4.5 Project evolution and design refinements

Since the inception of the M4-M5 Link and the WestConnex program of works, various options have been considered in the development of the key components of the project, including:

 Interchanges
 Mainline tunnels (including numbers of lanes)
The Iron Cove Link.

A comprehensive options identification and evaluation process using multi-criteria analysis (MCA) was carried out in 2016 to define the optimal project concept design for the Rozelle interchange and the Iron Cove Link. The MCA was undertaken for the Rozelle interchange and the Iron Cove Link as these are complex project components with a number of potential concept design options that could meet project objectives (compared to the mainline tunnels, which have fixed endpoints and therefore fewer viable concept design options). The criteria for the MCA, and their performance attributes, are listed in Table 4-4.

Table 4-4 MCA criteria and performance attributes for the Rozelle interchange and Iron Cove Link

MCA criteria	Performance attributes
Road network operation and safety	 Route connectivity  Road hierarchy  Network efficiency  Wayfinding  Contingency for growth.
Urban design	 Opportunities for multiple site uses  Clear road hierarchy  Opportunities for increased connectivity to public transport  Opportunities to facilitate improved active transport connectivity/linkages.
Constructability	 Construction complexity  Relocation of significant services  Spoil disposal  Flooding risk and drainage capability.
Environment and heritage	 Impact on state listed non-Aboriginal heritage items  Impact on local listed heritage items and heritage conservation areas  Impact on visual amenity  Impact from noise generation  Air emissions  Direct impact on endangered ecological communities, threatened flora and fauna species or groundwater dependent ecosystems  Area of vegetation removal  Impact on open space.
Programme and cost	 Estimate of construction program  Estimated capital construction cost  Estimated 50-year operation and maintenance cost  Estimate of future capacity enhancement cost.

Community and stakeholders	 Community benefits  Impact on business  Stakeholders impacted.

Various options for the components of the Rozelle interchange and the Iron Cove Link were scored and ranked against the MCA criteria with suitable options taken further for more in-depth technical and engineering investigation and analysis.

The sections below provide further detail on the evolution of the key project components.

4.5.1 Interchanges

Suitable interchange locations were identified for assessment based on the following criteria:

 Optimising the benefits to and minimising the adverse impacts on local communities and businesses, including minimising property acquisitions and impacts on heritage items and/or conservation areas and providing new and improved active transport outcomes
 Reducing impacts on open space/recreation areas and creating opportunities for new open space/recreation areas
 Integrating with existing and proposed public transport services
 Meeting the project objective to reduce traffic on Parramatta Road, between Haberfield and
Camperdown
 Maximising connectivity with, and effectively integrating into, the road network and nearby areas of potential urban development
 Facilitating connections to proposed future road projects
 Minimising impacts on the road network during construction.

4.5.2 Mainline Tunnel

Mainline tunnel corridor alignment

The mainline tunnel corridor alignment shown in the WestConnex Updated Strategic Business Case and the January 2016 SSIAR for the project was around 9.2 kilometres long (see Figure 4-6). The alignment was influenced by underground connections to the Wattle Street interchange at Haberfield and the St Peters interchange at St Peters (fixed locations) and by the location of the proposed Rozelle interchange.

The horizontal and vertical alignment of the tunnel corridor between the fixed points (ie the interchanges) was influenced by the following considerations:

 Investigations into geology, geotechnical (ie ground conditions) and groundwater conditions, especially at tunnel portals and crossings under creeks
 Potential for contamination
 Facilitating drainage
 Avoiding long, steep road gradients that would slow heavy vehicles and increase vehicle emissions
 Location of sensitive receivers above the tunnels (including heritage items, educational institutions, places of worship, hospital and medical facilities) that may be potentially affected during construction of the tunnels
 Location of major underground utilities and services (such as water and sewer mains and fibre optic telecommunications cables) that may be costly to relocate and would substantially extend the duration of construction of the project
 Location of existing or proposed subsurface infrastructure (such as for the Sydney Metro City and Southwest tunnels and the Sydney Water City and Pressure tunnels)
Future connections to the Sydney motorway network
Fire and life safety considerations (including emergency egress points from the tunnels).

Geotechnical conditions are a major consideration for tunnelling projects as they determine ground stability to support tunnel infrastructure and the potential for ground movement or settlement at the surface. Geotechnical conditions also affect constructability, including, how difficult, how long and how costly it would be to construct the tunnels.

The decision to remove the Camperdown interchange (see section 4.5.1) provided a trigger to review and confirm the suitability of the alignment of the mainline tunnels.

