2 BEST PRACTICE ENVIRONMENTAL MANAGEMENT IN MINING.

1BEST PRACTICE ENVIRONMENTAL MANAGEMENT IN MINING

BEST PRACTICE ENVIRONMENTAL MANAGEMENT IN MINING


Introduction


Examples of Best Practices in Mining

• Technical issues

– Water Management

– Cyanide Management

– Managing Sulphidic Mine Waste and Acid Drainage

– Tailings Containment

• Management issues

– Mine Planning for Environment Protection

• The environmental management issues and tools discussed in the previous section belong also to best practices, especially Environmental Management Systems

The following examples are chosen to illustrate best practices:


What is Best Practice?

• “Best practice” is the best way of doing things.

• “Best practice” in mining protects the environment and reduces the impacts of mining, and adheres to the principles of sustainable development.

• “Best practice” is identified by bench-marking the performance of companies in an industry.

• Best practice is linked to continual improvement; Improvements in technology or in industry standards usually call for further improvement.


Why strive for best practice?

Why environmental regulators and inspectors need to know best practice?


Why strive for best practice?• To improve environmental performance • To ensure legal compliance• To have good community relations• To reduce waste of the resources – to improve profits• To maintain competitiveness

• To be able to discuss with the industry • To know what can be expected/demanded from industry

• legislation (e.g. environmental guidelines and norms)• environmental permits, e.g. limits to emissions• environmental assessments

• To enforce environmental regulations more effciently

Why environmental regulators and inspectors need to know best practice?


How to learn more about Best Practices

Best Practices Environmental Management in Mining Booklet Series

• Series of booklets produced by the Australian Government and the Australian mining industry

• Specialises in mining

• Provide practical advice on understanding and responding to environmental problems

The World Bank Pollution Prevention and Abatement Handbook• Covers most types of industry and other activities• Being updated at present

The European Comission’s Reference Documents on Best Available Techniques• Covers several types of industry and other activities, e.g. smelters• Being updated periodically


BPEM in Mining Booklets

• Management topics

– Environmental management systems

– Mine planning

– Community consultation

– Environmental auditing

– Cleaner production

• Technical topics

– Tailings containment

– Rehabilitation and revegetation

– Hazardous materials

– Noise, vibration and air blast

– Dust control

Over 20 booklets published by Environment Australia covering:


Best Available Techniques (BAT)• The European Union’s Integrated Pollution Prevention and Control approach is based on the idea that all human activities that may have an impact on the environment must apply “best available techniques” (BAT).• BAT is defined as “the most effective and advanced stage in the development of activities and their methods of operation which indicate the practical suitability of particular techniques for providing in principle the basis for emission limit values designed to prevent and, where that is not practicable, generally to reduce emissions and the impact on the environment as a whole.”• “techniques” includes both the technology used and the way in which the installation is designed, built, maintained, operated and decommissioned;• “available” techniques are those developed on a scale which allows implementation in the relevant industrial sector, under economically and technically viable conditions, taking into consideration the costs and advantages…


Some Principles in Best Practices


What is Sustainable Development?

• Sustainable development was first defined in Brundtland Report:

– “Development that meets the needs of the present without compromising the ability of future generations to meet their own needs.”

• Another description:– Development that

improves the total quality of life, both now and in the future, in a way that maintains the ecological processes on which life depends.


What is Sustainable Development?

Social system

To improve the health, income and living conditions of the poor majority

Economic system

To accelerate economic growth with greater equity and self-reliance

Natural system

To ensure equitable and sustainable use of the environment and natural resources for the benefit of present and future generations

Sustainable development


Objectives of Sustainable Development

• Improve the well-being and welfare of individuals and the community by following a path of economic development that protects the welfare of future generations;

• Ensure equity within this generation and between generations;

• Protect biological diversity;

• Maintain essential ecological processes and life support systems.


