Month: May 2023

Water, Safety and Dendrobium coal mine

The danger of water inrush has increased over the life of the Dendrobium coal mining operation, reaching a crisis during the flooding rains of 2022 when the board dropped plans to mine Area 5. This surprising decision was justified on commercial grounds in a climate of buoyant metallurgical coal prices. The retreat also followed a political attack and legal challenge to the Independent Planning to Commission, who had refused planning consent to mine Area 5 and 6, based on issues of water ingress. South32 had managed to convince parliament to disregard the IPC and proceed with an extension regardless, and now … nope, not happening.

South32 Chief Executive Graham Kerr explained the decision as “directing capital towards other opportunities” while “confident South32 can squeeze more coal out of the existing mine and Nearby Appin colliery for years to come”. No mention made of water issues with the mine, the problem blocking mine progress since it’s inception. Financial analysts pushing for renewables took the South32 decision to retreat as a sign of the demise of coal, while investors confident in a future for metallurgical coal reported “wet weather” as an explanation for South32 walking away from lucrative returns. [REF D]

Wet weather in the case of a “wet mine” like Dendrobium leads to flooding which can slow coal production and endanger the lives of miners. Mining disasters represent massive financial risk. Where the government is politically sensitive to loss of life a disaster can spell the termination of a mining operation. In 2017 Planning minister Stokes had signalled an urgent interest in mine safety on the Dendrobium lease by establishing an expert panel and later an IPC inquiry that collected negative assessments offered by other agencies. Terms of reference for the initial inquiry concentrated on “the height of cracking” at Dendrobium, underlining concern about mine flooding. Loss of water from reservoirs and dam safety were flagged as possiblities where “unconventional” cracking penetrates from surface to seam. The IPC was concerned that a leaking mine could drain the catchment in perpetuity, with water flooding out of the mine entrance sited lower than the reservoir.

After the IPC delivered South32 an unfavourable decision the Department of Planning and Environment, who favoured development, helped construct a mine-friendly campaign around BlueScope steelworks. Serial Planning minister Anthony Roberts, a close friend to the mining lobby, joined the political coup organised by then deputy premier John Barillaro to deliver Dendrobium the status of State Significant Infrastructure, deposing Stokes and regaining control of planning. Factions intent on pushing through planning approval may have lost sight of the dangers of ignoring the risk of disaster. After demolishing the independent review process, established to guard against corrupt conduct in the granting of coal leases, South32 seemed to have lost the will to capitalise on political advantage. Cold feet perhaps, or a reassessment of risk?

With the change in state government there was no change in fortune for South32, no political reason to drop expansion ambitions. In the event of disaster on the Dendrobium lease, Labor Planning minister Paul Scully now has the job of explaining why he also chose to ignore red flags raised by the IPC and others. In a Zoom meeting Scully explained that longwall mining, though more environmentally destructive than traditional bord and pillar, was safer for mine workers. Such an assurance ignoring the fact that the mine was leaking like a sieve due to subsidence cracking.

By failing to predict or explain the extent of mine flooding during the rainfall of 2022 hydrogeologists employed by South32 helped build the empirical case that the Dendrobium mine is operating under dangerous conditions. For a time the volume of water flooding the mine exceeded the capacity to pump it out. The link between rainfall and mine inflow is undeniably correlated yet there is a persistent denial that the mine is draining surface water. Admit nothing.

The further risk of damaging reservoir infrastructure was flagged by the Dam Safety Committee who had to argue for increased set-back limits. Such demonstrated uncertainty might be considered a safety issue. The risk previously divested by BHP is now in the lap of South32 who may repeat history and look to find an even smaller operator who will deal with the responsibility of mitigating risk and paying for rehabilitation. “South32 has hinted in recent times that BlueScope was the natural owner of the Illawarra mines, rather than a Perth-based company that was increasingly focused on the metals needed for decarbonisation.” [REF D]

Background

Longwall coal mining in the Illawarra has a long history of disasters; gas outbursts, fire, water inflows and tunnel collapse contributing to death of miners and jeopardising coal production. Operators weigh the risk of disaster and reputational damage against potential profits. Regulators will shut down mining operations after disasters; Wongawilli mine adjoining the Dendrobium lease is currently shut due to fire and collapse of the mine roof. Breaching safe operating practice is the primary trigger for mine closure by government. Entering the Dendrobium project BHP Billiton as parent company to Australian Iron and Steel Ltd, now Bluescope, was linked to the Appin mine disaster where a gas explosion in 1979 killed 14 people. Further gas outbursts in the Appin mine have seen long closures while gas is drained.