A number of alignment options for the mainline tunnels were considered to achieve optimal connectivity between the M4 East and New M5 as well as with the Rozelle interchange. Issues considered as part of the alignment review included:

 The suitability of geological conditions
 The provision of the shortest travel distance/travel time
 The location of state heritage listed items at Camperdown
 The orientation of the Wattle Street ramps being constructed for the M4 East project
 The proximity of the mainline tunnels to potential construction sites for tunnelling

 Potential vibration and settlement impacts on sensitive equipment at the RPA Hospital and University of Sydney
The location of the Sydney Metro City and Southwest tunnels
The location of the Sydney Water Pressure Tunnel and Sydney Water City Tunnel
The design of the Rozelle interchange.

The alignment review resulted in a shorter mainline tunnel length of around 7.5 kilometres with a more direct connection between the Rozelle interchange and the St Peters interchange. The eastwest section of the alignment, between the Wattle Street interchange (being constructed as part of the M4 East project) and the Rozelle interchange, was moved slightly north, while the northsouth section between the Rozelle interchange and the St Peters interchange moved further west. These changes to the alignment mean that the mainline tunnels are located around 450 metres and 700 metres west of the RPA Hospital and the University of Sydney at Camperdown respectively.

A detailed description of the mainline tunnel alignment, including connections to the M4 East Motorway at Haberfield, the New M5 Motorway at St Peters, with the Rozelle interchange and the proposed future Western Harbour Tunnel and Beaches Link, is provided in Chapter 5 (Project description).

Number of tunnel lanes

Three options (two, three or four lanes in each direction, plus merges and tie-ins) were originally considered for the number of traffic lanes within each of the mainline tunnels, and assessed against the project objectives.

The key considerations for selection of the optimal lane configuration are outlined in Table 4-5. Table 4-5 Key considerations for the mainline tunnel lane options

Number of lanes in each direction	Key considerations
Two	 Not sufficient to carry the expected traffic volumes  Costly and disruptive to upgrade to three lanes, which would likely be required not long after project opening.
Three	 Would not allow for long-term capacity for forecast traffic volumes  Would integrate with the M4 East mainline tunnel and New M5 mainline tunnel.
Four	 Would allow for long term capacity for forecast traffic volume  Satisfactory levels of performance in the mainline tunnels  Ensures efficient and safe merging and diverging.

While the initial project concept described in the SSIAR included up to three lanes in each direction, revised traffic modelling, which incorporated updated land use inputs, indicated that amendments to the original three lane configuration were required to maintain acceptable lane functionality and traffic flow within the mainline tunnels in future years. Traffic modelling demonstrated that the mainline tunnels would operate more efficiently under a four-lane configuration, to allow for future demand increases. However, while the majority of the mainline tunnels are designed for four lanes (plus merges and tie-ins, they reduce to three lanes at the M4 East mainline tunnel interface and to two lanes at the New M5 mainline tunnel interface. Where the mainline tunnels connect to the Inner West subsurface interchange, they would be two lanes.

Refer to Chapter 8 (Traffic and transport) for further details on lane functionality. Further details on lane configurations and the direction of traffic flow within the tunnels, is provided in Chapter 5 (Project description).

Connection to the Wattle Street interchange

The initial project concept described in the SSIAR did not specify the nature of the entry ramps to the Wattle Street interchange. The initial design comprised one entry ramp consisting of two traffic lanes. During the project development the design was refined to divide the entry ramp into two one-lane entry ramps.

The Wattle Street interchange entry ramp would divide into two, one-lane entry ramps about midway along the entry ramp around Alt Street at Haberfield. These tunnels would then join with the southbound mainline tunnel before the Inner West subsurface interchange. Motorists traveling to the Rozelle interchange would join on the left side of the southbound mainline tunnel, while motorists traveling to the New M5 Motorway would join on the right side of the southbound mainline tunnel.

By giving motorists the ability to choose a merge location dependent on their destination, this arrangement would make driving in the tunnel safer by reducing the amount of lane changes that motorists may need to carry out on the approach to the Inner West subsurface interchange. Further detail on operational traffic is provided in Chapter 8 (Traffic and transport) and Appendix H (Technical working paper: Traffic and transport).

4.5.4 Construction of connections to the proposed future Western Harbour Tunnel and Beaches Link at Rozelle

The WestConnex program of works objectives includes providing the ability to connect an additional harbour road crossing and northern beaches motorway, the proposed future Western Harbour Tunnel and Beaches Link, to the WestConnex motorway. This objective builds on the recommendation of the State Infrastructure Strategy Update 2014 (Infrastructure NSW 2014) to prioritise the proposed future Western Harbour Tunnel and Beaches Link in tandem with, or immediately after, the M4-M5 Link. The location and design of the Rozelle interchange have been selected in consideration of this objective (see section 4.2).

