Sustainable development and the environmentLife of a mine

From cradle to grave

• Life cycle of mining need to taken into account

• Sustainability reporting and environmental management– The environmental impacts (and associated social impacts)– Economical sustainability and implementation of the polluter-

pays principle

• In this millennium, particularly, new aspects to sustainability assessment are brought by considering economical benefits resulting from improved ecological and social benefits

– Integrated mineral use and competitive advantages to end-products

• Joint use of primary mineral resources and/or recycled ones

– “ecolabeling” or green metals (attempted)• http://www.academia.edu/3578521/Prospects_for_sustainability

_certification_of_metals

Geochemical finger printing

– e.g. bloody diamonds – Coltan from Kongo

How “green mining” can be distinguished from “crimes against mother nature”?

• Development from discovery to mine over ten years

• (1 mine/1000 discoveries)

• Data management– Systems should be

designed to store all relevant data

Example of data-needs

• Tekes project “Hand book of mine closure”• Closure plan drafting implemented involved

– Exploration data (soil chemistry and geophysics)– Geotechnical data during construction

• Drilling and soil observations

– Water pumping and ground water monitoring• Preconstruction/ during construction/during operation

– Old maps preceding the mine– Reports of construction, groundwater monitoring

– Most of the data over 30-40 years old!

Exploration data

Geochemical exploration data

• Geochemical exploration searches for anomalous concentrations of chemical substances in a region.

• Geochemical data is collected also in site-specific investigations as a routine procedure

• The sampling density varies from a couple of metres to several hundred.

• In glaciated areas the most common sample material is till, – Contains ground bedrock material– indirectly reflects the composition of bedrock.

• In addition to the sampling of soil (till,) a percussion drill may be used to collect samples of drilling mud and crushed rock from the bedrock surface.

Other geochemical methods

• Mobile Metal Ion techniques: large number of surficial soil samples + selective leaching techniques

• humus and bedrock geochemistry heavy minerals • isotope studies.• Bedrock geochemistry (lithogeochemistry) is based on the analysis of the

chemical composition of bedrock samples. • Humus geochemistry is best suited for areas in which the vegetation and

moisture conditions do not vary much and the overburden is sufficiently thin. • In studies of heavy minerals, the heavy mineral material is concentrated

from the soil sample and then either studied using a microscope or analysed chemically.

• Geobotanical analyses use vegetation as samples– Arid areas– Thick weathering zone areas (Australia)

Geophysical data

• Geophysical measurements carried out during exploration provide information

• used to model the depth dimensions and below-surface structures of ore-critical rock masses

• Magnetic and EM and electrical methods are ordinarily used and occasionally gravimetric methods are employed as well. The most common

• Slingram, electrical measurements using the induced polarisation (IP) and self-potential (SP).

• Exploration can also employ seismic and radioactive methods

• Drilling data, geophysics, topographic data/laser scanning-> 3D models, volume calculationsmodels of impact

Pilot mining and concentrating trials

• Drilling– Recognizance, delineation, inventory

• Pilot processing and mining when decision of mine planning has been made

• to determine the feasibility or profitability of an ore deposit• to test and develop a concentrating method • methods corresponding to those used in full-scale mining • at laboratory scale a typical quantity of samples required for a trial run of grinding-

flotation is 100 to 300 tons. • Plant-scale tests mineral technology facilities generally requires 200 to 1000 tons of ore. • Larger quantities – 20,000–60,000 tons – are used if the concentrating trial is carried out

in a mill near the deposit • The amount of overburden and waste rock removed from on top of the deposit ordinarily

varies from several hundred to several hundred thousand cubic metres (in Finland)– Can have high natural metal concentrations

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3D-model of tailing pond-area

• This model has been build as a part of a mining closure plan. The data compiled was obtained during over 40 years of life of a mine

Planning phase and construction

• The methods selected in this point must be – controllable in respect of emissions and environmental impacts – comply with environmental protection requirements

• increase the versatile use of the excavated rock material (by-product development) and reduce the quantities of mining waste intended for long-term disposal above ground (e.g.eco-efficient use of materials, shifting to underground mining, and underground backfilling of mining waste).

• • Methods favoured for planning the excavation of ore, blasting, and transportation of ore are those which reduce dust, noise and vibration emissions, as well as reducing blasting chemical residue in the drainage within the mining area.

