The Britomart development, complete with underground train station and bus stops, Glass House, "Twin Tin Towers", kauri trees, waterfalls, and a refurbished historic Chief Post Office building. "Arguably the most significant project since the Harbour Bridge," commented councillor Douglas Armstrong, chair of Auckland City's Finance and Corporate Business Committee. And certainly one of the largest ever undertaken by a local government body. Covering 5.2 hectares in downtown Auckland, the $204 million development lies between Quay and Customs Streets, Britomart Place and Queen Elizabeth II Square.
Line drawings of station (click to enlarge lower two images)
The space is decorated with representations of Auckland's landforms and geologies in the form of volcanic gardens with native plants, a curved basalt waterfall, and stainless steel nikau palms up to 26 metres tall.
The ambitious project has multiple objectives: providing an underground railway station (approximately 300 metres long, 45 metres wide, 12 metres below ground level) and a bus interchange; restoring and modifying the former CPO; connecting the station to the square with an underground walkway; preserving adjoining heritage buildings; redesigning Queen Elizabeth II Square; and revitalising the Britomart area with new public spaces and buildings.
This massive undertaking is at the heart of the Auckland Regional Land Transport Strategy, a $1.2 billion plan for tackling the area's chronic traffic woes. The plan aims to link new rail services with existing ferry and bus provisions, with Britomart as its hub. The rail station has five platforms and is designed to accommodate 10,500 people per hour by 2020. But is "build it and they will come" a sound assumption? It remains to be seen whether Aucklanders will break off their love affair with the car.
Leading the engineering team was project manager Beca, whose involvement with the development began in 1996. They were involved in the development under Mayor Les Mills, taking the resource consent application through the environment court, and providing support to the council through the public consultation process. The project as it was executed began in November 1999, when new Mayor Christine Fletcher gave the go- ahead for a transport centre, but without the massive above-ground commercial development integral to its predecessor.
To find the best use for the Britomart site, Auckland City Council embarked on an extensive public consultation process culminating in a two-stage design competition. The first stage was an open competition with a wide brief, aimed at attracting as many ideas as possible (153 were received.) The second stage saw seven finalists fight it out on a more detailed brief. In November 2000, the winner was announced: Jasmax (designers ofTe Papa) and architect Mario Madayag.
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A Team Effort
Escalator into Britomart
Stairs and escalators into Britomart
Train information
The multiple groups involved in the project were brought together by Beca into an innovative partnership, involving the Auckland City Council, Beca Carter Hollings and Ferner (project management and geotechnical engineering), Downer Engineering (construction), Jasmax and Mario Madayag (architects), Occupational Safety and Health (OSH), Opus International Consultants (civil, structural, mechanical and electrical engineering), URS New Zealand (rail track and signals) andWT Partnership (quantity surveyors).
"Beca had a crucial role in managing all those involved," explained Auckland City's Eric Hennephof. "They did a lot of work to facilitate the team building that allowed us to meet the challenges of the technical issues." He describes the design process as "a true team approach", with strong collaboration between the engineering teams and the architects involving local residents and businesses, the Historic Places Trust, and representatives of disabled and community groups and NgatiWhatua.
Partnership plus
From the start Beca went in with a partnership approach. "The unusual thing was the number of stakeholders involved," explained James Macneil, Beca's project manager. "There were two ways to approach it: ignore them, or, as we preferred, open lines of communication, to talk to them and work through issues." The monthly meetings produced what were described as "frank exchanges of views", allowing those involved to communicate "on a level more meaningful than issuing enforcement notices," says Mr Macneil; and they meant issues could be resolved very quickly.
The collaboration with Occupational Safety and Health (OSH) was a first for New Zealand, and according to Mr Macneil, "One of the best things we did," despite initial scepticism on the part of the contractors. OSH staffwere invited to review tenders for health and safety content, and participate in meetings and decisions. In all, 2,500 staff were inducted for site safety. The result? Just three lost-time injuries during the nearly 1.5 million man-hours logged.
"This was breaking brand new ground," said OSH team leader Jim Bell. "I believe this was the best ever result we've had on a job this size." He notes that, despite the job's exceptionally high public profile, not one complaint was received from the public. "This was an open and honest relationship. We got a lot of plusses out of it and learned a few things ourselves." Among other benefits, Bell identified the value of using different inspectors to get "a fresh set of eyes" on proceedings. A blueprint for the future? "Of course," says Mr Macneil. "It's project management by engagement."
Made from 2,500 square metres of glass on a steel frame, the Glass House serves as an entry point to the station platforms, a giant light source for the station platforms, and a natural ventilation system .
"Volcanic" cones that provide natural light the length of the station .
Britomart was a large and complex project, so it should come as no surprise that there were engineering challenges aplenty. Take the utility lines, including a power line and the Quay Street stormwater culvert, which had to be protected and suspended beneath a temporary bridge (using crane sections) while work went on around it. And the "extra strong" 1912 CPO building, whose reinforced walls proved remarkably tough to cut through.
Its floor had to be lowered by 1.5 metres to allow ground-level access. And then the CPO was riddled with asbestos. "It had been used in the plaster and the concrete fill between the timber joists," says Mr Hennephof, "We had to encapsulate the whole building and remove the material. The joists were stripped and sprayed with epoxy. Everything we removed was bagged and taken to a special tip."
Several design elements were new for New Zealand, including the stainless steel mesh in the station's ceiling and the 11 eye-catching "volcanic" cones that provide natural light the length of the station. The 34-tonne cones were constructed from shotcrete and reinforcing steel on the station floor, then jacked up for bolting into the ceiling. There was even a question mark hanging over whether bolts would hold their weight (they did!).
