the current state of infrastructure within a suburban neighbourhood of metropolitan Melbourne.

It subsequently proposes the implementation of a number of green infrastructure elements that respond to observed urban and environmental conditions and which will substitute or supplement existing grey infrastructures.

The neighbourhood forming basis for investigation in this report is Altona, a suburb located in Melbourne’s western suburbs (see Figure 1.0). Altona is under the municipal jurisdiction of Hobsons Bay City Council.

The Council has prepared a number of reports bearing relation to the subject of this report which will be referred to throughout. The suburb is unique due to its bayside location, with Port Phillip Bay running the entire length of its southern boundary.

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Figure 1.0 - Aerial photograph showing the suburb of Altona, with subject site highlighted centrally.

1.3 Neighbourhood Selection The region within Altona that has been selected for analysis is represented in Figure 1.1. It is comprised of a variety of land uses including commercial, educational and residential. The key urban constituents of this area are; • Pier Street; Altona’s primary commercial district • Altona Primary School • The metropolitan rail line running east-west to Werribee • Altona Beach • Low density detached residential housing.

Figure 1.1 Key

Commercial Zone

Residential Zone

Educational Zone

Park Zone

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Civic Parad

Bent Street

Blyth Street

Pier Street

Sargood Str ee

t

t McBain Stree

David Stree t

Altona Primary School

Romawi Str ee

t

e

eet n Str

Quee

Logan Reserve

The Esplanade Altona Beach Figure 1.1 - Map showing the street layout and zoning of the neighbourhood selected for analysis within this report.

Port Phillip Bay

1.4 Target Ecosystem Service The suburb is one of the lowest above sea-level within metropolitain Melbourne, with much of it no greater than 2 metres above sea level. This topographical composition can result in a backflow of sea water into the storm water drainage network (WBM 2006: 3-9).

During periods of high tide, the water table can rise to approximately 1.5m (HydroCon 2012). Combined with heavy rainfall, this can cause substantial flooding at ground level, particularly along the foreshore, as water is no longer able to discharge into the bay - see Figures 1.2 - 1.5.

Altona beach also provides one of the highest amenity public recreational spaces within the western suburbs of Melbourne and is recognised as one of Hobsons Bay’s key tourist attractions (HBCC 2006).

It generates significant business for the adjoining commercial precinct. It is therefore essential that water quality within the bay remain high. Stormwater collected in Altona discharges directly into Port Phillip Bay via Altona Beach. Stormwater runoff can be heavily contaminated with pollutants that degrade water quality. Attempting to treat stormwater runoff before it enters the drainage systems prevents such pollutants from discharging into the bay and affecting the quality of water.

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Having identified the most prevalent local urban & environmental issues within this neighbourhood as flooding and stormwater quality, this report proposes a number of green infrastructure elements that seek to provide stormwater management as an ecosystem service. By reducing peak flows into the drainage system which might lead to foreshore flooding and by treating stormwater to remove litter and pollutants prior to entering the stormwater system.

Figure 1.2 - Image showing the Esplanade in Altona during dry weather. The image is taken looking towards Logan Reserve with ones back to the beach opposite.

Figure 1.3 - Image showing the Esplanade in Altona following a period of rainfall, the street has become inundated.

Figure 1.4 - Another image showing flooding of the Esplanade following a period of heavy rainfall.

Figure 1.5 - Flooding of the stormwater drainage outlet at the end of Sargood Street from which stormwater is discharged into Port Phillip Bay.

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2.0 EXISTING GREEN INFRASTRUCTURE 2.1 Assessment of Existing Green Infrastructure There exists little by way of contemporary engineered green infrastructure solutions within the built up residential zones of Hobsons Bay, including the subject neighbourhood. Although, there does exist a number of water sensitive urban design measures within the broader Altona region. Truganina Swamp and Cherry Lake are two such examples (Figures 2.0-2.1); both constructed wetlands, which retain some proportion of stormwater during heavy rainfall (Melbourne Water 2000). However; both exist on the fringe of Altona and do not receive stormwater from the commercial or residential zones of the suburb, but rather from heavily industrialised zones to its north. They were also constructed in the 1960’s, and do not offer a solution to contemporary stormwater management issues that have compounded with the growth of residential development in Altona.

