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Whittlesea and Mitchell Planning Schemes Amendment GC28

Expert Witness report provided to Planning Panels Victoria

Drainage Evidence (Property 20, 10 and 8)

Prepared for Mirvac (Victoria) Pty Ltd and Boral Property Group

Prepared by Jonathon McLean

May 2016

1

1 Witness Details

I, Jonathon McLean of Alluvium Consulting Australia (Alluvium), 105 – 115 Dover Street, Cremorne, Victoria

3121, prepared this report. I hold the position of Senior Consultant.

I have a Bachelor of Engineering (Civil) from Monash University 1990, Graduate Diploma Water Resources and

Environmental Engineering Monash University 1994, Graduate Diploma MBA Program Technology

Management APESMA Deakin University 2001.

I am a member of the River Basin Management Society (RBMS) and a former 10 year committee member of

the Victorian Stormwater Industry Association (2001-2010).

My major fields of expertise and interest are hydrology, hydraulics, urban drainage, catchment planning and

management, flood estimation, surface water modelling, stormwater treatment and waterway management.

Related Experience:

• Over a period of 20 years I have regularly been involved with the design and strategic planning of

drainage strategies and systems within residential, commercial and industrial developments.

• My expert advice has been sought by both the private sector (eg developers) and the public sector

(catchment management authorities and local government).

• I have been actively involved in the development of the Best Practice Environmental Guidelines for

Urban Stormwater.

• I have attended and presented at various industry conferences and seminars.

• I have a sound understanding of the role of Local Government, Catchment Management Authorities,

Environment Protection Authority and other agencies in stormwater planning and management.

Therefore my expertise and experience in flood modelling and urban stormwater management associated with

civil engineering and development projects, qualifies me to make this report.

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2 Instructions

Alluvium has provided stormwater management advice to the proponent – Mirvac (Victoria) Pty Ltd (Mirvac)

and Boral Property Group (Boral) – to address the issues associated with future residential development on

the subject site.

I have been instructed by Sean McArdle from Norton Rose Fulbright to provide expert evidence advice on the

drainage issues related to the Mirvac and Boral sites (identified as property nos. 20, 10 and 8 in the

Donnybrook/Woodstock Precinct Structure Plan) taking into account:

− the exhibited GC28 documents, background reports and submissions

In particular I have been briefed to specifically address the following issues:

− the appropriateness of the proposed surface water treatment in the Donnybrook/Woodstock Precinct

Structure Plan (PSP) and whether the overall network of surface water management in the PSP

provides an acceptable level of service, particularly as relevant to the Mirvac Land and the Boral Land;

− issues identified in any relevant submissions lodged with the MPA;

− unresolved matters raised in the Stakeholder’s register as relevant to your area of expertise;

− address, as necessary, the need for an additional wetland system on the Boral Land;

− the implications of modifying infrastructure in the manner suggested by submission 27 (Monteleone)

and whether such modifications are warranted.

This report responds directly to the above issue by providing a summary of the investigations, assumptions

and assessments that have been undertaken in defining and reviewing the surface water management

strategy for the Mirvac Land and Boral Land.

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3 Information / Documentation

In preparing this evidence Jonathon McLean has had regard to:

Reports:

• Donnybrook / Woodstock Precinct Structure Plan (1067/1096) – MPA (Public exhibition Nov 2015).

• PSP 1067, PSP 1096 Donnybrook / Woodstock Background Report (Public Exhibition Nov 2015).

• Whole of Water Cycle Assessment: PSP 1067 Donnybrook and PSP 1096 Woodstock (Arup 2014)

• Donnybrook Springs Developments: Response to proposed Donnybrook/Woodstock Precinct

Structure Plan (Dec 2015)

• Lockerbie East Drainage Scheme, advice provided by Pat Condina & Associates for 895/915

Donnybrook Road (October 2015)

Other Information:

• Melbourne Water’s Lockerbie East DSS 6508 Scheme plan

• Melbourne Water’s Langley Park Drive DSS 4566 Scheme plan

• Melbourne Water’s Woodstock West DSS 6503 Scheme plan

• Site Inspections

• Aerial Photography

• Constructed Waterways in New Urban Developments – Melbourne Water (2013)

• Waterway Corridors, Guidelines for greenfield development zones within the Port Phillip and

Westernport Region – Melbourne Water

• Australian Rainfall & Runoff (1997) – Engineers Australia

• Urban Stormwater Best Practice Environmental Management Guidelines (1999)

• Donnybrook/ Woodstock PSP: Stakeholder workshop agreed outcomes, MPA (March 2016)

Jonathon McLean adopts this evidence as a true and correct statement of his opinions and the facts he

believes to be true in this matter.

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4 Facts, Matters and Assumptions

This report is based upon an assessment and review of the information provided to me as referenced in

Section 3 and the numerous site visits undertaken.

The subject sites for this report covers an area of approximately 329 ha, which includes landholdings directly

owned by Mirvac (property no 20 on Figure 4 of the PSP – 127.8ha) and the Boral landholdings (property 10 –

60.9ha and property 8 – 140.3ha). The site is bound by Donnybrook Road to the south, Merri Creek to the

north, Patterson Drive to the west, and the Donnybrook PSP boundary to the east (refer to Figure 1).

The subject site is traversed by a minor tributary of the Merri Creek, which generally flows from east to west.

