Recent Advances in Mitigation and Rehabilitation
Technology in Major and Abandoned Mines in
Sub-Saharan Africa
T.C. Davies
Department of Mining and Environmental Geology
University of Venda
Private Bag X5050
Thohoyandou
Limpopo Province
Republic of South Africa
theo.clavellpr3@gmail.com
PROJECT DESCRIPTION
IGCP/SIDA/UNESCO/UNIVEN/KNUST Project No.
606 researches on improvements in mitigation and
rehabilitation strategies for environmental health
impacts of major and abandoned mines in SubSaharan Africa, as well as assess the current status
of research in pollution control technology. This
year, we have put the focus on ‘small scale mining’
because of the tremendous contribution this kind of
mining makes towards improving the lives and
livelihoods of millions of Sub-Saharan Africans. A
major scientific goal of the project is to identify
ways by which process optimisation for profitability
can be carried out sustainably, while at the same
time ensuring minimum amount of negative
environmental health consequences, and the
general preservation of ecosystem integrity.
PROJECT SYNTHESIS
* Impacts due to mining methods and mineral
processing operations;
* Dangers posed by abandoned mines;
* What do we know about the relationship
between mining, the fecundity of cultivable
lands in the vicinity of mines, and
environmental health?
* Addressing the issues
Abandoned Mines
 Abandoned mines in Sub-Saharan
Africa are often dangerous and can
contain deadly gases such as radon
and methane. Standing water in mines
from seepage or infiltration, poses a
significant hazard as the water can
conceal deep pits and trap gases
below the water. Old mine workings
and caves are sometimes hazardous,
simply due to the lack of oxygen in
the air.
Mining impacts
The mining industry is undoubtedly of major
importance to Sub-Saharan Africa’s economic
well-being. However, mining methods and mineral
processing operations are known to be associated
with diverse and often profound chemical and
physical impacts on miners and adjacent
communities, as well as on other elements of the
surrounding ecosystems. Mining in some quarters
have accelerated soil erosion rates, which is a
bane to agriculture; metals and toxins are often
mobilised far beyond natural rates, and natural
water resources are sometimes polluted beyond
measure. Accidents - deaths???
WHAT DO WE KNOW SO
FAR?
We need to define clearly the boundaries
of our present understanding of the
relationship between environmental health
and mining and mineral processing,
investigate new discoveries in relations
between them, and study much more
deeply, geochemical interactions at tailings
sites (e.g., the dreaded acid mine
drainage (AMD)), and wastewater courses
and effects on agriculture.
SPECIFIC AIMS AND OBJECTIVES OF
PROJECT 606
 Promoting and expediting the work of an
‘African Network of Earth Scientists’
researching the environmental health impacts
of mining and ore processing activities, and
seeking the best ways of addressing them;
 Compiling a complete inventory and
database of abandoned and derelict mines
in sub-Saharan Africa;
 Preparing a comprehensive documentation
embodying research activities on the
following 5 themes:
Theme 1
 Bridging knowledge gaps, and
specifically assessing the rate
of migration and distribution
pathways of selected heavy
metals known to be toxic, from
tailings dams and mine spoils
accumulated during several
years of mining in Sub-Saharan
Africa;
Theme 2
 Monitoring heavy metal
concentrations in agricultural
soils in the vicinity of major
and abandoned mines in order
to indicate the status of heavy
metal contamination (PHEs),
and assess environmental
quality of these soils;
Theme 3
 Providing practical
solutions to problems of
metal contamination and
the recommendations for
improved land remediation
strategies (rehabilitation
technology);
Theme 4
 Assessing long-term
impacts of mining on
public health and the
environment, and
recommendation of
strategies for protecting
the health of our
communities;
Theme 5
 Providing support to
governments of Sub-Saharan
African countries in
developing their national
strategic plans to combat the
public health and
environmental effects posed
by abandoned mines (other
organs of dissemination).
ADDRESSING THE ISSUES
 Only then would we be able to
properly address environmental
health issues pertaining to the
mining industry, point out the
way forward in improvement of
mitigation and rehabilitation
strategies, and direct new
research in the most fruitful
directions.
PHYSICAL REHABILITATION
Modern mine rehabilitation aims to minimise
and mitigate the environmental effects of
modern mining, which may in the case of
open pit mining, involve movement of
significant volumes of rock. Rehabilitation
management is an ongoing process, often
resulting in open pit mines being backfilled.