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The suburb is typical of most within outer-Melbourne, and although residential densities within the suburb are intensifying, the prevalent residential typology consists of low-density detached housing on large allotments, with the rear of the site dedicated to a well vegetated backyard. Streets are wide with generous nature strips (Figure 2.3), and well established canopy trees line these streets. The presence of these green spaces and vegetation provide significant health and aesthetic benefits but despite their existence, stormwater drainage and quality as previously noted remain a concern.

Figure 2.0 - Image showing Cherry Lake with heavily industrialised land use beyond.

Figure 2.1 - Image showing Truganina Swamp.

Figure 2.2 - Image showing the Altona foreshore with Altona Beach and pines.

Figure 2.3 - Image showing wide nature strips typical of the neighbourhood.

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3.0 GREEN INFRASTRUCTURES 3.1 Identifying Necessary GIs Clarifying the objectives of proposed green infrastructure elements is essential to selecting the most suitable technologies for implementation. As noted above, the expected ecosystem service benefits provided by the implementation of these technologies are; • To reduce peak stormwater flows; • To remove pollutants from stormwater.

When dealing with stormwater, it is also essential that the nature of the catchment be understood before selecting the appropriate green infrastructure strategy.

Melbourne Water poses a number of questions which assist in analysing the characteristics of catchments to determine the most suitable response (Melbourne Water 2013). These are addressed in Table 3.1.1.

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Table 3.1.1 - Neighbourhood Characteristics The following table attempts to analyse the characteristics of the neighbourhood to direct the appropriate green infrastructure response. The interrogations were adapted from Melbourne Water’s treatment selection criteria.

Interrogation

Observation

What is the catchment made up of?

Residential roads Residential roofs Large commercial properties & public areas Altona beach

What are the physical opportunities that present/limit opportunities within the catchment?

Large, grassy nature strips provide an opportunity for appropriation and readaptation to better provide ecosystem services.

The low lying topographical composition of the suburb results in flooding. This condition need necessarily be remediated through the provision of green infrastructure.

The coast line is a continuous stretch that offers little protection from off shore winds.

Winds disperse sand around the suburb, particularly along the foreshore. These sand particles could prevent green infrastructures from operating effectively and also settle in the stormwater drainage network, inhibiting stormwater discharge.

A number of major roads and the metropolitan rail line run through the neighbourhood, which add pollutants to stormwater runoff.

What social considerations, such as access and amenity are there?

It is essential for both residential and tourist amenity that Altona Beach be safeguarded from water pollution.

Due to the nature of the existing established residential suburb, any green infrastructure must adapt to the existing conditions without obstruction.

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3.1 Identifying Necessary GIs

Table 3.1.3 - Runoff Risk Cause & Effect

In addition to empirical observations made to characterise the catchment, Hobsons Bay City Council commissioned a Stormwater Management Plan (WBM 2006) which identified and ranked threats to the quality of stormwater within the various catchments of Hobsons Bay. The subject neighbourhood falls within the Altona Beach catchment. Table 3.1.2 shows the threat value of various runoff types to stormwater within this catchment.

Table 3.1.3 elaborates on those risks identified in Table 3.1.2 as representing the greatest threat to stormwater quality. These are extracted from the Hobsons Bay Stormwater Management Plan (WBM 2006: 4-16).

Source

Cause

Impact

Residential Runoff

Atmospheric deposition & build-up from traffic, washing cars, fertilisers, poor waste management (domestic refuse), dumping of residential rubbish, lawn clippings and vegetation.

Increased flow, sediment, nutrients, litter, oxygen depleting material, hydrocarbons, pathogens, trace metals, pesticides.

Table 3.1.2 - Runoff Risks

Commercial Runoff

Table 3.1.2 shows the threat value of various runoff types to stormwater within this catchment as classified in the Hobsons Bay Stormwater Management Plan (WBM 2006: 4-18).

Atmospheric deposition and build-up from Increased flow, sediment, nutrients, traffic, poor waste management practices. litter, oxygen depleting materials, hydro carbons, pathogens, trace metals, surfactants.

Major Road/Rail Runoff

Atmospheric and vehicular deposition and Sediment, litter, trace metals and hydrocarbons. accumulation and the effects of rail/road construction.

