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One of the most complex and challenging stages of the $600 metre upgrade of Auckland’s rail services is under way. HUGH DE LACY reports.
Road traffic at the roundabout slams to a halt and backs up sometimes for hundreds of metres as trains rush between Britomart and the outer suburbs of Waitakere no fewer than 80 times a day. The same thing happens to a lesser extent further down the line where the railway crosses a succession of other busy intersections. Not only has the railway caused major disruption to road-traffic flows through the suburb made notable by its pottery and stoneware industries, but it has stifled the development of New Lynn itself, which is otherwise a busy town centre and the hub of the area’s transport services. Now that’s in the process of changing thanks to a $120 million project to drop the railway and station into a trench as much as eight metres deep, allowing the road traffic to pass unhindered above on a series of bridges. It seems on the face of it a simple-enough expedient, but it’s hugely complicated by the necessity to keep both the road and rail traffic operating throughout the 18 months or so it will take to complete, and by the crumbly clay sub-surface – it’s said to have the consistency of ice cream - which gave rise to the pottery industry. Then there’s the complexity of the infrastructural bureaucracy which, in a greater Auckland notorious for its parochialism, brings together the Waitakere City Council (WCC), the Auckland Regional Transport Authority (ARTA), the Auckland Regional Authority (ARC), rail operator Toll NZ and rail network owner Ontrack. The New Lynn rail trench project is one of the two biggest single elements of Project Dart (Developing Auckland’s Rail Transport), the Auckland rail infrastructure upgrade that will eventually lead to electrification of the commuter rail network, and for which $600 metre was provided by central government in the 2006 Budget. Only the electrification itself, due for completion in 2013, will cost more. Called Dart 6, the New Lynn trench design-and-build contract went to tender in late 2006 and the initial design element was won last year by a consortium comprising Fletcher Construction, engineering planning and management firm Beca, and design company Synergine. The project manager bringing these diverse agencies together is Ontrack’s Peter King, with overall direction coming from line company’s Ted Calvert. “Building the trench is a big and challenging job which has to be done while the trains are kept running and the town centre traffic flowing as much as possible,” King told Contractor. “We’ve had on average about 50 people working full-time on the design, plus another 70 called in to cover various aspects of design and management.” The New Lynn line is presently a single track but will end up a double line with the station platform in between below the Clark Street/Ranking Avenue roundabout, and with commuter access from nearby Memorial Drive. Over seven kilometres of double-tracking of the rail-line west of the trench was completed by Ontrack last year, a further five kilometres is due by the middle of this year, while to the east the double-tracking to Whau Creek and Avondale is under way. The key machinery elements of the New Lynn project are the mobile cranes that will carry out the 100,000 cubic metres of excavation work along the one-kilometre trench. There will be up to 13 of them working in three spreads, each of which is dominated by one tracked crane of 100 tonne backed by another of 60 tonne. Only one of the 100-tonners was available for the project in New Zealand, while the two others and a couple of the 60 tonners have had to be hired in from as far afield as Hong Kong, Italy and Dubai. Their first job will be to install retaining walls up to 40 metres deep along the length of the trench, then to excavate the trench itself at the rate of 1200 tonne, or 180 truckloads, a day. To provide working room for the machinery the present single line has been shifted to the southern side of what will become the trench while the northern side is being excavated and the line laid and hooked up to the existing track. Once the track has been completed on the northern side of the trench it will be hooked up to the network, and the temporary track removed to allow excavation of the southern side. The preliminary work, including the installation of the temporary track and platform on the south side of the trench-line is under way, and the main excavation and construction is due to start soon with completion expected about the end of 2009. Other preliminary work begun earlier this year included moving water, power and communications services out of the way of the excavators, installing site access and clearing vegetation. Of the 60,000 cubic metres of concrete the full project will require, more than half will go into the retaining walls, as will most of the 1200 tonne of reinforcing steel, and at peak 600 cubic metres of concrete will be poured a day. On-site staff numbers will frequently be as high as 200. The trench will start from the Titirangi Road rail-overbridge at the western end, sloping downwards at a grade of one in 56 until levelling out at the station platform between Memorial Drive and Hetana Street. It will re-emerge onto the naturally flat contour at Portage Road, which will continue to be a level crossing, albeit with upgraded traffic control and safety features. Four bridges will be built over the trench, two of them funded by the WCC, eliminating in particular the notorious Clark Street/Rankin Avenue level crossing. The other bridges will be at Veronica Street, the Hetana Street/Totara Avenue intersection and at the Memorial Drive/Totara Avenue intersection. The upgraded New Lynn station and platform, sitting between the two tracks at the bottom of the trench, will be connected to a new bus station, on the surface on the south side, by the Memorial Drive bridge. While the trench is being dug and the new station installed, a second temporary station is being sited further down Totara Avenue, opposite the LynnMall shopping complex, to allow easy access to bus services. Inevitably a project of this scale will involve disruption of both road and rail services, and Ontrack chairman Cam Moore has appealed to the people of New Lynn for tolerance. “When the work is finished we will have more trains [up to one every 10 minutes] travelling through the heart of New Lynn causing a minimum of disruption to the movement of people and vehicles, and to the life of the community. There is a ‘but’, however. We won’t be able to do the work without causing disruption either to the community or to the rail services.” The community will feel the impact from about the middle of this year through construction diversions and road closures. Most of the work will be done during normal working hours but there will be times when the contractors will have to work at night, and over weekends and public holidays. All that will seem as nothing though once the project is complete, and the frustrations and delays – particularly at the Clark Street/Ranking Avenue roundabout – become a thing of the unmourned past. Contractor Vol.32 No.4 May 2008 |
If ever there was a nightmare of a road-rail traffic intersection, it’s the Clark Street/Rankin Avenue roundabout in the Auckland suburb of New Lynn. It’s the point where those two traffic-intensive streets meet Totara Avenue, which arrives at the roundabout from the south-west before swinging east to follow the path of the computer rail-line heading to the Britomart transport centre in Auckland’s CBD.