Native skinks cause cost blowout for Porirua sewage tank

A northern grass skink.

By Nick James of RNZ

Moving a native population of skinks has contributed to the doubling of the cost of a Porirua sewage tank.

Wellington Water started work on the tank near State Highway 59 in May 2022.

It was designed to capture and hold up to 7 million litres of sewage at peak times such as heavy rain events, then gradually release it back to a treatment plant.

However, an assessment of the project in October 2022 found northern grass skinks at the north end of the site.

About 60 skinks were rehomed between September and October last year, delaying the completion date by six months, from late 2025 to mid-2026.

Porirua City Council documents show the delay contributed to the cost increasing from $85 million in December to $97m, which was the new budget requested by Wellington Water.

The tank had an initial budget of $48m in 2021.

Other cost increases included upgrading the sewage overflow system at the site, the relocation of the Chorus North Island fibre ducts to the other side of SH59, and $5m for the potential of any other project risks.

Council officers have recommended the budget increase be approved and that the Te Puna Kōrero subcommittee refer the matter to the council in their meeting on Thursday.

– RNZ