Precautionary Approach

In order to protect the environment, the precautionary approach shall be widely applied by States according to their capabilities. Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation.

Principle 15, Rio Declaration


Concepts that Support the Precautionary Approach

• Valuing environmental assets

• Involving the community in decision-making

• Developing environmentally sound international competitiveness and an economy that can enhance environment protection

• When setting policies, actions, activities consider short-term and long-term:

– Economic goals

– Environmental goals

– Social goals

– Equity goals

• Recognising the global dimension of impacts on the environment


Precautionary Approach in Mining

• Adopting environmental codes of practice

• Consulting with key stakeholders

• Comprehensive environmental impact and risk assessment studies

• Environmental management systems • Setting targets for environmental protection to the highest level technically achievable

• Constantly reviewing technical developments which could be applied to further reduce impacts or the risk of impacts


Biological Diversity

• The different species (plants, animals and micro-organisms) in an area (species diversity)

• The differences that exist within species (genetic diversity)

• The different habitats and ecosystems in an area (ecosystem diversity)


Why is Biodiversity Important?

• Healthy ecosystems and ecosystem services

• Providing food, clothing, other raw materials

• Controlling pest plants, animals and diseases

• Resource for natural compounds

• Beauty, tranquillity, ethical values


What are the Impacts of Mining on the Environment (Worksheet 1)?


Impacts of Mining on the Environment

• Contamination of surface water or ground water

• Changes to flow rate of surface or ground water

• Air pollution

• Damage to soils

• Wind and water erosion

• Noise or vibration

• Impacts of tailings storage on soil, water and air

• Acid mine drainage

• Loss of flora and fauna

• Damage to heritage sites.


Mine Planning for Environmental Protection


Environmental Issues

• Air quality

• Noise & vibration

• Water management

• Water quality

• Soil conservation

• Biodiversity, flora & fauna

• Archaeology & heritage protection

• Transport

• Subsidence

• Rehabilitation

• Visual impacts

• Hazards & risks

• Solid wastes

• Socio-economic issues

• People’s health, nuisance


Air Quality

• Dust impacts

– Health hazard

– Loss of environmental amenity

– Aesthetic impact

• Planning solutions

– Minimise area of pre-stripping

– Rehabilitate mined areas as soon as possible

– Water haul road surfaces

– Consider using binders on haul roads


Noise & Vibration

• Noise and vibration impacts

– Disturbance of nearby residents and land holders

– Potential injury to human health

– Possible structural damage

– Nuisance


– Control noise sources

– Use good blast design

– Bunds and screens

– Develop operational plans

– Consider land use zoning


Water Management

• Flood impacts

– Worker safety

– Damage to equipment

– Inundation of surface workings

• Drought impacts

– Disruption of processing

– Conflict with other water users


– Design appropriate flood diversion works such as levees


– Model water balances

– Harvest and conserve water

– Build retention ponds/dams


Water Quality

• Impacts

– Increased sediment in runoff

– Metals in discharge

– Acid or saline waters

– Groundwater and surface water contamination

– Impacts on aquatic flora and fauna


– Develop a water management strategy

– Use sedimentation ponds

– Install grit and oil arresters in association with oil separators around workshops, vehicle wash-down pads and process plants


Soil

• Impacts

– Erosion

– Possible contamination

– Affects success of rehabilitation and revegetation programs


– Develop a topsoil management plan

– Reuse topsoil in rehabilitation programs

– Rehabilitate mined areas as soon as possible


Biodiversity, Flora and Fauna

• Impacts

– Displacement of animals

– Habitat reduction

– Loss of plants and animals

– Damage to the ecological integrity of the area


– Survey pre-mining flora and fauna and identify rare and endangered species

– Develop a rehabilitation strategy

– Minimise mine impacts on flora and fauna through layout and design


Archaeology & Heritage Protection

• Issues

– Potential damage to artefacts or sites of historical and heritage value

– Sites may be of scientific or spiritual significance


– Consult the local community for help in identifying these sites

– Carry out site surveys

– Plan to minimise disturbance and conserve archaeological & heritage sites


Transport

• Transport impacts

– Traffic noise

– Traffic congestion

– Potential reduction in road safety

– Increased road wear and tear


– Upgrade and use existing roads

– Construct new facilities dedicated to the mine

– Stagger shift times with surrounding industries to reduce road congestion


Subsidence

• Subsidence impacts

– Surface damage (ground movement and slope change)

