Maurice Milisi wrestles the thick hose of a concrete pump down through a honeycomb of reinforcing steel. His arms are caked with dried cement. His gear—clothes, boots, safety vest, lifejacket (yes, lifejacket)—wears the scars of weeks, months, of industrial labour. Behind him, the tip of the boom sways with each tug of the hose. Beyond the safety rails, 25 metres or more below, a pump vehicle and concrete truck stand at the head of a narrow, purpose-built jetty. An engine idles. The languid waters of the Manukau cast back a diffuse pearl light.

Milisi is the foreman of Pier Six, one of seven massive double-columned structures that, when linked up, will support a new 645-metre-long, four-lane motorway across Auckland’s Manukau Harbour. The crossing, built cheek-by-jowl with the existing Mangere bridge, which links northern and western suburbs with the city’s airport, is part of a larger project known as the Western Ring Route—an ambitious 48-km stretch of motorway that taps State Highway 1 south of Auckland and loops traffic west of the city, reintroducing it to State Highway 1 well north of the Harbour Bridge. When finished, the Ring Route will link all four cities on the isthmus—Auckland, Waitakere, North Shore and Manukau. The Government considers the Ring Route critical to the country’s economic transformation and has concocted a long list of benefits it will bring to everyone from commuters to port managers. As to the harbour crossing itself, almost everyone agrees that it would be a fine thing if it were to open in time for the 2011 Rugby World Cup.

Such lofty thoughts are for others. Milisi is fully occupied with the happenings on Pier Six itself, and with good reason. The bridge builders, Fletcher Construction, Beca Infrastructure and Higgins, opted for one of the most dramatic ways of putting up a bridge in the repertoire. Known as balanced-cantilever construction, it involves building out the road superstructure from the top of each pier in both directions at once, so that the whole edifice remains as steady as a trapeze artist until each creeping section meets its neighbour and is fixed in place.

Before the spectacular aerial ballet could begin, one or two preliminary matters needed attending to. First, a series of piles had to be sunk into rock, up to 50 m beneath the soft seabed. The piles were then capped and ringed with watertight boxes, called cofferdams, to keep the tide at bay. Pier columns were poured on those foundations and topped off with 300-tonne pre-cast pier tables.

The next part, building the canti-lever spans themselves, is the job of specialised pieces of equipment known as form travellers. Resembling giant mechanical lobsters, these sit on rails at either end of the pier tables and provide a moveable framework for fabricating new sections. They were designed in Malaysia and built in China specifically for the Manukau Harbour Crossing project.

“A few more concrete pours and we’ll be able to shake hands,” says Milisi, looking to fellow workers across 30 m of void.