Tommy Parker New Zealand Transport Agency's (NZTA) state highways manager for Auckland and Northland detailed the plans for the link
A landmark tunnelling project is commencing in New Zealand - Kristina Smith reports
New Zealand is preparing to embark on its biggest transport project ever.In August it announced that it had selected its preferred bidder for the NZ$1.4 billion Waterview Connection in Auckland, 5km of new motorway connecting highways to the North and South of the city.
It is also the biggest tunnelling job in New Zealand for decades: 2.5km of the three-lane route will run underground in twin bored 14m diameter tunnels. And the country's volcanic geology means that this could be an interesting challenge for the tunnelling contractors from the winning consortium.
"The biggest technical challenge has got to be the geology," said Tommy Parker,
"And also the biggest risk. The successful team had to have the best tunnelling knowledge that we can muster." The winning consortium is Well-Connected which comprises
Well-Connected also includes five suballiance partners: SICE,
As well as its size and technical challenges, this project is also notable for the innovative way in which client the NZTA is procuring the job. It has added a new twist to the Alliance form of contracting, adding a competitive element to the process.
Having selected two consortia from a shortlisted three on quality, the agency then worked with them both over eight months to develop the design, asking them to submit their costs at the end. The other shortlisted consortium was Tuhono which consisted of
There were over 40 interactive workshops over that period: "That's what gives us the reassurance that both schemes were fit for purpose and meet our requirements," said Parker. NZTA paid a portion of both consortia's costs so that it could retain the intellectual property and combine the best elements of both bids in the final scheme.
The Alliance form of contracting, similar to partnering contracts in the UK, has developed over the last 15 years. It seeks to share risk between the client and contractor, rather than offloading all the risk to the contractor and paying for that privilege. "This is a popular form of contract here and in Australia," said Parker.
"We have had a number of key successes with it." This contract also included an agreement to limit the geological risk which would be carried by the consortium partner in the alliance. An Alliance Geotechnical Baseline Report (GBR) sets out contractual definitions of the anticipated soil conditions - should ground conditions fall outside these limits, the client pays the direct cost impact of such an event but the consortia receives no additional profit or corporate overhead for this work, the principle being that the consortia will not incur loss from the event but will not profit from the client's misfortune.
The final selection was done on the basis of quality and cost, although both teams were very close on all the quality issues. "They were both good quality bids and both had good quality teams," said Parker. "Ultimately, in this case, it did come down to price." In parallel with the tender design process, the scheme was also going though New Zealand's statutory approvals process, receiving permission from the Board of Inquiry only in July. "It was a bit risky," admitted Parker, adding that this was a new consenting process for New Zealand, with the Waterview Connection the first project to go through it.
WATERVIEW CONNECTION
AUTHORITY: NZ transportation Agency
SPECIAL FEATURES:
•the Waterview Connection is the missing link in the Western Ring Route that will provide an alternative 48km motorway around Auckland that avoids the southern motorway and the Auckland Harbour Bridge
•2.5km of the three-lane route will run underground in twin bored 14m diameter tunnels
•Provides a motorway link from the Auckland Central Business district to the airport
•takes through traffic off local roads creating opportunities for passenger transport improvements
•Creates opportunities for employment development along the corridor, enabling more reliable and efficient transport of goods and services to boost the economy"We talked it through with the bidders so that everybody realised what the risks were and went into it with their eyes open," said Parker.
"Also the contractor market over here is very hungry, so there is a lot of pressure for major projects to come to the market." This dual process did mean that the bidding consortia had to be flexible in order to adapt to any changes coming out of the inquiry, another reason why the Alliance form worked well. For example, one of the ventilation stacks for the tunnel had to be relocated.
The Waterview Connection will connect the SH20 motorway at Mt Roskill in the North to the SH16 in the South, easing pressure on the SH1 and the Auckland Harbour Bridge. Once open in 2016, it will complete the Western Ring Route around Auckland which has been under construction for the last 30 years.
Because it is the final link, the Waterview Connection project must link and integrate other road projects at either end of its route.
To the southern end, there are ongoing interchange works and at its northern end, a sinking causeway needs to be widened and raised, a contract which the agency will tender soon. The Alliance route allows for the flexibility to integrate with these other works, said Parker: "With a hard dollar contract, this just wouldn't be possible." During the project's 10-year gestation, a number of different options have been considered for its route and for its method of construction. One solution suggested in 2007- 2008 saw the below-ground sections created in cut and cover tunnels, other options included sections of both bored and cut and cover tunnels.
The final solution - which sees half above ground and half below in bored tunnels - reduces the disruption to the limited urban space of Auckland. "Auckland is all surrounded by sea, so quality urban space is at a premium, so that was a good driver for taking the road below ground and preserving the surface," said Parker.
Work is expected to start on site before the end of this year, although tunnelling is not likely to get underway for another 18 months.
On the critical path is procuring the two Earth Pressure Balance Machines (EPBMs) which will carry out the tunnelling. Discussions with manufacturers from China and Europe are underway.
The huge tunnelling machines, with 14.5m diameter cutter heads, will be travelling beneath the basalt crust, deposited by New Zealand's volcanoes, through soft sedimentary bedrock and saturated silts. These types of ground require a closed-face tunnel boring machine, such as an EPBM; with an open, unsupported face, the ground would collapse causing settlement at the surface.
The first task for Well Connected is to sit down and work out the final details of the scheme, a task that Parker expected to be complete by the end of October. Part of this process will be bringing in the best from the two tenders, both in terms of construction method and design for longevity.
One of the technical improvements which emerged from both tenders was a change from the specimen design which reduced cut and cover sections at either end of the tunnels, saving cost and reducing the impact on local communities. "Overall, that is where they focussed the smart thinking," said Parker. Now the challenge is to consolidate the two tenders to produce the best solution.
The Alliance's contract includes 10 years of maintenance after the motorway has opened to try and focus minds on maintenance and operation costs as well as the capital expenditure. "It has been set up like this to drive better whole-of-life outcomes," says Parker.
The negotiation period will also see Well- Connected agree its costs and overheads with NZTA, together with the total out-turn costs that will become the target price. From then on in, one of the driving forces will be finding efficiencies and innovative solutions which allow the final cost to come in below that target price. Under the Alliance form, it is not just cost overruns that are shared - any savings are split between client and contractors too.
