Engineers look into water chemicals

Thursday January 16, 2020 Written by Published in Local

Anti-chemical lobby group wins battle for a new environmental assessment of a sedimentation chemical being proposed for treating drinking water. 


A Kiwi engineering firm will carry out an “independent” Environmental Impact Assessment on the use of chemical to treat water in Rarotonga, authorities say.

Government water company To Tatou Vai has hired Tonkin and Taylor International Ltd to investigate plans to treat drinking water with polyaluminium chloride, a sedimentation and coagulation chemical.

Two engineers arrive from New Zealand this week. Their assessment will be submitted to National Environment Service, whose officials will decide on the next step – and potentially refer it to the Environment Authority for approval.

To Tatou Vai chief executive Brent Manning says this will look at any potential effects of the sludge and discharge water from the coagulation, flocculation and sedimentation treatment process.

The move has been welcomed by anti-chlorine group Te Vai Ora Maori, which had repeated demanded an independent assessment.

But lobby group chairperson Anna Rasmussen says their members and water intake landowners would like detailed information on the “independence” of the firm hired to do the assessment.

Tonkin and Taylor International is part of a “well-respected and reputable” engineering and environmental consultancy firm, Manning said, that worked across Australasia, Asia and the Pacific.  Engaging them to prepare the Environmental Impact Assessment for the National Environment Service was an important step.

The New Zealand firm will be reliant on input from key stakeholders such as the Environment Service, To Tatou Vai and Te Ipukarea Society.

Government’s intention to chemically-treat water after the completion of $90 million Te Mato Vai project has received a mixed public response. Rasmussen had strongly opposed government’s plan to use polyaluminium chloride as a coagulant for water to remove turbidity, without an Environmental Impact Assessment.

In an email last month to Environment Service boss Nga Puna, Rasmussen said: “The government are clearly breaking the environmental laws of our country if they have, or do proceed with use of polyaluminium chloride and/or chlorine, without an EIA, and as chief executive of National Environment Service, you must take responsibility for this.

“Te Vai Ora Maori demand that NES carry out its responsibility, and order government to obtain an EIA for Te Mato Vai project and use of chemicals.”

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