Alves, AF, Braga, I & Pós, W 2008, 'Encapsulation of Old Tailings Deposits from Morro Velho Gold Mining in Minas Gerais, Brazil', in AB Fourie, M Tibbett, I Weiersbye & P Dye (eds), Mine Closure 2008: Proceedings of the Third International Seminar on Mine Closure
, Australian Centre for Geomechanics, Perth, pp. 451-457, https://doi.org/10.36487/ACG_repo/852_41
Nova Lima, hometown of the AngloGold Ashanti operation in the state of Minas Gerais, Brazil, has been a
gold centre since 1834. At that time, the tailings were dumped directly into local rivers and streams. Since
the 1930s, however, tailings at the Morro Velho Mining operations began to be deposited along the banks of
the Cardoso River, amounting to one million m3 of tailings being spread over 250,000 m2. Included in these
tailings is arsenic, at a concentration of approximately 20,000 mg/kg. Since 1985, tailings have been
disposed of at a properly-engineered tailings impoundment.
To address the potential hazard associated with the older tailings deposits, a risk assessment was conducted.
The assessment included a hydrogeologic and geochemical study, as well as a global risk analysis. The
findings indicated that encapsulation of tailings would be required in order to minimize the future risk of
human exposure. The main criteria for technology selection was that it provided the highest environmental
and health protection for the local area and its residents.
As a result, a clean-up and encapsulation process commenced in May 2003 with the rehabilitation of Morro
do Galo, an old arsenic trioxide recovery plant, which was completed in December 2003. The second site to
be addressed was the Galo tailings deposit in 2004, followed by Resende and Matadouro tailings deposits in
2006 and 2007. Up to 2008, approximately US$ 3.5 million had been spent on these projects, and
encapsulation of the remaining old tailings deposits is planned to commence next year, in 2009. All the
rehabilitation work completed to date has received the endorsement of the Brazilian Environmental
Authorities, and the encapsulation has resulted in a significant decrease in the mean arsenic concentration
of the shallow groundwater in contact with the old tailings.
This case study demonstrates how AngloGold Ashanti Mineração Brazil has addressed a challenging legacy
of contamination, in partnership with environmental authorities and the local community. This kind of
intervention demonstrates that it is possible to undertake the rehabilitation of old tailings deposits in a
populated area safely, without the relocation of residents.
Golder Associates (2002) Estudos Hidrogeológicos dos Depósitos de Rejeito do Vale do Ribeirão Cardoso, Nova Lima-
MG, Vol. 1, 224 p.
Huang, P.M. and Fujii, R. (1996) Selenium and Arsenic. In: Methods of Soil Analysis. Part 3 Chemical Methods. Soil
Science Society Book Series, Madison, Wisconsin, USA.