Marrickville dive site

Marrickville dive site will be used to launch and support two tunnel boring machines (TBMs) and support the construction of the southern services facility.

Construction activities include:

• excavating and constructing the Marrickville dive structure and tunnel portal
• launching and supporting two TBMs

• manufacturing the pre-cast concrete tunnel lining segments

• supporting the construction of the southern services facility
• supporting the fit-out of the tunnel rail systems.

The dive structure is about 400 metres long and includes an open section before closing into a tunnel portal. The dive structure is designed to be protected from the probable maximum flood level to avoid floodwater flowing into the tunnel.

The southern services facility includes a tunnel water-treatment plant and a traction substation and is located adjacent to the dive structure.

The tunnel water-treatment plant treats wastewater pumped from the tunnels, stations and other underground facilities. The building is about eight metres high, covering an area of about 500 square metres (m²).
 It houses holding tanks, chemical treatment tanks and filters. Drainage pipes connect the water treatment plant with the tunnels.

The substation supplies traction power to the metro trains. The above-ground building (around five metres high) houses the substation and electrical equipment. Trenches and/or above-ground conduits connect the electrical cables into the tunnels.

Surface metro tracks are required to connect the Chatswood to Sydenham component of City & Southwest to the Sydenham to Bankstown upgrade. This is subject to a separate assessment as part of the Sydenham to Bankstown upgrade project. 

• Building and operating a substation to supply power for the running of metro trains.

• Establishing a permanent water treatment plant to capture and treat water collected from the stations.

• Constructing a tunnel portal.

• Building a fire protection wall along the entire length of the dive structure to provide separation between the two metro tracks.

• Building a traction substation.

• Constructing traffic lights at the Edinburgh Road / Bedwin Road / Edgeware Road intersection.

• Investigating opportunities to provide a permanent wall for street art at the dive site in consultation with the local council. 

Dive structures and tunnel portals

Two dive structures and tunnel portals are being built, one at Chatswood and another at Marrickville. These sites, along with the Barangaroo Station site, form the TBM launch sites and provide support for tunnelling operations including:

• spoil storage and removal 

• pre–cast concrete ring segments storage 

• work trains (or similar) to transport staff and materials to the cutting face 

• water and power supply 

• 24–hour fresh air tunnel ventilation 

• separation plant (Barangaroo only) 

• grout batching plant 

• drainage, water treatment and disposal 

• material storage 

• office facilities, work amenities and parking.