Hopua Volcano and Gloucester Park Interchange

Date: 2003-

Location: Onehunga, Auckland 

Client: Auckland Volcanic Cones Society

Project status: Our alternative proposal for the GPI was preferred by hearing commissioners



The SH20 Manukau Harbour Crossing Project is part of the Western Ring Route, a regional transport route being constructed through Greater Auckland as an alternative to SH1. The project consists of widening six km of existing motorway between Mangere and Hillsborough. 


A feature on the route is Hopua Volcano. Hopua is not well known, partly due to its low profile but mainly because its presence has been erased through development. Hopua’s historic pincer shape, created by the sea breaching the crater wall, was a strong feature of the original coastline. However, European settlement has suppressed this, chiefly in the 1930’s with land reclamation of the crater harbour and then in the 1970’s with a motorway routed through the centre of the feature.


The Gloucester Park Interchange (GPI) uses the form of the volcano as the underlying geometry for its circulation. Transit NZ applied for a new designation to upgrade the GPI as part of their project. The Auckland Volcanic Cones Society opposed a proposed overbridge here because it would seriously compromise the volcano, the outcome likely to erode for all time its heritage value, as well as its future potential for enhancement.


Our practice developed an alternative design for the GPI, delivering a solution which Transit NZ never considered in its many years of analysis. The Auckland City Council commissioners hearing the application preferred this solution and recommended Transit NZ modify their design to be consistent with it.


Our design avoids the need for the overbridge and therefore protects the volcano from substantial damage. It does this by re-routing the southern half of the GPI over a railway corridor to connect with a distant cul-de-sac, Galway Street. The lateral bridging of these two areas produces better traffic movement and allows half the vehicles to be diverted around Onehunga Town Centre.


The commissioners also supported our design of a walking and cycling network because it keeps their movement separate from the roading system. One of its features is the re-routing of the Coast-to-Coast Walk through the Onehunga Town Centre and over the Manukau Harbour.


Auckland City Council has bought the privately-owned land at the end of Galway Street in order to protect our idea for future implementation. The transport agency has built our proposal for a footbridge over Onehunga Harbour Road. We developed other design recommendations which addressed the historic effects of the 1970’s motorway, although most of these were outside the terms of the application.


The design delivers the kind of multi-dimensional outcome now required of integrated planning. It not only improves the motorway’s social, urban and environmental outcomes but will significantly enhance the future locality.



All rights reserved © RRA Ltd 2017