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Published 19/02/2020

Wellington Water’s report on Martinborough’s wastewater overflows released

The investigation report on the two January overflow incidents at the Martinborough Wastewater Treatment Plant has been made available following SWDC’s Assets and Services Committee Meeting today.

The report states that the overflow discharges related to progressively discharging to land. The irrigator did not perform as it should have, which meant that there was a build-up of wastewater in the wastewater ponds. At the same time, the overflow preventer wasn’t working properly.

To fix the problem, a new valve and back-up inflatable bung have been installed. The irrigator is now working properly and the wastewater ponds are also at acceptable levels. A full review of potential points of operational failure has been completed with the aim of mitigating the risk of repeat overflow incidents.

Mayor Alex Beijen received the report saying that it clearly outlined the events that led up to the discharge incidents. 

“We know what caused the overflows and have challenged Wellington Water to ensure that they have undertaken the necessary urgent actions so the plant operates as it should and discharges within consent conditions”, says Mayor Beijen.

Ian McSherry, Chief Advisor Service Delivery at Wellington Water, says despite effects on the environment being minimal, these incidents are not in keeping with being respectful of the environment.

“We are committed to progressively moving away from discharging to watercourses to discharging to land”, says McSherry.

SWDC Assets and Services Committee was also advised today of a mechanical issue identified with the wastewater irrigator at the Greytown Wastewater Treatment Plant. This equipment is still under mechanical warranty and there is no threat of unconsented wastewater discharge.

The report Martinborough Wastewater Treatment Plant: Overflows Incident and Investigation and Report: January 2020 is available at

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