• • Appliances and methods selected for the planning of excavations and concentration are those which can minimise energy consumption.

• • Methods favoured for the processing of ore are those which reduce the quantity• of fresh water use and favour the recycling of service water. Additionally,• process chemicals are favoured that• −− break down into a harmless form in the pumping of tailings or waste slurry• and/or in the disposal areas of such prior to the final treatment of the waste• water, or• −− are broken down into a harmless form in the process prior to disposing the• waste slurry, or• −− can be recycled.

• The basis for land use planning of a mining area – must reconcile the land use interests of the environment

• Must be carried out with open dialogue with the local community (inhabitants, tourism, forestry and fishery enterprises), the local environmental protection authorities and the nature conservation associations.

• This is also associated with the management of incidents (accident, leakage) and planning of precautionary measures.

Risks of soil erosion

• The construction of a mining area breaks up large land areas, which increases. The management of erosion and related dust formation requires leaving the tree stands as protection zones for the waste areas and road network and/or the vegetation of the protection zones (barriers) or maintaining of vegetation. The action plan shall also include the making of a monitoring programme in case of possible detrimental impacts caused by erosion.

BEP planning for waste areas• Waste management plan must be made in order to

– reduce the proportion of iron sulphides in the waste • i.e. reducing the acid-generation potential of the waste

– enhance the neutralising capacity of the waste• (addition of lime/carbonate-containing mineral powder)

– break down harmful chemicals (e.g. cyanide in the process) prior to disposal of tailings and/or

– reduce the quantity of soluble chemical residues in the waste intended for disposal

– promote the binding of potentially harmful trace elements as weakly soluble into the waste intended for disposal (addition of chemicals)

– the potential by-products are separated in either excavations and/or the processing of ore and placed apart from the waste fractions intended for long-term disposal

– investigate the occurrence of various precious minerals and metals, such as high-tech elements (e.g. Ree, Ga, In, Nb, Li), which can promote the utilization of the waste fraction in the future.

Disposal site for mining waste • The planning of and the selection of placement site generally covers the entire life of the disposal area

from construction through to closure– the physical, chemical and geotechnical characteristics of the waste intended for disposal or by-products, and the

potential interactions with the disposal environment– specifying the basal and dam structures for the disposal area– influencing the selection of water management systems and rehabilitation methods– data pertaining to the condition of the environment, soil and bedrock characteristics,

• special hydrological and hydrogeological features for alternative placement sites • collection of seepage and drainage water for treatment, both during the operational stage and following

decommissioning, to– ensures the functioning of rehabilitation

• land use requirement during the operational stage and following decommissioning– (+ ownership rights and conflicts with the local inhabitants)

• possibility for backfilling mining waste into open pit/underground mine • proximity of housing existing road network and transportation obstacles• proximity of protected sites and the potential impacts focused on these• Current and future recreational, agricultural and forestry use of the operations• cost factors: transportation costs, costs for structures and maintenance, rehabilitation• costs and costs for the monitoring of rehabilitation• possible risks to health, the environment and safety following the decommissioning• extreme weather conditions (once in one hundred years).

Finnish guidance (2012) for waste planning and placement principles /EC 2009

Methods to preventing AMD and rehabilitation of acid generating wastes will be considered in a separate lecture!

Basal structures for mining waste areas

• The selection of basal structures guided by – the chemical and physical characteristics of the waste (waste class), – the hydrogeological characteristics and topography of the soil at the placement site.

• If the mining waste intended for long-term disposal is acid generating and/or it contains potentially soluble harmful substances, then the basal structure should:

• promote the stability of waste disposal as well as prevent/mitigate the environmental impacts of the disposal (on the groundwater, underlying soil),

• slow down the chemical alteration of the waste, especially in the base section of the disposal site,

• prevent oxygen-rich groundwater from accessing the waste (see also dam structures),

• guide the selection of rehabilitation method for the waste area.

