Tahmoor Colliery

In 1970 the Clutha Development Pty Ltd Company, the operator of all the collieries in the Burragorang Valley, commenced investigations into choosing a suitable site to develop a new mine. This activity by the Company was being driven by the need to maintain a continuity in the supply of coal, the diminishing coal reserves of the Burragorang Valley mines, and the emerging environmental issues associated with the mining of coal in the Valley.

In 1975 these investigations led to Clutha Development Pty Ltd commencing the sinking of two shafts and an inclined drift (sloping tunnel), from the surface to intersect the Bulli Seam for the purpose of opening Tahmoor Colliery several kilometres from the Tahmoor township.

The two shafts were to be used as ventilation airways, and the drift was designed to provide a second intake airway, a rail trackwork for the operation of a direct rope haulage and a seam-to-surface belt conveyor. This plant provided for the transport of personnel and materials to and from underground using the rope haulage and a conveyor belt, installed in the roof of the drift, to deliver the mined coal from the seam to the surface. The drift was driven on a grade of 1 in 3.4, a design concept that had been successfully used by the company in the development of the Brimstone No.1 and Brimstone No.2 Collieries in the Burragorang Valley.

With the shafts and drift completed, the driving of the underground roadways between No.1 Shaft and the drift commenced in 1978. This connection established a ventilation circuit, with No.1 Shaft as the upcast shaft, complete with a mine ventilation fan mounted on the surface, and the drift roadway serving as an intake airway. Production commenced in 1979, and in 1982, the development roadways driven in the mine holed into No.2 Shaft enabling that shaft to be used as an intake airway.

The Bulli Seam was intersected at a depth of 400 metres from the surface, and the mining conditions were found to be much more difficult than those found in mines operated in the shallow depths of the seam in the Burragorang Valley.

In 1981 a Coal Preparation Plant (washery) was constructed and commissioned on the mine site. This plant enabled “run of mine” coal’ to be washed to reduce the percentage of ash in the mined coal, to meet export market specifications. The coal produced by the mine is mainly a metallurgical coking coal, used for the production of steel, and is transported by the State Government Railways to the Port Kembla Coal Loader. 

The original mining method at Tahmoor Colliery was bord and pillar mining, utilising the Wongawilli method of “long lift and fender” for pillar extraction. Wooden props were utilised as roof supports in pillar extraction, as shown in the background of the following image.

When several of the Company’s collieries in the Burragorang Valley were being closed in the early 1980s, Clutha Development Pty Ltd was able to offer many of the displaced miners employment at Tahmoor Colliery in 1982.

Roof conditions encountered at mine were very difficult and the colliery became an industry leader in introducing full encapsulation roof bolting as the means of roof support. Previously the roof bolts were only point-anchored, using chemical resin. By utilising longer chemical resin cartridges, “full encapsulation” was achieved by having the roof bolt “glued’’ to the roof strata for the full length of the roof bolt. This additional bonding with the roof strata provided superior roof control and enabled the colliery to dispense with the use of heavy steel RSJs (steel beams) as a roof support. This latter form of roof support was replaced by using thin steel W-straps, with initially seven, then eight, fully encapsulated steel roof bolts, 2.1 metres in length, supporting each W- strap.

Roof bolts were installed initially using hand-held bolting machines, powered by compressed air. Typically these machines could apply up to 3 tonnes of tension on each roof bolt. Later on, hydraulic powered roof bolting rigs were mounted on the continuous miner machines. These rigs applied 8 tonnes of tension on each roof bolt and improved the support of the roof.

Eventually steel mesh sheets replaced the W-straps, providing complete mesh coverage of the roof and much better protection from pieces of stone falling from the roof.

Coal and gas Outbursts

During the early process of mining, Tahmoor Colliery had experienced some 68 minor outbursts of coal and gas.

In 1985, a major outburst caused a fatality at the Colliery. This outburst instantaneously released approximately 400 tonnes of broken coal and an estimated 4,500 cubic metres of irrespirable carbon dioxide gas. This was by far the largest outburst to have occurred in the southern coalfields.

In response to this major incident, the Tahmoor Colliery employees developed a “capsule” to protect the continuous miner driver from any future outburst in suspected outburst zones of the mine.

This capsule provided protection for the machine driver in two ways. The first being some physical protection from flying coal, ejected during an outburst. The second, was the capsule being equipped with three separate sources of a compressed air supply, so that the driver could breathe fresh air until the irrespirable gas had been flushed away by the mine ventilation system.

