KEY POINTS:
Sealing over contaminated soil at Mapua, near Nelson, may be safer and cheaper than trying to dig up a site and clean up the soil, says the independent Parliamentary Commissioner for the Environment (PCE).
"In most cases, the actual area of these individual sites is small, but the cost of remediating the soil will be prohibitive," Commissioner Jan Wright said today in a report on the nation's biggest and most expensive contaminated site.
"Sealing up contaminated sites ... may well be safer for people and better for the environment, than trying to clean them up," said Dr Wright
While the clean-up of the contaminated soil at the Mapua site "seems to have been successful," dioxins and other toxins may have escaped between September 2004 and November 2005 when operations at the site were not well run.
"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 in the nearby estuary had also been contaminated by copper used during the treatment process.
Effects of this pollution were still being investigated by health authorities and the Department of Labour.
The commissioner will release a second report on Mapua later this year, once final cleanup data is available from Ministry for the Environment.
The Fruitgrowers Chemical Company (FCC) built a pesticide plant at Mapua in 1932 and 13 years later began producing organochlorine pesticides.
When the plant closed in 1988, the site was abandoned and in 1999, the Government decided to assist Tasman District Council (TDC) with funding its cleanup.
The commissioner today called for future projects to have robust decision-making, clear separation of roles to avoid conflicts of interests, and respect for technical expertise.
Dr Wright criticised the decision to remediate the soil rather than contain the contamination, and the Ministry for the Environment's decision to hold the resource consent when the main contractor (Thiess) pulled out.
She questioned the capability of a policy agency to undertake operational management of such a project.
Tasman District Council obtained consents in 1997 to cap the site with clay and instal a subterranean bund wall to reduce the discharge of contaminants into groundwater, but the Government said it wanted to see the land remediated rather than contained.
The Government's costs have been double the initial estimates, but much of the land is now likely to be suitable for residential development and hugely valuable.
- NZPA