To further support this objective and the policy setting from which this objective has been derived, the construction of tunnels, ramps and associated infrastructure at the Rozelle interchange would be carried out to provide connections to the proposed future Western Harbour Tunnel and Beaches Link.

Constructing tunnels, ramps and associated infrastructure as part of the M4-M5 Link project would allow for orderly planning of these respective projects, and would minimise cumulative construction impacts on the community around the Rozelle interchange. This approach would also avoid or minimise potential delays to the delivery of the urban design and landscaping outcome at the Rozelle Rail Yards proposed as part of the project, which may otherwise be delayed and/or staged due to extended use of a portion of this land for construction activities associated with the proposed future Western Harbour Tunnel and Beaches Link.

The proposed future Western Harbour Tunnel and Beaches Link project would be delivered by Roads and Maritime and is currently in the early stages of environmental investigations and design development to support a separate consultation, assessment and approvals process in the future.

4.6 Other project options considered

The following section outlines options considered within the project including:

 Ventilation facilities
 Construction ancillary facility locations
 Construction methodologies
 Spoil transport and disposal.

4.6.1 Ventilation facilities

Ventilation system design

Most tunnels in NSW are unidirectional, meaning that traffic travels in one direction only within the tunnel. Usually two tunnels are constructed side by side (for example, the Lane Cove Tunnel), or one on top of the other (for example, the Eastern Distributor), to enable traffic to travel in both directions.

On an open roadway, vehicle emissions are diluted and dispersed by natural surface air flows. However, in a tunnel, mechanical ventilation is required to ensure that air quality standards are maintained. This is achieved by providing fresh air to, and removing exhaust air from, the tunnel. The requirements for tunnel ventilation are determined by the vehicle emissions in the tunnel and the limits of pollutant levels set by regulatory authorities. Air quality is managed by ensuring that the volume of fresh air coming into the tunnel adequately dilutes emissions.

The movement of vehicles through a tunnel drives air flow, called the ‘piston-effect’, drawing fresh air in through the tunnel entrance, diluting the vehicle exhaust emissions. In short tunnels up to around one-kilometre-long, air flow resulting from the piston effect of the vehicles is adequate to manage in- tunnel air quality. Emission levels increase as vehicles travel through the tunnel. As a result, in longer tunnels, the flow of fresh air can be supplemented by ventilation facilities which remove exhaust air and/or supply additional fresh air. The need for these features is dependent on tunnel size and length and the number and mix of vehicles using the tunnel. Fans may also be required when the piston effect is insufficient to maintain adequate air flow, such as during periods of low traffic or congested traffic conditions.

Elevated ventilation outlets are used for longer tunnels in urban areas in Australia to disperse tunnel air at a height that ensures dispersion of emissions complies with ambient air quality criteria. A number of options for the design of the ventilation system were considered. These systems are described below and illustrated in Figure 4-14.

Natural ventilation

Road tunnels with natural ventilation rely on vehicle movements, prevailing winds and differences in air pressure between the tunnel portals to move air through the tunnels without the assistance of mechanical ventilation (for example, through the use of fans). In the case of unidirectional naturally ventilated tunnels, the piston effect generated by traffic using the tunnels also assists in the movement of air. Because naturally ventilated tunnels do not have mechanical ventilation outlets, all air from within the tunnels is emitted via the tunnel portals.

Natural ventilation is only acceptable for use in relatively short tunnels (ie less than one kilometre). This is because without the assistance of mechanical ventilation, vehicle emissions can build up within the tunnels leading to unacceptable in-tunnel air quality under some traffic scenarios. Emergency smoke management considerations may also dictate a mechanical solution. For these reasons natural ventilation is not practical for longer road tunnels such as those proposed for the project. Natural ventilation would not achieve acceptable in-tunnel air quality under low vehicle speed conditions or during emergencies, and is therefore not a viable ventilation design for the project.

Longitudinal ventilation

The simplest form of ventilation for road tunnels is longitudinal ventilation, in which fresh air is drawn in at the entry portal and passes out through the exit portal with the flow of traffic. For longer tunnels, the air flow is supplemented by fans that are used when traffic is moving too slowly to maintain adequate air flow, or to draw air back from the exit portals against the flow of exiting traffic. This air is then exhausted through an elevated ventilation outlet to maximise dispersion. All road tunnels longer than one kilometre built in Australia in the last 20 years have been designed and operated with longitudinal ventilation systems. This includes the NorthConnex, M4 East and New M5 tunnels, which are all approved and under construction.

