Investigation into former New Plymouth chemical plant finds potential for contamination

The Dow AgroSciences plant at Paritutu, New Plymouth, photographed on February 15, 2001.
photo: Getty Images/David Hallett

• Investigation of former Dow Chemical plant concludes potential for contamination
• The herbicides 2,4,5-T and 2,4-D, which contained toxic dioxins, were produced in New Plymouth between 1960 and 1987.
• They are a key ingredient in Agent Orange, which has been linked to birth defects and cancer
• Dow has committed to a restoration project at Paritutu that is expected to take several years.

An investigation into contamination at a former chemical plant in New Plymouth has concluded there is potential contamination at the site that could impact human health and the environment.

Ivon Watkins – later Ivon Watkins-Dow – produced the herbicides 2,4,5-T and 2,4-D in Paritūtū from 1960 to 1987.

These herbicides contain toxic dioxins, the main ingredient in Agent Orange, a defoliant used by the U.S. military in the Vietnam War that has been linked to cancer and birth defects.

The Paritutu site was demolished in 2022, with Dow and its New Zealand remediation partner Tonkin & Taylor involved in a clean-up process that is expected to take several years.

Tonkin & Taylor was responsible for the preliminary site investigation (PSI) which has just been completed.

“The study concluded that contamination may be present in surface soil, subsoil and groundwater (shallow and deep) which could affect human health and/or the environment,” Dow said in a statement.

The company said the PSI is an important milestone in the remediation project and will help it understand the history of the Paritutu plant and the potential for any contamination.

Dow acknowledged that the investigation “did not involve the collection of samples from the site; however, the information provided by PSI will assist in planning future sampling, if necessary”.

PSI involves review of:

• Historical documents and data
• Activities in the Former Place
• Site environment settings
• Regulatory framework and consent requirements

Dow said the information collected and interpreted in the 137-page PSI will be used to help plan future soil and groundwater investigations and outline possible remedial measures.

“We remain committed to transparency and community engagement throughout the remediation process. The next step involves a detailed site investigation (DSI), focusing on comprehensive soil and groundwater sampling to better understand the current status of Paritūtū and whether there are any existing exposure pathways.

“Remediation work will commence where necessary, following the process outlined in the published remediation roadmap.”

Dow said the Paritūtū PSI was a comprehensive report that had been reviewed and endorsed by an independent peer reviewer (Becca) appointed by Taranaki Regional Council (TRC) and tāngata whenua.

The full Paritūtū PSI report will be submitted to the Truth and Reconciliation Commission.

one Four-page report summary include:

• A brief history of the site
• Description of the site geology and groundwater flows
• Overview of manufacturing operations from the early 1960s until the plant ceased operations in early 2021
• Description of the environmental context of the site, including pollution sources, exposure pathways and receptors.

For more information, visit Tonkin + Taylor project website.