Threat

Risk

Residential Runoff

Very High

Industrial Runoff

Low

Commercial Runoff

Very High

Major Road/Rail Runoff

High

Building Site Runoff

Moderate

Open Space Runoff

Moderate

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3.1 Identifying Necessary GIs It can be concluded from the determinations made above that residential and commercial runoff pose the greatest threat to stormwater discharge and quality within the neighbourhood. Considered in conjunction with the observed characteristics of the neighbourhood and the ecosystem service objectives, the following solutions are judged the most suitable for implementation; • Shorefront Swale (vegetated swale) • Residential Raingarden (bio-filtration) • Retail Roofing (green roof) Each of these is explained below with reference to the neighbourhood context and conditions giving rise to its proposal. Details of their construction methodology and classification of vegetation will be given below; their specific siting and ecosystem service benefits will be explained in greater detail under sections 4.0 & 6.0.

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3.2 Shorefront Swale

Table 3.2.1 - Swale Vegetation

Vegetated swales are used to convey stormwater inlieu of traditional grey infrastructural methods such as stormwater pipes (CSIRO 2005). These systems incorporate a mild gradient and overland flow to convey water downstream to an end point, in this case, a buffer strip that will direct water into the stormwater drainage system. Swales reduce and delay stormwater runoff, retain particulate pollutants, enhance streetscape aesthetic and are relatively inexpensive to construct (Melbourne Water 2013).

Table 3.2.1 illustrates some of the vegetation proposed to be incorporated into the vegetated shorefront swales. These selections seek to maintain the coastal aesthetic of the neighbourhood and provide a drought resistant solution for periods of low or no rainfall.

For this proposition, lightly vegetated swales are proposed adjacent to the foreshore area. These will reduce the rate at which stormwater discharges into the bay, allow for partial infiltration of stormwater, and retain large particulate matter. They will also contribute in part to a reduction in the rate of flooding occurring along the foreshore, a problem illustrated in Figures 1.3-1.5. Vegetation is preferred to grass, as grassy swales require significant maintenance and do not provide the same water retardant capacity.

Figures 3.0-3.2 show the typical details of the existing and proposed conditions of the vegetated swales.Â

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Species Juncas Flavidus - Yellow Rush Leucaphytabrownii - Cushion Bush Lomandra Longifolia - Mat Rush Carex Appressa - Tall Sedge

grass covering over topsoil selected vegetation to swale

perties

tial pro

siden ining re

adjo

existing

th

footpa

existing

de to 1% gra

buffer

strip te

arge

r disch

oint fo

on p rminati

ver

crosso

retain existing crossovers, excavate below as required and continue swale under proivde litter traps to ends of underpass typical grated pit for overflow connect to existing stormwater system

road existing

e)

planad

(the es

Figure 3.0 - Plan showing typically proposed implementation of the shorefront swales.

new side entry pits to existing kerb for stromwater entry from road 0

0.5

1

1.5

2

2.5m

dotted line denotes UPVC pipe discharging to kerb and channel from residential properties

existing concrete footpath on compacted sand base

ashphalt road (the esplanade) grading to concrete kerb and channel for water runoff

grassy nature strip

soil below

3000

0

Figure 3.1 - Typical cross section of the existing nature strip adjacent to the foreshore.

0.2

0.4

0.6

0.8

1m

slotted agi drain to connect to stormwater system for drainage unlined drainage trench to promote exfiltration to surrounding soil

filter sand 200mm to top of drainage trench

grass cover or similar to topsoil

600mm gravel filled trench

cut back existing UPVC pipe for direct discharge into vegetated swale

selected vegetation

600

200

350

cut kerb for entry point to swale beyond

1:6 max gradient

1:6 max grradient 3000

Figure 3.2 - Typical cross section of the proposed shorefront swales.

0

0.2

0.4

0.6

0.8

1m

3.3 Residential Raingarden

Table 3.3.1 - Raingarden Vegetation

Raingardens (or bio-filtration systems as they are otherwise known), use ponding above a bioretention surface to maximise the volume of runoff treated through a filtration media (CSIRO 2005). Raingardens do not experience the same velocity of runoff as swales, as they do not seek to convey stormwater over a distance.

Table 3.3.1 illustrates some of the vegetation proposed to be incorporated into the residential raingardens.

Their selection is based on a capacity to withstand inundation, to remove nutrients from stormwater and to survive during long periods of low or no rainfall.

