Transcript Environmental Impact Assessment (EIA)

BRE 211: Principles of
Agriculture and Forestry
LECTURE 11
MINERALS LANDS
Definition
 Mineral
Resources may be broadly
defined as
 Potentially
usable concentrations of
elements, chemical-compounds, mineral or
rocks in a particular location or on the
earth.
 These resources are technically
reasonable expectations of quantities of
mineralized rocks that will be developed by
exploitation.
Definition
A
mineral deposit is referred to as a
motoresource if it is expected to
become an economic resource at some
point in the future.
 A mineral that once had value may
become valueless as a result of new
discoveries.
 Such
a resource is referred to as a
paleoresource.
Definition
 Mineral
resources include reserves plus
all other mineral deposits either not yet
discovered or unobtainable due to
technological or economic reasons.
Valuation of Mineral Resources

The valuation of precious minerals is normally
carried out by Mining Engineers and
Geologists.
 There are however, a number of nonprecious surface minerals such as sand and
gravel, chalk and limestone etc, which often
fall within the practice of the valuer.
 Valuers may be called upon to assess for
various purposes clay deposits, gravel
deposits, sand deposits, or stone quarries.
 A valuer may also be called upon to value the
assets of a mining company for various
purposes.
Classification of Minerals
 Minerals
can be classified into two
groups, namely:
 Precious
minerals including metalliferous
deposits (iron, copper, tin), fossil fuels
(coal, petroleum, gas) etc.
 Non-precious minerals including structural
materials such as building stone, gravel,
sand etc.
 These are minerals other than precious
metal or precious stones.
Mineral Exploitation
A
mine is an excavation made in the
earth to extract minerals.
 The activity, occupation and industry
concerned with extraction of minerals is
called mining.
 The art and science applied to the
processes of mining and the operations
of the mine is called Mining
Engineering.
Mineral Exploitation
 The
essence of mining is to drive or
construct an excavation (a means of
entry) from the existing surface to the
mineral deposit.
 If the excavation is entirely open to or
operated from the surface, it is called
surface mine.
 If the excavation consists of openings
for human entry driven below the
surface, then it is an underground mine.
Mineral Exploitation
 The
specific details of the procedure,
layout, and equipment used distinguish
the mining method is uniquely
determined by:
 Physical
 Geological
 Environmental
 Economic
and
 Legal circumstances that prevail.
Mineral Exploitation
 Mining
is preceded by geological
investigations that locate the deposit
and economic analysis that prove it
financially viable.
 When deposits have been determined,
extraction takes place
Mineral Exploitation
 After
extraction mineral processing
takes place.
 The processed products undergo further
concentration, refinement or fabrication
during conversion, smelting or refining
to provide consumer products.
 The mining methods basically include:
 Surface
Mining.
 Underground Mining.
 Novel methods.
Surface Mining
 This
is the most common method of
exploitation world - wide.
 It includes mechanical excavation
methods such as open cast, open pit
and aqueous excavation.
 Open cast and open pit mining are used
to exploit a deposit near the surface e.g.
sand or stone quarrying.
Surface Mining
 Aqueous
extraction
 Uniquely
reliant on water.
 Includes:
 Dredging
 Solution
mining.
Surface Mining
 In
dredging
 Unconsolidated earth, sand and
gravel are excavated from beneath
water by a large hydraulic machine,
which usually floats on water.
 Valuable minerals are extracted and
earth discarded.
Surface Mining
 Solution
mining involves
 Injection of a special solvent into an
ore bed and pumping the solution
back to the surface for the extraction
of the solute.
 Water is the solvent injected into the
ore.
 Minerals produced in this manner
include common salt.
Underground Mining
 Underground
mining methods are
differentiated, by the type of wall and
roof supports used, the configuration of
production opening, and the dimension
into which mining operations progress.
 Methods include:
 Unsupported
 Supported
 Caving.
Underground Mining

Unsupported methods
 Used to extract mineral deposits that are
roughly tabular, flat or steeply dripping, and
generally in contact with strong rock.
 Supported methods
 The ore is drilled selectively so that roof
support is provided by natural pillars of ore
that are left standing in a systematic
pattern, and rooms are cut from access
entries to provide working faces.
Underground Mining
 Supported
 When
methods
necessary, additional support is
supplied by roof bolts or timbers.
 The pillars are composed of good ores that
cannot be retrieved.
 The percentage that must be left for
support varies with the depth of the Ore
bed and strength of overlying rocks.
 Ordinarily 40% - 60% of the Ore can be
mined.
Underground Mining: Caving
A
large block of ore, several meters to a
side, is undercut and thereby caused to
cave.
 As the block fragments and collapses,
the ore is drawn off through chutes or
loading points into haulage drifts.
 Alternatively, when mineral bed
underlies weak ground, headings are
driven to the limit of the ore zone and
most distant ore is mined first.
Underground Mining: Caving
 Temporary
support is provided beyond
the face, and as the ore retreats
towards the surface, the supports are
moved closer to the working zone.
 As a result the marked out area
collapses.
Novel Methods
 These
are new methods applicable to
unusual deposits or employ unusual
techniques or equipment.
 They include
 Automation
 Rapid
excavation in hard rock
 Underground gasification
 Clean mining.
Mining Method
 Method
selected for exploitation is
determined mainly by:
 The characteristics of mineral deposit
 Limits imposed by safety, technology
and economics.
 Geological conditions such as deposit
depth, and shape and strength of the
ore and wall rock
Stages in the Life of a Mine
 The
overall sequence of activities
involved in modern mining is often
compared to the stages in the life of a
mine.
 The stages include:
 Prospecting
 Exploration
 Development
 Exploitation.
Stages in the Life of a Mine

Prospecting and exploration, precursors to
actual mining, are linked and sometimes
combined.


