WATER PROTECTION

As its name suggests, the hydrometallurgy process used in the Vale Inco Nouvelle-Calédonie plant requires large quantities of water. The plant must have access to a reliable and abundant water supply; on the other hand, unrecycled water used during the process (two thirds are recycled) represents liquid waste which requires treatment before being discharged.

Port facilities are essential both for transporting raw materials and combustibles to the plant and for exporting finished products.

Moreover, due to the erosion caused by heavy rainfall during New Caledonia's wet season, an efficient runoff water management system is essential to protect rivers and subsurface water. Finally, as one of a range of compensatory measures, coral transplantation program has been undertaken.

• Water supply
• Runoff water management
• Soil morphology linked to natural erosion
• Freshwater protection: settling basins
• Subsurface water management
• Red rivers: a common phenomenon in New Caledonia's Southern region
• Marine effluent discharge
• Port activities
• Protecting the whales
• Coral transplantation
• Impact studies – seawater

Water supply

Water will be supplied from nearby Yaté Lake. Vale Inco Nouvelle-Calédonie has put in place a number of measures to reduce any impacts from this additional use of the lake resource:

• Water will be pumped via a pipe sunk along its whole length and running beneath the road as it crosses the Madeleine nature reserve to avoid any clearing of plant cover in the area. There reserve will be completely unaffected, even visually.
• The amount taken represents less than 1.5% of total outflow from the lake, which will therefore not be affected. 
• 60% of water requirements will be supplied from recycling. In other words, each operating cycle will only require 40% of the water used to be pumped from the lake. The remainder will consist of water used in the preceding cycle then treated before being re-used.The grounds for the decision not to recycle 100% of water were that this option would triple energy consumption and increase atmospheric emissions.

Runoff water management

The Goro plateau where the mine is located is a laterite massif comprising a surface soil layer (created by natural rock decomposition) and a network of underground infiltration paths and cavities. 

This sector receives New Caledonia's second heaviest rainfall, with over three metres of rain falling every year. During high rainfall periods, there is an increase in natural overland runoff resulting from both surface and subsurface water flow.

Soil morphology linked to natural erosion

The sides of the laterite plateau are characterised by erosion areas (« lavakas »), created by natural upwellings and runoffs in extreme conditions. The stripping of plant cover and, more particularly, of the duricrust surface has weakened soil stability.
An excellent knowledge of this water system and watershed geometry was essential to ensure that adequate sedimentation basins were constructed.

Freshwater protection: settling basins

The Vale Inco Nouvelle-Calédonie mine is located in the River Kwé basin on the Goro plateau. Structures have been designed and built to protect the river, located upstream from excavation work, and also subsurface water, as laid down by the first ICPE permit regarding the pilot plant (1999) and by the second permit regarding the final plant (2004).

These structures mainly comprise a series of settling basins to collect rainwater with a significant suspended solids content. As water flows through the basin, sedimentation of the heavier particles occurs and they sink to the bottom allowing the suspended solids-free clear water to flow out over the upper section of the basin.  The settling basins are frequently scoured to ensure their continued treatment efficiency.

These basins, which have been in use in all New Caledonian mines for the last 20 years, had to be made exceptionally large for use on the Goro plateau due to the depth of the laterite layers in the South and the vast scope of work:

• Since 2005, the mine has possessed 2 large main basins with a capacity of 20,700 m3 and 8,600 m3 respectively.
• Construction of a third basin in 2006 to provide back-up capacity will ensure there is an even smaller risk of suspended solids being carried down to the Kwé.
• These facilities will be expanded as the mine moves forward and plant construction progresses. 
• Forty other basins will be installed downhill from all cleared areas. Samples will be taken 2 to 3 times a day during the rainy season to monitor discharges.
• The plant, conveyor and port areas will also be provided with a system of settling basins.

Once completed, this water management system will be extremely efficient. At the mine, where the finished system is in place, its efficiency has been proved in dealing with heavy storms and rainfall. Indeed, the system is now used as a reference by the New Caledonia Mines and Energy Inspectorate (DIMENC) for many other mines in New Caledonia.