Transverse ventilation

Another way to ensure adequate dilution of emissions is to provide fresh air inlets along the length of the tunnel along one side, with outlets on the opposite side. This system requires two ducts to be constructed along the length of the tunnel: one for the fresh air supply and one for the exhaust air. Transverse ventilation has been used in the past when vehicle emissions produced greater levels of pollutants than they do today. A transverse ventilation system is more expensive to construct because of the additional ducts that need to be excavated for each tunnel. This type of system is less effective than a longitudinal system for controlling smoke in the tunnel in case of a fire. It is also more energy intensive as more power is consumed to manage air flows.

Semi-transverse ventilation

Semi-transverse ventilation combines both longitudinal and transverse ventilation. Fresh air can be supplied through the portals and be continuously exhausted through a duct along the length of the tunnel. Alternatively, fresh air can be supplied through a duct and exhausted through the portals.

Preferred option

The development of cleaner vehicles in response to cleaner fuel and emissions standards has led to a significant reduction in vehicle emissions over the past 20 years. Where longitudinal ventilation was once not suitable for long tunnels, due to the need to supply large volumes of fresh air to dilute vehicle emissions, a well-designed longitudinal ventilation system can maintain acceptable air quality in long tunnels and is considered the most efficient and effective tunnel ventilation system (Advisory Committee on Tunnel Air Quality (ACTAQ) 2014).

Although all three mechanical ventilation systems described above could be designed to meet in- tunnel air quality criteria, a longitudinal system with elevated ventilation outlets has been selected as the preferred option for the project, and the other tunnel projects forming part of the WestConnex program of works, for the following reasons:

 It is less costly to construct and operate than transverse systems
 It is able to ensure emissions are dispersed and diluted so that there is minimal or no effect on
ambient air quality
 It is more effective for the management of smoke in a tunnel in the event of a fire
 It is able to meet the requirement to minimise portal emissions as far as practicable.

The effectiveness of elevated ventilation outlets in dispersing emissions is well established. Chapter 9 (Air quality) presents the air quality assessments for both in-tunnel and external air quality. An overview of the ventilation system design and operation is provided in Chapter 5 (Project description).

Ventilation outlets and portal emissions

Since 1998, a key operating requirement for road tunnels longer than one kilometre in Sydney has been to minimise emissions through the portals, or tunnel exits. Essentially, this means that the ventilation systems are designed to have zero portal emissions, with all air being drawn in from the exit portals against the flow of traffic, and expelled through an elevated ventilation outlet. The ventilation system needed to achieve this requires more fans than it would if portal emissions were permitted, with higher capital and operational costs.

Drawing air from the exit portal increases the quantity of ventilation air to be discharged through the ventilation outlet and can increase the diameter of the outlet required, or require an additional outlet close to the exit portal. The need for zero portal emissions also means that the ventilation fans in the exit ramps need to operate all the time, regardless of whether in-tunnel or ambient air quality warrants this operation. This incurs higher energy usage than if portal emissions were permitted.

The feasibility of allowing portal emissions for the Iron Cove Link was investigated on the basis that it is a short tunnel (about one kilometre) with only two traffic lanes in each direction and therefore it would generate lower pollution concentrations than the larger and longer mainline tunnels. If portal emissions were acceptable, then the construction of at least one and potentially two outlets (ie one at each end of the tunnel), and associated infrastructure including ventilation tunnels, could be avoided. Health impact risk factors applied to the change in concentration of fine particles with a diameter less than 2.5 micrometres (ie PM2.5) were used as the criterion for acceptability of portal emissions. This initial screening assessment demonstrated that the criterion would be exceeded and there was therefore no further consideration of portal emissions for the Iron Cove Link.

Air filtration at the ventilation outlet

Only a small proportion of road tunnels around the world are fitted with air treatment systems. It has been shown that control of pollutants at the source is significantly more effective in improving local and regional air quality (ACTAQ 2014; National Health and Medical Research Council 2008). Control measures include minimising road gradients, increasing tunnel height and providing a large tunnel cross-sectional area. The tunnel ventilation system for the project would be designed with appropriate levels of conservatism and redundancy to ensure compliance with air quality goals and limits.

No in-tunnel filtration system is proposed for the project because the modelling undertaken demonstrates that the ventilation system would be effective in ensuring compliance with the in-tunnel air quality criteria. If in-tunnel air quality levels could not be achieved with the ventilation system proposed, the most effective solution would be the introduction of additional ventilation outlets and additional locations for fresh air supply. The inclusion of tunnel filtration was evaluated and found not to provide any material benefit to air quality or community health, and is discussed in the air quality impact assessment in Appendix I (Technical working paper: Air quality).