For this proposition, kerbside raingardens are proposed to be integrated into the existing kerb, channel and nature strips within the residential zones of the neighbourhood. As previously observed, residential runoff is deemed a very high threat to the quality of water discharging into Port Phillip Bay. Raingardens provide a filtration system that removes gross pollutants, coarse sediments, nutrients and heavy metals from stormwater. They are more suitably located away from the foreshore, as fine particulate matter such as sand can affect the capacity for water to drain through the filtration media (LLoyd, Wong & Chesterfield 2002). An unlined system is proposed, to promote filtration of water back into subsoil. The filter media is proposed to be of a sandy loam composition.

Figures 3.3-3.5 show the typical details of the existing and proposed conditions of raingardens.

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Species Anigozanthus - Kangaroo Paw Ficinia Nodosa - Knobby Club-Rush Juncas Amabilis - Hollow Rush Chrysocephalum Apiculatum - Common Everlast

adjoining properties existing concrete footpath existing wide grassy nature strip existing concrete crossover

existing stormwater side entry pit

existing road

Figure 3.3 - Plan showing the typically existing nature strip arrangement within the neighbourhood.

0

0.5

1

1.5

2

2.5m

100mm dia. slotted agi drain to grade to junction pit for stormwater discharge adjoining properties existing concrete footpath rock mulch to top layer of raingarden with selected vegetation

steel grate overflow drain to connect to existing side entry pit for discharge existing concrete crossover

existing grassy nature strip

150mm concrete perimetre deliniation strip to raingarden

existing side entry pit to remain

existing road

Figure 3.4 - Plan showing the typically proposed implementation of a raingarden within existing nature strips.

cut back existing kerb for raingarden inlet - provide graded rock for scour protection to inlet 0

0.5

1

1.5

2

2.5m

graded rock bed to entry for scour protection rock mulch to top layer of raingarden cut back existing kerb for stormwater entry

vegetation as selected

existing asphalt road

in-situ conrete perimetre 150mm

5000 (not to scale)

no lining to this side or bottom of raingarden to promote sub soil exfiltration

150

700 approx.

250

grass covering over topsoil

impervious membrance to road side to promote vertical exfiltration

sandy loam filtration media transition layer (river sand)

100mm slotted agi drain to connect to existing stormwater system drainage layer

Figure 3.5 - Typical cross section through proposed raingardens.

0

0.2

0.4

0.6

0.8

1m

3.4 Retail Rooftop

Table 3.4.1 - Greenroof Vegetation

Green roofs provide vegetation at rooftop level in-lieu of traditional roofing materials such as tiles or sheeting.

Green roofs, due to the presence of vegetation and substrate matter, retain a proportion of water that falls during periods of rain. This limits peak flow rates and overall water volume discharging into the stormwater drainage system (City of Melbourne 2013).

Table 3.4.1 illustrates some of the vegetation proposed to be incorporated into the retail rooftops. Vegetation is selected based on its capacity to withstand drought, absorb peak flows during periods of high rainfall, have a low nutrient dependence and sustain itself in a shallow substrate.

This proposition seeks to integrate green roofs into the commercial zone. Allotments within this zone have high levels of site coverage and small proportions of site permeability. Therefore, commercial premises contribute a comparatively high level of stormwater runoff. Integrating green roofs into commercial properties will primarily reduce peak flow rates. Due to the necessity of retrofitting green roofs to commercial properties, the most structurally feasible option is for the installation of extensive green roof systems. Those proposed here are of a shallow depth, approximately 100-200mm with a substrate that is both lightweight and has good capacity to retain water.

Figure 3.6 shows a typical detail of the proposed retrofit of green roof.

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Species Vittadinia Cuneata - Fuzzweed Leptorhynchos Tenuifolius - Wiry Buttons Chloris Truncata - Windmill Grass Poa Hiemata - Soft Snowgrass

slotted agi drain to connect to perimetre drainage cell to drain to existing box gutter for discharge

low herbaceous vegetation growing medium with high water water retaining capacity

steel angle fixed to existing roof sheeing for side support

filter sheeting drainage layer

steel grate over existing box gutter

protection mat existing double brick facade & parapet

100 - 200mm approx

root barrier

waterproofing layer

existing metal deck roof sheeting

existing steel roof purlins

existing box gutter to remain

Figure 3.6 - Sectional detail through the facade of an existing commercial premises showing green roof retrofit.

