Final milestone for Auckland’s central interceptor tunnel complete

Ghella tunnelers celebrate reaching halfway stage of building Watercare’s 16.2km Central Interceptor tunnel in 2023. — Ghella tunnellers celebrating reaching the halfway stage of building Watercare’s 16.2km Central Interceptor tunnel in 2023. Photo: Supplied / Simon Runting

Auckland’s Watercare says it has hit the final milestone in its long-awaited central interceptor tunnel.

The 16 kilometre wastewater tunnel leads from Herne Bay to the Māngere Wastewater Treatment Plant, and aims to reduce the number of overflows in wet weather.

Work on the project began in 2019 and construction started in early 2020.

The southern half of the tunnel has been operating since early 2025 - a massive bulkhead separating the tunnel into two halves.

Watercare chief programme delivery officer Mark Crowle said the bulkhead had now been removed, the last major step in the tunnel’s construction.

He said the tunnel was due to be fully operational by late July.

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