Soil contamination at Dow's former manufacturing facility at Paritūtū was in places more than 450 times that of previously acknowledged groundwater contamination. File photo. Photo: Getty Images / David Hallett
The extent of soil contamination at a controversial New Plymouth chemical plant has been revealed after a report 'lost' since the late 1990s emerged.
Taranaki Regional Council (TRC) has released the Soil and Groundwater Evaluation, after first seeking permission from multinational chemicals giant Dow.
It is part of a wider 1996 Environmental Assessment Project (EAP) at Dow's former manufacturing facility at Paritūtū.
It shows soil contamination was in places more than 450 times that of previously acknowledged groundwater contamination.
It was also more than 1400 times higher than a level the TRC said was acceptable - based on an overseas benchmark - during its 1996 investigation of the Ivon Watkins plant at Buller Street in New Plymouth.
Dioxins researcher Andrew Gibbs said new information in the rediscovered report added weight to an argument that a current investigation of the Paritūtū site should be extended into neighbouring Centennial Park.
The Paritūtū plant was demolished in 2022, and Dow and its New Zealand-based remediation partner Tonkin & Taylor are part way through a clean-up process expected to take several years.
Tonkin & Taylor has finished a Preliminary Site Investigation (PSI) which has been submitted to the TRC and is being independently reviewed by consultants Beca Group.
Ivon Watkins - later Ivon Watkins-Dow - made the herbicides 2,4,5-T and 2,4-D at Paritūtū from 1960 through to 1987.
The herbicides, which contained toxic dioxins, were a key component of Agent Orange - the defoliant used by the US military in the Vietnam War - which has been linked to cancers and birth defects.
It was expected given the average 46-day half-life of the chemicals - the time for 50 percent of it to breakdown cited in the 1996 EAP - any contamination discovered in the PSI would be at a reduced level.
Lost report found
A summary of the 'lost' Soil and Groundwater Evaluation was leaked to Gibbs, but it did not include soil testing data.
Gibbs and RNZ asked to see the full report, but were initially told it could not be found.
TRC director of environment quality Abby Matthews said the report - which was stamped "confidential" - was never "missing as such" as it had always been in its archives, but not where it was expected to be.
"It appears the report had been re-filed in the wrong box, possibly when our archiving system changed in the late 1990s.
"We have no way of knowing when it was last seen."
Dow did not respond directly to RNZ's questions about why the soil contamination data had not been released in 1996, instead it pointed to the current site investigation.
"These are good questions," the company said in a statement.
"[It is] exactly why Dow has committed to a detailed study of the current environmental status at the Paritūtū site rather than relying on information which in many cases is well over 30 years old.
"The objective is to obtain and work with accurate current data rather than speculation about what might or might not have been found or said decades ago."
The TRC reviewed and accepted the results, conclusions and recommendations of the 1996 EAP report, but Matthews said it was not responsible for releasing the data it contained.
"Dow (then DowElanco) voluntarily commissioned the 1996 report, which was shared with Taranaki Regional Council for information. The media release of 27 September 1996 was also written and issued by Dow (then DowElanco)," she said.
In June, RNZ reported documents leaked to Gibbs indicated the current investigation might need to be extended beyond the site's boundaries.
Gibbs argued groundwater contamination found at the site's northern boundary could have been caused by offsite liquid waste ponds once at the base of Paritūtū Rock.
The leaked documents were part of the EAP report that the TRC - which owned the 16-hectare site at the time - informally requested of Dow in the 1990s, and included a 1994 hydrology survey, a summary of the missing 1996 Soil and Groundwater Evaluation (minus soil data), and a 2020 groundwater management report.
The TRC sold the Paritūtū site to Dow for $1.7 million in 1997.
A year earlier, Dow's EAP report pointed to two areas of low-level phenoxy and chlorophenol contamination of groundwater on the site at quantities of less than 15ppm (parts per million).
This compared with a United States Environmental Protection Agency guideline - reviewed for New Zealand marine environment conditions - of 30ppm.