existing steel portal frame to remain - reinforce as required for green roof support 0

0.1

0.2

0.3

0.4

0.5m

4.0 LOCATING GREEN INFRASTRUCTURES 4.1 A Distributed System The proposed green infrastructure implementations follow a distributed system approach. This means that different green infrastructure elements are distributed across the neighbourhood to respond to specific localised conditions and avoid the need for an outlet approach that would otherwise need to perform all the tasks that smaller, more frequent systems will perform. Figure 4.0 illustrates the location of proposed GI elements within the neighbourhood. The rationale for their location is described following.

Figure 4.0 Key

Shorefront Swale Locations

Residential Raingarden Locations

Retail Rooftop Location

Properties

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Civic Parad

Bent Street

Blyth Street

Pier Street

Sargood Str ee

t

t McBain Stree

David Stree t

Romawi Str ee

t

e

eet n Str

Quee

Logan Reserve

The Esplanade Altona Beach Figure 4.0 - Map showing the proposed locations of green infrastructures.

Port Phillip Bay

4.2 Locating Shorefront Swales

4.3 Locating Residential Raingardens

Shorefront swales replace the existing nature strips running adjacent to residential properties along the Esplanade. Their siting in this location seeks to address flooding currently experienced along this interface. The catchment for these swales is the road itself and the residential properties fronting the Esplanade. The area of proposed swales equates to approximately 5% of the urban fabric constituting their catchment.

Part 3.1 identified residential stormwater runoff as a very high threat to the quality of stormwater discharging into Port Phillip Bay. This was due to a large concentration of pollutants within this discharge. The neighbourhood investigated for this report comprises a large proportion of residential development and therefore invites the integration of rainwater gardens to remediate residential stormwater runoff issues.

Vegetated swales are proposed in this location rather than raingardens due to the high susceptibility of raingardens to clogging (LLoyd, Wong & Chesterfield 2002), which is of particular importance given their close proximity to the beach. The success of raingardens within this location is also compromised by the high water table, particularly during severe wet weather events. This in part prevents exfiltration of the water into subsoil.

Site analysis observed the presence of traditional side entry pits approximately 150m apart, with generally no more than two present along any residential block (running north-south). It is estimated that each accepts stormwater discharge from a catchment area of approximately 6412 square metres. This accounts for residential discharge via kerb and channel and road runoff, but assumes that 50% of residential properties contain permeable surfaces.

Siting swales along this interface decreases the velocity at which stormwater would otherwise discharge into the stormwater drainage system.

Their roughness also assists with the collection of course and fine sediments, which contribute to drain blockages.

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The width of existing nature strips is 5m. Studies undertaken by the CSIRO (CSIRO 2005) observed that the effectiveness of raingardens in the removal of total soluble solids, nitrogen and phosphorus appeared relatively greatest for raingardens of an area equivalent to between 0.2 and 1% of the total impervious catchment. Locating two raingardens adjacent to existing side entry pits with an area of 32 square metres (5m x 6.5m; 0.5% of impervious catchment) would yield significant benefits in terms of pollutant reduction, and would greatly improve the quality of residential runoff.

4.4 Locating Retail Roofing Part 3.1 also identified commercial runoff as a very high threat to the quality of stormwater discharging into Port Phillip Bay. Although this is in large part due to the presence of pollutants within water discharging from these zones, it is difficult to implement pollutant reduction mechanisms within commercial zones because of space limitations and high volumes & frequency of pedestrian & vehicular traffic at street level. An approach such as raingardens is therefore difficult to implement, particularly retrospectively, within this context.

One such site within the commercial zone is Coles supermarket, which occupies the full extent of an allotment of 2470 square metres. As is the case with all premises within this zone, the roof material is flat metal tray sheeting. The building is of a warehouse typology, with face brickwork to its entire perimeter and a rigid steel portal frame internally, supporting wide spaning roof beams that provide an open floor plan internally. Columns are interspersed throughout the interior which provide vertical structural stability to the roof framing.

Stormwater runoff from the commercial zone is also problematic because sites have little permeable surface. This increases the need for stormwater runoff to be discharged via grey stormwater infrastructure;.It is therefore through the implementation of green roofs within commercial zones that the best opportunity to provide ecosystem services exists, via a reduction of peak flows.

