Year 4-7 Teacher Resource

Transcription

1 Year 4-7 Teacher Resource Introduction Alcoa s Australian operations form an integrated aluminium industry which includes bauxite mines and alumina refineries in Western Australia and an aluminium smelter in Victoria. The Alcoa education program offers a wide range of cross-curricula activities which apply to each of the elements of the aluminium process. Process information sheets and a tour worksheet are available below. In addition a list of classroom activities are listed under operational areas with the relevant learning areas indicated for each activity. Educators are invited to select from the list of available activities and contact the Alcoa Discovery Centre in Western Australia via tourcentre@alcoa.com.au or +61 (0) for copies. Information, worksheets and activities Mining Process Rehabilitation Process On Tour Worksheet Classroom Activities 1

2 Mining Process Alcoa s bauxite mining operations in Western Australia occur in the Darling Range. The bauxite occurs as a result of a lateritic weathering process and is often found on the sides of the hills. To access the bauxite there are a number of steps involved in the mining process. Pre-mining surveys are conducted in all new mining areas to provide information on fauna and vegetation; to map the extent of dieback disease; and to identify any significant Aboriginal or European heritage sites. If rare or protected species or significant sites are present, they are avoided or management plans are developed to minimise the impact of mining on them. Exploration drilling is undertaken to identify the specific location of ore bodies within the mine lease that are suitable for mining. Drilling starts at wide spacing (120 m) and then focuses in on identified ore bodies. Grade control drilling is undertaken to obtain detailed chemical composition information of the ore which is planned for mining. This information is used to plan when to mine different pits, as the mines must supply a constant grade of ore to the refineries by mixing ore of different grades from different pits together. Mine planning takes into account any significant vegetation, fauna or heritage sites identified during the pre-mining surveys as well as avoiding the spread of dieback disease. A number of mine plans are produced, including a conceptual 25 year mine plan, a ten year mine schedule and a detailed five year mine plan. The Five Year Mine Plan and the Mining and Management Program (MMP) are submitted to the Mining and Management Program Liaison Group each year for Ministerial approval. The MMP summarises the major environmental management programs that will be undertaken to minimise the impacts of mining, with emphasis on issues relevant to the next five years. Developing infrastructure is conducted when the mining activities move into a new area within the mineral lease, the crusher will be relocated closer to the new area to be mined to reduce the trucking distance. On average, the crusher will move approximately every years. New roads are created each year to allow access to areas to be mined in the following few years. Timber within Alcoa s mine lease belongs to the State Government. Before clearing, the Forest Products Commission takes any marketable timber from areas where mining is planned each year. Once all marketable timber has been taken by the Forest Products Commission, all remaining timber is cleared from the areas to be mined and positioned in rows. Historically wood waste was burnt, however to reduce burning the residue timber is also utilised by external organisations for charcoal production, as wood chips for Alcoa sites and as fauna habitats in the rehabilitated mine areas. 2

3 Topsoil and overburden make up the soil profile. The topsoil layer contains a large store of seed and nutrients that are vital to the success of the forest rehabilitation and is about 15 cm thick. The overburden layer is 20-80cm of gravely sub-soil material sitting above a cemented laterite layer known as caprock. These layers are removed separately using scrapers prior to mining. Due to the uneven nature of the caprock, the scrapers are unable to remove the entire overburden layer as some of this material will remain in the hollows in the caprock, this is known as secondary overburden. Secondary overburden is removed by a small excavator. Caprock is a solid rock layer containing bauxite and rests above the friable bauxite layer in the soil profile. This caprock layer is broken by blasting. Crushing and conveying to refineries occurs once the caprock layer has been broken and the bauxite is ready to be mined. An excavator or loader is used to load the bauxite onto haul trucks for transport to the crusher. The crusher is used to break the ore down to a smaller size suitable for transport along the conveyor belt to the refineries. Several pits are usually mined simultaneously in order to supply the refinery with a constant grade of ore. Bauxite profile before mining Jarrah forest Topsoil 15cm Soil layer Caprock 1-1.5m Friable Bauxite 4-8m Clay up to 40m Granite Bedrock 3

4 Rehabilitation Process Each year mine pits that have had the ore removed and roads that are no longer needed are rehabilitated. The long term objective of Alcoa s mine rehabilitation is to establish a self- sustaining jarrah forest ecosystem, planned to enhance or maintain conservation, timber, water, recreation and other forest values. Alcoa s rehabilitation process has been developed and improved since operations commenced in 1963 and currently involves a number of important steps. Pre-ripping and landscaping take place first. Pre-ripping breaks up the compaction of the pit floor caused by heavy rubber-tyred mining equipment. A bulldozer with a winged tyne attached rips the floor of the pit; this helps roots to penetrate through the soil profile. Large rocks are buried, vertical pit faces are flattened down and the pit floor is smoothed to blend the mined area into the surrounding landscape. Soil return takes place with overburden and topsoil layers being returned. Wherever possible, fresh topsoil is directly returned to rehabilitated areas from pits that have been recently cleared. This maximises the topsoil seed store, which is important for maximising the number of plant species in rehabilitated areas. Contour ripping is undertaken to increase the soil s water storage capacity. This contour ripping is undertaken with a multi-tine. Contour ripping creates mounds across the slopes in rehabilitation which are important for erosion control. In flat areas and areas with a low potential to erode, the rip lines may be partially flattened by a heavy bar dragged behind the ripping dozer. Seeding is done to encourage the return of plant species into rehabilitated areas. This seed mix has been specially formulated by Alcoa and contains species and is applied at a rate of about 1 kg per hectare. Recalcitrant planting takes place to ensure the return of plant species that are unable to be established from the seed in the topsoil or applied seed mix. These plants include many grasses and sedges that produce little viable seed. Alcoa grows seedlings of these species through tissue culture (cloning) or cuttings and plants these seedlings by hand in the rehabilitated areas. 4

