Esmond Road Interchange: Easing the traffic snarl

Fletcher Construction completes an important $48 million interchange linked to Auckland’s northern motorway busway.   BY GAVIN RILEY

Decades of failure to keep pace with rising traffic volumes in Auckland has led to the need for complex and, some might say, costly solutions.

The latest project to be completed by Transit New Zealand on the Auckland motorway network is the $48 million Esmonde Road interchange. The interchange is complementary to the $210 million, 7.3 kilometre northern-motorway busway and its five stations, funded at cost of $84 million by North Shore City Council and Auckland Regional Transport Authority. All are designed to make travel from the North Shore to the city and back easier and more convenient.

Esmonde Road interchange and associated local road upgrades have been carried out as a partnership between Transit and North Shore City Council. The interchange, opened on May 16, has been built by Fletcher Construction, which is also the main contractor on the northern-busway project (stage one of which is due to be completed at year’s end).

Esmonde Road features an underpass for the two-lane busway and a bridge built over “live” traffic on the motorway.

Other benefits are a new east-to-west cross-city movement, a new northbound access from Akoranga Drive and Esmonde Road to the motorway, a new southbound exit from the motorway to Esmonde Road, an additional northbound lane to the Northcote off-ramp, and connections across the motorway for pedestrians and cyclists.

The associated local-roads upgrade is being carried out by AC Blackmore and is intended to maximise the value of the interchange and improve connections between the Northcote, Takapuna and Devonport suburbs.

Fletcher Construction began work on the interchange in January 2005. The project engineer in charge of earthworks and pavements, Matthew Findlay, says the first major task was to construct an embankment for the new northbound off-ramp, which involved diverting the existing off-ramp.

The work was carried out in May-June 2005 outside the traditional earthworks season and required Auckland Regional Council approval. It was a cut-fill embankment and because the material was not particularly cohesive, the entire 9000 cubic metres was stabilised and cut to fill in about three weeks.

“It was a good achievement to get that done over the winter period. It wasn’t scheduled to be completed until the following earthworks season so it gave us a jump start on the following work,” Findlay says.

The next big task, completed in March last year, was to divert traffic off the motorway overpass onto the new overpass. The final major diversion was construction of the new southbound on-ramp, opened last October.

Esmonde Road interchange and the northern motorway border on the Waitemata Harbour. Findlay says that due to settlement that has occurred previously there have been significant level changes in roads surrounding the interchange. In some areas there were up to one-metre asphalt overlays where the road surfaces had been topped up as they continued to settle.

The specified deep-lift asphalt required design changes in some places. An example was where the design called for a significant area of cut through the nearby Barry’s Point Road intersection that would have required lowering of the existing pavement level into the clay subgrade – a high-risk exercise due to traffic volumes, Findlay says.

“Due to the traffic-control requirements and space we would only have had a weekend to undertake that work. So we went back to the designers and said, ‘Here’s a possible solution: lift the alignment, and that means pulling out some of the constructed kerbs, and undertake a deep-lift fill rather than a cut. Can we achieve the same outcome in terms of maintaining the grades and quality?’ 

“The designers looked at it and agreed it was going to be too much of an interruption to the stakeholders. It would have been a high-risk thing to open up a significant section of road.”

Findlay says another important piece of work was the construction of two northbound on-ramps and an auxiliary lane through to Northcote.

“That was specified to have a lime stabilised sub-grade, but when we got down there we found that pretty much none of the existing in-situ soil was suitable material. We had significant peat seams through part of the works up to 100 metres long.

“So we went away from stabilising and constructed the entire one kilometre-long stretch with granular backfills of varying depth to the undercuts, geogrids and geotextiles. In other areas, because it’s so close to sea level, drainage of those undercuts was pretty challenging. You were often working in tidal areas.”

Another challenge was that the link road in neighbouring Fred Thomas Drive had to be constructed over a landfill. So the design called for dynamic compaction before constructing the subgrade fill. Compaction

settlements were up to 240mm (average 140mm) and compaction was carried out using a 13-tonne roller towed by a Case four-wheel-drive tractor. 