– Waterlogging soils or making land more flood prone

– Potential damage to buildings or infrastructure


– Modify extraction methods

– Modify buildings or other surface structures before mining so they can better withstand subsidence


Rehabilitation

• A key goal of mine planning is ensure the rehabilitation of disturbed lands to a stable and productive post-mining land use which is acceptable to the community

– Design and create appropriate landforms for the minesite

– Establish appropriate and sustainable ecosystems


Visual Impacts• Visual impacts

– Removal of vegetation

– Modification of landforms

– Create colour contrasts

– Impose structures into a natural landscape


– Consider location of viewing points, quality of the visual resource

– Suitable colour choice for buildings and equipment

– Tree plantings

– Perimeter screening (bunds & vegetation)


Hazards & Risks

• Hazard issues

– Natural disasters

– Operational hazards

– Site accidents

– Blasting

– Spills


– Planning can assess and minimise hazards and risks to the environment, personnel & the community

– Training, emergency procedures, careful blast design, traffic rules, EMS, appropriate environment performance targets


Waste Management

• Waste issues

– Overburden

– Slimes, muds and tailings from ore concentrators and processing plants

– Maintenance wastes (oils and lubricants)

– Staff waste (sewage, wash water)


– In-pit disposal

– Mechanical de-watering

– Incineration (possible electricity generation)

– Effluent land irrigation systems


Socio-Economic Issues

• Issues

– Local and regional economic issues

– Community attitudes and concerns

– Impacts on neighbours


– Understand and accommodate the concerns and needs of the local people

– Effective and continuous community consultation

– Specific programmes to support the community


Mine Planning Components

1. Mine location

2. Pre-mining investigations

3. Construction

4. Pollution prevention

5. Biophysical impacts

6. Socio-economic issues

7. Environmental monitoring

8. Mine closure


Mine Location: Issues to Consider

• Location in drainage basin

• Surrounding land use

• Proximity to utility infrastructure

• Labour market • Visual exposure

• Cumulative impacts

• Location of processing plants

• Location of waste dumps

• Location of hazardous materials stores


Pre-Mining Investigations

• Baseline investigation is required to:

– Enable mine planners and environmental scientists to understand the environmental and social issues that need to be addressed

– Ensure the financial viability of the mining operation

– Gather sufficient information about flora, fauna, landscape, soil types and drainage system to provide a sound basis for planning rehabilitation


Construction

• Community concerns when large numbers of construction workers move in (housing, infrastructure, cultural issues)

• Transport issues (construction materials and bulk samples/trial shipments)

• Environmental safeguards during construction

• Worker housing


Pollution Prevention and Controls

• Incorporate pollution controls into the design phase of operations

• Control and contain contaminants on site

• Training of mine employees in environmental awareness and responsibilities

• Air pollution control systems

• Noise control

• Water pollution control


Biophysical Impacts

• Design safeguards can minimise biophysical impacts; for example, soil erosion can be minimised by:

– Understanding soil structure

– Landform design

– Drainage networks

– Incorporating runoff silt traps and dry detention ponds in the rehabilitated landform


Socio-Economic Issues

• Promote the positive aspects of mining while recognising and addressing adverse effects.