Subsequent to the fatal outburst in 1985, the Colliery adopted the “drill and drain” pre-mining technique for reducing the gas content in the coal seam, as discussed elsewhere in this website. This technique requires the drilling of boreholes in the coal seam prior to its mining, to enable gas to be drained out of the coal seam for a period of at least 90 days to reduce the gas content in the seam to a safe level.

In 1986, a Gas Extraction plant comprising a number of vacuum pumps was erected and commissioned on the surface at the mine. Underground, all of the boreholes drilled into the coal seam were individually connected to a gas pipeline in the mine that was connected to the gas extraction plant on the surface and discharged the coal seam gas to atmosphere.

In 1992, as technology had improved, Tahmoor Colliery was able to dispense with the “outburst capsule,” and became the first Australian colliery to introduce remote mining in suspected outburst zones of the mine. This method of mining required the fitting of television cameras to a continuous miner, which was operated by a person in a safe location, completely removed from the face area, using a television screen. These television cameras were to later provide the first televised outburst, when an incident involving some 60 tonnes of coal “outburst’’ during mining.

In 1992, Tahmoor Colliery was the first in Australia to conceive, develop and introduce an Outburst Management Plan (OMP). This plan required that that normal mining cease, until the recorded gas content of the coal seam was below the “outburst threshold limit”. The mining of an area where the gas content was found to be above the outburst threshold level was permitted providing the remote mining method was adopted. This meant that no person was permitted at the coalface during the remote mining operation.

There has not been an outburst at Tahmoor Colliery since the above outburst threshold limit scheme has been adopted, and maintained.

In 1999, Tahmoor Colliery adopted another form of remote mining called “grunching”. In this system shotholes were drilled into the coalface, loaded with explosives and detonated from a safe distance away. The introduction of large-scale “grunching’’ at Tahmoor was another first in outburst prevention in Australian collieries.

Technical note:  Grunching is the coal mining term used to describe full-face shotfiring without the presence of a kerf (often called a “cut”) in the coal face. A kerf is a 100-150 mm wide slot cut into the coalface to a similar depth as the shotholes that are drilled into the coalface.  The process of creating a kerf  in the coalface is highly likely to induce an outburst if the gas content is above the outburst threshold, so cannot be permitted.

Additional shotholes have to be drilled and loaded with explosives for grunching, therefore a larger quantity of explosives is required compared to shotfiring a coalface with a kerf.

Mine Ownership History

In 1976 the British Petroleum Oil Company (BP) purchased a 50 per cent ownership of Clutha Development Pty Ltd (the developer of Tahmoor Colliery) and in 1979 purchased the remaining 50%, gaining complete ownership of the Company. These events occurred in an era when the major international oil companies perceived themselves as energy companies and not merely oil companies, and invested heavily in coal mining throughout the world.

Coal mining commenced at Tahmoor Colliery in 1979, using the bord and pillar system of mining and the Wongawilli System of “long lift and fender” for pillar extraction, using continuous miners and shuttle cars.

In 1984 a review of management strategy took place within Clutha Development Pty Ltd and this led to a partial “management buy-out” where some senior members of the management of the company purchased the Burragorang Valley mines from Clutha Development Pty Ltd.  As a result of this change, ownership of Tahmoor Colliery was transferred from Clutha Development Pty Ltd to a division of the British Petroleum oil company known as BP Coal and Minerals Pty Ltd.

In 1985, the colliery was transferred to yet another division of the British Petroleum oil company, named BP Coal Development, who made the decision to adopt the longwall system of mining, and increase the production output of the Tahmoor Colliery. The Coal Preparation Plant and surface coal handling facilities were upgraded, a surface gas extraction plant was constructed, and the sinking of a No.3 Shaft was planned to improve the ventilation of the mine. A longwall equipment package was purchased and roadways were driven to form the first longwall block and make it ready for the installation of the longwall equipment.  In 1987, the bord and pillar system of mining and pillar extraction was replaced by longwall mining.

Longwall Mining

In 1987, the first year of longwall mining at the colliery, 1.7 million tonnes of coal were produced, and since that time, production has increased to average approximately, 2.0 million tonnes per annum.