The inclusion of filtration would result in no material change in air quality in the surrounding community when compared to the current project ventilation system and outlet design. Any predicted changes in the concentration of pollutants would be driven by changes in the surface road traffic.

Ventilation facility locations

The main considerations in relation to ventilation facilities include minimising local air quality impacts on nearby receptors and maximising the operational efficiency of the tunnel ventilation system. Minimising local air quality impacts is primarily achieved through the design and operation of the ventilation outlet. However, the location of road tunnel ventilation outlets is very important for the efficiency of the tunnel ventilation system. The project includes ventilation outlets at Haberfield, St Peters (Campbell Road) and Rozelle (in two locations). More detail on the location of the ventilation facilities is provided below and in Chapter 5 (Project description).

Background and design considerations that affect location of ventilation facilities

As described above, a longitudinal ventilation system is proposed for the project. A longitudinal system relies on single directional traffic flow; therefore, separate tunnels for northbound and southbound traffic would be required. This also results in the need for a ventilation outlet at each end of the mainline tunnels, with at least one outlet for each tunnel. The location of the project ventilation facilities is shown in Figure 4-15.

The ventilation outlets ideally need to be located close to the end of the tunnels, before the exit portals. This allows some air to be drawn into the portals against the traffic flow. This forced reverse flow is achieved by jet fans within the exit ramp and tunnel. Minimising the use of these fans increases the performance of the tunnels and reduces operational power consumption and cost, while providing environmental benefits, by reducing greenhouse gas emissions associated with energy generation.

The locations of ventilation facilities for the project were influenced by the design of the approved M4 East and New M5 projects. Both of these projects take into account the development of ventilation facilities for the M4-M5 Link by providing space in their respective project footprints for the development of these facilities. The construction of the ventilation facility at Haberfield (the Parramatta Road ventilation facility) that would be shared by the M4 East and M4-M5 Link projects was approved and is being constructed as part of the M4 East project, however the fitout and use of the M4-M5 Link section of the ventilation facility is subject to assessment and approval through the M4-M5 Link project. At St Peters, the ventilation facility would be located at the northern end of the project footprint of the New M5 project at the St Peters interchange, however the approval for the construction, fitout and operation of a new ventilation facility for the M4-M5 Link is subject to assessment and approval through the M4-M5 Link project. Locating ventilation facilities within the project footprints of the previous WestConnex projects minimises land acquisition requirements and streamlines the design and construction process for the M4-M5 Link.

The project also includes construction of a ventilation outlet for the proposed future Western Harbour Tunnel and Beaches Link project, as part of the Rozelle ventilation facility at the Rozelle Rail Yards (further detail is provided in Chapter 6 (Construction work)).

4.6.2 Construction ancillary facility locations

Twelve construction ancillary facilities have been identified to support the construction of the project. These are sites that would be used during construction of the project for a mix of civil surface works, tunnelling support and administrative purposes. The locations identified for the construction ancillary facilities also give consideration to the following criteria:

 The locations of key project infrastructure – where feasible, the construction ancillary facilities would be located within or adjacent to land which would be used for permanent operational infrastructure
 Co-locating sites with other WestConnex projects where possible – the project would use construction ancillary facilities approved for use by the M4 East and New M5 projects at Haberfield and St Peters respectively
 Land is suitable for use – this included consideration of surrounding land uses, biodiversity and heritage values and minimising disruption to communities
 Accessibility – sites would be located close to arterial routes for spoil haulage and would minimise use of local roads through residential areas

 Minimising private property acquisition – the aim is to utilise government owned properties where possible
Construction program implications – site selection that would enable construction works to be completed as efficiently as possible.

Twelve construction ancillary facilities are described and assessed in this EIS. The number, location and layout of construction ancillary facilities would be finalised as part of detailed construction planning during detailed design and would meet the environmental performance outcomes stated in the EIS and the Submissions and Preferred Infrastructure Report and satisfy criteria identified in any relevant conditions of approval.

To assist in informing the development of a construction methodology that would manage constructability constraints and the need for construction to occur in a safe and efficient manner, while minimising impacts on local communities, the environment, and users of the surrounding road and other transport networks, two possible combinations of construction ancillary facilities at Haberfield and Ashfield have been assessed in this EIS (see Table 4-6). The construction ancillary facilities that comprise these options have been grouped together in this EIS and are denoted by the suffix a (for Option A) or b (for Option B) eg C1a Wattle Street civil and tunnel site.