The topography of the site is characterised by relatively gentle grades with slopes around 1- 2%, and isolated

areas of steeper slopes or rocky knolls with grades around 4%.

Figure 1: Location of subject sites (red line)

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4.1 Stormwater Quantity – Assumptions

The following design rainfall parameters were adopted for Donnybrook based upon the Bureau of

Meteorology’s “Intensity Frequency Duration (IFD) Tool – AR&R 87).

Table 1: AR&R Design Rainfall parameters (Donnybrook)

Parameter Value

1hr 2yr 19.69

12hr 2yr 3.99

72hr 2yr 1.09

1hr 50yr 39.91

12hr 50yr 7.31

72hr 50yr 2.31

Skew 0.33

F2 4.3

F50 14.97

Zone 1

A hydrologic model (RORB) was utilised for the catchment analysis and assessment. The following rainfall loss

models were adopted for existing conditions (Table 2) and developed conditions (Table 3).

Table 2: RORB parameters for existing conditions model

Rainfall station Donnybrook

Initial loss 15 mm

Continuing Loss 2.5 mm/hr

Table 3: RORB parameters for developed conditions model

Rainfall station Donnybrook

Initial loss 15 mm

Runoff Coefficient (100yr) 0.60

To reflect ultimate development conditions the pre-developed scenario was modified to reflect post

development conditions. To understand the hydrologic impacts, the following standard Melbourne Water

fraction impervious values were used as a guide (Figure 2). The proposed PSP has identified this section of the

catchment as predominately future residential.

6

Figure 2: Fraction impervious values for various land uses

4.2 Stormwater Quality – Assumptions

In accordance with Melbourne Water’s MUSIC Guidelines and to be consistent with the Melbourne Water’s

scheme approach, Melbourne Airport rainfall station was used with a reference year of 1996 for stormwater

treatment modelling and concept designs.

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5 Catchment context

The Mirvac/Boral landholdings are located within the Donnybrook precinct. Whilst the majority of the subject

site ultimately outfalls to the Merri Creek system, a small portion in the south east outfalls to the Darebin

Creek system. As a result the overall Mirvac/Boral land interests span three different Melbourne Water

Development Services Schemes (DSS). The relevant DSS’s are provided in Table 4. The relationship between

the three Melbourne Water DSS’s and the Mirvac landholdings is shown in Figure 3.

Table 4: Relevant drainage schemes

Watershed DSS Flow direction

Merri Creek Lockerbie East DSS West (South – west)

Langley Park Drive DSS South - west

Darebin Creek Woodstock West DSS South - east

Figure 3: Relevant drainage schemes for the Mirvac/Boral landholdings

Legend

Lockerbie East DSS

Woodstock West DSS

Langley Park Drive DSS

Mirvac / Boral land

8

Within the three Melbourne Water DSS’s, the Mirvac and Boral landholdings are divided into five -catchments.

That is five locations where stormwater drainage will discharge across title boundaries. These catchments are

illustrated in Figure 4. I have assessed the appropriateness of the proposed surface water treatment in the

Donnybrook/Woodstock PSP based upon these five individual catchments.

Figure 4: Catchments within the Mirvac and Boral landholdings

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6 Catchment 1 – South East Outfall

6.1 Existing Conditions

Catchment 1 within the Mirvac site covers an area of approximately 39.1 hectares and is located within the

Woodstock West Development Services Scheme. The drainage outfall for catchment 1 is through the external

properties to the east (property no 21 and 31) before crossing Donnybrook Road via twin 450mm by 1200mm

culverts just west of the gas easement. Based upon my investigations, the overall catchment at the

Donnybrook Road crossing is 43.3 hectares (of which catchment 1 contributes 39.1ha). The invert level of the

existing culverts is RL 235.20, approximately 900mm below Donnybrook Road.

The existing culvert capacity at Donnybrook Road is approximately 2 cumecs. A local RORB model was

prepared for the undeveloped conditions and the model parameters were “calibrated” to the peak flow

estimates from the rational method. The peak 100 year flow rate under existing conditions is 2.35 cumecs.

Figure 5: Location of existing culverts

6.2 Developed Conditions

It appears that Melbourne Water, in conjunction with the MPA, determined that future development flows

should be reduced to pre-development peak flow rates at Donnybrook Road and also achieve the stormwater

quality targets for urban development set out in the Urban Stormwater Best Practice Guidelines. In my opinion

such criteria are sound and appropriate for the following reasons:

• Donnybrook Road is the southern boundary of the PSP

• No structure planning or drainage strategies have been undertaken for the land immediately to

the south of Donnybrook Road.

Other stormwater quantity criteria include the conveyance of major flows through the site via road reserves

and the conveyance of minor flows through local catchments in a piped network

The peak 100 year developed flows from the catchment upstream of Donnybrook Road are larger than 9

cumecs. This far exceeds the existing conditions peak flow and the capacity of the existing culverts. As a result

retardation would be required to mitigate the flows.

The PSP has responded to the above stormwater management criteria by locating a combined wetland and

retarding basin (RBWL-6) on property 31 immediately upstream of Donnybrook Road and west of the gas

easement (refer to Figure 6). Melbourne Water’s Woodstock West DSS is also consistent with the PSP layout

for this catchment (refer to Figure 7).

