The $55m bypass connects the end of the motorway and the Basin Reserve

The bypass resulted in a range of benefits for central Wellington – reduced travel times, lightened the impact of traffic in and out of the city, and helped preserve part of the Capital’s building heritage.

The $55 million Wellington Inner City Bypass (WICB) provides a cross-city link between the end of the motorway and the Basin Reserve. It comprises a two lane one-way arterial route in each direction - partly along existing streets and partly along a new road that includes a 450m below grade trenched section.

The trenched section posed design and construction challenges due to variable soil conditions, high seismicity, complex groundwater regime and the confined site.

WSP Opus came up with a cost-effective solution involving a propped trough section flanked by sections with soil nailed retaining walls. The soil nailed walls, some of the largest of their type in New Zealand, incorporate a post-grouting technique to enhance bond strength.

The main benefit to Wellingtonians has been reduced travel times, but the project offers other benefits. It has reduced the local impact of motorway traffic entering and leaving the city, catered for cyclists and pedestrians and – rare for a roading project – has helped preserve part of Wellington’s building heritage. Incidentally, the project gave the impetus for upgrading a major stormwater diversion and provided cut-to-waste soil to cap a city landfill.

The WICB is a good example of integrating a transportation solution with the needs of the community. The project’s complexity called for a collaborative approach and its success owes much to a partnering charter established by the clients, consultant and contractor.

Despite wide prior consultation, the WICB polarised public opinion and was the subject of heated challenge and protest. “Destruction of Te Aro – Cuba St culture and historic buildings and lack of information” were the main reasons for opposing the bypass. Central Wellington was divided three ways - 33.2% in favour, 33.3% opposed and 34.2% undecided.

Since the WICB opened in mid 2007 most feedback has been supportive. The engagement of the public, mitigation of adverse environmental effects during construction, the quality of the finished project and the benefits it has brought to Wellington have largely silenced criticism.

The WICB won the INGENIUM Excellence Award for projects over $1 million. This is a sixth award for the bypass presented to WSP Opus, clients the New Zealand Transport Agency (formerly Transit New Zealand) and Wellington City Council, and contractor Fulton Hogan.