Wellington's new water entity estimates $25b over 30 years for safe water, clean beaches

A burst water main floods a major Wellington street in August 2024.

Photo: RNZ / REECE BAKER

It will cost $25 billion over the next three decades to fix Wellington's failing water infrastructure, deliver a safe water supply and keep harbours and beaches clean, the new water entity says.

Tiaki Wai will spend $800 million in its first year as it takes over ownership and management of the region's water assets from 1 July.

Wellingtonians will pay an average of $2390 this coming financial year for their water bills to Tiaki Wai - a 13.3 percent increase to the average $2100 currently included in council rates.

The charges will vary depending on which of the four cities people live in - Wellington, Porirua, Upper Hutt and Lower Hutt. They are set to keep increasing across the next decade, jumping to an average bill of $4367 per year by 2032 and $6208 per year by 2036.

The projections are a slight decrease on initial forecasts, after residents and local leaders raised concerns residents would not be able to afford to pay the bills.

Chair of Tiaki Wai Will Peet.

Photo: Supplied / Tiaki Wai

Board chair Will Peet said the number of critical assets, including water treatment plants and outfall pipes, as well as the sheer-scale of pipes needing replacement, made up the multi-billion dollar estimate.

"Many of these assets are ageing and at risk of failing because of decades of underinvestment," Peet said.

In the future another storage lake might need to be built - there are currently two large lakes at Te Mārua north of Upper Hutt - to ensure drinking supply in a drought.

'We need to replace 100 kilometres of pipes a year' - chief executive

Chief executive Michael Brewster said about 20 percent of Wellington's pipes are in a poor, or very poor condition.

Tiaki Wai is taking on over 6800 kilometres of pipe, but currently only 13 kilometres were being replaced each year, Brewster said.

"We need to be replacing 100 kilometres a year."

He warned the pipes were "getting worse" and said the alternative to higher bills was more leaks, spills, and bursts as much of the system neared "the end of its life".

"It is not pretty, this is real impact on people's lives if we don't invest the money.

"If you haven't been directly impacted then you say, well why are the bills going up? ... A lot of people don't experience it ... until one day their house gets flooded, or sewage starts flowing down the street."

Photo: RNZ

Seaview pipe 'number one' risk - but solution not coming this year

According to its strategy, $396m of Tiaki Wai's $799m budget accounts for investment, while $403m is its operational annual cost - that included maintaining assets, and treatment plants, insurance and power costs.

About $437m of Tiaki Wai's budget comes from residents' bills, while $334m is from borrowing - the rest is made up through development contributions, capital grants and other revenue.

Brewster said top priorities for this year included fixing Seaview wastewater plant's sludge dryers - the cause of the plant's long-running stench issues, as well as fixing Moa Point, and upgrades to Porirua's sewage treatment plant.

Seaview's 18-kilometre-long outfall pipe, which is at times leaking into the harbour due to degrading rubber joints, is the "number one" risk for Tiaki Wai, but would be a "multi-year project".

A replacement pipe is estimated to cost up to $1b - so any cost would be spread over years, Brewster said.

"You've got to work out how to replace it, in a way where you don't have these leaks continuing - but until we get through, and take out the weaker parts, we are going to have leaks unfortunately."

The Seaview wastewater treatment plant.

Photo: RNZ / Samuel Rillstone

Peet said Tiaki Wai wanted to install water meters throughout Wellington, but initial figures said the programme could cost between $500-$590m and was being reviewed in a new business case.

He did not confirm whether he expected those forecasts to come down, but said he was confident the new business case would deliver "value for money".

Peet said a pilot programme would get underway this year in some areas to test cost, but the larger roll out was years away.

"Water meters are going to take years, there are 155,000 odd households in Wellington - very few have water meters, it's a long project."

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