10

Figure 6: PSP – location of wetland/basin to service catchment 1

Figure 7: Melbourne Water’s Woodstock West DSS – location of wetland/basin to service catchment 1

In reviewing this strategy I undertook the following analysis and investigations to assess the feasibility of the

high level PSP stormwater assets from both a location and land budget perspective:

• Site inspection

• Consideration of topography (survey, contours), feature survey and known physical or infrastructure

constraints

• Created a hydrologic model (RORB) to determine the required retardation volumes up to the 100 year

ARI event.

• Created a MUSIC (Model for Urban Stormwater Improvement Conceptualisation) model to establish

the proposed treatment train strategy. The model estimates the amount of pollutants the catchment

produces, the performance of treatment measures and the pollutant load generated once the

catchment is treated.

• Concept and preliminary functional designs

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My findings were as follows:

Stormwater quality

As identified earlier it is expected that stormwater quality treatment meets the best practice removal targets

at Donnybrook Road. As a result the criteria are:

• 80% removal of Total Suspended Solids (TSS)

• 45% removal of Total Phosphorus (TP)

• 45% removal of Total Nitrogen (TN)

Based upon the modelling undertaken the following stormwater treatment train is required to meet these

objectives:

• Sediment pond size of 750m2

• Wetland size of 6126m2

The obvious location for the stormwater treatment system is immediately upstream of the existing culverts at

Donnybrook Road (ie property 31). Whilst the topography in this location is well suited to the construction of a

wetland, it is constrained on the eastern side by the existing gas easement. The alignment of the gas easement

results in an isolated “triangular” parcel of land. Concept/preliminary functional designs were undertaken to

demonstrate how the wetland could be configured within the triangular parcel of land. The footprint includes

the treatment area, batter, sediment drying area, freeboard and room for maintenance. The concept design is

provided in Figure 8. The design has been informed by 3 dimensional modelling in 12d. For the wetland the

normal water level is determined by the subdivision drainage of its local catchment and the topography of the

wetland site. The normal water level must ensure free drainage of the subdivision system and also allow for a

reasonable fit of the wetland into the existing topography.

The batter slopes have been designed between 1 in 6 to 1 in 8 around the asset to allow for provision of

shared path and maintenance tracks where necessary. It is assumed that at 0.35 m below the normal water

level, the batter slope can increase to 1:3. For the wetland and sediment basin, the length is more than four

times the average width through the use of a flow divider (eg lined gabion). A minimum width of 23 metres is

required for the wetland in order to meet the velocity requirements.

Provision has been made for maintenance requirements. As described above, the wetland design allows for a

maintenance track, these would typically be 4 metres wide at a grade of 1:20. In order to optimise the use of

the site a 1 metre high retaining wall may be required around the perimeter of the access path.

Stormwater quantity

The hydrologic modelling considered a range of design storms, from 10 minutes duration through to 72 hours,

in order to determine the critical duration event with respect to storage.

Whilst the critical duration storm event is 20 minutes to produce the peak flow, the 2 hour storm is the critical

duration with respect to requiring the peak storage volume.

• 100 year ARI design event

o Peak outflow from retardation basin of 2.34 m3/s

o Peak storage volume required is 10,300 m3

The peak discharge rate from the retarding basin is less than the allowable peak 100 year flow of 2.35 m3/s.

The preliminary functional design has demonstrated that the required storage volume can be integrated within

the footprint provided by the wetland reserve. The required normal water level in the wetland will require the

invert level of the culvert under Donnybrook Road to be lowered. This may clash with the water main in

Donnybrook Road, which will require the water main to “lowered/cranked” to provide the appropriate

clearance.

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Figure 8: Concept/preliminary design of RBWL-6

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7 Catchment 2 – South West Outfall


Catchment 2 within the Mirvac site covers an area of approximately 22.9 hectares and is located within the

Langley Park Drive Development Services Scheme. The drainage outfall for catchment 2 is through the external

properties to the west (property no 19) before crossing Donnybrook Road via twin 450mm by 1200mm

culverts. Based upon my investigations, the overall catchment at the Donnybrook Road crossing is 45.2

hectares (of which catchment 1 contributes 22.9ha). The invert level of the existing culverts is RL 234.98,

approximately 1 metre below Donnybrook Road.

The existing culvert capacity at Donnybrook Road is approximately 2.3 cumecs. A local RORB model was

prepared for the undeveloped conditions and the model parameters were “calibrated” to the peak flow

estimates from the rational method. The peak 100 year flow rate under existing conditions is 2.43 cumecs.

Figure 9: Location of existing culverts

In my opinion the PSP layout with respect to drainage catchment 1 is appropriate from an engineering

feasibility perspective. The location for asset RBWL-6 (wetland and retarding basin) is sound and can

deliver on the design criteria to control peak flows to the equivalent pre-development peak flow rates and

best practice stormwater quality targets. However based upon the modelling and preliminary design

undertaken, I would recommend that the entire “triangular” parcel be set aside as a drainage reserve (ie

the area west of the gas easement, north of Donnybrook Road and east of the property 31 title

boundary). In comparison the PSP only shows a portion of the triangular parcel as drainage reserve.