Mining area must undergo rehabilitation.
SOME CONVENTIONAL APPROACHES
Waste dumps are contoured to flatten them out, to further stabilize
them against erosion.
If the ore contains sulphides, it is usually covered with a layer of
clay to prevent access of rain and oxygen from the air, which can
oxidise the sulphides to produce sulphuric acid (acid mine drainage
(AMD)).
Landfills are covered with topsoil, and indigenous vegetation common
to the applicable area is planted to help consolidate the material.
Dumps are usually fenced off to prevent livestock denuding them of
vegetation.
The open pit is then surrounded with a fence, to prevent access, and
it generally eventually fills up with groundwater.
Tailings dams are left to evaporate, then covered with waste rock, clay
if need be, and soil, which is planted to stabilize it.
Uranium ore. Image: United States Geological Survey and the Mineral Information Institute
Radon Gas - The Silent Killer
 Uranium mining - extraction of U ore from the ground
 Low concentrations, means U mining very volume-intensive
 Undertaken as open-pit mining
 Main use, as fuel for nuclear power plants
 Uranium ore emits radon gas; odourless, colourless
 Inadequate ventilation systems
 Radon, a cancer-causing agent (small cell carcinoma)
 Radioactive contamination of air, water and soil (radioactive
dust/contaminated groundwater)
Uranium Producing Countries
 Niger - Africa’s leading U producing nation (US
invasion of Iraq)
 Namibia - produces U at Rossing, where an
igneous deposit is mined from one of the World’s
largest open pit mines.
 Gabon - Deposits reported to be exhausted.
 South Africa - U from U deposits in PC quartzpebble conglomerates of the Wits Basin.
Uranium Resources of South Africa
First Uranium said it restarted its ‘Mine Waste Solutions’ facility in
South Africa on Tuesday 02 August, after nuclear regulators suspended
operations recently due to concerns about pipeline maintenance at the
gold and uranium tailings reprocessing plant. The company said ‘last
week’ that the suspension involved a pipeline used to pump tailings
material, which has been reprocessed to extract gold and uranium, into a
new tailings storage facility.
Potential negative impacts of uranium
mining and milling
 Serious health risks due to exposure to gamma radiation and the
inhalation of radon gas. This causes cancer. Radiation and
radioactive radon gas can affect mineworkers as well as people
living and working close to mining areas and roads that are used for
transport of ores and yellow cake.
 Destruction of the environment. An open-pit mine can be hundreds
of meters wide and deep. As the name suggests, large pits will be
dug which can entail the destruction of local ecosystems.
 Pollution of the environment with radioactive materials.
Radioactivity, either in solid, liquid or gaseous state, is transported
by air, water and in soils and therefore negatively affects their
quality.
 Water shortages. Uranium mining and milling needs the input of
large quantities of fresh water. This can lead to water shortages in
other sectors of society as in many places in Africa water supply is
already problematic.
Negative impacts of U mining and milling
(contd.)
 Waste rock. Waste-rock contains low grades of uranium which can be
carried away by the wind.
 Uranium mill tailings. Uranium mill tailings are normally dumped as a sludge
in special ponds or piles, where they are abandoned. The tailings still
contain 85% of the initial radioactivity of the original ore. Also, the sludge
contains heavy metals and other contaminants such as arsenic, as well as
chemical reagents used during the milling process. Additionally, uranium
mill tailings keep on emitting dangerous radon-222 gas for many years. The
dangerous components of tailings are transported into the environment by
wind, erosion or dam failures. This happened, for example, in Zambia in
2006 where failure of a tailings slurry pipeline of a copper mine caused the
contamination of a river that served as an important drinking water supply.
 Social impacts. Uranium mining can cause conflict. In Niger, an Areva base
was attacked by dissatisfied Tuareg rebels. At the same time, Areva was
accused by the Nigerian government of supporting Tuareg militia groups to
deter competitors. Social conflict due to uranium mining can also be caused
by the unequal distribution of mining profits and revenue.
