Mine stability ‘at risk’

Related coverage: Diversion fault report ‘damning’

At least three trouble spots in the state’s brown coal network are ‘at risk’ of failure, according to a “damning” review by an expert geotechnical panel, warning instability in the open cut sector has reached serious levels.

In the sternly worded report alluding to a vast array of shortfalls in Latrobe Valley’s coal mine stability, the Technical Review Board was unable to assure that all ‘at risk’ structures in the sector had yet been identified, “or that there will be no further failures of identified structures”.

Established by the State Government in 2008 in response to the 2007 Yallourn mine failure, where the Latrobe River collapsed through the open cut’s northern batter wall, the TRB report back to government on the region’s stability issues, in order to mitigate risks to public safety.

“It has become clear to the TRB that the situation with regard to brown coal mine stability has reached a serious state,” the report stated.

“The mines are complex structures that are large by world standards and continue to become larger and deeper.”

The Valley’s mine network has seen two further high profile incidents since the 2007 collapse; cracks appeared in the Princes Freeway between the Hazelwood open cut and Morwell residential areas, shutting the freeway for seven months in 2011.

In June last year, the Morwell River Diversion collapsed into the Yallourn open cut, temporarily crippling the operation, during a TRB reporting period which had included a “critical review” of the diversion’s performance.

Monash University environmental engineering senior lecturer Gavin Mudd said the report should be deemed a dire wake up call for the industry and Latrobe Valley community.

“From this report we can infer they are talking about (‘at risk’) situations similar to what we’ve already had in the Valley – in that sense it’s obvious that there’s some real issues here,” Dr Mudd said.

“The mine network is only becoming more challenging and logistically difficult; after reading this report, by hell is it clear we really need to get it right in future; I’m very glad the TRB has recognised this and detailed this so explicitly.

“Both the companies and government need to step up to the plate to address this.”

Department of Environment and Primary Industries executive director of earth resources Doug Sceney said knowledge and understanding surrounding the Valley’s large “world scale mines” was evolving “as we speak”.

“The Latrobe valley has a legacy of large mines here that have been here for a long time, designed and constructing during a time when standards were different – we need to learn from past to build for the future, to build our knowledge base … We cant undo what was done in the past,” Mr Sceney sai

A spokesperson for AGL, owner of Loy Yang Power station, said the company had received a draft audit report from DEPI which found the site had “effective ground control management plans”, and was awaiting the final report.

“AGL understands the only ‘at risk’ structure on the Loy Yang site referred to by TRB, is the one which has now been stabilised,” the spokesperson said.

“This structure was located on the southern batter, where rainfall in 2007 triggered coal movement. Following this, an extensive investigation was undertaken, resulting in repair works to rectify the situation and stabilise the area.”

A spokesperson for GDF SUEZ Australian Energy – owner of Hazelwood Power Station – said all industry stakeholders acknowledged mine stability was a very complex issue, and the company had taken a “proactive approach” to managing its mining environment.

“For example, we are constructing a comprehensive ground control management plan for the mine, we have developed a leading edge geographical information system and we are establishing technically advanced ground monitoring systems,” the spokesperson said.

“We are comfortable with the process the Victorian Government has adopted and will continue to work closely with the TRB, Department of Primary Industries and Environment and external technical experts to effectively manage this environment.”

Yallourn Power Station owner operator EnergyAustralia spokesperson said all input from the TRB was treated seriously.

“We have a comprehensive ground control management plan, which regularly monitors the stability of batters, allowing us to identify issues,” the spokesperson said.