14


It appears that Melbourne Water, in conjunction with the MPA, determined that future development flows

should be reduced to pre-development peak flow rates at Donnybrook Road and also achieve the stormwater

quality targets for urban development set out in the Urban Stormwater Best Practice Guidelines. In my opinion

such criteria are sound and appropriate for the following reasons:

• Donnybrook Road is the southern boundary of the PSP

• No structure planning or drainage strategies have been undertaken for the land immediately to

the south of Donnybrook Road.

Other stormwater quantity criteria include the conveyance of major flows through the site via road reserves

and the conveyance of minor flows through local catchments in a piped network

The peak 100 year developed flows from the catchment upstream of Donnybrook Road are larger than 10

cumecs. This far exceeds the existing conditions peak flow and the capacity of the existing culverts. As a result

retardation would be required to mitigate the flows.

The PSP has responded to the above stormwater management criteria by locating a combined wetland and

retarding basin that is split across Patterson Drive. RBWL-5 is located on property 20 within a local park and

RBWL-4 is located on property 20 immediately upstream of Donnybrook Road (refer to Figure 10). Melbourne

Water’s Langley Park Drive DSS is also consistent with the PSP layout for this catchment (refer to Figure 11).

Figure 10: PSP – location of wetland/basin to service catchment 2

Figure 11: Melbourne Water’s Langley Park Drive DSS – location of wetland/basin to service catchment 2

15


high level PSP stormwater assets from both a location and land budget perspective:

• Site inspection


constraints

• Created a hydrologic model (RORB) to determine the required retardation volumes up to the 100 year

ARI event.

• Created a MUSIC (Model for Urban Stormwater Improvement Conceptualisation) model to establish

the proposed treatment train strategy. The model estimates the amount of pollutants the catchment

produces, the performance of treatment measures and the pollutant load generated once the

catchment is treated.


My findings were as follows:

Stormwater quality

As identified earlier it is expected that stormwater quality treatment meets the best practice removal targets

at Donnybrook Road. As a result the criteria are:

• 80% removal of Total Suspended Solids (TSS)

• 45% removal of Total Phosphorus (TP)

• 45% removal of Total Nitrogen (TN)

Based upon the modelling undertaken the following stormwater treatment train is required to meet these

objectives:

RBWL-5

• Sediment pond size of 500 m2

• Wetland size of 3700 m2

RBWL-4

• Sediment pond size of 500 m2

• Wetland size of 5000 m2

The obvious location for the stormwater treatment system is immediately upstream of the existing culverts at

Donnybrook Road (ie property 19) as it is the low-point for the catchment and the topography in this location

is well suited to the construction of a wetland (RBWL-4). However the proposed local park in the south west

corner of property 20 provides an opportunity to split the wetland asset across Patterson Drive. The proposed

wetland system (RBWL-5) treats stormwater from catchment 2 (22.9ha) to best practice within the Mirvac

portion of the reserve. This approach assists with delivering assets equitably across landholders as well as

providing a potential staging approach to the delivery of the asset. Ultimately the assets are linked and can be

managed as a single entity.

Concept/preliminary functional designs were undertaken to demonstrate how the wetland could be

configured across Patterson Drive. The footprint includes the treatment area, batter, sediment drying area,

freeboard and room for maintenance. The concept design is provided in Figure 12. The design has been

informed by 3 dimensional modelling in 12d. For the wetland the normal water level is determined by the

subdivision drainage of its local catchment and the topography of the wetland site. The normal water level

must ensure free drainage of the subdivision system and also allow for a reasonable fit of the wetland into the

existing topography.

The batter slopes have been designed between 1 in 6 to 1 in 8 around the asset to allow for provision of

shared path and maintenance tracks where necessary. It is assumed that at 0.35 m below the normal water

level, the batter slope can increase to 1:3. For the wetland and sediment basin, the length is more than four

16

times the average width through the use of a flow divider (eg lined gabion). A minimum width of 20 metres is

required for the wetland in order to meet the velocity requirements.

Provision has been made for maintenance requirements. As described above, the wetland design allows for a

maintenance track, these would typically be 4 metres wide at a grade of 1:20. As a result a total footprint of

approximately 1.0ha is required for RBWL-5 and 1.3ha is required for RBWL-4.

Stormwater quantity

The hydrologic modelling considered a range of design storms, from 10 minutes duration through to 72 hours,

in order to determine the critical duration event with respect to storage.

Whilst the critical duration storm event is 20 minutes to produce the peak flow, the 2 hour storm is the critical

duration with respect to requiring the peak storage volume.

• 100 year ARI design event

RBWL-5


o Peak storage volume required is 5,330 m3

RBWL-4


o Peak storage volume required is 4910 m3

The proposed retarding basin on property 20 (RBWL-5) restricts the stormwater discharge from catchment 2

(22.9ha) to the equivalent peak rural discharge. When this asset is combined with the basin on property 19

(RBWL-4) the peak discharge rate is controlled to 2.14 m3/s at Donnybrook Road, which is less than the

allowable peak 100 year flow of 2.43 m3/s. The preliminary functional design has demonstrated that the

required storage volume can be integrated within the footprint provided by the wetland reserve. The required

normal water level in the wetland will require the invert level of the culvert under Donnybrook Road to be

lowered. This may clash with the water main in Donnybrook Road, which will require the water main to

“lowered/cranked” to provide the appropriate clearance.

