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Source: Rio Tinto

NZAS has today released a report undertaken by global professional services company GHD which concluded that there was a limited risk to marine ecology and no increased risk of health effects for people who come into contact with sediment and surface water or consume kai moana inhabiting the surrounding coastal marine area.

NZAS engaged GHD to complete extensive testing in and around the Tiwai smelter site to further build on the findings of a detailed site investigation undertaken in 2021 to establish baseline indicators for the site. NZAS is committed to further improving its environmental footprint and mitigating the impacts of the smelter.
The purpose of this report and the investigations was to understand discharges occurring from the smelter and to determine whether these were having an adverse effect on the ecology of the coastal marine area environment, or people using the coastal area for recreation and food gathering. As part of the investigation, concentrations of analytes in soil, sediment, groundwater and ocean water were compared to various regulatory criteria as per Ministry of Environment guidelines.
Given the importance of mahinga kai (food gathering) activities at or near Awarua/Tiwai peninsula to Ngāi Tahu, this work included testing of kaimoana (seafood) in the coastal marine area adjacent to the site.
The report made three key findings:

There is no increased risk of health effects from the smelter and its operations for people who come into contact with sediment and surface water within the coastal marine area or consume seafood inhabiting nearshore areas of the coastal marine area.
There is a limited risk to marine ecology related to discharges from the landfill.  While localised effects on aquatic organisms are plausible, elevated concentrations of copper found in marine water near the landfill are unlikely to have a measurable long-term effect. Elevated copper concentrations were evident in water quality samples from numerous locations around Bluff Harbour, including other locations distant from the NZAS smelter indicating secondary sources.
The three drains are the primary pathway for contaminant transport towards the coastal marine area.  Within the vicinity of the North Drain discharge point, adverse effects to aquatic organisms are plausible, however, once discharge reaches the coastal marine area, beyond the drain water mixing zone, there is a low risk of measurable adverse long-term effects on aquatic organisms.

The studies undertaken by GHD in 2021 – 2023 support the findings of previous studies released in 1995 and 2006 that discharges from NZAS drains were having a limited impact upon marine species within the coastal marine area.
NZAS Chief Executive Chris Blenkiron said, “We are pleased with the findings of the report as they provide us with confidence that we are implementing effective actions to mitigate the smelter’s environmental impact but it also provides us with clarity around where we can look to do better.”
“Tiwai is more than 50 years old, and we acknowledge that our practices haven’t always met expectations but we’ve worked hard to improve our environmental record and this report confirms we’re doing the right things.”
“In particular, I was really pleased that the report found that there was no increased risk of health effects for people consuming kai moana from the surrounding coastal marine area. Food gathering from the ocean is incredibly significant to our Ngāi Tahu partners but also our wider community here in Southland.”
Spokesperson for Ngāi Tahu, Jacqui Caine said “Ngāi Tahu has welcomed the partnership with NZAS on remediating the whenua (land) and coastal environment around Tiwai Point. Protection of mahinga kai activities is of upmost importance to Awarua and Ngāi Tahu more broadly.  It is reassuring to know that the kai moana in the harbour is safe to eat and that we can continue this important practice that we have done for several hundred years.”
A memorandum of understanding (MoU) was agreed in 2022 between Murihiku Rūnaka and Te Rūnanga o Ngāi Tahu with the New Zealand Aluminium Smelters Limited (NZAS) and Rio Tinto Aluminium Limited.  The parties have been working closely together over the last year to build a shared vision of remediation of the site.
The Advisory Group established under the MoU works to protect both Te Ao Tūroa (natural environment) and mahinga kai activities at or near Awarua/Tiwai peninsula coastal environment. With technical support from a joint Remediation Working Group, site specific remediation criteria have been co-designed with NZAS and Rio Tinto.  A plan for the remediation of the onsite drain network is currently under development.
“We are really pleased with the progress made in developing a partnership with NZAS to remediate the site. The first remediation plan we are co-designing is for the drain network.  The GHD report confirms we have selected the right focus area and we are looking forward to continuing this important mahi,” Caine said.
Siobhan Hartwell, Regional General Manager NZ Pacific for GHJD said “Our extensive programme of investigations has helped NZAS build a detailed picture of the site and the surrounding environment. Our technical support for NZAS will help the continuing environmental improvements and remediation of Tiwai.”
A full copy of the report, including an executive summary, can be found at: Sustainability | New Zealand’s Aluminium Smelter | NZAS

Background: Ongoing environmental testing and monitoring

As part of NZAS’ commitment to the environment, regular monitoring and testing of environmental impacts provides important indicators to ensure the measures in place are effective and further work is prioritised appropriately.
The detailed site Investigation (DSI), completed in 2021, started to provide a baseline of site conditions.
The 2021 DSI report recommended further testing to continue to build on knowledge of site conditions and understand any seasonal variation.
When NZAS released the DSI we committed to keeping the community updated as work progressed and we have proactively met this commitment.
GHD is a company with expertise in contamination assessment and remediation and have specialist skills in environmental testing and monitoring.
This GHD report was an important part of the work undertaken by the Advisory Group established to enable Te Rūnaka o Awarua and NZAS to work together to progress remediation priorities and criteria.