Geologists and mining engineers share
responsibilities for these two stages, geologists
more for the former and engineers more for the
latter.
Likewise development and exploitation are
closely related stages

Usually considered to constitute mining proper
and are the main province of mining engineer.
Prospecting (Mineral Deposit)
 Procedure:
 Search
for ore
 Locate favourable and choosing
appropriate prospecting methods.
 Spot anomaly, analyze and evaluate.
 Time
 1–3
years
Exploration (Ore body)
 Procedure
 Define
extent and value of ore.
 Sample drilling/excavation.
 Estimate tonnage/grade.
 Evaluate deposit using discounting method
e.g. PV=income-cost.
 Viability appraisal i.e.

Make decision to abandon or develop.
 Time
 2-5
years
Development
 Procedure
 Opening
up ore deposit for production.
 Acquire mining rights.
 File environmental impact statement.
 Construct access roads.
 Locate and construct facilities.
 Excavate deposit.
 Time
 2-5-
years
Exploitation
 Procedure
 Large
scale production of ore.
 Factors in choice of method of extraction.
 Types of mining methods.
 Monitors cost and economic pay back.
 Time
 10-30
years
Factors Affecting Mineral
Exploitation
 Physical
Characteristics of the ore body.
 Size, shape and type of ore body
 Nature and thickness of the
underlying and overlying rocks
 Structure of the ore including dip,
strike, folding, jointing and fault
 Probability of underground water may
affect safety.
Factors Affecting Mineral
Exploitation

External factors
 Arise due to the physical location of the ore
body.
 Accessibility
 Transportation to market.
 Labour availability.
 Environmental concerns i.e. environmental
impact of mineral extraction and processing.
 Topography, which influences a mine or
quarry planning.
Environmental Impact of Mineral
Exploitation
 The
environment of the life layer is
affected adversely in many varied ways
by removal of mineral deposits and by
processing these substances.
 There are also direct threats upon
man’s safety and health as he engages
in these activities.
Environmental Impact of Mineral
Exploitation
 Some
of important environmental
effects include the following: Scarification of the land i.e. excavation
and other land disturbances produced
for purposes of extracting mineral
resources, including concomitant
accumulation of waste matter e.g.
scarification arising from strip mines,
quarries etc.
Environmental Impact of Mineral
Exploitation

Mass movements of rock and overburden
caused by subsidence of land surface due to
collapse of mines or groundwater in excess;
sliding and flowage of soil and bedrock due to
removal of support in mining operations and
to instability of soil accumulations.
 Land subsidence i.e. Sinking of the ground
following the removal of mineral matter from
the rock beneath.
Environmental Impact of Mineral
Exploitation

Aggravation and sedimentation i.e. mining
operations that produce large volumes of
sediment may cause drastic increases in
bed load, which in turn cause channel
aggravation close to the source and also
increase the suspended load of the same
streams.


Suspended load travels down the stream and is
eventually deposited in lakes, reservoirs, and
estuaries far from the source areas.
The sediment is particularly damaging to the
bottom environments of acquatic life.
Environmental Impact of Mineral
Exploitation

Air pollution caused by smelting and
treatment of ores, especially sulfide ores
(copper, lead, zinc etc) result n the release
of SO2 into the air in enormous amounts.



Fall-out over the surrounding area is destructive
to both human health and vegetation.
Mining and quarrying operations send mineral
dusts into the air.
Combustion of fossil fuels resulting in formation
of oxides of carbon and hydrogen and of any
impurities within these fuels.
Environmental Impact of Mineral
Exploitation

Ocean Pollution


Development of offshore oil and gas fields
involves drilling wells on land or beneath the sea;
transporting oil by tanker, pipelines, or other
methods to refineries, and converting the crude oil
into useful products.
All along the way, the possibility of environmental
disruption resulting from accidental oil spills,
shipwreck of tankers, air pollution at refineries,
and other impacts are well known.
Health Hazards associated with
mining
 Death
and injury within mines due to
accidents from explosions, fires and
caving-inns.
 Respiratory disorders and diseases
related to mining and mineral process.
 There is Noise and vibration due to
blasting and transportation of the
products.
Minimizing the Impact of Mining
on the Environment
 The
adverse impacts of the mining and
processing of minerals whether on land
or below the sea call for further
research directed towards reducing
them.
 Accumulation of large waste heaps can
often be avoided by returning the waste
rock to the excavation, whether this is at
the surface of underground.
Minimizing the Impact of Mining
on the Environment
 Subsidence
of the surface can be
controlled so that it causes little or no
permanent damage to buildings by
using appropriate mining techniques, or
by filling the mined-out space with
waste material.
Minimizing the Impact of Mining
on the Environment

Potentially serious interference with ground
water including lowering the water table by
pumping to drain mines can be avoided for
example by introducing a barrier to limit the
affected areas.
 Modern blasting practices minimize one
source of noise, while intelligent siting of
crushing and other processing plants can
help to reduce another.
 Good maintenance and thoughtful planning
can reduce the noise from vehicles.