It identified test bore 39 on the site's western boundary and bore 42 on the northern fenceline as the areas of concern.
Dow's focus was on groundwater contamination, and it emphasised that the pollutants were not a risk to staff or nearby residents and would not reach the coastline which was now a marine park.
It did not test for dioxins.
"In soil situations, dioxins would bind to the clay soils and not move with groundwater and therefore would not pose a threat to the environment," its 1996 media release said.
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. Photo: Supplied
What the report shows
Drilling logs from the full Soil and Groundwater Evaluation revealed elevated levels of phenoxy weedkillers and related chlorophenol chemicals were found in the soil at 13 test bores.
The highest level of contamination was on the western boundary where historically chemical drums had been discarded.
At test bore 39c, phenoxy weedkiller was found at 5521.5 parts per million and chlorophenols at 1806.5ppm.
This far exceeded the 5ppm the TRC cited as a "clean-up" level at Buller St.
More than 80 percent (4659ppm) of the contaminants at bore 39c were 2,4,5-T and 2,4-D, the components of Agent Orange.
The report also showed 13 groundwater test bores were contaminated.
The highest levels of phenoxy and chlorophenol were at test bore 39J at 14.5ppm and 1.5ppm respectively, while bore 42 returned 6.5ppm and 1.4ppm.
Dow's modelling suggested no contaminated groundwater would reach the coast at above laboratory detection limit of 0.03ppm - the lowest level it could be found in a test sample.
The Soil and Groundwater Evaluation described bore 42 as a "point source" - according to one definition a single identifiable source of pollution from which pollutants are discharged - but said contaminants would be below laboratory detection limits at 100m from the bore.
The report recommended capping over contaminated soil with an impermeable seal to prevent further rainfall infiltration into the site's aquifers.
Report significant - Dioxins researcher
Gibbs said details revealed in 'missing' evaluation report were significant.
"Number one, the very high levels of contamination from 2,4-D and 2,4,5-T - the components of Agent Orange - were found in soil out the back of the plant on the western boundary where the TRC reported chemical drums had been discarded and the contents have leaked into the soil.
"These have never been reported before and they are much higher than the groundwater levels that were reported."
He said the report reinforced the argument that the current site investigation should be extended into neighbouring Centennial Park.
"The second highest level of groundwater contamination was over the northern end of the plant by the old ponds, but they did not find any soil contamination there.
"This is really compelling evidence that groundwater contamination is the legacy of the 1960s discharge ponds.
Gibbs believed the ponds were not just for cooling water as had been suggested but were used for discharging waste which drained down to Back Beach.
Taranaki Regional Council responds
TRC director of environment quality Abby Matthews said previous comments that the council "was not aware of soil contamination on the [Paritūtū] property" referred to under the building where 2, 4, 5-T was made.
No testing has ever been done there.
She reiterated the TRC's concern was about groundwater contamination.
"The risk to the environment arose from the potential migration of contamination within groundwater beyond the property boundary.
"To that end, an expanded groundwater monitoring network was agreed between the company and council, with additional monitoring put in place.
"The purpose of the groundwater programme was to detect any migration of contamination towards the property perimeter, along with tracking any changes in the levels of contaminants over time."
Asked about whether further testing should be done in Centennial Park near the site's boundary, Matthews referred to the current site investigation.
"Dow's preliminary and subsequent detailed site investigations are being undertaken by Tonkin and Taylor.
"Their report is currently being independently reviewed by Beca on behalf of New Plymouth District Council, iwi, hapū and ourselves and will be available soon. The report will bring together all available information about the site."
Dow responds
In its statement, Dow said to develop a comprehensive and accurate analysis of the site the first step was to prepare a Preliminary Site Investigation report, which was due out soon.
As requested by the TRC and the mana whenua, the PSI was being reviewed by an independent expert selected by the TRC and mana whenua.
This was designed to close any testing and data gaps identified during the preparation of the PSI, including points raised by RNZ's questions, it said.