• Issues that need special consideration:

– Land use planning

– Land acquisition and resettlement

– Community infrastructure

– Employment

– Archaeological and heritage issues


Environmental Monitoring

• Environmental monitoring provides information to:

– Demonstrate compliance with environmental legislation

– Assess and improve environmental performance

– Refine operational practices

– Safeguard the interests of both the mining company and the community


Mine Closure

• Mine closure should be planned before the commencement of operations

• Issues to consider:

– Long term water management

– Post-mining land use

– Final rehabilitation

– Safety of mining voids

– Sustainability


Water Management


Rivers and Streams

Mine operations can affect rivers and streams in an area.

– Quantitative changes: amount of water flowing in thestream

– Qualitative: adding dissolved or suspended solids to the water

– Effects on competing community uses for water, e.g.drinking water, transport, fishing


Water Management PlanImportant components of the minesite water management plan include:

Minesite water balance. Water supply. Drainage. Erosion management. Water treatment. Flood risk and hazard. Managing geo-chemically aggressive materials. Managing hazardous materials. Water monitoring.


The Hydrological Cycle

Minesite water management is about limiting adverse effects of mining operations on the regional hydrological cycle and ensuring that hydrological processes do not jeopardise mining operations.

The hydrological cycle is the interchange of water in all its physical forms between the atmosphere, earth’s surface and the biosphere:

• Rainfall • Infiltration• Surface runoff• Evapotranspiration• Percolation

• Stream flow• Ground water flow


The Hydrological Cycle


Infiltration• Infiltration occurs when rainfall reaching the ground

moves down into the soil profile

• Infiltration is affected by:

– The soil’s saturated hydraulic conductivity and its initial moisture content

– The surface condition of the soil– Intensity, duration and pattern of the rainfall event

• Compacted soil reduces infiltration which increases surface runoff and may increase soil erosion


Surface runoff

• Runoff occurs when water reaches the ground faster than it can infiltrate into the soil

• Surface runoff is a major cause of soil erosion

• A cover of vegetation slows surface runoff and binds the surface soil


Percolation and Ground Water Flow

• Percolation: vertical movement of water under gravity through saturated or nearly saturated soil to recharge aquifers

– Clearing vegetation reduces infiltration and percolation; this may adversely affect ground water tables

• Ground water flows from recharge areas to discharge areas

– Ground water flow is affected by geology and hydraulic variations in the aquifer


Streamflow

• Surface runoff which flows down a catchment and eventually into rivers and streams becomes ‘stream flow’

• Mining activities can alter stream flow regimes (water diversion, erosion behaviour)

• Streamflows can also affect mining operations (flood risk, water shortages)


Seasonal Variation

• Precipitation and evapotranspiration which largely drive the hydrological cycle may have distinct seasonal variations such as ‘wet’ or ‘dry’ seasons

• Seasonal rainfall variation can significantly affect minesite water management

• Mining operations may have to be scheduled by season to minimise environmental risk


Seasonal Variation

Average Monthly Rainfall in Copperbelt (1970 – 2000)


Water Balances

• A minesite water balance is a tool used to assess amounts of water entering, leaving and moving across the minesite

• The water balance equation incorporates:

– Rainfall– Infiltration– Surface runoff– Evapotranspiration– Percolation


Best practices

• Best practices in water management include:

– economical use of water resources, including recirculation

– collection of waste in tailings impoundments

– Minimising discharges to nature, e.g. with treatment systems

– progressive rehabilitation of pits, dumps and other waste facilities;

– continual improvement


Minesite Water Management System

• A minesite water management system consists of a number of physical elements plus a number of process elements

• The water management system should be expressed as a part of the environmental management plan or separate water management plan

• This is based on a proper knowledge of all water streams at the mine site (quantity and quality)

• Uncontrolled releases of water represent a failure of a water management system and is not best practice


Physical Elements

A minesite water management system has several inter-connected physical elements that:

– Supply water for mine operations

– Convey water

– Store water and liquid wastes (e.g.tailings)

– Dispose of water by evaporation or discharge

– Improve water quality


Physical Elements• Water supply: sources may include

– Dams

– Boreholes

– Natural water bodies

• The effect of using water for the mining operation must be carefully considered.