An extensive green roof as noted under section 3.4 is proposed for this building, the provision of which will substantially reduce the peak flows experienced at the site. A lightweight, shallow substrate comprising low herbaceous vegetation is likely to contribute additional weight loading of 10.2 kg/m2 (City of Melbourne 2013), for an overall additional dead weight of 25,194 kg. This will require some structural reinforcement but remains a feasible engineering prospect.

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5.0 COSTING GREEN INFRASTRUCTURE 5.1 Costing Shopfront Swales

5.2 Costing Residential Raingardens

The retrospective integration of swales into urban environments appears a relatively uncommon venture.

It has therefore been most difficult to estimate the cost of this element. The cost estimation attempts to factor in (for the installation of a vegetated swale along an entire residential block) the cost of demolition & excavation of the existing kerb & swale, reinstatement of the kerb, bridge crossovers and vegetation, by using the figures derived for residential raingardens as a comparison (see 5.2). The cost estimation for a swale of approximately 230m length is $305,000, with a maintenance fee of approximately $10,000 per year.

Moreland City Council has prepared a Raingarden Design Package that directs conceptualisation and implementation of these green infrastructures in urban environments (Moreland City Council 2013).

The package provides cost estimations for raingarden construction and maintenance. Based on the estimations provided within this package, the cost for construction of one raingarden (30 sqm) is $20,500.

Maintenance costs for a raingarden of this size are estimated to amount to $2,500 per year.

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5.3 Costing Retail Roofing

5.4 Providing a Funding Model

Although it is difficult to anticipate the exact costs of a green roof retrofit due to the high variability of existing conditions and circumstances necessary to complete such a project, assumptions can be made based on common project factors and compared to other existing projects. The newly developed Growing Green Guide 2013 (Melbourne City Council 2013) provides a cost analysis of a recently completed unspecified green roof project. The overall cost of that project was in excess of $3 million however; the project also includes a green facade and leisure facilities, it also appears an intensive green roof rather than extensive, as proposed. Using the itemised costs provided in the summary, an estimated figure of $523,740 for the proposed green roof is provided. This does not include maintenance.

Privately owned commercial properties such as the Coles supermarket could be tempted to integrate green roofs into their premises through Council incentives, such as a reduction in rates. This expense would be offset for the Council by a reduction in reliance on grey stormwater infrastructure. Generating finances for the integration of GI into public assets would likely pose a greater challenge for the Council, and require the development of a model that channels funds normally allocated to grey stormwater infrastructures into a green infrastructure fund. The Council should also coordinate their planned grey infrastructural upgrades with green infrastructure projections, such that they can achieve dual benefits when upgrading existing systems.

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6.0 GREEN INFRASTRUCTURE BENEFITS 6.1 Anticipating Ecosystem Service Benefits The two primary objectives of the implementation of these green infrastructure technologies were to reduce peak flows & remove stormwater pollutants. Table 6.1.1 details the likely achievable ecosystem service benefits of each GI technology in relation to these objectives.

Table 6.1.1 - Ecosystem Service Benefits

Method

Peak Flow Reduction

Pollution Reduction

Shorefront Swale

Diverting stormwater from traditional grey infrastructure drainage systems through vegetated swales reduces the rate at which stormwater will discharge into the bay. Taken as an indication of the overall ecosystem service benefit, the swale proposed between McBain Street & Romawi Street, during a 6mm rainfall event will reduce the rate of discharge for almost 50,000L of stormwater.

Research undertaken by the CSIRO shows that a swale of a size equivalent to 3% of the total impervious catchment and with vegetation of height 0.25 metres can reduce total soluble solids by 90%, phosphorus by 60% & nitrogen by 40% (CSIRO 2005). Taken as an indication of the overall ecosystem service benefit, the swale proposed between McBain Street & Romawi Street equates to approximately 6% of its impervious catchment area.

Residential Raingarden

Diverting stormwater to the proposed raingardens for soil infiltration will prevent it entering the grey stormwater drainage network, and reduce peak flows. As those proposed have ponding depths of 250mm and substrate hydraulic conductivity of 200mm/hr, a substantial quantity of water will be treated and exfiltrated. Notwithstanding, the capacity of these systems to reduce peak flows is limited during extreme rainfall events (>6mm).