In my opinion the PSP layout with respect to drainage catchment 2 is appropriate from an engineering

feasibility perspective. The location for assets RBWL-5 and RBWL-4 is sound and can deliver on the design

criteria to control peak flows to the equivalent pre-development peak flow rates and best practice

stormwater quality targets.

Table 9 of the PSP has allowed for a land budget of 0.55ha and 0.76ha respectively for RBWL-5 and RBWL-

4. Based upon the modelling and preliminary design undertaken, I would recommend that the land

budget be amended to 1.3ha for RBWL-4.

17

Figure 12: Concept/preliminary design of RBWL-5 and RBWL-4

18

8 Catchment 3 – Central Outfall


Catchment 3 within the Mirvac and Boral landholdings covers an area of approximately 127 hectares and is

located within the Lockerbie East Development Services Scheme. A drainage line / “valley floor” meanders

through catchment 3. This drainage line outfalls through the external property to the west (property 17),

approximately 300 metres south of Cameron Street. This drainage line “flattens out” into a broad depression

immediately west of the Mirvac title boundary. The drainage line / “valley floor” continues westwards where it

crosses the railway line before outfalling to Merri Creek.

The capacity of the existing culverts under the railway is limited and provides a drainage constraint for the PSP.

A scheme RORB model was prepared for the undeveloped conditions and the model parameters were

“calibrated” to the peak flow estimates from the rational method.

Figure 13: Location of catchment 3 (yellow)

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The stormwater management strategy for the Lockerbie East DSS has undergone a number of changes and

options over the last 24 months. This includes catchment 3 and the PSP layout. In order to understand and

evaluate the various options with respect to catchment 3, I have summarised them into three scenarios for

this report:

Scenario 1 – Wetland and retarding basin (RBWL-2) on property 17

Scenario 2 - Wetland and retarding basin (RBWL-2) split over Patterson Drive between property 17

and property 20

Scenario 3 - Wetland and retarding basin (RBWL-2) on property 17 and an additional

wetland/retarding basin on property 10


scenarios:

• Site inspection


constraints

• Hydrologic model (RORB) to determine the required retardation volumes up to the 100 year ARI

event.

• Water quality modelling using MUSIC (Model for Urban Stormwater Improvement Conceptualisation)

to establish the proposed treatment train strategy. The model estimates the amount of pollutants

the catchment produces, the performance of treatment measures and the pollutant load generated

once the catchment is treated.


Scenario 1

The northern portion of the Donnybrook Precinct Structure Plan is located within Melbourne Water’s

Lockerbie East Development Services Scheme (DSS). This DSS commenced investigations and planning in 2012.

Following hydraulic modelling and conceptual engineering designs for the key stormwater assets, Melbourne

Water contacted all property owners of the proposed scheme in May 2014.

A wetland / retarding basin (RBWL2 - refer to Figure 14) was located entirely on property 17 (Monteleone

land) and west of property 30 (Mirvac land). Under the original DSS the total wetland / retarding basin reserve

on property 27 was 5.6ha with nothing envisaged on property 30.

Based on topography, the broad and flat depression on property 17 is the most logical location for a major

wetland asset. From an engineering perspective this locality will deliver the most efficient system, both in

terms of construction cost and land footprint. As a result scenario 1 should therefore be considered the default

position.

• Sediment pond size of 0.3ha

• Wetland size of 3.3ha

• 100 year ARI storage of 50,300m3 to restrict the peak 100 year ARI design flow to 5.79 cumecs.

Table 5: RBWL-2 land take for Scenario 1

Property no. Treatment area (ha) Land budget (ha)

17 3.6 5.6

20 0 0

Total (17 + 20) 3.6 5.6

20

Figure 14 – Melbourne Water DSS (May 2014)

Monteleone WL1/RB1 land take (17):

• Treatment area of 3.6ha

• Total Wetland/RB reserve are of 5.6ha

(excludes the waterway)

Mirvac land take (20):

• Treatment area of 0ha

• Total Wetland/RB reserve area of 0ha

(excludes the waterway)

RBWL-2

20 19

21

The scheme identified that the RBWL-2 asset manages urban stormwater from the catchment as shown in

Figure 15.

Figure 15 – Contributing catchment for RBWL -2 asset (shaded yellow)

22

Scenario 2

Melbourne Water had discussions with the Monteleone’s and Mirvac in early-mid 2015. Mirvac also met with

the Monteleone’s during this period. The Monteleone’s were keen for Melbourne Water to pursue alternative

configurations for the location of RBWL-2. Mirvac indicated that it would consider the potential to distribute

part of the scheme asset on its landholdings depending upon the engineering feasibility. As a result Melbourne

Water prepared a preliminary scheme option to split RBWL-2 across the Monteleone and Mirvac landholdings

(ie either side of Patterson Drive). Refer to Figure 16. This version of the DSS was used by the MPA to inform

the layout and locations on the drainage reserves on the exhibited version of the PSP layout (Refer to Figure

17).

Figure 16 – Melbourne Water DSS option (Aug 2015)

Figure 17 Donnybrook/Woodstock Precinct Structure Plan (Nov 15)

23

Following an engineering feasibility investigation, I established that due to topographical constraints in the

eastern portion (property 20) of RBWL-2, it was not feasible to split the wetland across Patterson Drive. The

preliminary concept/functional layout is shown in Figure 18. The existing surface on the eastern side has a

grade of about 1 in 60, which results in an excavation depth of up to 5.5 - 6 metres. Excavation of over 5

metres in ground conditions where rock is close to the surface is extremely costly and somewhat impractical.