Physical Elements

Conveyance

• Pumps, pipelines and open channels for moving water

• Issues include:

– Capacity and reliability

– Integrity (potential for rupture)

– Channel capacity and bed and bank erosion

Storage

• Water storages (i.e. tanks or dams)

• Tailings dams

• Open cut pits

• Issues include:

– Capacity

– Spills: likelihood, impact

– Seepage and impact on ground water


Treatment

• Water treatment commonly used on minesites:

– Sediment basins

– Wetlands

– Chemical treatments

• Common issues include capacity, efficiency, retention time and safety


TreatmentSediment basins

• are an effective way to remove coarser-sized particles, i.e. sand-sized particles or greater (> 0.1 mm diameter)

• have to be large to remove significant quantities of silt-sized particles (0.01 - 0.05 mm), – e.g. for medium-sized silt (0.02 mm diameter), a surface

area of 2000 m2 per m3/s of inflow is required to achieve a removal efficiency of 50%).

• are not effective at removing clay-sized particles (<0.005 mm) unless supplemented by chemical dosing (typically gypsum).


TreatmentSediment basins

• Discharge volumes need to be estimated, and on the basis of these results and any regulatory requirements, an appropriate basin size can be selected.

• In selecting a basin size – 'Big is better' for sediment basins

• E.g. effluent from Nchanga concentrator and main tailings dam, and about 150 000 m3/d (1.7 m3/s) – 50% reduction (medium-sized silt) in sediment load, would require a pond with a surface area of 2000 x 1.7 = 3400 m2 (e.g. 100 m x 34 m)


Treatment

Constructed wetlands

• are being increasingly used as cost effective (and aesthetically attractive) components of minesite water management and treatment systems

• can be designed to remove fine suspended solids, polish the water produced by onsite sewage treatment plants, strip nitrate from pit water, remove heavy metals or process reagents (cyanide, xanthates) and neutralise the acidity in acid rock drainage.

• are especially suitable for treatment of seepage from waste dumps and tailing ponds after decommissioning of the mine, as they can be self-sustainable


Treatment

Conceptual design of a wetland system for treating Acid Mine Drainage


TreatmentRanger Uranium Mine, Australia•The current constructed wetland is one of the largest of its type in Australia.

•Results so far indicate effective removal of U, Mn and nitrate at flow rates up to 3 000 m3/day.


TreatmentHenty Gold Mine, Tasmania•Possible contaminants in minewater and surface runoff include suspended solids, and hydrocarbons from fuel and oil spills.•Mine water passes through a settling pond to remove suspended solids; flocculant and coagulant are added•The settling pond is drained periodically to remove accumulated sediments.•A floating plastic containment boom contains hydrocarbons in the settling pond

In addition a wetland system has been constructed: two cells between the settling pond and the polishing ponds with a contact area exceeding 1200m2 .


Disposal

• There are three ways to dispose of excess water on a best practice minesite:

– Evaporation (from evaporation basins, tailings dams, open cut pits, water storages, and application of water on land)

– Controlled release to surface waters from a storage

– Recharge to ground water


Process Elements

• Minesite water management system

– Erosion or sediment control plan

– Plans for management of hazardous materials and wastes (acidic, alkaline or highly reactive)

– Inspection and maintenance plan

– Water monitoring (volume, flow and quality)

– Reporting


Erosion and Sediment Control Plan

• Aim to control risk of sediment loss from disturbed areas

– Silt fences, sediment dams

– Revegetation of spoil piles and other disturbed areas

• Good sediment control protects streams from degradation by suspended sediments


Managing Hazardous Materials and Waste

• Mines use many hazardous materials.

– Grease, oils, petroleum products, toxic substances such as cyanide

• Spoil and other mine wastes may react with oxygen and water and generate water pollution.

