Abattle of two harbours
Auckland Council is investigating which Auckland harbour should receive overflowing sewage during extreme weather events.
Last week Auckland Council’s Healthy Water strategy and resilience manager Andrew Chin said it was investigating moving a proposed wastewater overflow outlet from the Manukau Harbour to the Waitemata Harbour.
In 2019 Auckland Council plans to build its massive ‘‘central interceptor’’ project which will include a $1 billion, 13km underground sewage tunnel that will deliver up to two million cubic metres of sewage and stormwater to a proposed Mangere treatment plant every year.
Auckland Council’s water management arm Watercare has consent to discharge untreated wastewater into the Manukau Harbour for times when emergency pressure release is needed such as during an extreme wet weather event or when the proposed Mangere pump station is unavailable.
There are also plans to build a $325 million waterfront interceptor in 2026, after the central interceptor is completed. The proposed harbour outlet would be part of the waterfront interceptor.
Wastewater, or sewage, is more than 99 per cent water while the remainder is organic matter such as human waste, food scraps, oil and debris.
Healthy Waters’ project manager Chris Allen said an overflow point in the Waitemata would be a way to prevent sewer overflows into urban streams, the Westhaven Marina or the Viaduct.
‘‘The Waitemata Harbour in the vicinity of the Harbour Bridge has good assimilation capacity and is therefore a likely candidate for an initial scientific, engineering and environmental evaluation.’’
Watercare would not clarify whether the waterfront interceptor overflow point would replace 41 existing wastewater overflow points at Auckland’s inner city beaches.
Hauraki Gulf Forum chairman John Tregigda said he was not aware of the proposal. It was important council recognised public concerns about the state of the gulf and invested in infrastructure to meet its responsibilities, he said.
Manukau Harbour Restoration Society spokesperson Bronwen Turner said it supported a Waitemata outlet.
Sewage overflow could be moved to near Auckland’s Harbour bridge.