The depth also increase batters and results in a significant overall land budget increase for drainage in

comparison with Scenario 1.



17 1.85 3.0

20 1.79 4.45

Total (17 + 20) 3.64 7.45

Figure 18 – Concept / preliminary functional design for RBWL-2 scenario 2

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Scenario 3

In November 2015, Melbourne Water approached Mirvac with an alternative option of putting additional

treatment assets (RBWL-2a) immediately to the south of Gunns Gully Road and within the Boral landholding.

The feasibility investigation identified that this approach would reduce the land take for RBWL-2 on the

Monteleone’s land (refer to Figure 19), in comparison to the original scenario (figure 14), and create an asset

on Boral land that can be efficiently delivered and managed. Under this scenario the total wetland / retarding

basin reserve on property 17 would be reduced from 5.6 ha to 3.3 ha. As a consequence, the total wetland /

retarding basin reserve on property 20 and property 10 has increased from 0.0ha to 4.0ha.

Figure 19 – Concept / preliminary functional layout for scenario 3



17 2.05 3.3

20 0.21 1.16

10 1.52 2.84

Total (10, 17 + 20) 3.64 7.3

Whilst the overall land budget requirements for RBWL-2 have still increased in Scenario 3, the topographic and

excavation requirements associated with a wetland construction immediately downstream of Gunns Gully

Road are much more practical and feasible compared to Scenario 2. Scenario 3 reduces the land take on

property 17 (Monteleone) by 2.3 hectares. The increase in land required on property 10 and 20 for the

25

treatment/retarding basin assets is offset to some degree by the reduction in constructed waterway due to the

retardation benefits from the Gunns Gully Road asset.

Melbourne Water have also reviewed the option of providing an asset immediately downstream of Gunns

Gully Road and their assessment has concluded that such an approach is practical and the preferred option.

This is reflected in their current Lockerbie East DSS layout (refer to Figure 20).

Figure 20 – Melbourne Water’s current Lockerbie East DSS layout (April 2016)

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9 Catchment 4 – North West Outfall


Catchment 4 within the Boral landholdings (property 8 and 10) covers an area of approximately 71 hectares

and is located within the northern portion of the Lockerbie East Development Services Scheme. The drainage

outfall for catchment 4 is via sheet flow along a valley floor through the external property to the west just

north of Cameron Street (property 9).

Figure 21: Location of catchment 4 outfall.

In my opinion the PSP layout with respect to drainage catchment 3 should reflect either scenario 1 or

scenario 3.

Locating the entire wetland and retarding basin (Scenario 1) within the “broad, flat depression” on

property 17 is the most efficient in terms of overall land take, construction cost and on-going asset

management.

However I do recognise that from a land equity perspective that an option that distributes some of the

“load” may be an attractive planning proposition. Nevertheless in my opinion any option would need to

include a wetland/basin asset within the “broad, flat depression” of property 17 to deliver a sound

engineering or economic outcome that works with the opportunities presented by the existing landform.

In my opinion Scenario 3 is the best alternative strategy, which now aligns with Melbourne Water’s

current scheme. Scenario 3 distributes the land take across properties 17, 20 and 10.

The current exhibited PSP reflects a drainage strategy similar to Scenario 2. However as demonstrated

through my investigations Scenario 2 is not feasible on topographic and economic grounds. Therefore I

would recommend that the PSP be updated to reflect Melbourne Water’s current Lockerbie East DSS

(which is aligned with Scenario 3).

27


Downstream of the existing drainage line through property 9, the capacity of the existing culverts under the

railway is limited and provides a drainage constraint for the PSP. Both the Lockerbie East DSS and the PSP do

not show any stormwater assets within Boral’s catchment 4 boundary.

The PSP and DSS drainage strategy is based on the conveyance of major flows through the site via road

reserves and the control of minor flows in a piped network. The DSS shows a future drainage pipe connection

and overland flow path in the south west corner of the Boral property (refer to Figure 22). Stormwater quality

treatment and retardation is provided further downstream, adjacent to the railway reserve.

In my opinion the PSP drainage provisions for Catchment 4 are sound and appropriate. The major overland

flows can be safely conveyed along two road reserves. From an asset management perspective, the

consolidation of a single wetland and retarding basin upstream of the railway provides a cost effective

drainage network. The Boral landholding (based on the area of catchment 4) will pay a hydraulic and water

quality contribution towards the construction cost of the off-site wetland/basin and any required land

acquisition costs to deliver the drainage reserve. This will be facilitated and managed through Melbourne

Water’s Development Services Scheme.

Figure 22: Lockerbie East DSS provisions for Catchment 4

In my opinion the current PSP layout provides an appropriate response to manage stormwater runoff

from Catchment 4.

Catchment 4 pipe

connection locations

Stormwater quality treatment and retardation for

catchment 4 provided in this scheme wetland/basin

28

10 Catchment 5 – North Outfall


Catchment 5 within the Boral landholdings (property 8) covers an area of approximately 25 hectares and is

located within the northern portion of the Lockerbie East Development Services Scheme. This catchment is

isolated from the balance of the Lockerbie East DSS and is contained entirely within the Boral property. The

drainage outfall for catchment 5 is via a meandering drainage line/depression that flows through a short

section of the “Nature Conservation Reserve” before entering the Merri Creek.