– Pyritic material oxidises to form sulphuric acid (acid mine drainage).


Inspection and Maintenance

• The water management plan must be maintained, inspected and modified if necessary. Some issues include:

– Bed and bank erosion in channels

– Silt build-up

– Damage to pipelines

– Calibrating monitoring equipment


Monitoring

• Baseline monitoring

– Essential pre-mining information

• Design monitoring

– Data required to design the physical and process elements of the management system

• Operations monitoring

– Data from daily measurements of the system

• Incident monitoring


Best Practice Minesite Water Management Plan

• Community expectations

• Statutory requirements

• Risk Management

• Minesite water balance

• Monitoring hydrological processes

• Operational monitoring

• Emergency monitoring

• Flood risk and hazard

• Water supply

• Soil erosion

• Water quality

• Computer models

• Performance indicators

• Training and research


Community Expectations

• Communities expect responsible management of mining operations

– Community consultation from planning to closure

– Liaison with stakeholders from areas that might be affected

– Protection of water quality for downstream users and habitats during operation, during closure,

and after rehabilitation


Statutory Requirements

• Best practice includes:

– Identifying all relevant environmental and water resources legislation

• Legislation may apply to the mine lease or to the broader catchments containing the lease

– Effective communication with regulatory agencies to make sure legal requirements are met


Risk Management• Hydrological Risk

– Risk associated with processes that fluctuate randomly such as floods or drought

• Operational Risk– Risk to safety, the environment or the economics

of the mine arising from its operations


Minesite Water Balance

• An minesite water balance summarises the major sources and destinations of water flows onto, across and off the minesite

• For a storage dam values include:

– Inputs (rainfall, ground water flow, runoff, returns from process)

– Outputs (inputs to process, evaporation, seepage, discharge, pump transfers)


Monitoring of Hydrological Processes

• There are three phases of hydrological monitoring:

– Baseline monitoring

– Operational monitoring

– Post-mining monitoring

• Typical hydrological processes monitored include rainfall, evaporation, stream flow and water quality


Streamflow and Water Quality• To monitor stream flow the mine management should:

– Identify existing or past official stream-gauging stations near the minesite

– Establish at least one ‘key’ stream-gauging station

• Water quality monitoring points are needed at both upstream and downstream of the minesite on all major streams that are at risk from mining operations

• All liquid releases to the envionment need to be monitored, both quantity and quality


Operational Monitoring

• Flows in key pipelines

• Inspection of hydraulic integrity of key pipelines

• Water levels and water quality in key storages (especially ‘dirty’ water storages)

• Minesite rainfalls

• Silt build-up in silt traps and wetlands

• Bed and bank erosion in channels


Emergency Monitoring

• The emergency monitoring plan should address:

– The volume, discharge rate and quality of water that ‘escaped’ and the impact on downstream water bodies;

– The possibility of alerting downstream landholders and water users of what has happened and what the consequences might be.


Water Supply

• Recycle as much water as possible

• Evaluate the risks and plan for supply shortfalls

• Evaluate impacts on downstream flow, habitats and other users

• Assess risks and consequences of dam failure

• Assess uses of water storages after mining (e.g.irrigation, recreation)


Soil Erosion

An erosion management plan should:

– Identify areas of existing or likely erosion

– Plan appropriate controls

– Seek regulatory advice and approval of the plan before implementing the plan

– Try to control erosion at the source


Water Quality

A water quality management plan should:

– Identify water quality issues and plan controls

– Seek approval from regulatory authorities before implementing plan

– Separate runoff from ‘clean’ areas of the minesite from ‘dirty’ area runoff

– Control pollutants at the source

– Design and implement water quality monitoring programs

2 BEST PRACTICE ENVIRONMENTAL MANAGEMENT IN MINING.

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Transcript of 2 BEST PRACTICE ENVIRONMENTAL MANAGEMENT IN MINING.