Cleanup of the Former FCC Pesticide Factory Site, Mapua: the End in Sight
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Cleanup of the Former FCC Pesticide Factory Site, Mapua: The End in Sight Andrew Fenemor1, Jenny Easton1, Tony Cussins2 1 Tasman District Council, Private Bag 4, Richmond, Nelson (Andrew Fenemor is now with Landcare Research Ltd, Nelson, but retains a project management role) 2 Tonkin & Taylor Ltd PO Box 5271, Wellesley Street, Newmarket 1036 1. INTRODUCTION The Fruitgrowers Chemical Company (FCC) site at Mapua has been described as New Zealand’s worst contaminated site. Tasman District Council, with a Government funding contribution, has contracted Thiess Services/EDL to remediate the pesticide- contaminated soils and estuarine sediments over the next two years. This case study summarises the history and status of the FCC site. We then identify the key communication tools used to obtain support for the project to this stage, and the risk communication challenges for the coming clean-up. 2. BACKGROUND The FCC site occupies some 3.8ha of prime coastal land in the heart of Mapua village, between Richmond and Motueka. The Fruitgrowers Chemical Company pesticide factory operated from 1932 to 1988. FCC formulated over 100 different pesticides, including persistent organochlorines such as DDT and dieldrin which have contaminated the site and environs, the underlying groundwater and adjacent estuary. Since the plant began, the surrounding land has gradually been developed for residential land uses. To undertake effective clean-up and avoid lengthy legal proceedings, Council negotiated to take over ownership of the whole site. This was completed in July 1996 after two years negotiations with Ceres Pacific and Mintech, who also contributed funding for site clearance and clean-up. Site concentrations of contaminants, as sampled to date, far exceed levels considered acceptable for residential use and needed to protect the estuarine environment. Maximum (worst case) concentrations found on site are as follows: Total Aldrin+ DDX dieldrin Maximum concentration (mg/kg) 11,560 200 Residential Soil Acceptance Criteria to 0.5m deep (mg/kg) 5 3 *DDX = total DDT, DDD and DDE. In addition, soil contamination on Tahi St properties bordering the site slightly exceeds residential criteria. Exposures to DDT and dieldrin are possible from the ingestion of the contaminants by the direct eating of soil by young children, and from food grown on the garden. Present impacts on the estuarine environment of the Waimea inlet include: the exceedance of the New Zealand Food Regulations for the eating of sediment-feeding shellfish in the estuarine mudflats next to the site, and the bio-accumulation of contaminants through the foodchain by fish and birds that eat the contaminated shellfish. 3. TENDERS FOR CLEANUP Tenders were sought in February 2001 from three companies whose treatment technologies had been proven in earlier trials for this project. Tenders were sought for soil clean up to: • residential standards over the whole site (requires no caveats on titles) • a combination of residential and commercial/open space standards across the site (commercial and open space clean-up criteria are the same) • commercial/open space standards for the whole site. It is important to note that all three clean-up standards protect the off-site environment from rainfall runoff and further leaching of contaminants to groundwater. See Table 2 Section 6.2. The Council has awarded the tender to Thiess Services Pty of Australia, a highly experienced contaminated site remediation contractor, for a clean-up to the second standard listed above (“Scenario B”). The expected project cost is $6.5 million. Government funding is in place for proceeding with Stages I and II of a four stage process of remediation. The separate stages are: Stage I: final characterisation of the site to obtain reliable data on contaminant distribution; Stage II: resource consents are obtained for the proposed works; Stage III: physical remediation of the site in accordance with the approved remedial action plan, including auditing that the site meets the target criteria; Stage IV: any ongoing monitoring and aftercare 4. CONTAMINATION LEVELS During 1992-96, detailed reports were obtained on contamination in soils, groundwater, tidal water, estuary sediments and shellfish. In 1998, clean-up targets for the site were derived using risk based acceptance criteria for human and environmental health (these acceptance criteria are discussed in detail below). Technical information and costs were obtained for suitable clean-up methods, and a cost- benefit analysis undertaken. Two-thirds of the site is contaminated above residential standards, mainly up to 2.0 metres deep. Contaminated soils and chemical wastes buried on-site are the major sources of contaminated groundwater and stormwater that has, and continues to, contaminate adjacent areas of the Waimea Inlet. Historically, wastes from plant operations were disposed of indiscriminately to a low lying area on the East side (known locally as Lake Tas), and to a reclamation of the Waimea Inlet on the western boundary, now referred to as the FCC landfill. Further site investigations were undertaken in September-October 2001 to characterise in more detail the nature and extent on soil and groundwater contamination on the FCC site, and provide information for Thiess to undertake revised volume analysis based on Clean- Up Scenario B (refer Table 1). 