7.3 Rehabilitation of old tailings deposit at Nova Lima
AngloGold Ashanti operates a number of mines in old mining districts where environmental controls were not what they are today. In these areas, the group is actively engaged in finding cost-effective ways to deal with problem pollution sites, often going beyond the strict definitions of legal liability and addressing legacy issues. Examples of this can be found in Brazil, Ghana and in the Witwatersrand Basin in South Africa.
A major environmental project currently being undertaken by AngloGold Ashanti Mineração is the rehabilitation of old tailings dams and the site of the Morro do Galo arsenic plant at a cost of some $4 million. As agreed with the Environmental Agency - FEAM - rehabilitation is only carried out during the dry season (May to November) to avoid the risk of environmental contamination.
The town of Nova Lima, in the Minas Gerais province of Brazil, has been a gold mining centre since 1834, when large-scale mining first began. At that time, the tailings (which are the residues left over once the gold has been extracted from its host rock) were dumped directly into local rivers and streams. Included in these tailings was arsenic in an inorganic form, including arsenic trioxide. Arsenic is present in many gold-bearing ores (such as arsenopyrite) and is common in the Nova Lima region, the home of the old Morro Velho operations.
From the 1930s, tailings at the Morro Velho operations were no longer dumped in the rivers, but deposited along the banks of the Cardoso River and an arsenic recovery plant was constructed. At the time, this was considered the best available technology for arsenic treatment. Today, much more is understood about the potential impact of concentrated arsenic on human health, and completely different disposal technology is used. Currently, arsenic trioxide is buried in lined hazardous waste cells.
To address the potential hazard associated with the historic tailings disposal practices, AngloGold Ashanti Mineração initiated a rehabilitation project in 1995 covering the old tailings dumps and the arsenic recovery plant site. This included a massive re-vegetation programme at a cost of $500,000.
In 2002, a group of risk assessment specialists were brought in to re-evaluate the site - the team included tailings disposal specialists and scientists familiar with arsenic biogeochemistry. Their findings indicated that tailings encapsulation would be required to avoid future risk of human exposure. FEAM, also aware of the possible contamination of the area, performed an independent review of the tailings deposits and came up with the same recommendations.
As a result, rehabilitation of the site began in May 2004 with the full agreement of the environmental authorities, and under the leadership of Dr Willer Pos, Head of Environmental Affairs in AngloGold Ashanti's South America Region. Initially, the programme focused on the complete removal of topsoil and tailings from the Morro do Galo old arsenic trioxide recovery plant. The Morro do Galo hillside has now been completely rehabilitated and the Galo tailings deposit is in its final stage of recovery. Starting in May 2005, rehabilitation is planned for the old tailings deposits at Resende, Matadouro and Fabrica de Balas. Rehabilitation will be concluded in May 2006.
An extensive communications programme has been undertaken with the local residents (some 40 families - approximately 160 people - surrounding the Morro do Galo and Galo tailings deposits). This has included personal visits from AngloGold Ashanti Mineração representatives and the provision of informational material to create awareness of what the company has planned. As part of these efforts, a 'Leisure Street Day' was sponsored by the company on 17 October 2004.