The Eramet group uses specific techniques at each of its sites. However, they all share the same priority, namely guaranteeing the very best safety conditions. Each facility scrupulously follows the most stringent international practices on the subject.
In New Caledonia, nickel extraction involves handling a large volume of waste material (i.e. natural materials that have no financial value). Being able to store these materials in appropriate structures and revegetate them is a long-standing challenge for the company. Over the decades, SLN has therefore developed various solutions to limit erosion as much as possible, as well as its impact on the ecosystem and landscapes. These include:
- creating waste rock dumps
Thanks to their stability, these structures guarantee the long-term safety of stored tailings, even in the event of cyclonic rain. SLN's teams also carry out continuous monitoring and external experts regularly conduct audits to verify their condition. Operated directly or outsourced, all of the waste rock dumps meet identical construction and sizing conditions, which are compiled in a technical guide published by SLN, updated in 2012.
- creating dumps in former mining pits
Constructed where technically possible, these facilities reduce clearing to a minimum and foster the restoration of sites.
In Gabon, the volumes of waste rock handled are significantly lower. The operating technique, involving successively opening and closing "lockers", enables much of the waste rock to be directly placed in neighboring "lockers" already in use. Once again, the goal is to reduce clearing to a minimum and foster the continuous restoration of sites.
Another issue involves storing tailings comprised of clayey fractions of ore obtained through a process of physical separation by washing with water, without adding chemically abrasive products. To achieve this, the Eramet subsidiary Comilog operates tailings dams. Every measure is taken to ensure these structures are safe. Furthermore, each one is limited in size and can never be made higher: a new structure is built every 18 to 24 months. Eleven storage structures have been built so far, ten of which are in the process of being closed and permanently stabilized.
The Marietta metallurgical plant in the US also has a tailings dam. This is used to store tailings from industrial activities that are now discontinued, but still operated by Eramet. Measuring 35 meters high, the dam has a volume of 4.3 million m3. The structure is regularly inspected by the Ohio department of natural resources. The latest audit was conducted in 2018.
The issue is different at the GCO plant in Senegal: a very low quantity of tailings are produced and their characteristics mean they can be returned to the natural environment when the dune is rebuilt.
Non-hazardous mine tailings
An important point is that the mine tailings produced in the mine ore milling facilities in Gabon or on the Népoui and Tiébaghi sites in New Caledonia are chemically stable. In other words, they are not hazardous waste as defined under French regulations. This natural sandy soil is separated from the larger ore using mechanical washing procedures without adding abrasive chemical products.
It should also be noted that every effort is made to recirculate the washing water where possible in order to minimize extractions and discharges into the environment.