Wellington sludge plant cost increase

The story so far

Wellington City Council's $400 million sludge treatment plant was reported in August 2025 to be facing a budget blowout of about $80 million, with costs possibly rising by around 20 per cent.^{8 Aug 2025} The sludge minimisation facility under construction at Moa Point was then reported to face a possible $83 million blowout, and officials had not confirmed how the extra costs would be paid.^{14 Aug 2025} Councillors voted to provide an additional $83 million to complete the plant, which has pushed total projected costs above $500 million, more than double the original 2021 estimate.^{20 Aug 2025} Requests for an immediate independent review of the cost increase were voted down.^{20 Aug 2025}

Latest

Councillors approved the extra $83 million, but rejected calls for an immediate independent review of the cost increase.^{20 Aug 2025}

What's next

The plant is scheduled for completion next year.^{8 Aug 2025}

Key moments

1. 8 Aug 2025Council told the $400 million sludge plant faces about $80 million blowout
2. 14 Aug 2025Possible blowout now put at $83 million; funding source unconfirmed
3. 20 Aug 2025Councillors vote to approve an extra $83 million for the plant
4. 20 Aug 2025Total projected cost now over $500 million, more than double 2021 estimate
5. 20 Aug 2025Motions for an immediate independent review of costs voted down

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