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Isaac Downs and Isaac Plains are two adjacent metallurgical coal mining projects owned by Stanmore Coal in Central Queensland, Australia.

The Isaac Plains mine was previously owned by Isaac Plains Coal Management, a 50/50 joint venture between Aquila Resources and Vale, and it was placed under care and maintenance in 2014. Stanmore acquired the property in November 2015 and recommenced mining operations at the site in January 2016. Mining operations were transitioned from the Isaac Plains Mine to the Issac Plains East mine in July 2018.

The Isaac Downs coal mine is a proposed open-cut green-field metallurgical coal mining development south of the Isaac Plains Complex. The mining permit for the project was acquired in 2018.

IP South,  a wholly-owned subsidiary of Stanmore Coal, will be the developer and operator of the Isaac Downs project, while the Isaac Plains Coal mine is being operated by IP Coal, another subsidiary of Stanmore.

The Isaac Downs project will utilise the existing infrastructure facilities at the Isaac coal complex including the coal handling and preparation plant (CHPP), rejects management, raw water supply, mine water management, and power supply systems.

Scheduled to commence operations in 2022, the Isaac Downs project is expected to produce approximately 35 million tonnes (Mt) of run-of-the-mine (ROM) coal over an estimated mine life of 16 years.

Stantmore also completed a bankable feasibility study (BFS) to develop an underground mine in the Isaac plains complex in 2019. The project decision is currently deferred until Stantmore is able to secure additional port and coal handling capacity and construction of the Isaac Downs project is completed.

An on-market takeover offer by Golden Investments was completed in May 2020 wherein Golden Investments acquired 75.33% of Stanmore’s shares.

Project location and geology

The  Isaac Downs and the Isaac Plains projects are located in the Bowen Basin coal field of Central Queensland, approximately 10km south-east of Moranbah, within the Isaac Regional Council area.

The Isaac Downs project has three mining leases, MLA 700046, MLA 700047, and MLA 700048 covering a total area of approximately 2,366ha.

The Isaac Plains complex is located 10km north of the Isaac Downs project and comprises the mining leases ML 7032, ML 700016, ML 700017, ML 700018, and ML 700019.

Coal reserves

The Isaac Plains complex that includes the Isaac Plains and Isaac Plains East mines was estimated to hold 13Mt of coal reserves, while the Isaac Downs deposit was estimated to contain 24.5Mt of proven and probable coal reserves as of June 2019.

Mining and coal processing

The Isaac Downs Coal mine will be a single open-cut mine using traditional methods of drilling and blasting with the overburden removal and coal extraction carried out with the use of dragline, shovel, and excavators.

The initial nine years of operation will involve mining at a rate of 3.2Mtpa  of ROM coal which will be reduced to approximately 1Mtpa during the remaining seven years of operation.

The extracted coal will be transported by haul trucks to a 200,000t ROM stockpile near the pit. Ore from the stockpile will be loaded onto road trains and transported to the Isaac Plains Mine coal handling and preparation plant (CHPP).

The mining fleet will comprise a dragline, two main excavators, a smaller 190t excavator for waste removal, one small straight blade excavator for thin coal and scalping, approximately 10 units of 240t, and four units of 190t rear dump trucks, apart from four-track dozers and one rubber tyre dozer.

Mining operations at Isaac Plains mine have been put on hold and current operations are focussed at Isaac Plains East mine where overburden removal commenced in July 2018. Open-pit mining at Isaac Plains East is expected to continue at a rate of 2.4Mtpa over a period of four years. The mining fleet comprises of a dragline supported by excavators, dump trucks and dozers.

The ROM coal output from both the mining sites will be processed at the existing Isaac Plains CHPP which has a processing capacity of 3.5Mtpa.

Project infrastructure

An access road to the Isaac Downs project will be constructed which will intersect with the Peak Downs Highway. The haul road to the Isaac Plains Mine will also intersect the highway via an underpass.

Power supply required for the project will be delivered via a 66kV overhead line from Isaac Plains Mine substation which is connected to the regional power grid.

The water requirement will primarily be for dust suppression and vehicle washdowns which will be obtained from mine and sediment affected water stored on site. The pumped water facility is also available from the existing void and dam water storage at Isaac Plains mine. A pipeline will be installed adjacent to the haul road for the transfer of pumped water from the Isaac Plains mine complex.

Contractors involved

Palaris Australia was engaged for the bankable feasibility study for the Isaac Downs project which is currently in progress.

Stanmore awarded a five-year mining service contract extension for the Isaac Plains Complex to Golding Contractors, a subsidiary of NRW Holdings in November 2018.

Mastermyne Group was engaged in the Isaac Plains Underground mine feasibility study in March 2018.