Subsurface water management

Subsurface water is monitored rigorously and frequently by a dense network of observation pipes (sampling pits), particularly around the solid waste storage area. In the event of a problem being detected, in spite of all the measures implemented, a pumping system in a filter drain network (system of pits) upstream from the storage area will prevent any contamination of the water table by recycling mineralized water to the plant for treatment.

Red rivers: a common phenomenon in New Caledonia's Southern region

Rivers running red after heavy rain are a well-known phenomenon in New Caledonia, especially in the south of the Main Island. The area’s laterite-rich geological context means  friable layers are easily eroded by surface or ground water runoff flow and this is particularly true of red laterites (their reddish colour being due to their high iron content), which tend to disintegrate under the pressure of water.   

There are very extensive natural laterite sedimentary basins where eroded matter has been accumulating for around 36 million years. As riverbeds deepen, they eat into these sediments causing reddish matter to be carried away.  

It is therefore quite natural for such sediments to be present in the Kwé, Plum, Kuebini, Pirogue and even Tontouta rivers. However, sediment content can be increased by human activity and above all by mining operations and intensive deforesting when this is done without taking necessary steps to protect the environment, as was unfortunately the case in past centuries.  

The possible negative effects of such fine particles being transported by rivers down to the sea include:

• an increase in water turbidity (reduced transparency) that prevents corals from receiving sufficient light
• silt being deposited on the sea bed, which tends to cover living organisms with a fine film and can lead to their partial asphyxiation.

However, past experience and recent studies have shown that habitat vitality in conjunction with strong currents along the coast keeps ecosystem impact to a minimum. Vale Inco Nouvelle-Calédonie nevertheless continues to maintain all measures required to ensure surface and subsurface water protection.   

Marine effluent discharge

Liquid waste from the process and its treatment

The process used in the plant produces two downstream products: firstly, the finished products sold on the market and secondly, liquid waste containing metals found in the mineral ore that are not recovered by the process and solid waste, in the form of a leached mineral sludge, channelled towards the final neutralisation circuit.

Once liquid waste or effluent has been neutralised in the waste treatment plant, it must be discharged. Disposal at sea was the chosen option because the properties of the effluent (salinity, acidity, etc.) are similar to those of seawater.

Need for disposal at sea

It was decided to discharge the effluent in the lagoon, in the Havannah channel rather than in the open sea for two main reasons:

• numerous laboratory and field currentology studies have shown that impacts at this point will be kept to a minimum because the strength and direction of prevailing currents will ensure rapid dispersion.

• rigorous environmental monitoring can be carried out, which would not be the case if the effluent was discharged in the open sea.

Carefully researched and appropriately designed disposal at sea

The effluent will therefore be discharged at sea 5 kilometres from the coast and one kilometre from the nearest coral reef. It will be discharged via a diffuser pipeline designed to ensure rapid dispersion:

• The final kilometre of the pipe will be perforated to ensure gradual dispersal of the effluent and speedier dissolution in the seawater. 

• Thanks to the strong currents, it will be impossible to detect any difference between the discharged effluent and the lagoon water at a distance of only a few dozen metres from the diffuser.

• 18 checkpoints are planned to ensure rapid detection of any variance from the specified model and the rapid mobilisation of corrective measures before irreversible damage can occur.  

Treated water comparable to lagoon water

According to studies to date, there are no grounds for thinking that the effluent, once neutralised, could have a significant effect on marine fauna or flora. The effluent will have a composition compatible with the marine environment into which it is discharged.  It has been identified as marine effluent because:

• It has an acidity (pH) comparable to seawater.

• The chemicals and metals found in its composition already occur in the natural environment, often in very similar proportions: in mineral ore taken from the earth, in plants, in seawater and, where certain metals are concerned, in the human body.  
  At a distance of a few dozen metres from the diffuser, with the exception of manganese, concentrations are within the range of natural variations found in seawater.
  At this distance, the manganese content of seawater will comply with US aquaculture standards (fish and shellfish farming).

Dispensation applying to manganese concentration

There is no European standard applying to manganese discharges and most European countries have not deemed it necessary to set one. Only two countries have established standards: France, which specifies a discharge standard of 1mg/L and Belgium which applies a 10 mg/L standard.

Vale Inco Nouvelle-Calédonie was accordingly granted a dispensation under the terms of the first ICPE order issued in 2004. In accordance with the precautionary principle, further studies have been undertaken to ensure an even greater reduction in manganese concentration so as to achieve a level very close to the French standard. 
Studies carried out to date by Inco are able to guarantee a level of concentration less than 100 mg/litre.
Manganese concentration in the effluent will be reviewed as part of the new ICPE order process.  

Manganese does not pose a health hazard.  It is present in the human body and is even essential to health. According to experts, ingestion poses no long term threat to health because manganese does not accumulate, any surplus being naturally eliminated by the body.

Port activities

Prony port plays an important role in the Vale Inco Nouvelle-Calédonie project.

Rigorous tests and controls are in place to prevent any spills or dumping. There will be very little anchorage in the bay because port operation will be extremely flexible, keeping waiting times for unloading to a minimum. As the port is located in a very enclosed bay and is under private management, it will be an easy matter to ensure port surveillance and adherence to the rules and regulations laid down by Vale Inco Nouvelle-Calédonie.

Protecting the whales

Monitoring the whale and dugong populations is a key environmental tracking indicator.
Although whales occasionally come into the bay itself, they are mainly found in the channels (Havannah and Woodin) where there is a certain amount of shipping (merchant and pleasure boats en route for Noumea harbour) unrelated to the project. 
There will only be a moderate increase in shipping in the area due to maritime traffic generated by plant construction and operation. There should therefore be no fundamental disturbance of whale population habits.
Ships will reduce their approach speed and the risks of a collision are very slight. Evidence goes to show that the noise made by a ship is more likely to cause whales to move away while it goes past.  

Since port construction has been delayed mainly due to blockades organised by a number of project opponents in April 2006, work will have to continue throughout the whale breeding season which lasts from June to September.
A study of noise propagation from pile driving was carried out in June to discover whether this could produce any behavioural impact on the whales, which use sounds to communicate. Strict monitoring is carried out to ensure rapid detection of any marine mammals present in the area. The local association Opérations Cétacés, which monitors the arrival and behaviour of the whales every year, will be responsible for notifying the Vale Inco Nouvelle-Calédonie port authorities as soon as a whale is observed in the area. If there is any cause to fear an impact, the necessary steps will be taken.

Coral transplantation

The port facilities site location was chosen because of its proximity to the industrial site and because Prony Bay is sheltered from the winds and possesses almost no coral reefs.
Despite the very limited degree of coral destruction brought about by port construction (around 200 m2), Vale Inco Nouvelle-Calédonie has agreed, as a compensatory measure, to implement a coral biotope restoration program over a surface of 2000m² in Prony Bay. Transplantations were carried out in December 2005 and January 2006 on Montravel islet and in the Casy islet marine nature reserve to ensure partial replacement of the coral destroyed by cyclone Erika. Early observations indicate that the coral has taken well. The coral will be monitored over a five year period.

Impact studies – seawater

Numerous studies undertaken by Vale Inco Nouvelle-Calédonie to date have shown that there will be no significant impact on marine organisms.

Ecotoxicity tests

Aim:	experimental identification of maximum concentrations to avoid any impact on the marine environment
Results	a dilution safety factor of 280 to 1000 is required to avoid any observable effects (corresponding to a manganese concentration of 0.1mg/l )
Action	the diffuser is designed to ensure the effluent is diluted by 1000 times its volume of seawater at a few dozen metres from the pipe

 

Modélisation des courants marins

Aim:	Modelling: currentology studies to position the diffuser in the area of maximum currents
Results	Identification of the optimal area
Action	The diffuser will be placed in the maximum current area

 

Final phase research programs:

• Physico-chemical characterisation of lagoon water
• Metal bio-accumulation study and bio-indicator selection
• Study of bio-tests and biomarkers

Ongoing research programs:

• Metal geochemistry and potential bioavailability
• Ecotoxicity studies on local species
• Further studies on status of reef populations and associated fish species
• Development of a dispersion model to factor in precipitation data