Mining along the Munda Biddi Trail

The Darling Scarp started to form about 570 million years ago. In the past 100 years, the Darling Scarp has been exploited for stone from quarries, forestry and bauxite (used to make aluminium) mining. Laterite covers much off the Darling Plateau. It consists of mottled soils overlain by duricrust, which is a hard red/brown cap that looks like cemented gravel. When it weathers it forms "pea gravel", small-ball like rocks which can be hard to ride through when deep. Where laterite is aluminium rich it is called bauxite, and often mined.

Rock Quarries

In the early to mid-twentieth century numerous rock quarries existed on the edge of the scarp - some are visible and affect both the aesthetics and the environment of the escarpment.
In the area where the Helena River emerges from its valley to the sandplain, there are still four quarries evident, despite being unused as quarries for fifty years or more. Some that the Munda Biddi or Railway heritage trails goes near include
• Bluestone quarry (1850s name), later known as Greenmount Quarry (1850s to 1920s), at Greenmount Hill on the west side of Greenmount National Park.
• Mountain Quarry (now usually signed as Boya Quarry), south of Greenmount Hill, which ceased operation in 1963. Now managed as rock climbing location.
• Fremantle Harbour Works Quarry (sometimes, C. Y. O'Connor's Mole Reconstruction Quarry, and later known as the Public Works Quarry), now Hudman Road Amphitheatre at edge of Darlington - Boya localities border, operated from the 1900s to the 1930s.
There have also been visible quarries on the scarp in the Gosnells and Herne Hill areas.
Legislative restrictions upon such developments were initiated in the late twentieth century to prevent further visible scars on the western face of the scarp.

Bauxite Mining

Bauxite mining has been occurring in the Darling Range since the 1960's. These bauxite mines have some of the world's lowest grade bauxite ore mined on a commercial scale (around 27-30%). Despite the low grade, these mines accounted for 23% of global alumina production. This is partly because the bauxite contains lower levels of silica, so it needs less caustic soda for processing. 7 tonnes of bauxite can produce 2 tonnes of alumina, which can be refined into 1 tonne of aluminium. The low-grade bauxite ore which produces alumina is recovered from below the thin (1-2m) laterite caprock that covers most of the Darling Range by strip mining. The mature forest and the laterite are removed and then "rehabilitated" after mining with the beginnings of a young replacement forest on the restored topsoil. Post-mining rehabilitation of mined areas does not re-create the original ancient forested landscape, even in the long-term. For example, a survey of the Willowdale Arboretum in 1980 concluded the ants did not return to the area after rehabilitation in the same diversity. It can only be hoped that the new mine areas will be minimized so that as much as possible of that value is preserved.

I have attached a map from WalkGPS.com which shows mining tenements in the Scarp. It also shows the Munda Biddi and Bibbulmun Track. I can not guarantee its accuracy. But Bauxite Resources Limited proudly claim on their investor fact sheets they have tenements of 17,710 km square km in the Darling Range, so the areas concerned are huge. Scary, especially when it is so close to Perth, our drinking water catchment areas, and the only tall trees growing in a Mediterranean climate. In 2012, WA's northern jarrah forest was added to a list of Australia's ten most endangered landscapes. The list was compiled by a network of 26 leading ecologists from around Australia as part of the Innovative Research Universities.

In 1963, Alcoa commenced bauxite mining at Jarrahdale. The first mine pit was at the Jarrahdale site now known as Langford Park. The mine provided 168 million tonnes of bauxite to the Kwinana refinery, producing 45 million tonnes of alumina. The mining operation was concluded in 1998. Alcoa removed most of their plant fittings when they departed.

