Investing for the future: Managing nitrates at Letšeng
Protecting the environment in which we operate is an essential focus for Gem Diamonds. We recognise, however, that environmental impacts do occur. We endeavour to avoid these if at all possible and remediate when negative impacts do occur.
At Letšeng, ongoing water analysis over the years has indicated an increase in nitrates in our water due to mining explosives residue.
It is also important to note that all communities have potable water. Although water largely remains in a closed loop system, some water emanating from the site as a result of stormwater runoff is affected by nitrate. In 2014, in response to the upward trend in the nitrate levels, Letšeng commissioned a nitrate management study to find and implement solutions to the problem of nitrate-infused water leaving the lease area. The study was extensive and the solutions put in place have been far-reaching in combating this problem. An official nitrate task team, which works in collaboration with the Lesotho Government, was also established. The nitrate management project began with a nitrate audit conducted to improve blasting procedures and management, as well as reducing the levels of nitrates produced at the source.
Further studies were then conducted, including an investigation into the feasibility of a fertigation and bioremediation project and leach testing to better understand the scale of the issue.
In June 2015, a team from the University of the Free State conducted field testing at Letšeng to analyse the viability of the bioremediation project. Bioremediation is a strategy that uses naturally occurring organisms to break down pollutants such as nitrates into less toxic substances. Species in the bacterial genus Pseudomonas present high potential for bioremediation. During testing, the team discovered a dominance of Pseudomonas species in the water. Bioremediation proved viable for the removal of nitrates, sulphates and various other salts. Bioremediation and other management options are currently being explored to assess management options available to the operation.
In our ongoing efforts to pursue environmental best practice, in June 2015, Gem Diamonds sent representatives from both Letšeng and Gem Diamonds Limited to Canada to attend the 2015 Mine Closure Planning Conference and visit the local diamond mines. The trip was successful, and the team was able to gather vital information on nitrate management and rehabilitation planning which will be implemented in the year ahead.