Western tunnel entrance construction plans
The options for the Western tunnel entrance involve construction works on Childers Street to build a retaining wall to support the embankment on the northern side of the rail corridor (east of Kensington Road), which is to be widened to accommodate the Metro Tunnel tracks.
A 'decline structure', or descending tracks, will be built so trains can enter the Metro Tunnel.
The decline structure and tunnel entrance are proposed to be built via a 'cut and cover' method, which will see them excavated from the top down and the surface then reinstated over the top of the tunnels.
A construction support site on Hobsons Road is proposed for both options and a tunnel boring machine (TBM) retrieval box will also be built to support tunnelling works.
It is not proposed that any construction activities for the Metro Tunnel will be undertaken in JJ Holland Park, other than potential upgrades to the shared use path.
Under Option A, there is an option to locate a substation in the Lloyd Street Business Estate to provide power for the operation of the project's tunnels and stations. The preferred site for the substation is on Government owned land to the north of Arden Street (between CityLink to the west and Langford Street to the east).
Key construction activities
Key construction activities to build the western tunnel entrance would include:
- Preparatory works including tree protection and removal, and relocation of utilities including the electrical high voltage transmission towers, gas main, and water and drainage services.
- Demolition of acquired buildings.
- Relocation of public car parking and the shared pedestrian and cyclist path on Childers Street.
- Construction of TBM retrieval shaft.
- Works to install temporary access to the Lloyd Street Business Estate (Option A only).
- Construction works to widen the rail reserve to accommodate additional tracks and install retaining structures alongside Childers Street.
- Cut and cover excavation of the decline structure and tunnel entrance construction.
- Track works and the installation of signalling and communications systems.
- Site reinstatement including upgrading shared pedestrian and cyclist path, altered parking and road management and landscaping.
During construction, Childers Street will be closed to traffic and used for construction activities. This will require the occupation of car parks along Childers Street and the permanent diversion of the shared use path along the railway line. In Option A, some car parking in Childers Street will be removed. For Option B, most of the car parks will be retained.
In addition to the temporary closure of Childers Street, the construction of the western tunnel entrance is expected to impact traffic and car parking on Ormond, Tennyson and Altona streets, Bakehouse Road and McClure Road during different stages of works.
Proposed construction traffic routes for the western tunnel entrance precinct take advantage of the site's close proximity to CityLink and a number of major arterial roads. The proposed routes aim to move construction traffic away from local streets and on to these major connections as quickly as possible.
A number of rail occupations (periods where trains stop running so works can take place) will be required to connect the Metro Tunnel to the Sunbury line. These occupations would potentially disrupt services on parts of the rail network.
The construction contractors will be required to develop and implement measures to minimise disruption to the transport network during construction of the Metro Tunnel.
A number of mitigation measures, or 'Environmental Performance Requirements', have been proposed to avoid, reduce or manage construction impacts for the western tunnel entrance precinct in Kensington.
Some of the recommended mitigation measures for the western tunnel entrance include:
- Planning and carefully managing access routes to minimise impacts on residents and users of the area.
- Undertaking property condition surveys before construction begins to record the existing condition of buildings and residences in close proximity to tunnels and construction sites.
- Providing alternative routes for pedestrians, cyclists and vehicles to maintain connectivity and safety for road and shared path users of Childers Street, JJ Holland Park and South Kensington Station.
- Finding alternative routes for trucks to access the Lloyd Street Business Estate in Kensington.
- Developing an occupations plan that minimises the disruption to railway services during construction.
- Implementing measures for providing advance notice of significant milestones, changed traffic conditions and periods of potential high noise and vibration activities.
- Monitoring dust and air quality, in line with Environment Protection Authority Victoria requirements, and addressing air quality requirements for nearby residents and businesses.
- Ensuring above-ground structures are responsive to heritage places in terms of height, massing, form, façade articulation and materials.
- Preserving the broader landscape and recreational values in the reinstatement of shared pathways and other public spaces.
It is estimated that construction of the western tunnel entrance will take around three years. Subject to planning approval, early works would begin in early 2017 with major works commencing in 2018.