Source: Radio New Zealand
The DOW Agroscience plant in Paritutu, New Plymouth pictured on 15 February, 2001. Getty Images / David Hallett
Soil tests done as part of a remediation project at a controversial former chemicals plant in New Plymouth have given a large section of the site a clean bill of health.
However, dioxins researcher and community advocate Andrew Gibbs has questioned why the area tested – the least likely contaminated section of the 16 hectare site – was chosen, and said the results amount to “green washing”.
Ivon Watkins – later Ivon Watkins-Dow – made the herbicides 2,4,5-T and 2,4-D at Paritūtū from 1962 through to 1987.
The herbicides 4,5-T and 2,4-D, which contained toxic dioxins, were a key component of Agent Orange – the defoliant used by the US military in the Vietnam War – which had been linked to cancers and birth defects.
The Paritūtū plant was demolished in 2022, and a five-stage clean-up process was expected to take several years.
Dow Chemicals which bought back the site in 2023 has partnered with New Zealand firm Tonkin & Taylor to undertake the remediation programme.
Paritūtū Remediation Project field staff took soil samples in November 2024 from 61 locations across a 2.6 hectare grassed area in the southwest corner of the site, known as Zone 1, which borders residential housing and Centennial Park.
An aerial view of the Paritūtū site showing the different zones. Supplied / Tonkin+Taylor
They were then independently analysed.
The analysis – which has been summarised on the Paritūtū Remediation Project website – found the main soil types were interbedded sands and clay.
“[There was] some evidence of fill material was found in two sample locations; however, these were tested for specific analytes (chemical entities) and there was no evidence of contamination.”
Dioxins levels “were all well below the relevant New Zealand Soil Contaminant Standards”.
Zinc at above typical levels was found in samples taken from an area near the site boundary, but they appeared to be unrelated to Dow operations, the summary said.
Area tested had low contamination – dioxin researcher
Dioxins researcher Andrew Gibbs questioned why the Paritūtū Remediation Project team had decided to test Zone 1 first.
“They haven’t tested the most contaminated sites that were identified in 1985 and the late 90s. They’ve gone straight to an area where contamination was low, which makes for a good soundbite for them, but it doesn’t really look at the core problem.
“You would have thought they would have tested where they found the highest contamination in ’85 where the extracted dioxin and waste was stored, which is just north of Zone 1.
“And underneath the two soak ponds, one of which has never been tested, the northern one, and the western one that straddled both sides of the boundary fence, where extremely high levels of contamination were found.”
The Ivon Watkins Dow site at Paritūtū with red dots indicating locations of test bores 39 and 42. The test bore 42 is adjacent to the waste ponds across the road at the foot of Paritūtū Rock. Supplied
Gibbs said while it was good news for Zone 1, publishing these test results smacked of “green washing”.
Paritūtū Remediation Project said it was a deliberate choice to first test in Zone 1.
“This area was chosen for the first phase because it was expected to have low contamination levels and presented a good opportunity to test investigation methods before moving on to other areas of the site.”
This logical sequence of investigation was agreed with the independent peer reviewer before work commenced in November 2024, the project team said.
Testing in Zone 1 would help refine the plan for the next stages of the site investigation.
Last year, the Paritūtū Remediation Project team completed a desktop Preliminary Site Investigation which acknowledged the potential for contamination to still exist at Paritūtū which could affect human health and/or the environment.
It had since divided the site into 10 zones as part of a Sampling and Analysis Plan.
The new bore samples taken in Zone 1 were part of Phase 1 of that plan and field staff drilled to depths varying from 1m to 3m.
A further round of soil sampling was completed in June 2025 focused on grassed areas, with a limited number collected in the hardstand (paved) area on the west of the site.
According to the project website, 68 soil samples were taken from 31 locations which had been analysed by an independent laboratory for future reporting.
Process too slow, says mayor
Meanwhile, New Plymouth mayor Max Brough was disappointed with how long the remediation process was taking.
“It seems to be taking a very long time and I question whether we have enough will being applied to getting through this process fast enough.”
New Plymouth mayor Max Brough. ROBIN MARTIN / RNZ
Brough’s predecessor Neil Holdom was adamant the site was contaminated.
“I absolutely believe that site is full of some of the most toxic materials that you can imagine in New Zealand and at very high levels of concentration and that they pose a real risk to human health and to the environment, particularly the neighbouring marine park,” he told RNZ last year.
He declined to comment on the latest test results deferring to New Plymouth’s current leaders.
Iwi monitors accompanied field staff during the testing, but were not it a position to comment on its results at this stage.
Brough said he was happy to take up the baton from Holdom.
“So my predecessor, as you know, has had some very strong opinions around that site. He’s probably come off a much greater level of knowledge than what I’ve walked into here in the first few weeks, but actually one of the organisations that’s on my list of people to set up a meeting with is the owner of that site from the early days.
“I’m happy to pick it up and take it on where Neil left off. Actually, that’s part of what we need to do in this city is clean up that site.”
Brough said he did not know whether to feel optimistic or not about the latest test results.
“I understand process can take a long time, but this is, this has been going on for far too long now already. Get on with it. That’s my message to the owners of that site. The people undertaking [the] job, get on with it.”
Paritūtū Remediation Project said the Taranaki Regional Council had scheduled a briefing for New Plymouth district councillors in early December.
“This will provide a comprehensive update of the Paritūtū project, including a high-level overview of the timeline and long-term outlook.”
According to the project website, results from the Sampling and Analysis Plan would feed into a more complex Detailed Site Investigation (DSI) which would evolve as data became available.
“The DSI will be completed and submitted to the Regulators (Taranaki Regional Council) in due course, once the whole site has been investigated and the full report has been independently reviewed by the Council-appointed independent peer reviewer.”
A detailed remediation progress report, including an overview of the process being undertaken, was scheduled to be presented at Taranaki Regional Council in December.
Sign up for Ngā Pitopito Kōrero, a daily newsletter curated by our editors and delivered straight to your inbox every weekday.
– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand
