Petone wharf to go but aquifer concerns linger

Wednesday, 22 November 2023

Petone’s historic wharf is set for demolition but locals say the health of the Waiwhetū Aquifer under it is a reason for second thoughts.

The wharf is being eaten by marine worms and has been damaged by earthquakes. It has been closed to the public since 2021, and Hutt City councillors have voted to spend $6 million to demolish it.

But deputy mayor Tui Lewis is hoping that a combination of heritage concerns and the needs to safeguard the aquifer can help save it.

The aquifer supplies 70% of Wellington’s drinking water in a dry summer and, without it, Lewis says the region would be in serious trouble.

She is aware of claims that the wharf’s piles have punctured the aquifer and their removal could allow seawater to enter the aquifer.

The aquifer is a layer of buried gravel 20 metres below Lower Hutt and Wellington Harbour. It allows water, much of which comes from Te Awa Kairangi/the Hutt River, to slowly flow down towards the harbour.

Wellington Water takes water from the aquifer with eight bores along Knights Rd in Lower Hutt. Over summer, the volume of water that can be taken from local rivers drops, making the aquifer the major source of drinking water for the region.

Lower Hutt’s Three Waters adviser Bruce Hodgins agreed that protecting the aquifer was important but he disputed that removing the piles posed a threat.

“Based on expert advice from Tonkin + Taylor, [environment and enginerring consultants],’’ he said he would reject that claim.

Hodgins said that in 2017, Tonkin + Taylor gave advice about the threat to the aquifer posed by the wharf.

The wharf sits above the aquifer on a layer of material known as the Petone Marine Beds, which is 20 to 30 metres thick. The report said the risk to the aquifer of removing piles was “relatively low” as they penetrated only 3.4m of the marine bed.

The wharf has effectively been in limbo for a decade as city council politicians decided whether to save or demolish it.

Built in 1907, it is much loved by locals for fishing, wharf jumping and as a favourite spot for photographers. The current wharf replaced one built for the Gear Meat Company to export meat products to England.

Lewis said her preference was to retain part of the wharf, to acknowledge its historical significance and the role it played in the development of Petone.

“All of Petone heritage, things that tell our story, would be lost and I think that would be really shortsighted.”

Lewis also wanted more information on the impact of removing piles.

But she said the issue of cost could not be ignored.

The council had budgeted to spend $21m to repair the wharf but that money has been allocated for its demolition and for work required on the Petone Library and the grandstand on the Petone Recreation Ground.

The council recently received a submission by Jim Mikoz who has been studying the aquifer since the 1950s.

He argued that demolishing the wharf and removing the piles risked permanently damaging the aquifer.

“Removing the Petone Wharf has the potential to cause a massive drop in artesian water pressure and quite likely we will be the last generation to have had access to the artesian water.”

Describing himself as a “QBE” (Qualified by Experience) he claimed that pressure in the aquifer had already been reduced by actions such as removing part of the Pt Howard Wharf.

Wellington Water chief executive Tonia Hoskell said she “would expect a high standard of care to be applied when assessing the potential impacts to the Waiwhetu Aquifer”.

Earlier this month, Greater Wellington chair Daran Ponter wrote to Mikoz confirming he was aware the wharf could be demolished. Demolition would require resource consent and the safety of the aquifer would be included in the consent.