18 January 2012
NZ Transport Agency is starting construction a trial causeway to test the impact the larger project will have on the immediate environment.
The work is part of Auckland's Northwestern Motorway, State Highway 16. The trial involves building a 50m-long temporary causeway and carrying out tests in the surrounding Motu Manawa – Pollen Island Marine Reserve. The work will trial the most effective methods for constructing the larger causeway upgrade.
“We’re starting this trial on the causeway so we can get a good idea of the conditions inside the reserve and ensure that the construction footprint is as environmentally light as possible,” says the NZTA’s acting state highways manager for Auckland and Northland, Steve Mutton. “We recognise that this is an important and sensitive area.”
The NZTA has invited expressions of interest for the larger 4.2km-long US$216 million causeway upgrade project between Waterview and Te Atatu. “We’re looking at announcing the successful consortia in September and aiming to get going on construction early next year, saving time and money in the long term by having completed the testing work already,” said Mutton.
The US$4.8 million trial is scheduled to be completed in July. The NZTA and its contractor, Downer, will focus on monitoring plants and wildlife in the marine area to minimise the impact of building the improved motorway.
A cofferdam will be built around the trial area to protect it from tides and to keep the construction area dry while the temporary causeway is constructed. The cofferdam will be constructed from shipping containers covered with a waterproof sheet and will be removed once the temporary causeway is completed. The temporary causeway will sit 1.5m higher than the adjacent motorway. It will be constantly monitored by the NZTA until it is eventually absorbed by the main causeway upgrade.
The project also includes upgrading the Rosebank and Patiki interchanges, providing treatment to stormwater runoff, widening bridges and improving the Northwestern Cycleway and pedestrian facilities along the route. It is expected to be completed in 2017.
The causeway upgrade is part of a suite of projects in the western ring route – road of national significance, prioritised by the government to support growth and economic development in Auckland. The alternative route to SH1 will improve connections between Manukau in the south, Auckland International Airport, Waitakere in the west and the North Shore, and ease congestion on the Auckland Harbour Bridge and the central city.