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2. Mt Eden Main Works Description
2.1 Overview of Works
The main works involve construction along several active work fronts concurrently within the Mt Eden area at any one time, to enable the redevelopment of Mt Eden Station and establish the CRL tie-ins to the NAL. Works will be carried out in a staged fashion. The construction staging and methodologies are described in greater detail in the CEMP.
Within the main works area, there are already other works occurring in accordance with the Mt Eden Enabling Works (OPW60350039) and Normanby Road Early Works (OPW60351423) outline plan packages. This CNV DWP has been prepared to address the cumulative effect where the main works and those works overlap each other.
This CNV DWP has been prepared to address the entire main works area as outlined in Figure 2-1.
In summary, the main works involve:
Ground improvements, in the form of deep soil mixing (contiguous piling and grout injection), within the NAL corridor between Mt Eden Road Bridge and Normanby Road; Bulk excavations and construction of retaining walls along the NAL to provide for the rail trenches and installation of new tracks. The excavation will encounter basalt, which will be removed via rock-breaking and blasting. In places, softer ground conditions are anticipated to be encountered, which may require the use of sheet piles; Construction of the eastern and western crossover structures that enable the CRL rail lines to tie-in to the NAL; Construction of the Porters Avenue and Fenton Street pedestrian and cyclist bridges. Construction of the Normanby Road grade separation bridge, including regrading of Normanby Road and realigning the Boston Road roundabout; Redevelopment of the existing NAL platform; Construction of the CRL platform and the foundations and building structures for the Mt Eden Station building and the ventilation building; and Operation of the TBM, including the conveying of spoil material from the tunnels and the refuelling and general maintenance of the TBM within CSA 4.
2.2 Site Description
The main works will be undertaken in the vicinity of the existing Mt Eden Station and along the NAL, in an existing urban environment. The main works area is generally bounded by the NAL (south), State Highway 1 (east), Dominion Road (west), and Nikau Street (north). The main works will include construction activity along Nikau Street, Ruru Street, Porters Avenue, Fenton Street, Haultain Street, Ngahura Street, Flower Street, Shaddock Street, Mt Eden Road, Normanby Road, Boston Road and Nugent Street.
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CRL Designation 2500-6 KiwiRail Designation 6300
Figure 2-1: Site and extent of main works
2.3 Construction Staging and Methodology
The main works will be divided into several stages across the various work areas.
Generally, the works along the NAL are divided into two stages to allow works on the northern (downmain) or southern (upmain) sections to correspond with the ‘single line running’ of train services through the construction area.
Works within the Mt Eden Station area are divided into 12 stages. Stages 1-4 have already been addressed in the Mt Eden Enabling Works outline plan package, and stages 5-12 will be undertaken as part of the main works. For the new Mt Eden Station building and ventilation building, construction of the foundations and building structures will be undertaken as part of stages 5-12, while the finishing of the buildings, including internal and external fittings, will be completed as part of the future public realm reinstatement.
The construction staging and methodologies are described in sections 2.3 and 2.4 of the CEMP. The night and weekend works (during NAL block-of-line periods) are summarised below.
Normal hours of works are 7am to 10pm Monday to Friday and 7am to 7pm Saturday.
Limited construction works (e.g. oversized plant delivery, Block of Line (BOL) works, or off-peak network utility works) may be undertaken outside the typical working hours. This is to enable worker safety or to minimise traffic disruption, in accordance with the CRL designation and resource
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consent conditions. Operating procedures will be implemented, including communication with affected residents and businesses, to minimise any potential disturbance.
Like many projects, Mt Eden main works construction is restricted at night, during weekends and public holidays because they are times of rest. But there will be times during the main works when night, weekend and public holiday construction cannot be avoided, for the following reasons:
Work in the NAL railway corridor needs to occur when the trains are not running, but the NAL will remain open and active for the duration of construction. This means that BOL periods are critical times for construction. These occur during public holidays, weekends and night-times –because the commuter demand is much less –so the main works must provide for some construction during these times Some construction activities –such as trenching, tunnelling and some forms of piling –need to be completed once they have begun because, if they stop, there is a risk of ground collapse or subsidence
Section 9.2 of this CNV DWP sets out construction hours and noise and vibration conditions that require specific timing. Section 9.2.2 provides guidance for works when they must happen at night.
2.4 Transitioning from Early Works to Main Works
Two enabling/early works packages at Mt Eden have been addressed in separate Outline Plans and have their own CNV DWP and associated SSCNVMPs. Those works and their DWP references are:
Normanby Road Early Works –CRL-MTE-RME-LKA-PLN-800007 Mt Eden Enabling Works –CRL-MTE-RME-LKA-PLN-800016
This main works CNV DWP will become the overarching management document for both the early works and main works, addressing the cumulative effects where the works overlap.
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