AMD Chemistry
The following are the equations that show the generalised
reaction pathway for pyrite to start to produce AMD:
(1) 2FeS2 (s) + 7O2 (g) +2H2O (l) →2Fe2+ (aq) + 4 SO42- (aq) +
4H+ (aq)
(2) 4Fe2+ (aq) + O2 (g) + 4H+ (aq) →4 Fe3+(aq) + 2H2O (l)
(3) 4Fe3+ (aq) + 12H2O (l) → 4Fe(OH)3 (s) + 12 H+ (aq)
(4) FeS2 (s) + 14 Fe3+ (aq) + 8H2O (l) → 15Fe2+ (aq) + 2SO42(aq) + 16H+(aq)
Pollutant Pathways
We have identified SIX main pathways by which pollutants derived from natural
processes of mineralization, or from mining and ore processing operations, can
enter the human body:
* Through consumption of food crops having anomalous concentrations of elements
derived from agricultural soils developed over mineralized bedrock;
* Consumption of food crops from soils contaminated by leachates, effluents and
emissions from nearby mining sites, e.g., as in AMD;
* Consumption of water contaminated by AMD or by some other forms of mining waste;
* Inhalation of particulate matter / dust in the mining environment or from other industrial
sites;
* Direct dermal contact with ores and associated materials.
* Intake of contaminants through geophagic practices.
Treatment of acid mine drainage (AMD)
AMD is highly acidic water, usually containing high concentrations of
metals, sulphides, and salts as a consequence of mining activity.
The potential volume of AMD for the Witwatersrand Goldfield alone
amounts to an estimated 350ML/day (1ML = 1000m3). This represents
10% of the potable water supplied daily by Rand Water to municipal
authorities for urban distribution in Gauteng province and surrounding
areas, at a cost of R3000/ML.
In his Budget Speech to Parliament in Cape Town in February this year,
Finance Minister Pravin Gordhan allocated R 3.6-billion for water
infrastructure and services in 2011/12, "including funding for the acid
water drainage threat associated with abandoned underground mines”.
There is still a tremendous need for further technical research and
innovation in the treatment of AMD, to enable cost-effective treatment of
the range of AMD waters present in South Africa.
Integrated solutions would be supported through improved links between
universities, research organisations and the international research
community.
EUTECTIC ICE CRYSTALLISATION
Eutectic Freeze Crystallization (EFC)
provides an alternative method for the
treatment of hypersaline aqueous waste
streams emanating from mining and other
industrial operations. The process is
capable of producing potable water, as
well as pure salt(s), by operating at the
eutectic point with lower energy
consumption than evaporative crystallization
REVEGETATION
Replanting and re-building the soil of
mined-out land.
• Establishing long-term plant communities requires forethought as to
appropriate species for the climate, size of stock required, and impact
of replanted vegetation on local fauna;
• The motivations behind revegetation are diverse, but it is usually
erosion prevention that is the primary reason;
• Revegetation helps prevent soil erosion, enhances the ability of the soil
to absorb more water in significant rain events, and in conjunction
reduces turbidity dramatically in adjoining bodies of water;
* Revegetation also aids protection of engineered grades and other
earthworks;
• Revegetation is often used to join up patches of natural habitat that
have been lost, and can be a very important tool in places where
much of the natural vegetation has been cleared.
Environmental monitors inspect revegetated growth on a rehabilitated site near
Venetia mine, South Africa
Anglo Coal South Africa has an active land rehabilitation programme. Ecologist Johan van der Walt inspects a
rehabilitated pit area at Kriel colliery where grass species have started to diversify.
An environmentalist is studying natural
biodiversity and indexing species for their
importance in reforestation.
COMBATING SOIL EROSION FROM MINING
Soil erosion is perhaps the world’s most chronic environmental problem
that is literally costing the Earth. The soil it carries off now totals 20
billion tons a year and this loss is not only severely degrading the
environment, it is eroding the economic viability of countries. Despite
enormous effort, standard soil conservation methods have been largely
unsuccessful. However, a remarkable tropical grass may hold the key to
a cheap, practical solution for controlling soil erosion on a huge scale in
tropical and semi-arid regions. It also has many attributes that make it
useful to farmers. Vetiver (Vetiveria zizanoides) is a densely tufted,
perennial clump grass with stiff leaf bases which overlap.
HOW EFFECTIVE IS VETIVER IN CONTROLLING SOIL EROSION?