Waste classification

See p. 166

Dam structures

• Things to be considered– Availability of dam material– E.g. till comprises 70 % of

Finland's area but suitable till for dam construction can be scarce in certain regions

– Sulphide containing waste rocks or mechanically weak rocks cannot be used for construction

• In some mines crushed rock aggregates are brought from nearby quarry

Water treatment

• The chemical and physical characteristics of the water intended for treatment needs to be clarified, and on the basis of the water quality, the water treatment method will be selected, structures for the treatment facility will be designed and goals set for the quality of treated water.

• The probability and quantity of the formation of ARD and/or neutral metal concentrated water, fluctuation in acidity at the various collection system sites, and the seasonal and medium-term fluctuation in acidity are assessed.

• The occurrence and quantities of chemical residues from the process water and blasting agent residues from the dewatering water are established and the fluctuations in the quantities of such are monitored.

• On the basis of research, an assessment of the separate treatment of chemicals at the concentration plant or process plant (e.g. cyanide) is conducted, and in respect to blasting agents in the excavated spaces prior to discharging the water to the outdoor treatment basin.

• A flexible water management, treatment and monitoring system shall be made that takes into account not only the short-term alterations in operations, but also the medium-term alterations and the post-mining operational phase rehabilitation solutions.

• This is also associated with the planning of precautionary measures in order to prevent the harm caused by unpredictable emissions (restoration measures).

• Assessment of the functioning of the water management system and dimensioning of treatment objectives for mitigating environmental risks (inhabitants of the surroundings and nature).

• Assessment of the impact of climatic factors on the long-term fluctuation in the quantity of water for treatment and the sufficiency of the treatment capacity. Contingency plans are made for extreme weather conditions (flooding, storms, drought).

• The quantity of slurry produced in the treatment process is assessed, along with the composition and chemical state of the slurry (stability-solubility of precipitate compounds in different conditions), and the rehabilitation of the treatment basins are designed on the basis of these.

• At this stage, the chemical elements that have become concentrated in the slurry and the possibilities for recycling the compounds should be taken into consideration.

Operational phase of the mine

• Maintain actions aiming to reduce environmental and social impacts

• The environmental management system must be implemented and maintained

• The waste management system must be implemented– This must enable recycling of wastes if possible– Implementation of disposal– Reduction of mine water releases (AMD)

• The waste rocks must characterized carefully– Mineralogy and texture (“liberation degree of sulphides,

neutralization capacity)– Block level modelling for waste rocks!

Other plans to be made

• Plans for • Noise reduction• Emissions to air

Operational phase of the mine

• The environmental management system must be established including

• operational guidelines/documents (more information from EC 2009, Environment Canada 2009), – documentation of emissions monitoring findings,– updates to the waste management plan,– documentation of alterations to the operational methods

• (e.g. processing of ore, water management and treatment, neutralisation and cleaning of flue gases),

– service and restoration programme and the measures performed,– responsible persons for various operations (+ description of competence) and tasks, training programme and

training implemented,

• guidelines for internal and external communications,

• instructions for precautionary measures for preventing incidents, documentation of implemented measures,

• environmental damage and measures for rectification,

• rescue plan for hazardous situations (staff, environment),

• work accidents,

• rescue drills and training,

• auditing,

• authority inspections and inspection minutes.

Energy

• Particularly, grinding of rocks takes about 60-75 % of the total energy consumption of mining processes

• Optimization blasting and subsequent processes (e.g. by geometallurgical approach) is essential for the emissions and electricity consumption

• Selection of right methods for crushing and grinding essentially determines the energy efficiency of the process

• Mining induces currently in Finland CO2-emissions “worth” of 540 M€ (with allowance rate of 20 €/CO2-ton)

• At the moment mining is not a subject of CO2-emissions trade

•

Environmental management

• Set of ISO-140000 standards for assessing environmental performance and management

• Supposed to give scientific base for new incentives to energy efficiency, allowance trading and carbon capture

– These will likely concern also mining activities and mining waste management

• ISO 14040:2006 describes the principles and framework for life cycle assessment (LCA) including: definition of the goal and scope of the LCA, the life cycle inventory analysis (LCI) phase, the life cycle impact assessment (LCIA) phase, the life cycle interpretation phase, reporting and critical review of the LCA, limitations of the LCA, the relationship between the LCA phases, and conditions for use of value choices and optional elements.

• Typical application of the standard is to compare environmental performance of product A and product B (which one is better in terms of CO2-releases)

• Application of the standard without site-specific information can lead to obscured assessments e.g. associated carbondioxide releases.