Table 4-6 Possible construction ancillary facility combinations at Haberfield and Ashfield assessed in this EIS

While the Option A sites were identified to minimise the project footprint of the M4-M5 Link and to maximise the use of facilities and infrastructure to be constructed by the M4 East project, the Option B sites provide a number of benefits over the Option A sites including:

 Avoid or minimise impacts to the timing of delivery of the M4 East Urban Design and Landscape Plan and the M4 East Legacy Project around Walker Avenue at Haberfield, by minimising the amount of land at the surface that would be used for construction of the M4-M5 Link project
 Avoid construction fatigue for receivers adjacent to the Option A sites such as along Wattle Street, Walker Avenue and Northcote Street due to concurrent project construction for the M4 East and M4-M5 Link projects. Notwithstanding this, the Parramatta Road West civil and tunnel site (C2b) would be adjacent to a construction site for the M4 East project, which would mean nearby receivers, particularly around Bland Street at Ashfield, would be subject to cumulative construction impacts (such as construction fatigue)
Safeguard the project program by limiting dependence on the completion of M4 East works at the Option A sites before these sites can be made available for use for construction of the project.

Throughout the development of the project, a number of potential construction ancillary facility sites were investigated but were excluded from the project for various reasons. These sites and the reasons they do not form part of the project are outlined in Table 4-7. The location of these sites is shown in Figure 4-17. Other design refinements related to construction ancillary facilities included limiting construction activities at Darley Road civil and tunnel site (C4) to standard construction hours only, where out-of-hours works were initially proposed. The refinement was included to minimise noise impacts on surrounding receivers and minimise heavy vehicle movements on local roads outside standard construction hours. This refinement was made following consultation with relevant stakeholders and the community.

Chapter 5 (Project description) includes details of the locations of the construction ancillary facilities that do form part of the project. Refer to Chapter 6 (Construction work) for further information on the anticipated works planned at each site and the indicative timing for these works. The potential impacts associated with the construction ancillary facility sites are presented in the relevant technical impact assessment chapters in this EIS.

Table 4-7 Construction ancillary facility options that were investigated but do not form part of the project

Site name	Works proposed	Reasons for excluding this site	Project function provided by
Blackmore Park, Leichhardt	Tunnel and civil site – support tunnelling of the mainline tunnels including launching road headers and spoil management and haulage	Would require temporary loss of passive and active open space and vegetation removal. Community and stakeholder feedback requesting that impacts on public open space be avoided was also taken into consideration during relocation of the ancillary facility site. Access to the site was constrained by a narrow road (Canal Road) and the restricted height clearance under the light rail bridge.	Darley Road civil and tunnel site (C4)
Easton Park, Rozelle	Tunnel and civil site – construct the dive and cut and cover tunnel portals to connect the surface roads at the Rozelle interchange to the Iron Cove Link tunnel	Would require temporary loss of passive and active open space, vegetation removal and impacts on heritage items (Easton Park and Sydney Water sewage pumping station). Community and stakeholder feedback requesting that impacts on public open space be avoided was also taken into consideration during relocation of the ancillary facility site. Design optimisation led to the relocation of cut-and-cover tunnel structures to within the Rozelle Rail Yards, therefore this site could be avoided. Community and stakeholder feedback requesting that impacts on public open space be avoided were also taken into consideration during relocation of the ancillary facility site. Use of this site also required closure of part of Lilyfield Road.	Rozelle civil and tunnel site (C5)
Moore Street, Leichhardt	Tunnel and civil site – support tunnelling of the mainline tunnels including launching road headers and spoil management and haulage	There is the potential for the site to be contaminated given current and previous land uses. Alternative sites in the vicinity that would result in less property impacts were identified. Potential access constraints for heavy vehicles between the site and the arterial road network, and the associated amenity impacts on nearby receivers along the haulage route, were also taken into consideration.	Darley Road civil and tunnel site (C4)
Ross Street, Forest Lodge	Tunnel and civil site – support tunnelling of the mainline tunnels including launching road headers and spoil management and haulage	Removal of the Camperdown interchange and subsequent change to the mainline tunnel alignment meant that the length of the temporary construction access tunnel from this site increased, which would have resulted in significant delays to the construction program. Limitations on access for heavy vehicles between this site and the arterial road network were also taken into consideration during relocation of the construction ancillary facility. Proximity to heritage items and the education precinct of University of Sydney were raised as concerns by stakeholders.	Pyrmont Bridge Road tunnel site (C9)

Site name	Works proposed	Reasons for excluding this site	Project function provided by

