Watercare has found a silver lining to the massive sinkhole in Parnell - it is spending a further $60 million to reline another section of the century-old Ōrākei Main Sewer.

Watercare chief operations officer Mark Bourne today said the board approved on Tuesday $26.1 million to cover the cost of repairing the damage to the old sewer pipe and relining an additional 600m of the sewer.

The sinkhole developed above the Ōrākei Main Sewer on September 25 when a brick sewer 13m underground at St Georges Bay Rd in Parnell collapsed, allowing about 8 million litres of wastewater to pour daily into Waitematā Harbour.

Workers at the Parnell sinkhole site today. Photo / Michael Craig

Bourne said the $26m includes the cost of building the access shafts, buying the glass-reinforced plastic liner (including freight), and installing it over several months early next year.

The $26m bill includes $5.8m in operational costs to stabilise the sinkhole, construct the bypass, pumping, environmental, monitoring, and other costs related to responding to the incident.

He said Watercare was also taking the opportunity to reline another 1.4km of the sewer between Carlaw Park and the Hobson Bay Tunnel over the next few years.

“Our board approved an additional $60.6m capex between now and June 2026 to fund this work, which will be carried out in stages. This rehabilitation work will extend the life of this section of the sewer by 100 years,” said Bourne.

The Ōrākei Main Sewer was installed in the early 1900s. It flowed from Point Chevalier to Okahu Point where screened but untreated wastewater was discharged through a 300-metre outfall pipe to Okahu Bay until the 1950s. The Hobson Bay Sewer pipe was also constructed as part of this scheme. The majority of the sewer pipelines constructed under this scheme remain in use today.

The sinkhole is one of several headaches for the council-controlled organisation (CCO).

Watercare this week said the cost of Auckland’s Central Interceptor giant wastewater pipe has risen from $1.2 billion to $1.52b, blaming “unprecedented inflation since late 2021″ leading to higher labour costs.

The council-owned water company is also grappling with setting water prices for next year, which could land anywhere between 9.5 per cent and 30 per cent for residents.

A bypass pipe for the damaged sewer pipe in Parnell. Michael Craig

This is due to the uncertainty created by the Government repealing Labour’s controversial Three Waters reforms, and replacing them its own water reforms.

Labour’s reforms would have separated Watercare’s balance sheet from Auckland Council and allowed it to borrow more and keep prices closer to its existing price path of 9.5 per cent next year.

National’s policy will leave Watercare’s debt on the council’s books with insufficient headroom to fund Watercare’s $13 billion capital investment programme, leaving the CCO with two choices - cut the programme or increase prices by up to 30 per cent.

Mayor Wayne Brown is seeking a “simple fix” from the Government, which is a Crown guarantee for new debt by Watercare.

Infrastructure New Zealand policy director Michelle McCormick has also urged the Government to ensure it secured council balance sheet separation as part of the new model.

She said that would ensure the long-term sustainable funding of water networks.

The sinkhole that appeared on College Hill in July. Photo / Dean Purcell

Meanwhile, the main pipe work on another sinkhole on College Hill in Freemans Bay is expected to be completed by December 21, said Auckland Council Healthy Waters general manager Craig McIlroy.

The 1m deep sinkhole appeared in July when a 108-year-old stormwater pipe below College Hill cracked, leading groundwater to seep in during this year’s heavy rain, taking fill with it, and leading it to collapse.

McIlroy said work will resume on site on January 8 to install some catch pits and roadworks, which should be completed by the end of February.

The cost of the work has risen from $2.5m to $2.8m due to numerous unknown underground services and a bigger area that needs to be reinstated.

Bernard Orsman is an Auckland-based reporter who has been covering local government and transport since 1998. He joined the Herald in 1990 and worked in the parliamentary press gallery for six years.