Environmental risk of mining - Environmental Deterioration and Contamination: Problems and their Management - page 120

tonnes. Canada dropped to the second place with 9 thousand tonnes and Australia
to the third with 6 thousand tonnes. The largest economic uranium deposits are
in sedimentary rocks. The most common uranium mineral is uraninite (uranium
oxide), known as pitchblende when in its massive form. The product shipped from all
uranium mines is a purified solid U 3 O 8 known as “yellowcake,'' produced by leach-
ing either crushed or in situ ore, followed by solvent extraction, precipitation and
calcining.
Bauxite mining at the world level is also intensive. Bauxite is the most common ore
of aluminum. Gibbsite is the dominant form mined. The largest reserves of bauxite
are in Guinea (7,400 million tonnes), Australia (5,800 million tonnes) and Jamaica
(2,000 million tonnes). Australia mined the most bauxite in 2011, extracting 70 million
tonnes, 28% of the world's total of 248 million tonnes. Indonesia overtook China and
Brazil to become the second largest bauxite miner in the world with 16% of the world's
total output. Other significant bauxite producers in the world are Guinea, India and
Jamaica (BGS, 2013).
5 MANAGING ENVIRONMENTAL RISK OF MINING
Similarly to the environmental risk assessment of contaminants from other activities,
risk assessment of mining starts with the preparation of the inventory of the produced,
used and emitted materials as well as of the disposed wastes. The European directive
on the management of waste from the extractive industries (The Mining Waste Direc-
tive, 2006) aims to reduce the impacts of mining on the environment. According to
the directive each Member State must produce a risk-based inventory of closed min-
ing waste facilities that cause serious environmental impacts by May 2012. Europe
hopes that it will facilitate rehabilitation, particularly to help deliver the environmen-
tal improvements necessary to achieve good ecological and chemical status according
to the European Water Framework Directive (WFD, 2000).
To fulfill the requirement of the mining waste directive in Europe, or other obliga-
tions for assessing and managing the risk of abandoned mining sites, the management
system, the organizational structure, the procedures and methodologies should be
established. The steps of risk management are identification and evaluation of haz-
ards and risks, monitoring and maintenance of the sites and reduction of the risks in
a sequence, according to size. The stepwise, risk-based prioritization will ensure the
efficient risk management, by concentrating and spending only on the high risk cases.
A tiered assessment procedure should be applied, starting with collecting and assessing
available documents and making a site visit. The next assessment step should include
the characterization of the catchment hydrology, topography, the conditions of the
dams and other structures, tailings ponds, existing water management and monitoring
system, former incidents, etc. After this second assessment step it should be possible to
classify the site—according to a uniform protocol—as low, medium or high risk site.
From the risk assessment point of view abandoned or active mining sites can be man-
aged similarly. Those which are labeled as medium or high risk sites should undergo a
more detailed assessment by gathering all existing documents, monitoring data, other
information e.g. from residents and characterize all the identified risks as much as