Parramatta Road, Forest Lodge	Tunnel and civil site – support tunnelling of the mainline tunnels including launching road headers and spoil management and haulage	Removal of the Camperdown interchange and subsequent change to the mainline tunnel alignment meant that the length of the temporary construction access tunnel from this site increased, which would have resulted in significant delays to the construction program. Limitations on access for heavy vehicles between this site and the arterial road network were also taken into consideration during relocation of the construction ancillary facility. Proximity to heritage items and the education precinct of University of Sydney were raised as concerns by stakeholders.	Pyrmont Bridge Road tunnel site (C9)
City West Link, Lilyfield	Tunnel and civil site – support tunnelling of the mainline tunnels including launching road headers and spoil management and haulage	The temporary access tunnel between the site and the mainline tunnels would be around 750 metres in length. Constructing this temporary access tunnel before tunnelling of the mainline could begin from this site would have resulted in substantial construction program delays. There is the potential for the site to be contaminated given current and previous land uses. The site is in proximity to active light rail corridor facilities and would require tunnelling under the light rail line. There are level differences between the site and surrounding roads which would constrain access.	Rozelle civil and tunnel site (C5)
Angel Street/ Railway Lane, Newtown	Tunnel and civil site – support tunnelling of the mainline tunnels including launching road headers and spoil management and haulage	The site, including the buildings associated with the former Newtown Tram Depot, is listed on the state heritage register. There is the potential for the site to be contaminated given current and previous land uses. Heavy vehicles would need to use narrow, one-way local roads to access the site, which would have resulted in amenity impacts on nearby receivers. There was a high potential for the site to be contamination, given its previous land uses. The site was in close proximity to an active rail corridor and residential areas. Distance of this site to the arterial road network posed constraints for spoil haulage.	Campbell Road civil and tunnel site (C10)

Site name	Works proposed	Reasons for excluding this site	Project function provided by

Derbyshire Road, Leichhardt	Tunnel and civil site – support tunnelling of the mainline tunnels including launching road headers and spoil management and haulage Subsequently, construction workforce parking	The site was immediately adjacent to Sydney Secondary College Leichhardt Campus, a sports oval, the State Transit – Leichhardt Depot and Pioneers Memorial Park. Heavy vehicles would have to utilise Derbyshire Road. A locally listed heritage item (Former State Rail Authority cable store and traffic office, including interiors, which includes two buildings) would be required to be demolished. Community and stakeholder feedback requested that consideration be given to relocating this site.	Darley Road civil and tunnel site (C4)

4.6.3 Tunnel construction methodologies

A number of tunnel construction methods were considered and are described in the following sections.

Tunnel boring machine

A tunnel boring machine (TBM) is a specialist machine that excavates a circular bore of fixed diameter by rotary action. The machine comprises a rotating head fitted with disc cutters, drag bits and clay spade. Soft ground TBMs include a facility for the fixing of fabricated permanent wall lining panels (generally precast concrete) immediately behind the cutting face. Hard ground (rock) TBMs include a gripper facility that allows the TBM to push off the wall of the excavation. TBMs are normally custom made to suit the particular requirements of the project and require considerable time to deliver and mobilise for full operation. They also require a large open area on site to assemble and align in position for driving.

Drill and blast

The drill and blast excavation method involves a sequence of drilling holes, charging the holes with explosive, blasting, mucking out, and installing roof and wall ground support. The method is an efficient and cost effective way of excavating in rock, and provides an effective tunnel excavation method which assists in achieving an overall shorter project delivery. This method offers the shortest exposure to noise and vibration for residents and businesses above the tunnels, compared to other methods of tunnel excavation.

Roadheader excavation

Roadheaders are commonly used for excavation in sandstone and have been successfully used in other tunnel projects in Sydney, including other WestConnex projects. A roadheader is specialised tunnelling equipment that excavates with picks mounted on a rotary cutter head attached to a hydraulically operated boom. In areas of very hard rock, ripper dozers and rock breakers would also be used to assist with the excavation. The excavated material would be continually removed by conveyors onto dump trucks designed to operate underground. The excavated material would then be stockpiled near the tunnel entrance, from where it would be removed via truck for disposal or reuse. As the excavation advances, temporary or permanent ground support would be installed behind the excavation face. The support could be permanent or temporary and would normally include rock bolts, steel mesh and sprayed concrete.

Roadheaders offer advantages over tunnel boring machines for:  The excavation of varying cross sections, caverns and niches

 The excavation of cross passages
The ease by which roadheaders can be moved to different parts of the tunnel alignment.