Feasibility studies for the Dendrobium project begun in 2000 assessed the safety risks of the mine project and whether those risks were acceptable to BHP. The Dendrobium project extending underneath three previous mines and jammed between Avon and Cordeaux reservoirs, with a driveway passing beneath Cordeaux reservoir, carried a high risk of water inflow that would be both expensive and dangerous to deal with. “The restricted mining areas has meant that geophysical parameters such as stress direction, roof strength variability and coal quality variations, have, for all intents and purposes, had to be dealt with as outcomes of the chosen mine layout rather than drivers of it.” [REF A pg. 25]. By 2015 the BHP board decided to drop the risks of coal mining in the Illawarra by creating another company South32 to transfer these risky mining assets.

In order to reach the larger untapped coal measures the mine progressed through Area1 with 2 longwall panels and Area 2 with 3 panels to establish a 6 km long underground driveway to begin transporting coal from the 14 panels comprising Areas 3A and 3B.  As mining advanced with another 5 km of additional driveway, water inflows from the previous mines and collapsed panels in Areas 1 & 2 added to water collecting in Area 3 until pumping was unable to clear Area 3. “During March-April, very high rainfall resulted in high inflows to Area 2. Pumping from Area 3B was limited to prioritise pumping from Area 2 during that time.” [REF B pg. 15]

The prolonged period of flooding in 2022 preceded the decision to drop plans for the extension into Area 5; plans which would have added yet another 5km to the underground driveway, placing a flood-prone mine under further pressure to pump out an unpredictable volume of water while sending miners deeper into remote territory.

Consultants Advice

In April 2022 hydrogeology consultants HEC predicted groundwater inflows for Area 2 of Dendrobium mine to be stable at approx 1.1 ML/day. The total groundwater inflows of all mined areas were predicted to be 9.9 ML/day. Unfortunately wet weather intervened and the HEC predictions did not reflect the real situation, as can be seen in the report prepared by another consultant HGEO in September 2022. Area 2 inflows correlate closely with rainfall, and pumping from Area 3 was limited to prioritise Area 2 during this time. South32 had maintained that surface water hydrology was not directly related to groundwater discharge in the mine. Longer lag times and a low level of Tritium isotopes had been presented as evidence of an isolated groundwater balance. The rains of 2022 put a question mark to such assurances and it became imperative to understand why and where the increased inflow was coming from. In January of 2022 water ingress into Area 3 spiked at 16.21 ML/day as seen in Table2, section 3 of the Hgeo report, excerpt below. By September 2022 the daily inflow had climbed as high as 19 ML/day – nearly double the predictions offered in the previous HEC report.

Note: Units used in graphs are not consistent, changing from ML/year to ML/day

Timeline of Advice

1st April 2022 Appendix C HEC  Surface Water Assessment for ICH Pty Ltd [REF C]

Review of Dendrobium Mine Extension Project SSI-33143123 EIS

•23rd  August South32 announces end of expansion plans for Area 5

•9th Sept 2022 South32 withdraws SSI application to mine Area 5

•15th Sept 2022 HGEO End of Panel Groundwater Assessment for Longwall 18 (Area 3B) Dendrobium 

DENDROBIUM MINE End of Panel Groundwater Assessment For Longwall18 

[REF B Pg. 15] “During March-April [2022] very high rainfall resulted in high inflows to Area 2.” Graph maps progress of each Longwall panel with panel 18 extending through 2022

Excerpts

An Olympic swimming pool containing 2.5 ML of water. During 2022 no less than 3 and sometimes 7 Olympic pools of water were pumped daily out of Dendrobium mine.

References

[REF A]

P. Whittall, Dendrobium Mine: From Paper to Production, in Naj Aziz and Bob Kininmonth (eds.), Proceedings of the 2004 Coal Operators’ Conference, Mining Engineering, University of Wollongong, 18-20 February 2019 https://ro.uow.edu.au/coal/125

[REF B]

DENDROBIUM MINE End of Panel Groundwater Assessment For Longwall18

[REF C]

Appendix C HEC  Surface Water Assessment for ICH Pty Ltd 

Review of Dendrobium Mine Extension Project SSI-33143123 EIS

[REF D]

Coal mine closure a test for BlueScope, Peter Ker & Simon Evans, AFR, 23 August 2022