In 1989-1990, No.3 Shaft was sunk from the colliery surface yard area, and two mine ventilation fans, operating in parallel, were installed on the shaft to improve ventilation of the mine. The original No.1 and No.2 Shafts were arranged to become intake airways.

More Changes in Ownership

In 1992 ownership of the colliery changed again, when the Kembla Coal and Coke (KCC) Company, a division within Conzinc Rio Tinto of Australia (CRA), purchased the fully operational Tahmoor Colliery, from BP Coal Development.

The Kembla Coal and Coke Company (KCC) was at that time operating the West Cliff and Coal Cliff Collieries. As the Coal Cliff Colliery was close to exhausting its available coal reserves, after operating for more than one hundred years, KCC was keen to maintain the production levels required to meet the demands of its customers and the company’s coke ovens plants.

In 1997 CRA announced that it would sell both the Tahmoor and West Cliff Collieries, to enable the company to focus on collieries producing in excess of 5 million tonnes of coal per annum, and in 1997 the West Cliff Colliery was purchased by BHPBilliton and joined the BHP Illawarra Coal group.

In 1997 Tahmoor Colliery was purchased from CRA by senior managers of the Kembla Coal and Coke Company (KCC). This new company was named Austral Coal Limited, operated the mine under the commercial name of Tahmoor Coal Pty Ltd and Austral Coal Limited, and listed on the Australian Stock Exchange (ASX) as Austral Coal Limited.

The new owners of Tahmoor Colliery were able to purchase the mining rights for the neighbouring Bargo lease, to the south of Tahmoor Colliery, to provide additional coal reserves and extend the potential operating life of Tahmoor Colliery. The Bulli coal seam in the Bargo lease was known to have an increased seam thickness when compared to the 2.1 metre average seam thickness in most of the Tahmoor lease area.

Gas Power Plant

In the year 2000, Envirogen Pty Ltd commissioned a 5 MW capacity methane gas powered generating plant, after having established a commercial agreement with the Tahmoor Colliery to utilise methane gas from the mine’s gas extraction plant. The power generated by this plant was to be supplied to the State electricity grid.

The generating plant was installed on a neighbouring property to the Colliery, and in 2003 two additional generating units were added, to increase the total output from the Plant to 7.0 MW. This power generation concept of utilising methane gas had already been applied at the West Cliff, Appin and Tower collieries.  In April 2014, the ownership of the electricity generation facility at the Tahmoor Colliery was transferred from Envirogen Pty Ltd to Energy Developments Limited.

In April 2005 the Tahmoor Colliery had another change in ownership, when it was purchased by the Centennial Coal Company, a purchase that had been keenly sought by a rival bidder, Xstrata Coal NSW for a variety of reasons including rail access to the Port Kembla Coal Loading Terminal.

In October 2007, the Centennial Coal Company sold Tahmoor Colliery to Xstrata Coal NSW.

In 2007, Xstrata Coal commissioned two new mine ventilation fans at the existing No.2 Shaft, and arranged the No.3 Shaft as an intake airway. This change improved the ventilation of the area of the mine being worked at that time.

By May 2013, Xstrata Coal merged with Glencore to become Glencore Xstrata.

In May 2014, Glencore Xstrata changed its name, to Glencore Public Limited Company, a multinational company with its headquarters in Switzerland.

The colliery submitted an application to extend its mining operations into its Bargo lease area, to be known as Tahmoor South as it is located to the south of the Tahmoor Colliery lease. A substantial capital expenditure would be required to extend the mine into this area and the operating life of the mine could be extended to about the year 2040.

In June 2016, Glencore announced that the continued low coal prices caused by the ongoing downturn in the global coal market, would not justify the capital expenditure required to extend the life of the mine. That announcement also stated that Tahmoor Colliery would be closed, by early 2019.

In 2018, the mine was sold to SIMEC that operates a (former BHP) steelworks in South Australia which had been purchasing most of its coking coal from Tahmoor Colliery.

In 2021 the NSW Government approved a ten year extension of life for the mine, likely to lead to a further 33 million tonnes production for that facility.  In 2021, the company produced a Heritage Management Plan to support their Extraction Plan for additional longwall extraction.   The Plan may be found at https://www.tahmoorcolliery.com.au/wp-content/uploads/sites/8/2022/10/50-heritage-management-plan-1.pdf .

The mine has now been extended into the former Bargo lease in an area now known as Tahmoor South. Extraction of its first longwall block in the new area was highly successful which bodes well for the future of the mine.