Preferred tunnel construction method

It is anticipated that a combination of the roadheader excavation and drill and blast methods would be used for the project, for the following reasons:

 The combination of methods speeds up excavation compared to work being undertaken solely with roadheaders
 It is more economic because it takes less time and generates less spoil than a tunnel boring machine
 The road geometry and cross-sectional dimensions of the project tunnels precludes the use of TBMs for excavation
 It reduces the noise and vibration impacts on residential and commercial properties due to the shorter duration impacts associated with blasting compared to other tunnel construction methods
Geological conditions along the alignment are suitable for both roadheader excavation and drill and blast methods.

Further detail on the tunnelling construction approach is provided in Chapter 6 (Construction work).

4.6.4 Spoil storage, transport and disposal options

Construction of the project would generate around 4.5 million cubic metres of spoil, which allows for numerous spoil reuse and disposal options. Consideration has been given to the various modes available to store and transport spoil, as outlined below.

Spoil storage options

The development of the project identified and incorporated the opportunity to store spoil within the M4 East project tunnels at Haberfield. The refinement was included to reduce heavy vehicle movements on surface roads (and associated traffic congestion and noise impacts on adjacent receivers) and minimise potential for dust mobilisation and associated air quality impacts.

Spoil transport options

Rail

The benefit of rail as a spoil transport option is the ability to move large volumes, while reducing the number of heavy vehicle movements on the wider road network. However, this method presents the following issues:

 There are very few spare train paths on the Sydney rail network, which presents logistical challenges
 The material would need to be double (or possibly triple) handled, as trucks would be required to move material to the train loading facility, and potentially from the rail facility to its final location, if this does not have rail access
Infrastructure upgrades would potentially be required at rail yards which are part of the Sydney Metropolitan Freight Network (at Port Botany or Enfield) to allow the train loading facility to receive the material.

Barge

As with rail, the main benefit of barge transport is the ability to move large volumes of spoil, while reducing the number of heavy vehicle movements on the wider road network. However, this option presents a number of issues including:

 The material would need to be double (or possibly triple) handled, as trucks would be required to move material to the barge loading facility, and potentially from the barge to its final location, if this does not have barge access
 Infrastructure upgrades would potentially be required to allow the barge loading facility to receive the material.

Notwithstanding this, further investigations would be undertaken of spoil transport options, including the potential barging of spoil, during detailed design.

Heavy vehicle

Spoil removal using heavy vehicles (ie trucks) would involve transporting material from the construction sites directly to its final destination and would occur primarily via the arterial road network. However, as trucks would be limited to transporting relatively small volumes of spoil (around 25–30 cubic metres per truck), a large number of truck movements would be required. The use of trucks would therefore streamline the handling of spoil as no double or triple handling would be required, but would result in a higher number of trucks on the road. This increase is considered acceptable given trucks are the most appropriate transport option for the location of the spoil disposal sites. Transport by other transport options (rail and barging) would still require trucks to initially move material to the loading facility and, potentially, to the final destination.

Heavy vehicles are the preferred spoil transport option for the project. Chapter 8 (Traffic and transport) provides a summary of heavy vehicle movements, including spoil related haulage. A summary of spoil haulage routes from the various construction sites is provided in Chapter 23 (Resource use and waste minimisation). Use of local roads would be avoided where possible, with the main haulage routes being via major arterial roads such as City West Link, Parramatta Road, the M4 Motorway, the Princes Highway and the M5 Motorway. There may be an opportunity for spoil generated at the Haberfield and St Peters ends of the mainline tunnel to be transported via the completed M4 East and New M5 tunnels rather than via surface roads, where practicable. This option would be investigated further by the construction contractor.

Spoil reuse and disposal options

As described in Chapter 23 (Resource use and waste minimisation), spoil would be beneficially reused as part of the project before alternative spoil disposal options, such as other infrastructure or development projects, were pursued. Residual spoil waste which cannot be reused or recycled would be disposed of to a suitably licensed landfill or waste management facility. Potential opportunities for reuse of spoil within the project include use for the formation of embankments and earth mound noise barriers, site rehabilitation and landscaping, road upgrades, and infill for temporary tunnel access shafts and declines. At least 95 per cent of usable (eg uncontaminated) construction and demolition waste is anticipated to be reused and/or recycled as part of the project.

Six potential spoil management sites, ranging from between 25 to 50 kilometres from the project footprint, have been identified as possible receiving sites for excess spoil from the project. During the development of the project, the proposed Western Sydney Airport was also identified as a potential spoil management site. Determination of the final destination(s) for spoil from construction of the project would be made during the detailed design stage, and may include more than one disposal site.

Alternative and/or additional spoil reuse options may be identified by the construction contractor as the project progresses.