An Introduction to Mining and Metallurgy - Thanatia: The Destiny of the Earth's Mineral Resources - page 174

Mining Minerals and Sustainable Development Project (MMSD, 2002) 8 .
The authors now go on to describe, briefly, some of the most important envi-
ronmental impacts and the necessary actions to mitigate them.
7.6.1.1 Water pollution
Both open-pit and underground mining may modify local watersheds, changing their
dynamics and chemical quality. Indeed water, the first resource affected by mining,
is a primary vehicle for contamination. This is because large amounts of water are
required in the leaching process resulting in the release of wastewaters which can be
extremely acidic. The lack of su cient buffering materials such as limestone with
which to neutralise the acid is the primary cause of acid rock drainage. Drainage
from waste rock in dumps occurs when they are not su ciently lined. Acid rock
drainage and management of cyanide are a major concern to companies, the general
public and their governments. In regions with high water stress, water consumption
is an especially sensitive issue, since the resource is diverted towards the mine at
the expense of other local users.
The larger water footprints which occur as mine ore grade decreases, leads to
ever graver conflicts and water shortages. For mining companies however, very
large wastewater facilities greatly increase production costs. This is because the
relationship between decreasing ore grade and increasing water demand is not linear
but exponential. Consequently water demand and wastewater treatment may well
become a determinant factor in mine closure. Water affected by mining may also
contain metals in low concentrations and those toxic residues used in the separation
processes. Even at very low concentrations such species are detrimental to aquatic
ecosystems and agriculture which serves to exacerbate social and environmental
issues.
All these phenomena require serious wastewater flow treatment and a conscious
planning of the mine site to avoid the pollution of aquifers and the surrounding
rivers and wetlands.
7.6.1.2 Solid waste and materials handling
The 2004 Earthworks and Oxfam America Report (Earthworks and Oxfam, 2004)
states that “Open-pit mines produce 8 to 10 times as much waste rubble as under-
ground mines. This rubble is generally piled into enormous mounds, some of them
8 The Mining, Minerals, and Sustainable Development Project was launched in 2000 by the Global
Mining Initiative and culminated in the report “Breaking New Ground” released in 2002 for the Jo-
hannesburg Summit (MMSD, 2002). Other projects include: Extractive Industries Review (EIR);
the World Conservation Union (IUCN)-International Council on Mining and Metals (ICMM) di-
alogue; the Global Reporting Initiative mining sector supplement which provides the basis for
sustainability reporting and the Euromines- ICMM common approach to include ores and concen-
trates under the EU REACH legislation. Worth noting is also the Extractive Industries Trans-
parency Initiative (EITI), a global coalition of governments, companies and civil society working
together to improve openness and accountable management of revenues from natural resources.