Up to 100 litres of contaminated water per second gushed into Wellington Harbour after a wastewater tunnel collapsed in Willis St.

As Wellington's pipes crumble below its streets, the terms of reference for a mayoral taskforce looking into the city's water infrastructure is being released.

The taskforce - expected to be endorsed at a Wellington City Council meeting on Wednesday - will review issues around pipe damage, management and water quality.

The team will look into the state of the city's water infrastructure including how much leakage is occurring and the adequacy of the maintenance programme.

ROSA WOODS/STUFF The terms for Wellington's mayoral taskforce into the city's crumbling water infrastructure have been released.

The team, to be chaired by Wellington Mayor Andy Foster, will also examine what is needed to deliver a resilient system in the long-term, and whether the existing annual and long-term plan budgets for this are sufficient.

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A review of the service level key performance indicators including timeframes for response and repair issues, and resident support would also be undertaken.

KEVIN STENT/STUFF Additional funding to fix Wellington's underground pipe network looks set to bump up Wellington rates.

Governance arrangements and the relationship between the council, Wellington Water and iwi mana whenua would be put under the microscope.

The taskforce would report back to the council, making recommendations in time for additions to be made to the 2020/2021 Annual Plan.

The taskforce comes following a series of events relating to failures in Wellington's aging water infrastructure after years of underinvestment.

KEVIN STENT/STUFF Wellington Water contractors take sludge from the Moa Point Treatment Plant to the Southern Landfill after a wastewater pipe broke under Mt Albert.

In the lead up to Christmas Day, a wastewater pipe collapsed beneath Dixon St in the central city. By the time workers had toiled through the night on a stop-gap measure, two swimming pool's worth of wastewater had leaked into the harbour.

Part of Willis St will remain closed until March while Wellington Water fixes the pipe.

​Meanwhile, trucks are running around the clock to remove sludge from a break at the Moa Point waste water treatment plant to the Southern Landfill.

In early February, pollution in the water at Owhiro Bay was measured at 43 times higher than acceptable levels after contaminated water made its was into the sea.

A recent report from Water New Zealand, a non-profit representing the water industry, revealed systematic issues across the entire network. Thirty-three per cent of wastewater pipes in Wellington are in poor or very poor condition - the worst of any of New Zealand's major cities - the Water NZ National Performance review found.