The proposed raingardens are of a size equivalent to approximately 0.5% of their catchment size. Such raingardens can reduce total soluble solids in stormwater by 85%, total phosphorus by 65% and total nitrogen by 45% (CSIRO 2005); effectively limiting pollutants discharging into Port Phillip Bay.

Retail Roofing On a green roof, plants and growing substrate intercept rainfall.

Subsequently, both the time to onset and the time to peak flow of stormwater entry are delayed. Based on available research, the proposed commercial extensive green roof would, during a period of heavy rain, be able to retain over 50% of rainfall (City of Melbourne 2013). For a 6mm rainfall event this would reduce the peak stormwater flow by 7410L.

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The green roof will add little additional benefit in the removal of pollutants from stormwater. Rather, it is likely to increase the nutrient content within discharge and should be used in conjunction with other green infrastructures to offset this. Green roof vegetation has been selected for its strong capacity to absorb nutrients (such as from fertalisers) and its installation is not anticipated to affect stormwater quality in this regard.

RAINGARDENS ARE LIKELY TO REDUCE TOTAL SOLUABLE SOLIDS IN STORMWATER BY 85%, PHOSPHORUS BY 65% AND NITROGEN BY 45%.

The expected pollutant removal benefits of the residential raingarden green infrastructure solution.

7.0 SUCCESS 7.1 Monitoring & Measuring Success The greatest measure of the successful implementation of green infrastructures is in their capacity to provide the ecosystem service benefits outlined previously in this report. As highlighted in part 6.0, there exists a strong theoretical and technical grounding to suggest that these technologies would be able to substitute traditional grey stormwater infrastructure to succesfully provide effective stormwater management that both reduces peak flows and minimises pollutants.

Despite this theoretical success, due to the presence of living organisms within these systems, a constant monitoring and maintenance regime need necessarily be undertaken to ensure the sustained presence of vegetation and effective operation of green infrastructures. Performance criteria should always reference back to the objectives which underpinned the conceptualisation and implementation of these infrastructures to begin with. And as with any other infrastructural developments, the success of green infrastructures cannot be quantified self-referentially, fluctuations in environmental and urban conditions may necessitate review and subsequent adaption or expansion of green infrastructures.

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8.0 CONCLUSION As urban areas seek to adapt to the challenges of climate variability, urban management authorities are turning to green infrastructure to substitute the costly, energy intensive and environmentally detrimental products of traditional grey infrastructural development. In Altona, a suburb where climate variability and urban growth are increasing pressures on existing grey stormwater infrastructure, green infrastructure provides a cost effective, energy efficient and environmentally friendly remedy to these issues via the provision of ecosystem service. Through careful analysis of the environmental conditions, urban fabric and topographical composition, this report has proposed a number of green infrastructure technologies which have proven effective conveyors of stormwater management and could, given their successful monitoring and maintenance, provide a model for green infrastructure interventions throughout the rest of the suburb and metropolitan Melbourne en masse.

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9.0 REFERENCES 9.1. Body Argue, J 2004, WSUD: Basic Procedures for â&#x20AC;&#x2DC;Source Controlâ&#x20AC;&#x2122; of Stormwater: A Handbook for Australian Practice, University of South Australia, Adelaide, Australia CSIRO 2005, WSUD Engineering Procedures: Stormwater, CSIRO, Collingwood, Australia City of Melbourne 2013, Growing Green Guide: Draft, City of Melbourne, Melbourne, Australia, viewed 20 December 2013, <http://imap.vic.gov.au/uploads/ Growing%20Green%20Guide/Growing%20Green%20 Guide%20FINAL%20DRAFT%20website4.pdf> Hobsons Bay City Council 2006, Sustainable Tourism Strategy 2006-2012, Hobsons Bay City Council, Altona, Australia, viewed 20 December 2013, <http:// www.hobsonsbay.vic.gov.au/files/7ac64d23-95cc-47ffa223-9fdb00c2b6da/SustainableTourismStrategy. pdf> Hoyer, J, Dickhaut, W, Kronawitter, L & Weber, B 2011, Water Sensitive Urban Design: Principles & Inspiration for Sustainable Stormwater Management in the City of the Future, Jovis, Hamburg, Germany