* This deeply rooted, persistent grass has restrained erodable soils for
decades in India, the Caribbean and in Fiji, where its use was
discovered by John Greenfield in the late 1950s;
* The key is to plant the grass as a hedge along the contour, preferably
set out with the aid of a simple “A” frame, with a space of 10 cms
between the grass slips;
* Vetiver grows to a height of around one metre but should be cut back
to a planting height of 150 mm;
* The thatch can then be placed behind the newly planted slips to
provide an instant filter to control run-off.
An African Baobab tree typical of those found in the area around Venetia Mine in South Africa
sustainable management of the natural environment is key to the future prosperity of the
ntries and communities in which we operate. By tackling environmental challenges in
nership with government, NGOs and our communities we can help build sustainable
ronments wherever we operate.
HYDROSEEDING
Hydroseeding is the fastest, most cost effective
and highest quality method of seeding vegetation,
land rehabilitation and erosion control practices.
Hydroseeding, also known as hydromulching, is the
process of combining seed, fibre mulch, fertilizer
tackifiers, bonding agents and optional soil
amendments with water to mix in a HydroSeeder™
tank to form thick slurry. This slurry is applied with
pressure via hose or tower onto the soil to create the
ideal environment for seed germination and turf
development. Vegetation establishes quickly providing
uniform cover for erosion control.
The nickel hyperaccumulator Berkheya coddii native
to South Africa (Source: Anderson and Meech, 2002)
CONCLUSION
• Of all the advances that have been reported here today, I must say
that serious challenges still remain, as rehabilitated land is not
always returned to a land capability equivalent to its pre-mining state.
This can only be achieved by careful management of soil resources,
promotion of biodiversity and management of latent risks post-closure.

*
According to Limpitlaw in South Africa (2005), to promote effective
management of old mines, Government extension officers must
become more involved with the stewardship of rehabilitated lands.
This effort may be bolstered by creating a system of tradable
pollution permits whereby active mines could offset their pollution
loads by participating in the rehabilitation of abandoned mines, without
assuming liability for those sites.

*
Ultimately, an integrated approach to closure planning is required
whereby joint action of stakeholders – mining companies,
Governments and communities – assume responsibility for the long
term sustainability of closed mines.
Goals of the GEM Working Group on “DUSTS”
The aim is to improve responses to emissions of dust and other
particulates.
The objectives are to:
a) review, collate and disseminate material on the existing understanding of
the nature, behaviour and impacts of dust and particulates in the Earth
system and to stimulate new investigations into associated underresearched areas;
b) review existing legislation, regulation and management responses and
to set out good practices in forms that can be readily appreciated and
followed by administrators, land managers and the public; and
c) to develop and disseminate innovative approaches to dealing with dust
issues.
The Group will organise conference sessions and aims to produce a book
on emissions of dust from geological sources by 2013-2014.
GRN Cells in Africa
ASSOCIATION OF APPLIED
GEOCHEMISTS
ABOUT THE ORGANIZATION
Founded in 1970, the Association of Applied
Geochemists is an international organisation
specialising in the field of applied
geochemistry whose purpose is to:
* Advance the science of geochemistry as it
relates to exploration and the environment
* Facilitate the acquisition and distribution
of scientific knowledge
* Promote exchange of scientific information
* Encourage research and development
* Sponsor symposia, seminars and technical
meetings
* Support students in applied geochemistry
To achieve these goals, the Association
of Applied Geochemists:
 published the Journal of Geochemical Exploration from 1972
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until 2000, and currently publishes GEOCHEMISTRY:
Exploration, Environment, Analysis starting in 2001
publishes quarterly a newsletter, EXPLORE
publishes in a digital format a bibliography of geochemically
oriented papers, now available to AAG Members on the
ASSOCIATION OF APPLIED GEOCHEMISTS web page
holds biennial International Geochemical Exploration
Symposia with associated field trips
holds regional meetings of specialised interest and co-sponsors
meetings with other scientific societies
organises workshops and short courses
supports a student paper prize
supports a distinguished lecture series
IGCP/SIDA/UNESCO PROJECT 606
UNIVEN PROJECT/SES/11/MEG/03
FUTURE PERSPECTIVES ????
Theme:
“Together in Africa for a Leading
Role in Geosciences”
THANK YOU
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