News

Start date nearing for Transmission Gully

By Iain MacIntyre

A revised 27-kilometre and four-lane route with a 100km/h speed limit proposed for Wellington’s Transmission Gully is understood to have been supported by about 90 per cent of 2400 recent public submissions.



Consensus on the preferred route had earlier been reached by Transit New Zealand (now encompassed within the New Zealand Transport Agency) and Wellington’s regional and territorial councils, following a detailed investigation into the geological and environmental impact of the previously-designated alignment.

The Transmission Gully project team is now understood to be analysing the feedback received during the subsequent public consultation process, which concluded on August 20, prior to announcing a finalised plan.

Running inland through mostly rural areas, the preferred route spans from MacKays Crossing (north of Paekakariki) across State Highway 58 at Pauatahanui and reconnects to State Highway 1 at Linden (south of Porirua).

Although the revised plan is understood to require fewer bridges and viaducts and hugs ridgelines rather than passing through valleys, it is nonetheless expected to affect 93 property owners – 30 more than the previous designation – and have an impact on the viability of the Battle Hill Farm Forest Park.

However, Transmission Gully principal project manager, Rob Whight says deviating slightly from the previously-designated alignment will deliver better outcomes for both the environment and road durability.

The previous route was designed without the benefit of the onsite investigations and the detailed study that were recently completed, he says.

Drilling and seismic survey testing, a road safety audit, traffic modelling, cost, risk and value engineering assessments have been undertaken in order to arrive at an option that provides the most appropriate environmental, transport and engineering solution and is value-for-money.

Advantages of the preferred route include greater resilience to earthquakes and less impact on waterways. It minimises the impact of geological hazards like fault lines, landslides and soft terrain. The preferred route is also cheaper to construct in real terms than the designated alignment.

Estimated to cost $1.025 billion, the revised alignment would effectively result in a saving of about $275 million compared to the originally-designated route (this calculation is based on an inflation adjustment to the $985 initially forecast for the project).

Transport Minister, Annette King says she hopes that by late 2009, the region will be able to confirm its funding plans for projects such as Transmission Gully and other strategic priorities. Once the preferred option has been finalised, the Government will release a promised $405 million contribution towards the project.

The purpose of Transmission Gully is to provide an alternative access to and from Wellington and the South Island from the established coastal State Highway 1 route, which narrows in places and becomes congested during peak hours.

An alignment for the Transmission Gully route was designed in 1996 and land was designated in local plans, in 2004. After many years’ debate, community feedback in 2005 finally favoured Transmission Gully and it was included in the Greater Wellington Regional Council’s Western Corridor Plan the following year.

It is anticipated the public consultation process will only result in the Transport Gully project team making minor changes to the current preferred alignment. Although a final plan is expected to be presented to the NZTA board at the end of this year, the agency is understood to have initiated preliminary work towards resource consents, which it may lodge applications by late next year.