‘Sound’ Westpac Stadium spared fate of NP ground

Westpac Stadium is not about to go the way of New Plymouth’s former international rugby ground.

Yarrow Stadium faces demolition after its western embankment was deemed an excessive earthquake risk. It’s not a question of trying to earthquake proof the stands there now, because it’s the land that isn’t safe.

The ground’s main tenant, the Taranaki Rugby Football Union (TRFU), was told this week the embankment had the potential to collapse in an earthquake, bringing the West Stand down with it.

In Wellington, Westpac Stadium, built adjacent to city’s harbour, is on reclaimed land and therefore vulnerable to liquefaction in the event of an earthquake. That was most recently put to the test in the Kaikoura earthquake of 2016.

In subsequent investigations, Westpac Stadium chief executive Shane Harmon says the stadium bowl was shown to be sufficiently structurally sound, along with the ground beneath it.

‘‘The assessment included a review of the post-liquefaction foundation performance and took into account the soilstructure interaction and expected behaviour of the structure in various ground movement scenarios. The analysis confirmed that the stadium foundations have an estimated seismic rating of 70-80 per cent NBS at IL3 taking into account the soil structure,’’ Harmon said via email.

New Building Standard (NBS) and Importance Level 3 (IL3) are the standard industry measures and show the stadium ‘‘is not earthquake prone,’’ said Harmon.

‘‘Also we are a flat site and don’t have the embankment structure that Yarrow has,’’ he added.

Work has already begun at the stadium ‘‘to improve resilience further in the event of a major seismic event.’’

Starting with the walkway up to the main entrance, flooring within the stadium itself will be strengthened either late this year or early next.

The TRFU was aware of some structural issues with Yarrow Stadium’s East Stand, but the news about the earth beneath the West Stand came as a complete shock. Plans are now being hurriedly put in place for Taranaki to stage their national provincial games at TET Stadium in Inglewood this season.

A temporary facility in New Plymouth is the favoured option beyond this campaign, before a new stadium is built. TRFU chairman Lindsay Thomson estimated it could take ‘‘three to five years’’ to get construction of a new ground completed, provided the relevant local bodies were prepared to go ahead with such a project.

However, the Christchurch experience looms large in these situations. In the wake of the devastating 2011 earthquake, a temporary stadium was erected on the old Addington Showgrounds.

Seven years on, Canterbury and the Crusaders are still there, with no plans for a permanent home on the horizon.