• More realistic LCA data on energy, water and chemical consumption during mining - mines are different!

• Site-specific measures of energy, water and chemical consumption can provide substantially better environmental performance (compared to ISO-standard LCA databases)

Mining wastes for CCS?• Mineralogy, & volumes of tailings and waste rock piles

– Uncertainties about the composition of old waste piles– Secondary processes alter mineralogy– Also possible means of remediation of AMD – Suitability to CCS?

• Mines, dimension stone quarries• Serpentinite (Outokumpu, Hitura)• Wollastonite (Lappeenranta)• Olivine (Kevitsa, Mäntyharju Quarry)• Spectrolite (Quarries in Virolahti)• Ca-feldspars (technology by Quicha Innovation)

• Mining induces 540 M€ “worth “ of emissions– Not part of emission trade

– Enormous concealed energy that has already used to grind the rock • Hitura mine (20 Mtonnes serpentinite) the blasting, hoisting and

grinding has taken about 1,2 TWh

• allowance 20-30 €/tonCO2, crushing and grinding 4-10 €/ton (0.14 €/kWh), 400 kg CO2/ton serpentinite i.e 8-16 €/ton in situ!

Water

• Mining operations require large quantities of water, for example, – drilling water– process water (grinding and concentration in water slurry)– sealing water (pumps, suction devices, etc.)– manufacturing of chemicals– rinse water (e.g. for rinsing equipment and floors)– cleaning water (e.g. cleaning filter cloth), and– tap water (drinking water, etc.)

Challenges of mine water management

• Recycling of water and “closed systems”– Represented too often and too long as “an ultimate solution for everything”,

which has not continued without a recoil to the image of mining industry• “They talk about it but that’s all what they do about it”

– In practice considers beneficiation process waters and is reality today only in few mines!

• Mining can consume also high quality drinking water– Source of such water can become an “environmental or social issue”

• In metal mining areas natural background of groundwater and soil can be high. Use of surface water or ground water (e.g. drilling fluids) can divert natural gw-flow,

• Removal and replacement of soil in the mining sites can induce contamination long after..

• Etc.

Closure of the mine

• Decommissioning of a mining works and rehabilitation of the site when the commercially exploitable ore runs out or when mining operations at the site are terminated permanently.

• The principal aim in mine closure is to restore the mining works to a condition where they pose no detriment to human health or the environment.

• Plans must also take into account the need to use the area again.

• Ensure opportunities for the future exploitation of any valuable materials remaining in the ore deposit and/or the continued use of buildings and waste areas with a view to the needs of future mining activities.

• All unnecessary infrastructure at the mine site is removed

• Steps are taken to ensure that the remaining structures will not pose risks or cause harm to the natural environment and human health or form an obstacle to future use of the site.

• What can remain is rehabilitated storage areas for tailings and waste rock and the mined out spaces.

• If the buildings in the area are sound and possibilities for their continued use are found, then the infrastructure associated with them may be preserved as well.

In Finland

• Under the current mining legislation, operations are deemed to have ceased when the mining permit expires or is revoked (Mining Act 621/2011).

• However, according to the Environmental Protection Act (EPA), the operator of the mine has the responsibility even after the cessation of operations to implement the measures required, in the manner prescribed by the permit conditions,– to prevent contamination of the environment,

• to ascertain the environmental impact of the operations • to monitor the site for the period prescribed in the permit (EPA

• If parts of the mining works or its auxiliary area are relinquished prior to closure, closure and rehabilitation measures are carried out for these areas at the time.

Closure planning

• The planning of closure should be initiated at an early stage in the life-cycle of a mine.

• In Finland :

• The first plans for closure and for the related rehabilitation measures are to be made already during planning of the mining activities and feasibility study or, at the latest,

• when the permit application is submitted!– preliminary plans already exist for the scope of the activities including technical solutions and

location of operations, – -> tentative plans for closure can be drawn up.

• Closure costs and financing plan (an account)

• The closure costs can be taken into account in determining the overall costs of the mine.

• Helps to reduce potentially detrimental environmental impacts from the activities.

• Promotes the efficient use of materials

• Cost-effective implementation of closure measures.

.

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Kulkeutuminen II