The area also has historical significance, and archaeological experts were always on hand. During the work, part of a 138-year-old structure was unearthed, complete with "interesting" artefacts, including bottles and cups of the period. "It took a couple of digs before they realised what was under there," says Dale Burtenshaw, Downer Engineering's senior project manager, "but it soon became quite obvious it was a wharf or jetty." It turned out to be Gore Street Jetty – whose construction was commissioned in January 1865 for the princely sum of £3,318 19s lid.
Made from an unidentifiable Australian hardwood, the wharf had been demolished when the site was reclaimed in the late 1800s. Its remains were removed by simply cutting off the superstructure at low tide. The remaining piles were easily cut through during further excavation. A second wharf was found at the end of Customs Street, as well as the pile foundations of tracks from the original railway station.
The location in the middle of downtown Auckland meant difficult access to the site, and much potential for upsetting the neighbours. "There were homes and businesses all around us," says Mr Burtenshaw, "and trying not to be a nuisance was difficult at times." They concentrated the work in the noisier parts of the day, and stepped up monitoring to minimise the effect on people.
A major construction headache was controlling water draw-down in the surrounding area. New and old buildings surround the site, some as close as 15 metres, and the majority of them are extremely sensitive to settlement. With the underground station's platforms 12 metres below ground-level, and eight to nine metres below sea level, there was a considerable amount to excavate – 200,000 cubic metres of spoil, to be exact. A long-buried valley to the back of the CPO was filled with insecure, soft material, including consolidated clays, marine deposits and rubbish; and a flood plain draining Queen Street further complicated the equation.
To solve the problem at the western end of the site, hundreds of secant piles, varying in diameter from 900mm to 1,200mm, were constructed to create watertight retaining walls that could withstand the hydrostatic pressures. "The secant pile walls provided an impermeable barrier that prevented draw-down and settlement on the outside," explained Opus project director Melvyn Maylin (MIPENZ). "They enabled us to meet the maximum horizontal displacement limits of 25mm at the west end, down to 12.5mm immediately adjacent to the CPO."The bored concrete piles were embedded a minimum of four metres into the Waitemata bedrock. Beneath the base of the station, 600mm tension piles had to go eight metres into the rock to secure against the uplift pressure of the water below. At the eastern end of the site, the bedrock is considerably closer to the surface, and more conventional construction techniques could be used. Temporary sheet-pile walls could be built, the hole excavated and then the station constructed from the bottom up.
Forming the secant piles was in itself a multi-stage operation. "We put in a guide beam at ground level," says Mr Maylin, "through which we drilled the pile, and filled with 20mPa concrete. We then over-drilled every second pile and filled with reinforced 35mPa concrete." Very precise drilling was called for.
Secant piles were further used to provide additional support to the new station wall behind the CPO. "We used them like buttresses," continues Mr Maylin. "The design drew on our experiences on the Jubilee Line extension in London and the new airport railway in Hong Kong. It was nice to bring an innovation back to New Zealand having practised it first!"
This is the first time anybody in the world has built an underground station for diesel trains. This claim to fame brings significant challenges for the ventilation system, which needed in any case to be fairly robust to deal with the possibility of fire. Opus lead fire engineer Roger Feasey (MIPENZ) explains that the worst-case scenario is covered – "For example, a diesel spill could catch fire. If this happens, automatic fibre-optic heat detectors, within 32 zones, will identify heat above a certain level and deluge the area with foam."
A mixture of 49 unidirectional and reversible fans — including two 250kW extractors — have been installed to circulate air from east to west, venting through two 35-metre-high stacks. Dubbed the "Twin Tin Towers", they look fairly basic — the thinking is that future developments will surround them and effectively hide them from the public gaze. The ventilation's system's fans will use 85% of the station's electrical supply.
"In the platform area, air will be pumped in at passenger level, and air and fumes extracted from above the train and from around wheels," said Eric Hennephof. "The aim is to encapsulate people on the platform in a bubble of clean air." The volume of air involved? Well, it takes eight minutes to change the entire air mass at an extraction rate of 350 cubic metres/sec-you can do the maths.
The station itself is designed to be waterproof. This has primarily been achieved by limiting the widths of cracks in the concrete. Thermal cracking was not a problem as the walls and slabs are relatively thin. Construction joints were formed with hydrophilic waterbars, and additional hydrophilic material on the outside of the walls. The station's roof and external walls at the eastern end were tanked with bentonite waterproofing membrane, which is self- healing if damaged.
Being underground, the ceiling of the station effectively becomes the ground for the city above. The design requires parts of it to support roads, and in the future possibly buildings; four acres' worth of special pre-stressed concrete was provided by Stresscrete to meet these exacting demands. "We worked closely with the engineering design team to ensure that the product met the requirements of the job," said Peter Wyatt, Stresscrete's senior project manager. Highly-stressed 400 hollowcore
units for the ceiling were designed and cut to be placed between the beams at 11-metre intervals.
In all, Stresscrete provided 1,500 pieces of pre-stressed concrete from its Papakura factory, covering 8,500 square metres of the ceiling/ground level and about 3,000 square metres of the service/platform level.
Made from 2,500 square metres of glass on a steel frame, the imposing structure serves as an entry point to the station and dropping-off point for passengers in front. It will also act as a giant light source to the station platforms – and as a natural ventilation system, thanks to its 1,664 louvre panels (all easy-clean, by the way). Its roof structure spans 18 metres. Inside, a glass bridge connects the station to the CPO building at ground level. The space is decorated with representations of Auckland's landforms and geologies in the form of volcanic gardens with native plants, a curved basalt waterfall, and stainless steel nikau palms up to 26 metres tall.
After years of public and political debate, Britomart station was opened in July. On Monday 7 July the Britomart Express was the first train to roll into a central Auckland station for 73 years.
