By PHILIP HOPKINS
WATER is a key part of the operation of the Loy Yang mine – and will still be a key part of the brown coal mine’s future.
The scheduled closure of the Loy Yang A power station in 2035 is looming larger on the horizon, and the water issue needs to be sorted out.
AGL, the mine owner and operator, has applied for a Bulk Water Entitlement (BWE), which will determine how much water the company can take from the Latrobe River system to rehabilitate the mine, with a lake the most favoured current option. Public comment on the proposal is open until Sunday, December 15.
The mine supplies brown coal to both Loy Yang A and B power stations. Consisting of two separate companies, together the complex is the largest single power station in Australia.
Loy Yang A General Manager, Christo van Niekerk said it was obviously important for AGL to get final certainty around the final land formation and rehabilitation pathway for the mine.
“We have always had the position that the final landform will be a pit lake and that’s why the application is there – to bed that down and do our planning appropriately. It’s critical for us to understand the final landform,” he told the Express in an interview.
He indicated this would work in with the company’s progressive rehabilitation of the mine.
The BWE centres on the company having a secure allocation of water for the mine rehabilitation. AGL emphasises that the future amount of water use for rehabilitation will be the same amount of water that is currently used for power station operations.
The BWE is based on the Latrobe Valley Regional Rehabilitation Strategy (LVRRS), formed as part of the Hazelwood mine fire inquiry. The inquiry made many recommendations on what take of water could be utilised best for mine-filling. It was not written specifically for Loy Yang, but also for the other declared mines, Hazelwood and Yallourn.
“Based on the study that the LVRRS has done, we have looked at surface water access conditions, particularly for mine rehabilitation planning. The study gives community stakeholders certainty about the timing of when it will happen. We will always make sure other water users are not impacted; our application very much in line with the Latrobe Valley rehabilitation strategy,” Mr van Niekerk said.
“Any water is restricted to the wetter months; we are focussed on when water is available during those wet months.”
The specific conditions in AGL’s application include taking the water would be restricted to the period from June to November. A threshold will be in place to stop winter-spring base flow being diverted into the Latrobe River. A limit will be placed on annual releases from the Blue Rock Reservoir. Surface water would be available for rehabilitation for 30 years from the initial supply date (June 30 2035) or until 2065, assuming Loy Yang A’s closure date of 2035.
The Loy Yang mine is a stark presence in the Latrobe Valley landscape. From a vantage point, during a tour of the mine by the Express, the various layers of the mine are clearly visible. Sitting on the ground in parts of the mine is water.
This is rainwater but includes some artesian water pumped from hundreds of metres below the surface, helping to stabilise the mine. The water is pumped to reservoirs where it’s used in the power station.
“It’s also used for dust suppression and fire suppression, which is critical – particularly in summer. We manage it through the year; goes up and down due to rainy season and drier months,” Mr van Niekerk said.
AGL estimates that the total water volume required to fill the mine void is about 1087 gigalitres, with a fill time of 22 years. The surface water required is 630GL and ground water needed is 462GL. Evaporation over the period is estimated at 90GL, with top-up requirements to counter that 6GL a year.
Work done by AGL indicates a full-pit lake is the best option; it is technically the best solution (it promotes stability as the weight of the water stops ground movement) and would also create new habitats for wildlife and areas for public use.
The mine, which is more than five kilometres long, has an area of 1200 hectares. Annual output is more than 30 million tonnes of coal and up to four million cubic metres of overburden. Four dredgers, which are 150 metres long, 50 metres high and weigh 5000 tonnes, operate in the mine. The coal extracted will be burnt within 24 hours in contrast to black coal in Queensland and NSW that can be stockpiled. Brown coal, because of the moisture content, can’t be stockpiled for long periods.
Loy Yang’s 1200ha mining licence area is only a fraction of the Latrobe’s vast brown coal resource, which extends to Rosedale. Under AGL’s licence excavation limit, Mr van Niekerk said the plan was to progress the mine towards the eastern bloc, to the south of the power station.
“Then we will mine back, pivot the mine by 180 degrees and mine from east to west, back to the start of the mine,” he said.
AGL engineers estimate the current depth of the mine at 180-190 metres below the surrounding natural surface area.
Rehabilitation also includes experiments in rehabilitating along the western batters of the mine after excavation of the coal.
“We had some catch-up to do over the last 10 years. We have done significant work on the western batter, using grasses for rehabilitation with Federation University. We see what works best. The intent has always been, as we mine towards the east, to do that,” Mr van Niekerk said.
By doing permutation trials with different plants and grasses, mixes of topsoil blends and clay thicknesses, AGL aims to understand what will constitute resilient covering to close up and finish the rehabilitation.
Mr van Niekerk said Japan’s HESC project, which aims to use Loy Yang brown coal to produce hydrogen, would not affect the mine rehabilitation.
“Our intentions are very clear: rehab will be in line with what our bulk water rehabilitation is. That effectively starts in 2035 after our targeted closure of the power station. It’s up to them to model and progress. We have always said we will support it, but we can’t speak on their behalf. It’s up to them,” he said.
Under HECS, carbon dioxide produced by using hydrogen from brown coal would be stored in empty aquifers under Bass Strait. HESC has proven the process in a pilot plant and is now moving towards commercialisation by 2028.
Another rehabilitation headache is the ash produced by the power station. Mr van Niekerk said finding a use for the ash produced from brown coal mining was “definitely” on AGL’s agenda. Latrobe Magnesium is using ash from the Yallourn Power Station to produce magnesium.
“We have done studies in the past and are currently looking at options. We work with colleagues in the energy hubs team for alternative uses of ash. It would be beneficial for everybody if we can use it and don’t have to put it into landform. It’s something we are looking at for the future,” he said.
The current outages at Loy Yang highlights the power station’s economic importance for the Valley and its vital role as an energy supplier to Victoria. The $94 million maintenance and repair project on Loy Yang Unit 4 and Dredger 15 involves up to 850 contract workers, boosting local businesses. The power station, which has a capacity of 2210 megawatts, employs 600 permanent workers.
“We are supplying last year just over 30 per cent of electricity consumption in Victoria and with Loy Yang B using the same mine, we are supplying about 50 per cent – a big chunk – of state electricity we supply,” Mr van Niekerk said.
Reminders pop up that coal excavation is also playing with history. Curiosities include clumps of fossilised tree before it was transformed into coal. Sometimes the imprint of bark is visible. The coal fields are about 30 million years old.