5. REMEDIATION WORKS 5.1 Scale of Cleanup The cleanup will involve the excavation, treatment and reinstatement of approximately 21,000 cubic metres of organochlorine contaminated soil and marine sediments at the site. Table 1 - Estimated Volumes of Contaminated Material requiring remediation (m3) West and FCC Landfill Marine Neighbouring Totals East FCC Sediments Properties Sites 9,950 9,300 1,000 1,200 21,450 Source: Thiess RAP (April 2002) 5.2 Mechano-Chemical Destruction (MCD) A number of alternative treatment technologies were considered to be potentially applicable from a technical and commercial standpoint, including thermal desorption (either direct or indirect) and ex-situ bioremediation. Thiess selected the MCD process which involves the dechlorination of organic compounds by the input of mechanical energy as impact forces in the presence of proprietary additives as electron and hydrogen donors. The MCD process comprises the following elements: • Soil pretreatment and preparation, including screening and predrying. • Material feed system where additives are metered and mixed. • A reactor where contaminants are dechlorinated in the presence of electron and hydrogen donors using impact forces from tonnes of ball bearings. • Treated soil handling and reconditioning. During the process the contaminated material is crushed to a fine particle size by the aggressive addition of mechanical energy as impact forces (and not by friction). The plant is fully enclosed and has a comprehensive dust filtering system, such that dust emissions are not predicted to be an issue for the process. Preliminary trialling of the MCD plant has been completed, and further trials are proposed later in 2002. The recently completed field trial of the commercial scale plant included associated materials handling and emission control equipment. Throughput of the commercial scale MCD plant ranges from 3 to 15 tonne/hour. 6. RISK ASSESSMENT 6.1 Potential Human Health and Environmental Effects Risks on the FCC site do not just relate to the existing contamination. The works to be undertaken for cleaning up the site bring their own risks. Obtaining resource consents during Stage II of the project will respond to local residents’ concerns about those risks. Based on our experience already in demolishing the FCC buildings in 1996, and excavating soil for treatment trials in 2000, the obvious risks to neighbours are from dust, odour and noise. Less obvious risks are to the estuary from runoff of contaminated stormwater, the dangers of excavating and handling unidentified potentially toxic wastes, and the contractual risks of possible budget blow-out or contractor default. Quantitative risk assessment methodologies were applied in two key areas of the Mapua site remediation. These are risk based site acceptance criteria and risk assessment of environmental affects. 6.2 Risk-Based Site Acceptance Criteria The Mapua site, once remediated, may be used for a variety of purposes including residential, recreational, and commercial. Therefore site specific risk-based soil and sediment acceptance criteria (SAC) were developed by Egis Consulting Ltd, Australia for the various landuse scenarios. SAC for key organochlorine contaminants of concern are presented in Table 2. The purpose of developing the criteria was to provide a basis for planning remediation and management works at the Site. The methodology used by Egis in the development of the acceptance criteria was as follows: • A screening level assessment of current contamination on and offsite (in order to support the selection of the contaminants of potential concern and to assist in understanding the relationship between contaminant concentration in various environmental media); • Development of a conceptual model for the site and its environs, i.e. residential habitation and interactions between environmental compartments and biota, both on and offsite, and the development of a generic food chain to assist in understanding the possible impact of sediment contamination. • The contaminants of potential concern were determined to be DDT and dieldrin, and these contaminants formed the focus of the risk assessment.