Chatham Rock Phosphate tackles analysis of wealth of data

Chatham Rock Phosphate tackles analysis of wealth of data

2 May 2012
Scientists and engineers working for Chatham Rock Phosphate have started the huge job of studying the wealth of data gathered during 48 days of surveying on the Chatham Rise this summer.

“We have 35 tonnes of phosphate rock and sandy silt to analyse, with the results being used to design our mining and environmental management systems and prepare the reports for our applications for a Mining Licence and Marine Consent that we plan to submit later this year,” CRP chief executive Chris Castle said.

The analysis will assist the design of systems for phosphate recovery, on-board separation of the nodules, and redeposition of sediment back to the sea floor. In addition, CRP will use the data for a very detailed range of environmental studies, the rock phosphate beneficiation studies already underway, the feasibility of on-board glauconite separation systems, and fertiliser market development.

The information, targeted at the Rise’s significant phosphate resource and the environment in which it is located, also contributes significantly to the store of public good information used by scientists to understand New Zealand’s oceanic environment.

CRP gathered the data during four research surveys of the Chatham Rise licence area using a range of high tech equipment. The surveys collected geophysical data in December, bottom samples in February, environmental data in March and geotechnical data in April. Boskalis engineers who were on the survey have remained in Wellington for the analytical work.

The design of mining system will bring together technologies used in a wide variety of extraction systems. Considerations range from evaluating the nature of the material and where it is deposited, to how it is lifted, separated and returned, the vessel design, and off-loading port selection.

The design process also includes developing a model to assess the environmental impacts of each stage of extraction. The research is also looking at the potential impact of extraction and sediment deposition on local ecosystems and identifying sensitive species and areas of special environmental conservation, as part of habitat mapping.

The modelling and analysis will also consider the natural dynamics of the area – the variation of water flow speed and direction over depth, turbidity, light attenuation in the water column, occurrence of upwelling events, natural settlement behaviour of fines, possible density currents and ecosystem resilience.

The research Boskalis has conducted so far has identified four main elements relating to the extraction of phosphate that will contribute to environmental changes. These are:

Removal of the top layer from the seabed
Turbidity generated by the extraction and sediment return process
Deposition of returned sediment, mainly on just mined areas of the seabed
Possible changes to and mixing of the water column, due to the outflow of water at a slightly different depth than the intake.

CRP has commissioned NIWA to study the wider Chatham Rise ecosystem to contribute to the Environmental Impact Report being coordinated by consultants Golders.

Environmental monitoring is crucial to ensure the impact of extraction activities are minimised and to identify any necessary mitigation measures. Requirements for the Environmental Management Plan that will form part of a Marine Consent will be determined during the Environmental Impact Assessment, based on the work method chosen and the outcome of the various studies.

CRP and its agents will carry out all mining activities in accordance with any Marine Consent issued by the Environmental Protection Authority pursuant to the (forthcoming) EEZ environmental consenting regime legislation, which Act and associated regulations are due to be passed later this year. Guidance provided by International Marine Minerals Society Code for Environmental Management of Marine Mining will also be of assistance in this regard.
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