5 Fertilising is done improve the establishment and early growth rates of trees and understorey in revegetated areas, fertiliser is applied by helicopter to the newly rehabilitated areas during August of each year. Ongoing monitoring and management of rehabilitated areas takes place to ensure the return of plant species into rehabilitated areas. In March each year when the rehabilitation is nine months old, the previous year s rehabilitation is monitored to check that the number of established plants meets targets agreed by Department of Parks and Wildlife (DPAW) and Alcoa, and to identify any areas which need further treatment to control weeds or repair any erosion damage. At 15 months of age, botanical species richness (number of different plant species) is monitored against internal and government standards. Relinquishment of mined areas to the State is the aim of rehabilitation. Alcoa s regulatory body (the Mining and Management Program Liaison Group) in consultation with the community and other stakeholders have developed a set of Completion Criteria for rehabilitation areas. Due to improvement in rehabilitation standards and techniques, two sets of completion criteria exist for pre-1988 and post-1988 rehabilitation. These criteria were developed to allow government agencies to assess whether rehabilitation is of a satisfactory standard so that Alcoa can hand the land back to DPAW for future management. World s best mined land rehabilitation to return a self-sustaining jarrah forest ecosystem to enhance or maintain water, timber, recreation and conservation values. 5

6 On Tour Worksheet Name: Date: Before You Visit: What Do You Know? What is bauxite? What does it look like? Based on you current knowledge of Alcoa s operations and bauxite mining, what do you expect to see at the mine site? Draw a sketch of what you think a mine pit looks like. 6

7 Alcoa s Mineral Lease (1SA): On the lease map below: Draw a line from your school to the areas you will visit today. Circle those areas. Add the rail line linking the refineries to the ports. Use arrows to indicate Bunbury and Kwinana are export ports. 7

8 Pre-mining: What is exploration drilling and what is its purpose? List the types of surveys that are carried out prior to mining. What information do they give and why is this important? 8

9 Mining: Number the steps of the mining process in order. Scrape off topsoil Fertilising with helicopter Remove and store overburden Exploration and drilling Clear timber Bauxite into crusher Load bauxite into haul truck Landscaping the ground Direct return topsoil Transport to refinery on conveyor Blasting and ripping Ripping, seeding and planting 9

10 Crushers and Conveying: What is the role of the crusher in the mining process? How is the bauxite transported to the refineries? How long is the conveyor? Rehabilitation: Match the steps in the rehabilitation process with the reasons they are done by drawing a line. STEPS REASONS A. LANDSCAPING the steep pit walls are reshaped to return seeds and nutrients contained in the soil to the mine pit B. SOIL is spread on the pit floor to ensure the jarrah forest plants and animals are returning. C. RIPPING the soil is loosened and broken up to make the mine pit blend into the. surrounding forest. D. SEEDING, PLANTING and FERTILISING is allow the plants roots to grow performed to and to prevent erosion by allowing the water to sink into the soil instead of running off. E. MONTIORING plant species return the jarrah forest plants. tree growth and the return of native animals to rehabilitated areas to 10

11 Reflection: What did you learn during your visit? 11

12 Classroom Activities Classroom activities are listed under operational areas with the relevant learning areas indicated for each activity. Educators are invited to select from the list of available activities and contact the Alcoa Discovery Centre in Western Australia via or +61 (0) for copies. Learning Areas: Society & Environment Science Maths English Technology & Enterprise Mining and Rehabilitation Activities Aboriginal land uses Animal habitats Bauxite mine diorama Bauxite profile Diorama Big equipment Choc chip mining Design a brochure Design a soil collector Dialogue of the Jarrah forest Early European land uses Economic and environmental sustainability Environmental consultant Excavator arms Exploration drilling Fauna survey Flora survey Flow chart the mining process Flow chart on rehabilitation process Fungi, spores and micro-organisms Geology of bauxite Importance of Jarrah forests Looking for green Mapping bauxite Minimising impacts Mining and rehabilitation board game 12

13 Mining and rehabilitation cartoon/poster Mining careers Mining polyhedron Plan to mine your own backyard Plant and animal monitoring Plant uses in Jarrah forest Rehabilitation polyhedron Rock collections Sampling soil So what do you know about bauxite mining? So what do you know about rehabilitation? Soil profile jar Spread your wings Treating seeds Water monitoring What s in the hills? What s in the soil? Refining and Smelting Activities Clarification Flow chart the refining process Simulated Bayer process So what do you know about refining bauxite? Who was Karl Bayer? Design a car for the future The story of aluminium in transport Solutions Activities 12 things you can do 1000km walk competition A hiking trip Advertisement Aluminium in transport Around your home Build a jumbo jet Communicating in comics Design a car of the future Design a green village 13

14 Design a sculpture using recycled aluminium cans Fossil fuels or no fossil fuels Have your say How can you make an impact? Looking for green Recycling instructions School audit Snowball So what do you know about greenhouse gas? Stranded The carbon cycle What do you mean? Which car? 14