At the Akoranga bus station Fulton Hogan had installed wick drains during an enabling-works contract. And, as part of the earlier Constellation station enabling-works package, 30,000 cubic metres of clay had already been stockpiled at the Akoranga site.

Fletcher used the material for the interchange embankments and found when it got down to the in-situ level that the specified design of a stabilised subgrade needed to be changed to granular undercuts of varying depths because of the organics and peat seams.

The Esmonde Road interchange features six structures, some of which had to be done in stages due to traffic-management considerations.

“Shoal Bay Bridge had to be built in three stages and the busway underpass in two,” says the area engineer in charge of structures, Jim Washbrooke.

“Shoal Bay Bridge involved a very tight working space. At times we were working in the middle with eastbound and westbound traffic going either side of us.

“A frequently used subcontractor cut the bridge into sections. It was an easier way to control the work site and prevent the debris getting into the estuary.

“The subcontractor did an excellent job containing slurry and debris without incident. It was a high-risk area environmentally for us. There was no second chance in planning, so we had to make sure the environmental controls worked.”

Also requiring considerable planning and upfront work with the designers was a section of road between the busway underpass and Hillcrest Creek Bridge. The lightweight fill construction called for large polystyrene blocks to reduce surcharge to the poor ground conditions, and there were a number of geometrical challenges in placing the blocks, coupled with strict quality constraints.

Reassessment and amendment of the design were needed in the difficult retrofit of the existing underpass bridge over the motorway, where the work involved a seismic upgrade, deck realignment and barrier upgrade.

Such design inputs “on the run” were made easier by having the designer, Opus, on site six days a week.

Matthew Findlay and Jim Washbrooke agree Esmonde Road has not been as technically challenging as some projects they have worked on. But Washbrooke, who came to the interchange from the award-winning Freeflow alliance central-motorway-junction stage-one scheme, concedes Esmonde Road has been “tricky”. And Findlay says it has had “the whole range”.

He adds: ”Parts of it are greenfields, parts brownfields. Being so visible to the public is a big factor, compared to other major projects which tend to be more separated from where existing roads are.

“We’ve had to deal with everything from building through open paddocks to doing night works and multiple overlays of deep lifts.”

Stakeholder manager Louise Gibson says Fletcher Construction has tried to self-perform at Esmonde Road wherever possible so it can plan and manage the project, particularly traffic switches, stakeholders and high-risk parts of the work. “We have strong support from head office and our head-office design teams.”

However, on a project that has proved labour intensive (50 carpenters alone), it is inevitable that subcontractors have played key roles. Of the peak workforce of about 300 only about half have been Fletcher staff, including 80 engineers.

Subcontractors (several of them Fletcher subsidiaries) have included: Smith & Davies, bulk earthworks (101,191 cubic metres); Brian Perry Civil, piling; AC Blackmore, pavements (6.05 kilometres, one to four lanes, 240mm deep); Fulton Hogan, surfacing (about five kilometres of new roads and alignments); Firth, concrete supply (4570 cubic metres, not including the buslink bridge); Stresscrete, concrete beams (127, not including the buslink bridge); Resource Search, the tricky Shoal Bay Bridge; Hiway Stabilizers, fill drying for the embankments (both lime and cement); Broons Hire, dynamic compaction; Higgins Contractors, traffic management; and CSL Traffic, traffic signals and lighting (six intersections).

Initially the weather on the 29-month interchange contract was wet and continued to be erratic, but the construction team took advantage of the long summers of last and this year to keep abreast of schedule. Possibly the weather proved in the end to be less of a headache than an important environmental consideration, the dotterels.

Transit had created a new permanent habitat for these endangered birds (at a reported cost of $200,000), but some relocated and a pair began breeding about one metre off the carriageway when pavements were being constructed on the northern on-ramps.

“There was a three-week period where we restricted access and pulled out of that area and reprogammed our works,” Jim Washbrooke says.

“We put in controls to encourage them to move, including a fake hawk on a stick, which seemed to work.”

Indeed it did. Just before Contractor went to press an Auckland newspaper reported that five pairs of dotterels had hatched six chicks. It was the birds’ most successful breeding season since they were encouraged to relocate.

Contractor Vol.31 No.5 June 2007