The Parliamentary Commissioner for the Environment, Jan Wright, says the Government's costs in its fraught clean up of contaminated soil at Mapua, near Nelson, are double the original estimates.
Tasman District Council initially pledged $2 million and the Government $3.8 million for the clean-up, but the final bill is expected to be over $8 million.
The 3.5ha former Fruitgrowers' Chemical Company site, the Lime and Marble site, and a Tasman District Council-owned landfill - carried the legacy of five decades of production of organochloride and organophosphate pesticides such as DDT, dieldrin and lindane, by the agrichemical company, which stopped operating in 1987.
The Resource Management Act in 1991 made landowners responsible for clean-up costs, but Tasman District Council took over much of the land in 1996 and agreed to split the clean-up costs with the Government.
Today Dr Wright said some of the problems in the clean-up stemmed from the Ministry for the Environment taking over the operation when the original contractor pulled out, and the escape of toxins such as mercury and copper to the air and water around Mapua.
She recommended:
* Establishment of a pool of independent, technically expert environmental auditors and guidelines for auditing remediation of contaminated land;
* Completion of a validation report on the Mapua clean-up no later than October 31, and have it audited by the end of the year;
* Outlining the experience gained from use of the NZ-developed mechano-chemical dehalogenation technology;
* Tasman District Council test residential land at the site for mercury residues in the top soil layer;
* Assessment of probable environmental impacts of copper use in the remedial works at Mapua, and recommending any further work needed to prevent further degradation of the estuary;
* Taking any remedial action advised by the site auditor, to bring groundwater and sediment contaminants down as much as possible by May 2009;
* Making sure that if the Ministry for the Environment is to take on operational functions, it has appropriate in-house technical capability;
* Recognising that a containment strategy for many contaminated sites may be the best choice for both environmental and financial reasons.