Figure 23: Location of catchment 5 (shaded pink)


As the outfall for Catchment 5 flows directly through the Nature Conservation Reserve and into Merri Creek,

urban stormwater runoff will need to be treated and managed before being discharged to the surrounding

environs. However it appears that Melbourne Water’s Lockerbie East DSS has not adequately considered this

local catchment outfall (refer to Figure 24). The PSP has also not addressed the drainage requirements for

Catchment 5.

Figure 24: Melbourne Water Lockerbie DSS (no assets shown in Catchment 5)

Catchment 5

low point

29

It appears that the DSS assumed that the stormwater flows from the catchment 25 low point could be diverted

south and connect to the proposed scheme pipeline at Gunns Gully Road. As a result the diversion of the

catchment will increase the wetland/basin requirements on property 9 and 11. In my opinion it is always

preferable for the drainage strategy to work with the natural topography and catchments, therefore my

recommendation would be to remove the diversion and provide a wetland within the low point of catchment

5.

Following recent discussions with Melbourne Water, they have reviewed the proposed approach for

Catchment 5 and have advised that this area (25ha) could be removed from the scheme and considered as a

standalone drainage strategy.

Based upon stormwater quality treatment modelling using MUSIC, the following treatment train is required to

meet the best practice pollutant reduction targets for urban stormwater:

• Sediment pond size of 600m2

• Wetland size of 6350m2

A concept/preliminary functional design of the wetland asset was undertaken to inform the required footprint

and land budget (refer to Figure 25). The overall footprint required for the drainage reserve is 1.7 hectares

which includes the treatment area, batter, sediment drying area, freeboard and room for maintenance.

Figure 25: Wetland concept layout for Catchment 5

In my opinion the current PSP layout is not an appropriate response to manage stormwater runoff from

Catchment 5 as it does not provide a wetland asset in the north western corner of property 8.

I would recommend that the response to manage stormwater runoff should be based upon the natural

catchment boundaries. As a result I believe that he PSP should include a wetland at the low point of

Catchment 5 and provide a drainage reserve land budget of 1.7 hectares.

30

11 Review of Submission 27 (property no 17 – Monteleone family)

I have reviewed submission 27 to the MPA (Monteleone family) in terms of its relevance to drainage and

stormwater in the context of the Mirvac and Boral landholdings. The relevant objections have been extracted

below:

Table 8: Objections raised by submission 27 to the MPA

Page Objection Recommendation

5 The preponderance of the integrated

water management and utilities on their

land without regard to the financial

burden on a single landowner for

infrastructure to deliver the Lockerbie

East DSS, that ultimately benefits the

whole of the scheme

-

11 In addition the Integrated Water design

detailed in plan 14 is inappropriate

doesn’t deliver the “highest and best

uses”; and places a disproportionate

burden on the Monteleone land holding

to deliver the Lockerbie East Drainage

Scheme

A complete independent review of the integrated water

management plan. To remove the excessive and economically

crippling burden on one landholder (the Monteleone

landholder) to deliver the Lockerbie East Drainage Scheme. To

provide suitable compensation for landtake ….

38 The integrated water management plan

grossly burdens the Monteleone

landholdings in terms of land take and

financially in terms of funding

construction costs.

Melbourne Water (MW) totally to revise. Integrated surface

water design for Lockerbie East Drainage Services Scheme

(LEDSS), to eliminate the burden on the Land.

Retarding Basin Wetland – 2 should not

be located as shown on Plan 14

Remove Retarding Basin Wetland – 2 off Land and put onto

adjacent landholder’s Land.

Retarding Basin Wetland – 2 is sized at

4.9ha and straddles two landholders, but

does not show proportions for each

landholder.

MW to provide size and contour of Retarding Basin Wetland –

2 and determine the cost/efficiency of locating RBWL-2 as

shown on the Integrated Water Management Plan No 14.

The submitter recommends removal of that section of RBWL-2

of their land and relocation on the landholder’s land where

surface water is generated

In summary, the objections in Table 8 can be categorised into two key issues:

• Issue 1: The burden in terms of land take and being financially compensated for the loss of land and

construction costs.

• Issue 2: The relocation of RBWL-2 off the property number 17 and relocated to the adjacent

landholder to the east (property 20)

Issue 1:

The planning and provision of new drainage infrastructure to support greenfield development is usually

managed using a development services scheme. A development services scheme comprises a drainage

strategy for an area together with a pricing arrangement that allows Melbourne Water to require developers

to contribute to the cost of the construction of works by Melbourne Water in connection with a development.

Melbourne Water has worked closely with the land development industry over many years in developing

agreed principles for the creation of schemes. A key principle is that “schemes should propose infrastructure

to service development that is optimal in terms of cost and performance”. This generally means working with

the opportunities provided by the natural topography. The scheme approach ensures that planning for urban

development is conducted on a catchment basis (not a property boundary basis) and meets appropriate

31

standards for flood protection and environmental performance, including protection and enhancement of

waterway and biodiversity values. The infrastructure within the scheme is funded by financial contributions

from developers or landowners when development occurs, with all developable properties contributing on the

basis of land area and land zoning.