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HydroCon 2012, HydroCon Pipes Improve Stormwater Drainage Outfall at Altona Beach, HydroCon Australiasia, Chippendale, NSW, viewed 20 December 2013, <http://hydrocon.com.au/wp-content/ uploads/2013/03/Altona-Beach-Renourishment.pdf> Lloyd, S, Wong, T & Chesterfield, C, Water Sensitive Urban Design: A Stormwater Management Perspective, Cooperative Research Centre for Catchment Hydrology, Monah University, Victoria Melbourne Water 2000, Cherry Lake & Truganina Swamp, Melbourne Water, Melbourne, Australia, viewed 20 December 2013, <http://wmcn.org. au/attachments/article/230/cherry_lake_and_ truganina_swamp.pdf> Melbourne Water 2010, Instruction Sheet: Building an Infiltration Raingarden, Melbourne Water, Melbourne Australia, viewed 20 December 2013, <http://raingardens.melbournewater.com.au/library/ Swale_-_Building_a_raingarden_instruction_sheet. pdf> Melbourne Water 2010, Instruction Sheet: Building a Swale, Melbourne Water, Melbourne Australia, viewed 20 December 2013, <http://raingardens. melbournewater.com.au/library/Swale_-_ Building_a_raingarden_instruction_sheet.pdf>

Melbourne Water 2013, Water Sensitive Urban Design: Selecting a Treatment, Melbourne, Australia, viewed 20 December 2013, <http://www.melbournewater. com.au/Planning-and-building/Stormwater management/Water-Sensitive-Urban-Design/Pages/ How-to-select-a-treatment.aspx> Melbourne Water 2013, Water Sensitive Urban Design Treatments: Swales, Melbourne, Australia, viewed 20 December 2013, <http://www.melbournewater.com.au/ Planning-and-building/Stormwater-management/ WSUD%20treatments/Pages/Swales.aspx> Moreland City Council 2013, Streetscape WSUD Raingarden & Tree Pit Design Package, Moreland City Council & GHD, Melbourne, Australia, viewed 20 December 2013, <http://www.moreland.vic.gov. au/mccwr/publications/brochures-factsheetsguidelines/000_moreland%20wsud%20design%20 package.pdf> WBM Engineering & Environmental Consultants 2006, Hobsons Bay Stormwater Management Plan 2006, Volumes 1-3, Melbourne, Australia

9.2 Figures

9.3 Images

Figure 1.0: Satellite image of Altona, Google Earth 2013, Satellite Image, viewed 20 December 2013, <http://www.google.com/earth/>

Figure 2.3: Image of streetscape & nature strip in Altona, Google Streetview, Image, viewed 20 December 2013, <http://www.google.com/maps/>

Cover Image: The Esplanade in Altona showing Altona Beach and adjoining residential housing, By Author, Image, captured December 2013

Figure 1.1: Map of neighbourhood area, By Author, Map, created December 2013

Figure 2.2: Retrofitting existing car park at Plum St in Lancaster, LIVE Green 2013, Trench during construction, Photo, viewed 21 November 2013, <http://www.saveitlancaster.com/local-projects/ parking-lots/>

Page 2-3: The Altona foreshore looking out from Logan Reserve, By Author, Image, captured December 2013

Figures 1.2-1.5: Images of forseshore flooding along Altona Esplanade, Hobsons Bay City Council, Images, obtained December 2013 Figure 2.0: Photo of Cherry Lake, Melbourne Day Walks, Altonaâ&#x20AC;&#x2122;s industrial area in the distance, Photo, viewed 20 December 2013, <http://www.melbournedaywalks. com/wp-content/uploads/2011/02/cherry3.jpg> Figure 2.1: Photo of Truganina Swamp, Beautiful Altona, Truganina Swamp, Photo, viewed 20 December 2013, <http://altonabeauty.blogspot.com. au/2010/07/attraction-8-truganina-swamp.html>

Figures 3.0-3.6: Plans & sections of proposed green infrastructure technologies, By Author, details adapted from previously referenced sources (see section 6.1), Authographic drawings, created December 2013

Page 31: Background image of stormwater drainage outlet at Sargood Street, By Author, Image, captured December 2013

Figure 4.0: Map of neighbourhood area with proposed green infrastructure interventions, By Author, Map, created December 2013

Figure 2.2: Photo of Altona Foreshore, By Author, Photo, taken December 2013

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