'While the clean-up of the contaminated soil at the Mapua site seems to have been successful, site operations during one period – September 2004 until November 2005 – were not well run. This may have led to some dioxins and other toxins being discharged during the clean-up process.'
When the investigation was started following complaints in 2006, the then Commissioner asked health authorities and the Department of Labour to look into the situation as well. 'These authorities have been working within the community and will complete their investigation over the coming months.'
Large volumes of a wide range of agricultural chemicals had been manufactured and stored at the site over several decades. 'The treatment process used did successfully treat the soil but, in doing so, may have released some dioxins,' said Dr Wright.
'There is also a small risk that the soil may have some residual mercury contamination. The soil needs further sampling before building on the site.'
Ground water and sediment have also been contaminated by copper used during the treatment process. 'This copper is not toxic to people, but is not good for the estuary. However it can be dealt with relatively easily.'
The PCE report makes several recommendations for public agencies to implement, to improve management of other contaminated sites. 'Public agencies must respect technical expertise – and have that expertise in house if they are to take on operational projects,' said Dr Wright.
The PCE will release a second report on Mapua later this year, once final cleanup data is available from Ministry for the Environment, which managed the project.