You may hear the Alcoa conveyor on Map 2 before you see it. The conveyor carries bauxite from the Huntley mine to the Pinjarra refinery, where it is converted into alumina, which is later made into aluminium. The trail actually crosses over the conveyor so you will get a good chance to see it. Established in 1976, Huntley is the largest bauxite mine in the world. Pinjarra refinery is one of the world's largest with a capacity of 4.2 million tonnes per year, which is about seven per cent of the world's alumina. The arboretum nearby was planted to see which trees are best suited for use on rehabilitated land. We also have a permanent realignment of the map (see here) and I can only presume it is for the same reason as the Map 3 diversion - ie mining. I am happy to stand corrected if anyone knows more. Not surprisingly there are few references to Huntley or Willowdale mine and Wagerup Refinery (map 3) on the Munda Biddi maps or most map books. It could be because Alcoa is (or was) a sponsor of the Munda Biddi. I support environmentally sustainable managed mining (my bike is aluminium, and chances are so is yours), but it seems the mining in this area is kept out of public scrutiny. Because the bauxite mined is low quality Pinjarra refinery currently consumes about 90 MegaWatts of energy every hour, which is enough energy to power 50,000 homes during the same period. Aluminium is occasionally described as "solid electricity" for the amount required to produce it.

Established in 1984, the Willowdale bauxite mine is located east of Waroona and we will ride close to it. It supplies bauxite to the Wagerup refinery. In the quiet of the night at Bidjar hut, you can hear the distant rumbling of the mine. Alcoa obtained permission in September 2006 to double the size of Wagerup refinery to become the biggest aluminum refinery in the world. I think the constant noise scares the birds away from Bidjar hut compared to other huts. Bidjar Ngoulin means 'place of rest' in Nyoongar, which, for the birds anyway, is ironic really.
The Willowdale Arboretum (marked on map 3) was planted in the 1960's or 1970's to see how trees regenerated on mined areas. Alcoa previously mined in the Mt William area (nearby), but I cant find out when the arboretum was planted, or if the area was actually mined.

Just before we cross Gastaldo Rd, we are near Worsley alumina refinery, owned by BHP. In the 1890s a railway siding was constructed here to service the timber industry. The town peaked in 1902 when its population was in excess of 1,500 but it began to decline in the 1920s and all but disappear by the 1950s. Construction of a mine site and refinery began in 1980 and the first alumina was produced in 1984. Bauxite is mined from reserves mainly within State forest on the eastern edge of the Darling Range, near Boddington. The bauxite is crushed and carried 52 km on a conveyor belt. It is believed to be one of the longest conveyor belts in the world.

Coal

WA's only producing coalfield is Collie, and generates 80% of the state's electricity. The four open cut mines contain 2,400 million tonnes of coal. Muja Power station is located east of the town. The high voltage transmission lines we rode under in map 2 originate here, and we will go under more on this map. The power station is clearly visible on the last section into Collie.The Collie replica underground coal mine is on Throssell St, part of the Collie Museum. The building was designed by C Y O'Connor and was built in 1898, who recognised the importance of coal to the development of the State. The shed has recently been restored by the Collie Heritage Group. See the working lives and conditions of the early underground miners, as well as other Collie history including a strong cycling history and timber milling.

Gold

Gold is found in the laterite of the Darling Scarp near Boddington and Pinjarra, on map 3. In 1987, the largest producer of gold in Australia, now owned by Newmont Mining, commenced mining. The mine is estimated to produce more than 1,000,000 ounces of gold per year until 2030.

Gold was discovered about 6 kilometres south of Donnybrook in 1897. A mini gold rush occurred, resulting in the Government gazetting the Donnybrook Goldfield. The excitement was short-lived however, and the mine closed in 1903.

Graphite

Graphite was first found near the Donnelly River by a shepherd. In 1904 the mine was opened and the first 65 tons of ore was shipped to New York. All companies that tested it declared it commercially useless. That didn't stop a glowing prospectus being circulated amongst investors in London in 1916. For an investment of £8000, investors could expect an estimated profit of £1.5 million. The prospectus was basically full of lies. It said there was 70 000 tons of finest quality graphite, 95% pure carbon (in fact the average carbon content was 29%), only three miles from the nearest railhead (in fact 30 miles through dense karri), the WA government had been buying from this deposit for years (it had never bought any though it tested a sample once and found it useless). The consulting engineers of the exploration report denied having written it. The graphite lease has changed hands many times since then and no one has had any success with it.

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