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A notorious black-spot on State Highway 1 is getting a long-overdue makeover. BY HUGH DE LACY.
Now the $12 million project looks like being finished a year ahead of schedule. On track for completion about June or July if the weather holds, the State Highway 1 realignment eliminates the level crossing by the Royal Hotel at Ohingaiti village with the installation 700 metres to the south of a train tunnel-cum-culvert over which the highway crosses to the western side of the railway line. The steep and windy road up from the valley of the Makohine Stream, framed by the 72.5 metre high Makohine railway viaduct, has long been an accident black-spot in its own right, compounded by the level crossing on the plateau at Ohingaiti where South African immigrants Renee and Brent Coombes were killed in a collision with a goods train in July 2007. The 3.6 kilometre realignment, which has been a top priority for the Manawatu-Wanganui region, will eliminate the curves on the Makohine hill as well as the two 25kph right-angled bends on the level crossing, bringing the whole stretch of highway up to 100kph standards. The main contract was won by the Palmerston North company Stringfellows Civil Engineering Contractors with a bid of $10.6 million, and work began in March 2008.
“One of the unfortunate problems on the existing highway has been the geometry of the top curve as you come up the hill,” NZ Transport Agency manager for the Wanganui district Errol Christiansen told Contractor. “For southbound traffic it’s got a speed advisory sign of 65km an hour, which in fact is well below the negotiating speed but, regardless of that, it’s still a very accident-prone location.” Stringfellows launched the project by building, with the Dannevirke company Morrison Bailey as subcontractor, the bridge at the bottom of the gully. The site, a little to the south of the existing bridge, was chosen for its vertical alignment with the uphill cutting, and enjoyed the advantages of a greenfields operation.
The second stage of the project was the installation of the Multiplate rail tunnel, and for this Stringfellows called in the Wanganui firm of Emmetts Civil Construction – formerly known as Emmett Brothers, and with a long history of bridging work in the region – as subcontractors. The tunnel is 110 metres long and is made of four corrugated steel arches manufactured by CSP Pacific. “We assembled the tunnel on the side of the track and then lifted it inwards with a couple of big cranes,” Stringfellows general manager, Graeme de Rose, told Contractor. “It was lifted in four sections with two-metre-wide joining bands that filled the gaps.” This work was started on a Sunday morning when there was little traffic on the railway line, and continued into the Monday, which is KiwiRail’s usual maintenance day. The electrification lines over the track were dropped to the ground between the rails during a 48-hour power shut-down, then lifted up and connected to brackets on the inside roof after the tunnel assembly had been completed. There was no disruption to rail traffic because diesel locomotives were substituted for electric ones during the shutdown.
Apart from the two 40-tonne cranes used to hoist the rail tunnel components into place, the project has used only standard earthmoving and road-making gear, and Stringfellows has had a staff of about 15 working on it, supplemented by those of the two subcontractors. “We’ve got till about June of next year to finish the job, but we’re on track to have it done about a year early as long as the weather continues to behave itself,” Graeme says. The completion of the project may help bring some closure to little Reef Coombes, who was five when the accident at the Ohingaiti level crossing killed her parents. Reef, who now lives with relatives in Auckland, was in the back of the car and was unhurt in the collision. She had reported that her parents were complaining of being dazzled by early morning sunlight as they approached the level crossing, and the Coroner apportioned blame for the double tragedy to neither the Coombes nor the train driver.
Contractor Vol.34 No.2 March 2010 |
There has been an average of 50 accidents every five years on the Ohingaiti to Makohine stretch of road 30 kilometres south of Taihape, but by the time of a double fatality three years ago the decision had already been made to upgrade it by 2011.
Besides the railway tunnel/culvert, the project involves a new three-span road bridge at the bottom of the Makohine gully, the re-routing of the Makohine Stream to pass under it, and the construction of a 30 metre high cutting, incorporating a 1.3 kilometre passing lane, up the hill. More than 500,000 cubic metres of earthworks is involved. A new intersection will also be formed where Onslow Road met the old highway at the level crossing, maintaining access for the Ohingaiti community.
There is a planting programme currently under way around the new bridge to enhance the rest area at the bottom of the gully, with its handsome view up to the railway viaduct. This is being done in conjunction with the Horizons Regional Council and local iwi. Once the planting’s completed the stream will be diverted under the new bridge and the old road filled over.
Stringfellows then did the backfilling over the tunnel and formed the road along the west side of the line to join up with the existing highway at the point where the level crossing used to be. The northern end of the project is now virtually complete, and attention has turned to the cut-and-fill operation straightening and forming the road down to the new bridge.