Development charges provide an equitable means of sharing the costs of drainage infrastructure required for

urban development. The schemes include land acquisition costs plus construction costs so that landholders

who have an asset allocated to their property are appropriately compensated. Melbourne Water in

implementing and managing the scheme have a range of models or options to assist with financing and

delivering the assets.

Therefore based on the above, the DSS principles that have been developed in conjunction with the

development industry (eg UDIA and ALDE) ensure that all landowners are equitably compensated.

Issue 2:

The location, feasibility and assessment of RBWL-2 was documented in Section 8 of this report. I reviewed 3

potential scenarios for the location of RBWL-2 as follows:

Scenario 1 – Wetland and retarding basin (RBWL-2) on property 17

Scenario 2 - Wetland and retarding basin (RBWL-2) split over Patterson Drive between property 17

and property 20

Scenario 3 - Wetland and retarding basin (RBWL-2) on property 17 and an additional

wetland/retarding basin on property 10

The recommendation from Submission 27 was to put RBWL-2 onto the adjacent landholders’s land (property

20). Scenario 2 reviewed this suggestion and in doing so I established that due to topographical constraints it

was not feasible to construct a wetland on the east side of Patterson Drive. The existing surface on the eastern

side has a grade of about 1 in 60, which results in an excavation depth of up to 5.5 - 6 metres. Excavation of

over 5 metres in ground conditions where rock is close to the surface is extremely costly and somewhat

impractical. The depth also increases batters and results in a significant overall land budget increase for

drainage in comparison with Scenario 1.

Locating the entire wetland and retarding basin (Scenario 1) within the “broad, flat depression” on property 17

is the most efficient in terms of overall land take, construction cost and on-going asset management.

However I do recognise that from a land equity perspective that an option that distributes some of the “load”

may be an attractive planning proposition. Nevertheless in my opinion any option would need to include a

wetland/basin asset within the “broad, flat depression” of property 17 to deliver a sound engineering or

economic outcome that works with the opportunities presented by the existing landform. In my opinion

Scenario 3 is the best alternative strategy, which now aligns with Melbourne Water’s current scheme. Scenario

3 distributes the land take across properties 17, 20 and 10 (refer to Figure 20).

32

12 Summary

In summary, my findings with respect to the appropriateness of the proposed surface water treatment in the

PSP relevant to the Mirvac and Boral land are:

The PSP layout with respect to drainage catchment 1 is appropriate from an engineering feasibility

perspective. The location for asset RBWL-6 (wetland and retarding basin) is sound and can deliver on the

design criteria to control peak flows to the equivalent pre-development peak flow rates and best practice

stormwater quality targets. However based upon the modelling and preliminary design undertaken, I

would recommend that the entire “triangular” parcel be set aside as a drainage reserve (ie the area west

of the gas easement, north of Donnybrook Road and east of the property 31 title boundary). In

comparison the PSP only shows a portion of the triangular parcel as drainage reserve.

The PSP layout with respect to drainage catchment 2 is appropriate from an engineering feasibility

perspective. The location for assets RBWL-5 and RBWL-4 is sound and can deliver on the design criteria to

control peak flows to the equivalent pre-development peak flow rates and best practice stormwater

quality targets.

Table 9 of the PSP has allowed for a land budget of 0.55ha and 0.76ha respectively for RBWL-5 and RBWL-

4. Based upon the modelling and preliminary design undertaken, I would recommend that the land

budget be amended to 1.3ha for RBWL-4.

The PSP layout with respect to drainage catchment 3 should reflect either scenario 1 or scenario 3.

Locating the entire wetland and retarding basin (Scenario 1) within the “broad, flat depression” on

property 17 is the most efficient in terms of overall land take, construction cost and on-going asset

management.

However I do recognise that from a land equity perspective that an option that distributes some of the

“load” may be an attractive planning proposition. Nevertheless in my opinion any option would need to

include a wetland/basin asset within the “broad, flat depression” of property 17 to deliver a sound

engineering or economic outcome that works with the opportunities presented by the existing landform.

In my opinion Scenario 3 is the best alternative strategy, which now aligns with Melbourne Water’s

current scheme. Scenario 3 distributes the land take across properties 17, 20 and 10.

The current exhibited PSP reflects a drainage strategy similar to Scenario 2. However as demonstrated

through my investigations Scenario 2 is not feasible on topographic and economic grounds. Therefore I

would recommend that the PSP be updated to reflect Melbourne Water’s current Lockerbie East DSS

(which is aligned with Scenario 3).

The current PSP layout provides an appropriate response to manage stormwater runoff from Catchment

4.

33

I have made all the enquiries that I believe are desirable and appropriate and that no matters of significance

which I regard as relevant have to my knowledge been withheld from the Panel.

The current PSP layout is not an appropriate response to manage stormwater runoff from Catchment 5 as

it does not provide a wetland asset in the north western corner of property 8.

I would recommend that the response to manage stormwater runoff should be based upon the natural

catchment boundaries. As a result I believe that he PSP should include a wetland at the low point of

Catchment 5 and provide a drainage reserve land budget of 1.7 hectares.

whittlesea and mitchell planning schemes amendment gc28 ... · skew 0.33 f2 4.3 f50 14.97 zone 1 a...

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