Quarrying & Mining Magazine
Health & Safety

SMA for Waterview's tunnels

This article first appeared in Q&M‘s February-March issue.

Q&M magazine was invited into the nearly completed Waterview tunnels in Auckland to witness one of the safety feature tests, which was one of many carried out during the final fit out of the tunnels and testing and commissioning of safety systems.

Testing will continue through to mid-April, when the entire Waterview Connection project is open to the public.
The twin tunnels, the longest in the country at 2.4 kilometres each (twice the distance of Auckland’s Harbour Bridge) feature: 74,500 cubic metres of aggregate for backfill, five kilometres of drainage pipes, 140,000 square metres of paint (black for the roof and magnolia for the walls), and 400 kilometres (270 tonnes) of cables and wiring.
Around 800,000 cubic metres of spoil (enough to fill 320 Olympic-sized swimming pools) from the tunnel extractions has been compacted at a disused quarry at Wiri in South Auckland.
Stone Mastic Asphalt (SMA) pavement had already been laid for each tunnel to carry three lanes of traffic with speed restricted to 80kph and a ban on lane changing (good luck on that one with Auckland motorists!).
The giant motorway-to-motorway interchange at Great North Road, connecting the Northwestern and Southwestern Motorways, had been largely finished by the end of last year.
The project has been delivered on time and budget by the Well-Connected Alliance made up of the NZTA; Fletcher Construction; McConnell Dowell; Parson Brinckerhoff; Beca Infrastructure; Tonkin & Taylor; and Japanese construction company Obayashi Corporation. Sub-alliance partners are Auckland-based Wilson Tunnelling and Spanish tunnel control specialist SICE.
“We are very excited and very happy with how the contractors have performed and they have done a fantastic job on a very risky project, especially with the tunnel boring machine,” Brett Gliddon, Auckland highway manager, NZTA, told Q&M.
“They were no major issues and now we are in the testing stage it is all going very well and it is all on track for an April opening.”
Iain Simmons, project manager, Well-Connected Alliance, says the SMA used in the tunnels features blast furnish slag from the Glenbrook steel mill.
“It has a very high skid resistance and is bound together with a bitumen emulsion heated and mixed with cut-back oils and water. The mastic material is sprayed on top to provide a very dense, resistant, long-lasting surface.”
All pavement surfacing for the project was supplied by Downer and Higgins.
“Outside the tunnels we used an open-graded porous graded asphalt – because of its quiet surface to reduce noise, especially on the ramps where we have used a thick double layer of open-porous asphalt.
“We have made an effort to achieve a pavement life as long as we can, while remaining within reasonable costs.”

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