Parliamentary Commissioner for the Environment - Te Kaitiaki Taiao a Te Whare Pāremata

Investigation into the remediation of the contaminated site at Mapua

Commissioner's preface

The settlement of Mapua has grown beside a particularly beautiful estuary a few kilometres west of Nelson. My childhood memory of Nelson-Tasman is of sunshine, beaches and apple orchards. In 1932 Mapua would have been a logical place for the Fruitgrowers Chemical Company (FCC) to build its plant for manufacturing pesticides. Thirteen years later, production of the powerful new organochlorine pesticides (OCPs) began.

The FCC plant was established in a time of far less scientific understanding of chemical toxins, and consequently little appreciation of the need for protecting people or the environment from exposure to them. By the time the plant closed in 1988, this situation had changed. The site was abandoned and its legacy of contaminated soil inherited by the people of the Tasman District.

The Mapua site was considered to be one of the worst contaminated sites in the country. It was a problem of a complexity and scale that was clearly beyond the resources of many councils. In 1999, with a growing awareness of the contaminated land issue in New Zealand, the government decided to assist Tasman District Council (TDC) with funding, as well as research and advice. From that time the Ministry for the Environment (MfE) began to work actively towards the remediation of the site.

In 2008, the remediation was completed. The long process was fraught with challenges. The type and scale of remediation was new territory for New Zealand, and indeed it would be astonishing if there had been no mistakes or errors of judgement. Further, although the remediation technology is now being used successfully overseas, that success must, to some extent, be based on the lessons learned by its owner from the less-than-satisfactory operation in its first commercial application.

It is my hope that this investigation will be seen as providing the opportunity to learn and feed positively into contaminated sites policy and management. To help reduce risks to people and the environment, a number of lessons can be drawn from the Mapua experience. These include the need for:

• Robust decision-making
• Clear separation of roles to avoid conflicts of interests, and management of such conflicts where they are unavoidable
• Respect for, and appropriate use of, technical expertise.

The environmental outcomes are mixed. The OCPs in the soil have almost certainly been mostly destroyed, although confirmation must await the final Validation Report. The use of a large quantity of an ecotoxic copper compound as a reagent should have been controlled; and there is a possible residual problem with mercury.

During the process of destroying the OCPs, a variety of toxins may have been released into air and water. Discharges to air are mainly of concern because of the potential risk to human health; discharges to water are mainly of concern because of the risk to the ecology of the Waimea Estuary.

The problems with discharges to air stem from the design and operation of the soil clean-up plant and inadequate monitoring of emissions. Of greatest concern is the possible creation of dioxin in the soil drier and its release, due to deficient control systems. Certainly a small amount of dioxin was created and emitted during one of the early trials. If dioxin (and other toxins) were emitted to air later, the amount may well be insignificant; the problem is that inadequate monitoring systems have rendered the monitoring data of little value.

My predecessor, Dr Morgan Williams, initiated this investigation in 2006 in response to complaints from members of the public. At that time, he appropriately referred matters relating to human health to the Ministry of Health, and matters relating to workplace health and safety to the Department of Labour. For this reason, I have not made any recommendations regarding the potential health impacts on people on the site or in the vicinity of the plant. However, I appreciate the anxieties local people may have about this matter, and understand that reports from the Ministry of Health and the Department of Labour will be forthcoming.

The problems with discharges to water chiefly arise from the use of certain reagents during the remediation process, namely copper sulphate, diammonium phosphate and urea. These can make their way to the estuary via groundwater and runoff. Copper is highly toxic to marine life; phosphate and nitrate (from the urea) degrade water quality by promoting the growth of algae. Residual OCPs are also still elevated in the groundwater. There is still an opportunity to reduce future discharges to the estuary through relatively inexpensive technical fixes.

Two decisions seem to have been fundamental in creating the risks that have undermined the success of the project – the decision to remediate the soil rather than contain the contamination, and MfE's decision to hold the resource consent when the main contractor (Thiess) pulled out.

The decision to remediate the soil

In 1997, Tasman District Council obtained consents for capping the site with clay and installing a subterranean bund wall to reduce the discharge of contaminants into groundwater. However, this containment strategy would have limited the use of the land to open space and possibly some commercial development.

In 1997, the Government expressed a desire to see the land remediated rather than contained. Funding was provided in the 1999 Budget, and expected to be sufficient for remediation to a standard that would allow a wider range of future land uses. The final amount of funding provided by the Government has turned out to be approximately double the initial amount envisaged. However, much of the land is now likely to be suitable for residential development and thus of considerable value.

In hindsight, remediation of the soil on a site in the middle of a residential area and adjacent to a sensitive estuary was a high-risk strategy. Trucking the soil offsite for treatment was considered and rejected, although it may well have been preferable. However, the original containment strategy had much to commend it.

There is a more general lesson here. There are many contaminated sites in New Zealand – an unwitting legacy from past activities like timber treatment. The correct solution for each site will depend on its particular circumstances. In most cases, the actual area of these individual sites is small, but the cost of remediating the soil will be prohibitive. Expectations will need to be addressed, as policy on contaminated sites is developed. Moreover, containment strategies that close or limit pathways by which the contaminants can be mobilised may often be superior environmentally as well as financially, as it is only when contaminants are mobilised that they become dangerous.

MfE's decision to take over the resource consent

When the relationship between Thiess and EDL "broke down", MfE elected to become the holder of the resource consent. This gave MfE a much greater operational management role alongside its responsibilities as agent of the Crown. Multiple roles set the stage for conflicts of interest.

The capability of a policy agency to undertake operational management is another concern. MfE was created as a small policy advisory agency in 1986 in accord with the prevailing public sector philosophy. Over recent years, its role has become increasingly operational.

I make no judgement as to whether or not this is appropriate, but some thinking about its role is clearly needed. If MfE is to perform operational functions, those functions need to be clearly defined and supported by the appropriate in-house technical capability.

Finally, I would like to thank the staff, past and present, who have spent many hours wrestling with the complexity of this investigation. I am particularly grateful to Dr Simon Watts who has led the investigation to its conclusion with grace and rigour.

Recommendations

That:

1. The Minister for the Environment establishes a mechanism for appointing a pool of independent, technically expert environmental auditors to assist with the management and remediation of contaminated land; and develops guidelines for when an accredited environmental auditor may be required, and the matters that such auditors may certify.
2. The Minister for the Environment directs the Ministry for the Environment to complete the validation report no later than 31 October 2008, and have it reviewed by another site auditor no later than 31 December 2008.
3. The Minister for the Environment issues a short technical statement outlining the experience gained from use of the MCD technology for remediating soil contaminated with OCPs for the benefit of future users of this technology.
4. Tasman District Council, as site owner, conduct further soil sampling across parts of the site zoned for residential development, to assess whether or not any residual mercury exceeds remedial criteria in the cover layer.
5. The site auditor's review include an assessment of the probable environmental impacts of copper use in the remedial works at Mapua, and make recommendations as to any further studies, remedial actions or covenants that may be necessary to prevent further degradation of the estuary.
6. The Minister for the Environment directs the Ministry for the Environment to take further remedial action as advised by the site auditor, to ensure that groundwater and sediment impacted by contaminants from the Mapua site meet remedial criteria to the extent currently achievable, before May 2009.
7. If MfE is to perform operational functions, the Secretary for the Environment ensures that these functions are clearly defined and supported by the appropriate in-house technical capability.
8. National and regional policy-makers recognise that a containment strategy for many contaminated sites may be optimal environmentally as well as financially.

The update report is available here.